Merge "nblog: split NBLog.cpp into multiple files"
diff --git a/media/audioserver/Android.mk b/media/audioserver/Android.mk
index 8a97299..ddf98f6 100644
--- a/media/audioserver/Android.mk
+++ b/media/audioserver/Android.mk
@@ -18,6 +18,7 @@
 	libmedia \
 	libmedialogservice \
 	libnbaio \
+	libnblog \
 	libsoundtriggerservice \
 	libutils
 
diff --git a/media/libaudioclient/Android.bp b/media/libaudioclient/Android.bp
index 6146c0e..1fa1c6e 100644
--- a/media/libaudioclient/Android.bp
+++ b/media/libaudioclient/Android.bp
@@ -40,16 +40,17 @@
         "TrackPlayerBase.cpp",
     ],
     shared_libs: [
-        "liblog",
-        "libcutils",
-        "libutils",
-        "libbinder",
-        "libdl",
         "libaudioutils",
         "libaudiomanager",
+        "libbinder",
+        "libcutils",
+        "libdl",
+        "liblog",
         "libmedia_helper",
         "libmediametrics",
         "libmediautils",
+        "libnblog",
+        "libutils",
     ],
     export_shared_lib_headers: ["libbinder"],
 
diff --git a/media/libaudioclient/include/media/AudioMixer.h b/media/libaudioclient/include/media/AudioMixer.h
index cf7d90f..aa036a8 100644
--- a/media/libaudioclient/include/media/AudioMixer.h
+++ b/media/libaudioclient/include/media/AudioMixer.h
@@ -18,17 +18,18 @@
 #ifndef ANDROID_AUDIO_MIXER_H
 #define ANDROID_AUDIO_MIXER_H
 
+#include <map>
 #include <pthread.h>
 #include <sstream>
 #include <stdint.h>
 #include <sys/types.h>
 #include <unordered_map>
+#include <vector>
 
 #include <media/AudioBufferProvider.h>
 #include <media/AudioResampler.h>
 #include <media/AudioResamplerPublic.h>
 #include <media/BufferProviders.h>
-#include <media/nblog/NBLog.h>
 #include <system/audio.h>
 #include <utils/Compat.h>
 #include <utils/threads.h>
@@ -41,6 +42,10 @@
 
 namespace android {
 
+namespace NBLog {
+class Writer;
+}   // namespace NBLog
+
 // ----------------------------------------------------------------------------
 
 class AudioMixer
diff --git a/media/libnblog/Android.bp b/media/libnblog/Android.bp
index 4a4aac1..1188320 100644
--- a/media/libnblog/Android.bp
+++ b/media/libnblog/Android.bp
@@ -3,9 +3,13 @@
     name: "libnblog",
 
     srcs: [
-        "NBLog.cpp",
+        "Entry.cpp",
+        "Merger.cpp",
         "PerformanceAnalysis.cpp",
+        "Reader.cpp",
         "ReportPerformance.cpp",
+        "Timeline.cpp",
+        "Writer.cpp",
     ],
 
     shared_libs: [
diff --git a/media/libnblog/Entry.cpp b/media/libnblog/Entry.cpp
new file mode 100644
index 0000000..e875639
--- /dev/null
+++ b/media/libnblog/Entry.cpp
@@ -0,0 +1,262 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#define LOG_TAG "NBLog"
+//#define LOG_NDEBUG 0
+
+#include <memory>
+#include <stddef.h>
+#include <stdint.h>
+
+#include <audio_utils/fifo.h>
+#include <media/nblog/Entry.h>
+#include <media/nblog/Events.h>
+#include <utils/Log.h>
+
+namespace android {
+namespace NBLog {
+
+int Entry::copyEntryDataAt(size_t offset) const
+{
+    // FIXME This is too slow
+    if (offset == 0) {
+        return mEvent;
+    } else if (offset == 1) {
+        return mLength;
+    } else if (offset < (size_t) (mLength + 2)) {
+        return (int) ((char *) mData)[offset - 2];
+    } else if (offset == (size_t) (mLength + 2)) {
+        return mLength;
+    } else {
+        return 0;   // FIXME is this an error?
+    }
+}
+
+EntryIterator::EntryIterator()   // Dummy initialization.
+    : mPtr(nullptr)
+{
+}
+
+EntryIterator::EntryIterator(const uint8_t *entry)
+    : mPtr(entry)
+{
+}
+
+EntryIterator::EntryIterator(const EntryIterator &other)
+    : mPtr(other.mPtr)
+{
+}
+
+const entry& EntryIterator::operator*() const
+{
+    return *(entry*) mPtr;
+}
+
+const entry* EntryIterator::operator->() const
+{
+    return (entry*) mPtr;
+}
+
+EntryIterator& EntryIterator::operator++()
+{
+    mPtr += mPtr[offsetof(entry, length)] + Entry::kOverhead;
+    return *this;
+}
+
+EntryIterator& EntryIterator::operator--()
+{
+    mPtr -= mPtr[Entry::kPreviousLengthOffset] + Entry::kOverhead;
+    return *this;
+}
+
+EntryIterator EntryIterator::next() const
+{
+    EntryIterator aux(*this);
+    return ++aux;
+}
+
+EntryIterator EntryIterator::prev() const
+{
+    EntryIterator aux(*this);
+    return --aux;
+}
+
+bool EntryIterator::operator!=(const EntryIterator &other) const
+{
+    return mPtr != other.mPtr;
+}
+
+int EntryIterator::operator-(const EntryIterator &other) const
+{
+    return mPtr - other.mPtr;
+}
+
+bool EntryIterator::hasConsistentLength() const
+{
+    return mPtr[offsetof(entry, length)] == mPtr[mPtr[offsetof(entry, length)] +
+        Entry::kOverhead + Entry::kPreviousLengthOffset];
+}
+
+void EntryIterator::copyTo(std::unique_ptr<audio_utils_fifo_writer> &dst) const
+{
+    size_t length = mPtr[offsetof(entry, length)] + Entry::kOverhead;
+    dst->write(mPtr, length);
+}
+
+void EntryIterator::copyData(uint8_t *dst) const
+{
+    memcpy((void*) dst, mPtr + offsetof(entry, data), mPtr[offsetof(entry, length)]);
+}
+
+// ---------------------------------------------------------------------------
+
+std::unique_ptr<AbstractEntry> AbstractEntry::buildEntry(const uint8_t *ptr)
+{
+    if (ptr == nullptr) {
+        return nullptr;
+    }
+    const uint8_t type = EntryIterator(ptr)->type;
+    switch (type) {
+    case EVENT_FMT_START:
+        return std::make_unique<FormatEntry>(FormatEntry(ptr));
+    case EVENT_AUDIO_STATE:
+    case EVENT_HISTOGRAM_ENTRY_TS:
+        return std::make_unique<HistogramEntry>(HistogramEntry(ptr));
+    default:
+        ALOGW("Tried to create AbstractEntry of type %d", type);
+        return nullptr;
+    }
+}
+
+EntryIterator FormatEntry::begin() const
+{
+    return EntryIterator(mEntry);
+}
+
+const char *FormatEntry::formatString() const
+{
+    return (const char*) mEntry + offsetof(entry, data);
+}
+
+size_t FormatEntry::formatStringLength() const
+{
+    return mEntry[offsetof(entry, length)];
+}
+
+EntryIterator FormatEntry::args() const
+{
+    auto it = begin();
+    ++it; // skip start fmt
+    ++it; // skip timestamp
+    ++it; // skip hash
+    // Skip author if present
+    if (it->type == EVENT_FMT_AUTHOR) {
+        ++it;
+    }
+    return it;
+}
+
+int64_t FormatEntry::timestamp() const
+{
+    auto it = begin();
+    ++it; // skip start fmt
+    return it.payload<int64_t>();
+}
+
+log_hash_t FormatEntry::hash() const
+{
+    auto it = begin();
+    ++it; // skip start fmt
+    ++it; // skip timestamp
+    // unaligned 64-bit read not supported
+    log_hash_t hash;
+    memcpy(&hash, it->data, sizeof(hash));
+    return hash;
+}
+
+int FormatEntry::author() const
+{
+    auto it = begin();
+    ++it; // skip start fmt
+    ++it; // skip timestamp
+    ++it; // skip hash
+    // if there is an author entry, return it, return -1 otherwise
+    return it->type == EVENT_FMT_AUTHOR ? it.payload<int>() : -1;
+}
+
+EntryIterator FormatEntry::copyWithAuthor(
+        std::unique_ptr<audio_utils_fifo_writer> &dst, int author) const
+{
+    auto it = begin();
+    it.copyTo(dst);     // copy fmt start entry
+    (++it).copyTo(dst); // copy timestamp
+    (++it).copyTo(dst); // copy hash
+    // insert author entry
+    size_t authorEntrySize = Entry::kOverhead + sizeof(author);
+    uint8_t authorEntry[authorEntrySize];
+    authorEntry[offsetof(entry, type)] = EVENT_FMT_AUTHOR;
+    authorEntry[offsetof(entry, length)] =
+        authorEntry[authorEntrySize + Entry::kPreviousLengthOffset] =
+        sizeof(author);
+    *(int*) (&authorEntry[offsetof(entry, data)]) = author;
+    dst->write(authorEntry, authorEntrySize);
+    // copy rest of entries
+    while ((++it)->type != EVENT_FMT_END) {
+        it.copyTo(dst);
+    }
+    it.copyTo(dst);
+    ++it;
+    return it;
+}
+
+int64_t HistogramEntry::timestamp() const
+{
+    return EntryIterator(mEntry).payload<HistTsEntry>().ts;
+}
+
+log_hash_t HistogramEntry::hash() const
+{
+    return EntryIterator(mEntry).payload<HistTsEntry>().hash;
+}
+
+int HistogramEntry::author() const
+{
+    EntryIterator it(mEntry);
+    return it->length == sizeof(HistTsEntryWithAuthor)
+            ? it.payload<HistTsEntryWithAuthor>().author : -1;
+}
+
+EntryIterator HistogramEntry::copyWithAuthor(
+        std::unique_ptr<audio_utils_fifo_writer> &dst, int author) const
+{
+    // Current histogram entry has {type, length, struct HistTsEntry, length}.
+    // We now want {type, length, struct HistTsEntryWithAuthor, length}
+    uint8_t buffer[Entry::kOverhead + sizeof(HistTsEntryWithAuthor)];
+    // Copy content until the point we want to add the author
+    memcpy(buffer, mEntry, sizeof(entry) + sizeof(HistTsEntry));
+    // Copy the author
+    *(int*) (buffer + sizeof(entry) + sizeof(HistTsEntry)) = author;
+    // Update lengths
+    buffer[offsetof(entry, length)] = sizeof(HistTsEntryWithAuthor);
+    buffer[offsetof(entry, data) + sizeof(HistTsEntryWithAuthor) + offsetof(ending, length)]
+        = sizeof(HistTsEntryWithAuthor);
+    // Write new buffer into FIFO
+    dst->write(buffer, sizeof(buffer));
+    return EntryIterator(mEntry).next();
+}
+
+}   // namespace NBLog
+}   // namespace android
diff --git a/media/libnblog/Merger.cpp b/media/libnblog/Merger.cpp
new file mode 100644
index 0000000..5f6e0d1
--- /dev/null
+++ b/media/libnblog/Merger.cpp
@@ -0,0 +1,297 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#define LOG_TAG "NBLog"
+//#define LOG_NDEBUG 0
+
+#include <memory>
+#include <queue>
+#include <stddef.h>
+#include <stdint.h>
+#include <vector>
+
+#include <audio_utils/fifo.h>
+#include <json/json.h>
+#include <media/nblog/Merger.h>
+#include <media/nblog/PerformanceAnalysis.h>
+#include <media/nblog/ReportPerformance.h>
+#include <media/nblog/Reader.h>
+#include <media/nblog/Timeline.h>
+#include <utils/Condition.h>
+#include <utils/Log.h>
+#include <utils/Mutex.h>
+#include <utils/RefBase.h>
+#include <utils/String8.h>
+#include <utils/Timers.h>
+#include <utils/Thread.h>
+
+namespace android {
+namespace NBLog {
+
+Merger::Merger(const void *shared, size_t size):
+      mShared((Shared *) shared),
+      mFifo(mShared != NULL ?
+        new audio_utils_fifo(size, sizeof(uint8_t),
+            mShared->mBuffer, mShared->mRear, NULL /*throttlesFront*/) : NULL),
+      mFifoWriter(mFifo != NULL ? new audio_utils_fifo_writer(*mFifo) : NULL)
+{
+}
+
+void Merger::addReader(const sp<Reader> &reader)
+{
+    // FIXME This is called by binder thread in MediaLogService::registerWriter
+    //       but the access to shared variable mReaders is not yet protected by a lock.
+    mReaders.push_back(reader);
+}
+
+// items placed in priority queue during merge
+// composed by a timestamp and the index of the snapshot where the timestamp came from
+struct MergeItem
+{
+    int64_t ts;
+    int index;
+    MergeItem(int64_t ts, int index): ts(ts), index(index) {}
+};
+
+bool operator>(const struct MergeItem &i1, const struct MergeItem &i2)
+{
+    return i1.ts > i2.ts || (i1.ts == i2.ts && i1.index > i2.index);
+}
+
+// Merge registered readers, sorted by timestamp, and write data to a single FIFO in local memory
+void Merger::merge()
+{
+    if (true) return; // Merging is not necessary at the moment, so this is to disable it
+                      // and bypass compiler warnings about member variables not being used.
+    const int nLogs = mReaders.size();
+    std::vector<std::unique_ptr<Snapshot>> snapshots(nLogs);
+    std::vector<EntryIterator> offsets;
+    offsets.reserve(nLogs);
+    for (int i = 0; i < nLogs; ++i) {
+        snapshots[i] = mReaders[i]->getSnapshot();
+        offsets.push_back(snapshots[i]->begin());
+    }
+    // initialize offsets
+    // TODO custom heap implementation could allow to update top, improving performance
+    // for bursty buffers
+    std::priority_queue<MergeItem, std::vector<MergeItem>, std::greater<MergeItem>> timestamps;
+    for (int i = 0; i < nLogs; ++i)
+    {
+        if (offsets[i] != snapshots[i]->end()) {
+            std::unique_ptr<AbstractEntry> abstractEntry = AbstractEntry::buildEntry(offsets[i]);
+            if (abstractEntry == nullptr) {
+                continue;
+            }
+            timestamps.emplace(abstractEntry->timestamp(), i);
+        }
+    }
+
+    while (!timestamps.empty()) {
+        int index = timestamps.top().index;     // find minimum timestamp
+        // copy it to the log, increasing offset
+        offsets[index] = AbstractEntry::buildEntry(offsets[index])->
+            copyWithAuthor(mFifoWriter, index);
+        // update data structures
+        timestamps.pop();
+        if (offsets[index] != snapshots[index]->end()) {
+            int64_t ts = AbstractEntry::buildEntry(offsets[index])->timestamp();
+            timestamps.emplace(ts, index);
+        }
+    }
+}
+
+const std::vector<sp<Reader>>& Merger::getReaders() const
+{
+    //AutoMutex _l(mLock);
+    return mReaders;
+}
+
+// ---------------------------------------------------------------------------
+
+MergeReader::MergeReader(const void *shared, size_t size, Merger &merger)
+    : Reader(shared, size, "MergeReader"), mReaders(merger.getReaders())
+{
+}
+
+// Takes raw content of the local merger FIFO, processes log entries, and
+// writes the data to a map of class PerformanceAnalysis, based on their thread ID.
+void MergeReader::processSnapshot(Snapshot &snapshot, int author)
+{
+    ReportPerformance::PerformanceData& data = mThreadPerformanceData[author];
+    // We don't do "auto it" because it reduces readability in this case.
+    for (EntryIterator it = snapshot.begin(); it != snapshot.end(); ++it) {
+        switch (it->type) {
+        case EVENT_HISTOGRAM_ENTRY_TS: {
+            const HistTsEntry payload = it.payload<HistTsEntry>();
+            // TODO: hash for histogram ts and audio state need to match
+            // and correspond to audio production source file location
+            mThreadPerformanceAnalysis[author][0 /*hash*/].logTsEntry(payload.ts);
+        } break;
+        case EVENT_AUDIO_STATE: {
+            mThreadPerformanceAnalysis[author][0 /*hash*/].handleStateChange();
+        } break;
+        case EVENT_THREAD_INFO: {
+            const thread_info_t info = it.payload<thread_info_t>();
+            // TODO make PerformanceData hold a type of thread_info_t.
+            // Currently, thread_info_t is defined in NBLog.h, which includes
+            // PerformanceAnalysis.h. PerformanceData is defined in PerformanceAnalysis.h,
+            // where including NBLog.h would result in circular includes. The organization
+            // of files will need to change to avoid this problem.
+            data.threadInfo = info;
+        } break;
+        case EVENT_LATENCY: {
+            const double latencyMs = it.payload<double>();
+            data.latencyHist.add(latencyMs);
+        } break;
+        case EVENT_WORK_TIME: {
+            const int64_t monotonicNs = it.payload<int64_t>();
+            const double monotonicMs = monotonicNs * 1e-6;
+            data.workHist.add(monotonicMs);
+            data.active += monotonicNs;
+        } break;
+        case EVENT_WARMUP_TIME: {
+            const double timeMs = it.payload<double>();
+            data.warmupHist.add(timeMs);
+        } break;
+        case EVENT_UNDERRUN:
+            data.underruns++;
+            break;
+        case EVENT_OVERRUN:
+            data.overruns++;
+            break;
+        case EVENT_RESERVED:
+        case EVENT_UPPER_BOUND:
+            ALOGW("warning: unexpected event %d", it->type);
+        default:
+            break;
+        }
+    }
+}
+
+void MergeReader::getAndProcessSnapshot()
+{
+    // get a snapshot of each reader and process them
+    // TODO insert lock here
+    const size_t nLogs = mReaders.size();
+    std::vector<std::unique_ptr<Snapshot>> snapshots(nLogs);
+    for (size_t i = 0; i < nLogs; i++) {
+        snapshots[i] = mReaders[i]->getSnapshot();
+    }
+    // TODO unlock lock here
+    for (size_t i = 0; i < nLogs; i++) {
+        if (snapshots[i] != nullptr) {
+            processSnapshot(*(snapshots[i]), i);
+        }
+    }
+    checkPushToMediaMetrics();
+}
+
+void MergeReader::checkPushToMediaMetrics()
+{
+    const nsecs_t now = systemTime();
+    for (auto& item : mThreadPerformanceData) {
+        ReportPerformance::PerformanceData& data = item.second;
+        if (now - data.start >= kPeriodicMediaMetricsPush) {
+            (void)ReportPerformance::sendToMediaMetrics(data);
+            data.reset();   // data is persistent per thread
+        }
+    }
+}
+
+void MergeReader::dump(int fd, int indent)
+{
+    // TODO: add a mutex around media.log dump
+    ReportPerformance::dump(fd, indent, mThreadPerformanceAnalysis);
+    Json::Value root(Json::arrayValue);
+    for (const auto& item : mThreadPerformanceData) {
+        const ReportPerformance::PerformanceData& data = item.second;
+        std::unique_ptr<Json::Value> threadData = ReportPerformance::dumpToJson(data);
+        if (threadData == nullptr) {
+            continue;
+        }
+        (*threadData)["threadNum"] = item.first;
+        root.append(*threadData);
+    }
+    Json::StyledWriter writer;
+    std::string rootStr = writer.write(root);
+    write(fd, rootStr.c_str(), rootStr.size());
+}
+
+void MergeReader::handleAuthor(const AbstractEntry &entry, String8 *body)
+{
+    int author = entry.author();
+    if (author == -1) {
+        return;
+    }
+    // FIXME Needs a lock
+    const char* name = mReaders[author]->name().c_str();
+    body->appendFormat("%s: ", name);
+}
+
+// ---------------------------------------------------------------------------
+
+MergeThread::MergeThread(Merger &merger, MergeReader &mergeReader)
+    : mMerger(merger),
+      mMergeReader(mergeReader),
+      mTimeoutUs(0)
+{
+}
+
+MergeThread::~MergeThread()
+{
+    // set exit flag, set timeout to 0 to force threadLoop to exit and wait for the thread to join
+    requestExit();
+    setTimeoutUs(0);
+    join();
+}
+
+bool MergeThread::threadLoop()
+{
+    bool doMerge;
+    {
+        AutoMutex _l(mMutex);
+        // If mTimeoutUs is negative, wait on the condition variable until it's positive.
+        // If it's positive, merge. The minimum period between waking the condition variable
+        // is handled in AudioFlinger::MediaLogNotifier::threadLoop().
+        mCond.wait(mMutex);
+        doMerge = mTimeoutUs > 0;
+        mTimeoutUs -= kThreadSleepPeriodUs;
+    }
+    if (doMerge) {
+        // Merge data from all the readers
+        mMerger.merge();
+        // Process the data collected by mMerger and write it to PerformanceAnalysis
+        // FIXME: decide whether to call getAndProcessSnapshot every time
+        // or whether to have a separate thread that calls it with a lower frequency
+        mMergeReader.getAndProcessSnapshot();
+    }
+    return true;
+}
+
+void MergeThread::wakeup()
+{
+    setTimeoutUs(kThreadWakeupPeriodUs);
+}
+
+void MergeThread::setTimeoutUs(int time)
+{
+    AutoMutex _l(mMutex);
+    mTimeoutUs = time;
+    mCond.signal();
+}
+
+}   // namespace NBLog
+}   // namespace android
diff --git a/media/libnblog/NBLog.cpp b/media/libnblog/NBLog.cpp
deleted file mode 100644
index aee0ea3..0000000
--- a/media/libnblog/NBLog.cpp
+++ /dev/null
@@ -1,1246 +0,0 @@
-/*
- * Copyright (C) 2013 The Android Open Source Project
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- *
- *
- */
-
-#define LOG_TAG "NBLog"
-
-#include <algorithm>
-#include <climits>
-#include <math.h>
-#include <memory>
-#include <unordered_set>
-#include <vector>
-#include <stdarg.h>
-#include <stdint.h>
-#include <stdio.h>
-#include <string.h>
-#include <sys/prctl.h>
-#include <time.h>
-#include <new>
-#include <audio_utils/roundup.h>
-#include <json/json.h>
-#include <media/nblog/NBLog.h>
-#include <media/nblog/PerformanceAnalysis.h>
-#include <media/nblog/ReportPerformance.h>
-#include <utils/CallStack.h>
-#include <utils/Log.h>
-#include <utils/String8.h>
-#include <utils/Timers.h>
-
-#include <queue>
-#include <utility>
-
-namespace android {
-
-int NBLog::Entry::copyEntryDataAt(size_t offset) const
-{
-    // FIXME This is too slow
-    if (offset == 0)
-        return mEvent;
-    else if (offset == 1)
-        return mLength;
-    else if (offset < (size_t) (mLength + 2))
-        return ((char *) mData)[offset - 2];
-    else if (offset == (size_t) (mLength + 2))
-        return mLength;
-    else
-        return 0;
-}
-
-// ---------------------------------------------------------------------------
-
-/*static*/
-std::unique_ptr<NBLog::AbstractEntry> NBLog::AbstractEntry::buildEntry(const uint8_t *ptr)
-{
-    if (ptr == nullptr) {
-        return nullptr;
-    }
-    const uint8_t type = EntryIterator(ptr)->type;
-    switch (type) {
-    case EVENT_FMT_START:
-        return std::make_unique<FormatEntry>(FormatEntry(ptr));
-    case EVENT_AUDIO_STATE:
-    case EVENT_HISTOGRAM_ENTRY_TS:
-        return std::make_unique<HistogramEntry>(HistogramEntry(ptr));
-    default:
-        ALOGW("Tried to create AbstractEntry of type %d", type);
-        return nullptr;
-    }
-}
-
-NBLog::AbstractEntry::AbstractEntry(const uint8_t *entry) : mEntry(entry)
-{
-}
-
-// ---------------------------------------------------------------------------
-
-NBLog::EntryIterator NBLog::FormatEntry::begin() const
-{
-    return EntryIterator(mEntry);
-}
-
-const char *NBLog::FormatEntry::formatString() const
-{
-    return (const char*) mEntry + offsetof(entry, data);
-}
-
-size_t NBLog::FormatEntry::formatStringLength() const
-{
-    return mEntry[offsetof(entry, length)];
-}
-
-NBLog::EntryIterator NBLog::FormatEntry::args() const
-{
-    auto it = begin();
-    ++it; // skip start fmt
-    ++it; // skip timestamp
-    ++it; // skip hash
-    // Skip author if present
-    if (it->type == EVENT_FMT_AUTHOR) {
-        ++it;
-    }
-    return it;
-}
-
-int64_t NBLog::FormatEntry::timestamp() const
-{
-    auto it = begin();
-    ++it; // skip start fmt
-    return it.payload<int64_t>();
-}
-
-NBLog::log_hash_t NBLog::FormatEntry::hash() const
-{
-    auto it = begin();
-    ++it; // skip start fmt
-    ++it; // skip timestamp
-    // unaligned 64-bit read not supported
-    log_hash_t hash;
-    memcpy(&hash, it->data, sizeof(hash));
-    return hash;
-}
-
-int NBLog::FormatEntry::author() const
-{
-    auto it = begin();
-    ++it; // skip start fmt
-    ++it; // skip timestamp
-    ++it; // skip hash
-    // if there is an author entry, return it, return -1 otherwise
-    return it->type == EVENT_FMT_AUTHOR ? it.payload<int>() : -1;
-}
-
-NBLog::EntryIterator NBLog::FormatEntry::copyWithAuthor(
-        std::unique_ptr<audio_utils_fifo_writer> &dst, int author) const
-{
-    auto it = begin();
-    it.copyTo(dst);     // copy fmt start entry
-    (++it).copyTo(dst); // copy timestamp
-    (++it).copyTo(dst); // copy hash
-    // insert author entry
-    size_t authorEntrySize = Entry::kOverhead + sizeof(author);
-    uint8_t authorEntry[authorEntrySize];
-    authorEntry[offsetof(entry, type)] = EVENT_FMT_AUTHOR;
-    authorEntry[offsetof(entry, length)] =
-        authorEntry[authorEntrySize + Entry::kPreviousLengthOffset] =
-        sizeof(author);
-    *(int*) (&authorEntry[offsetof(entry, data)]) = author;
-    dst->write(authorEntry, authorEntrySize);
-    // copy rest of entries
-    while ((++it)->type != EVENT_FMT_END) {
-        it.copyTo(dst);
-    }
-    it.copyTo(dst);
-    ++it;
-    return it;
-}
-
-void NBLog::EntryIterator::copyTo(std::unique_ptr<audio_utils_fifo_writer> &dst) const
-{
-    size_t length = mPtr[offsetof(entry, length)] + Entry::kOverhead;
-    dst->write(mPtr, length);
-}
-
-void NBLog::EntryIterator::copyData(uint8_t *dst) const
-{
-    memcpy((void*) dst, mPtr + offsetof(entry, data), mPtr[offsetof(entry, length)]);
-}
-
-NBLog::EntryIterator::EntryIterator()   // Dummy initialization.
-    : mPtr(nullptr)
-{
-}
-
-NBLog::EntryIterator::EntryIterator(const uint8_t *entry)
-    : mPtr(entry)
-{
-}
-
-NBLog::EntryIterator::EntryIterator(const NBLog::EntryIterator &other)
-    : mPtr(other.mPtr)
-{
-}
-
-const NBLog::entry& NBLog::EntryIterator::operator*() const
-{
-    return *(entry*) mPtr;
-}
-
-const NBLog::entry* NBLog::EntryIterator::operator->() const
-{
-    return (entry*) mPtr;
-}
-
-NBLog::EntryIterator& NBLog::EntryIterator::operator++()
-{
-    mPtr += mPtr[offsetof(entry, length)] + Entry::kOverhead;
-    return *this;
-}
-
-NBLog::EntryIterator& NBLog::EntryIterator::operator--()
-{
-    mPtr -= mPtr[Entry::kPreviousLengthOffset] + Entry::kOverhead;
-    return *this;
-}
-
-NBLog::EntryIterator NBLog::EntryIterator::next() const
-{
-    EntryIterator aux(*this);
-    return ++aux;
-}
-
-NBLog::EntryIterator NBLog::EntryIterator::prev() const
-{
-    EntryIterator aux(*this);
-    return --aux;
-}
-
-int NBLog::EntryIterator::operator-(const NBLog::EntryIterator &other) const
-{
-    return mPtr - other.mPtr;
-}
-
-bool NBLog::EntryIterator::operator!=(const EntryIterator &other) const
-{
-    return mPtr != other.mPtr;
-}
-
-bool NBLog::EntryIterator::hasConsistentLength() const
-{
-    return mPtr[offsetof(entry, length)] == mPtr[mPtr[offsetof(entry, length)] +
-        Entry::kOverhead + Entry::kPreviousLengthOffset];
-}
-
-// ---------------------------------------------------------------------------
-
-int64_t NBLog::HistogramEntry::timestamp() const
-{
-    return EntryIterator(mEntry).payload<HistTsEntry>().ts;
-}
-
-NBLog::log_hash_t NBLog::HistogramEntry::hash() const
-{
-    return EntryIterator(mEntry).payload<HistTsEntry>().hash;
-}
-
-int NBLog::HistogramEntry::author() const
-{
-    EntryIterator it(mEntry);
-    return it->length == sizeof(HistTsEntryWithAuthor)
-            ? it.payload<HistTsEntryWithAuthor>().author : -1;
-}
-
-NBLog::EntryIterator NBLog::HistogramEntry::copyWithAuthor(
-        std::unique_ptr<audio_utils_fifo_writer> &dst, int author) const
-{
-    // Current histogram entry has {type, length, struct HistTsEntry, length}.
-    // We now want {type, length, struct HistTsEntryWithAuthor, length}
-    uint8_t buffer[Entry::kOverhead + sizeof(HistTsEntryWithAuthor)];
-    // Copy content until the point we want to add the author
-    memcpy(buffer, mEntry, sizeof(entry) + sizeof(HistTsEntry));
-    // Copy the author
-    *(int*) (buffer + sizeof(entry) + sizeof(HistTsEntry)) = author;
-    // Update lengths
-    buffer[offsetof(entry, length)] = sizeof(HistTsEntryWithAuthor);
-    buffer[offsetof(entry, data) + sizeof(HistTsEntryWithAuthor) + offsetof(ending, length)]
-        = sizeof(HistTsEntryWithAuthor);
-    // Write new buffer into FIFO
-    dst->write(buffer, sizeof(buffer));
-    return EntryIterator(mEntry).next();
-}
-
-// ---------------------------------------------------------------------------
-
-#if 0   // FIXME see note in NBLog.h
-NBLog::Timeline::Timeline(size_t size, void *shared)
-    : mSize(roundup(size)), mOwn(shared == NULL),
-      mShared((Shared *) (mOwn ? new char[sharedSize(size)] : shared))
-{
-    new (mShared) Shared;
-}
-
-NBLog::Timeline::~Timeline()
-{
-    mShared->~Shared();
-    if (mOwn) {
-        delete[] (char *) mShared;
-    }
-}
-#endif
-
-/*static*/
-size_t NBLog::Timeline::sharedSize(size_t size)
-{
-    // TODO fifo now supports non-power-of-2 buffer sizes, so could remove the roundup
-    return sizeof(Shared) + roundup(size);
-}
-
-// ---------------------------------------------------------------------------
-
-NBLog::Writer::Writer()
-    : mShared(NULL), mFifo(NULL), mFifoWriter(NULL), mEnabled(false), mPidTag(NULL), mPidTagSize(0)
-{
-}
-
-NBLog::Writer::Writer(void *shared, size_t size)
-    : mShared((Shared *) shared),
-      mFifo(mShared != NULL ?
-        new audio_utils_fifo(size, sizeof(uint8_t),
-            mShared->mBuffer, mShared->mRear, NULL /*throttlesFront*/) : NULL),
-      mFifoWriter(mFifo != NULL ? new audio_utils_fifo_writer(*mFifo) : NULL),
-      mEnabled(mFifoWriter != NULL)
-{
-    // caching pid and process name
-    pid_t id = ::getpid();
-    char procName[16];
-    int status = prctl(PR_GET_NAME, procName);
-    if (status) {  // error getting process name
-        procName[0] = '\0';
-    }
-    size_t length = strlen(procName);
-    mPidTagSize = length + sizeof(pid_t);
-    mPidTag = new char[mPidTagSize];
-    memcpy(mPidTag, &id, sizeof(pid_t));
-    memcpy(mPidTag + sizeof(pid_t), procName, length);
-}
-
-NBLog::Writer::Writer(const sp<IMemory>& iMemory, size_t size)
-    : Writer(iMemory != 0 ? (Shared *) iMemory->pointer() : NULL, size)
-{
-    mIMemory = iMemory;
-}
-
-NBLog::Writer::~Writer()
-{
-    delete mFifoWriter;
-    delete mFifo;
-    delete[] mPidTag;
-}
-
-void NBLog::Writer::log(const char *string)
-{
-    if (!mEnabled) {
-        return;
-    }
-    LOG_ALWAYS_FATAL_IF(string == NULL, "Attempted to log NULL string");
-    size_t length = strlen(string);
-    if (length > Entry::kMaxLength) {
-        length = Entry::kMaxLength;
-    }
-    log(EVENT_STRING, string, length);
-}
-
-void NBLog::Writer::logf(const char *fmt, ...)
-{
-    if (!mEnabled) {
-        return;
-    }
-    va_list ap;
-    va_start(ap, fmt);
-    Writer::logvf(fmt, ap);     // the Writer:: is needed to avoid virtual dispatch for LockedWriter
-    va_end(ap);
-}
-
-void NBLog::Writer::logvf(const char *fmt, va_list ap)
-{
-    if (!mEnabled) {
-        return;
-    }
-    char buffer[Entry::kMaxLength + 1 /*NUL*/];
-    int length = vsnprintf(buffer, sizeof(buffer), fmt, ap);
-    if (length >= (int) sizeof(buffer)) {
-        length = sizeof(buffer) - 1;
-        // NUL termination is not required
-        // buffer[length] = '\0';
-    }
-    if (length >= 0) {
-        log(EVENT_STRING, buffer, length);
-    }
-}
-
-void NBLog::Writer::logTimestamp()
-{
-    if (!mEnabled) {
-        return;
-    }
-    struct timespec ts;
-    if (!clock_gettime(CLOCK_MONOTONIC, &ts)) {
-        log(EVENT_TIMESTAMP, &ts, sizeof(ts));
-    }
-}
-
-void NBLog::Writer::logStart(const char *fmt)
-{
-    if (!mEnabled) {
-        return;
-    }
-    size_t length = strlen(fmt);
-    if (length > Entry::kMaxLength) {
-        length = Entry::kMaxLength;
-    }
-    log(EVENT_FMT_START, fmt, length);
-}
-
-void NBLog::Writer::logTimestampFormat()
-{
-    if (!mEnabled) {
-        return;
-    }
-    const nsecs_t ts = systemTime();
-    if (ts > 0) {
-        log(EVENT_FMT_TIMESTAMP, &ts, sizeof(ts));
-    } else {
-        ALOGE("Failed to get timestamp");
-    }
-}
-
-void NBLog::Writer::logEventHistTs(Event event, log_hash_t hash)
-{
-    if (!mEnabled) {
-        return;
-    }
-    HistTsEntry data;
-    data.hash = hash;
-    data.ts = systemTime();
-    if (data.ts > 0) {
-        log(event, &data, sizeof(data));
-    } else {
-        ALOGE("Failed to get timestamp");
-    }
-}
-
-void NBLog::Writer::logFormat(const char *fmt, log_hash_t hash, ...)
-{
-    if (!mEnabled) {
-        return;
-    }
-    va_list ap;
-    va_start(ap, hash);
-    Writer::logVFormat(fmt, hash, ap);
-    va_end(ap);
-}
-
-void NBLog::Writer::logVFormat(const char *fmt, log_hash_t hash, va_list argp)
-{
-    if (!mEnabled) {
-        return;
-    }
-    Writer::logStart(fmt);
-    int i;
-    double d;
-    float f;
-    char* s;
-    size_t length;
-    int64_t t;
-    Writer::logTimestampFormat();
-    log(EVENT_FMT_HASH, &hash, sizeof(hash));
-    for (const char *p = fmt; *p != '\0'; p++) {
-        // TODO: implement more complex formatting such as %.3f
-        if (*p != '%') {
-            continue;
-        }
-        switch(*++p) {
-        case 's': // string
-            s = va_arg(argp, char *);
-            length = strlen(s);
-            if (length > Entry::kMaxLength) {
-                length = Entry::kMaxLength;
-            }
-            log(EVENT_FMT_STRING, s, length);
-            break;
-
-        case 't': // timestamp
-            t = va_arg(argp, int64_t);
-            log(EVENT_FMT_TIMESTAMP, &t, sizeof(t));
-            break;
-
-        case 'd': // integer
-            i = va_arg(argp, int);
-            log(EVENT_FMT_INTEGER, &i, sizeof(i));
-            break;
-
-        case 'f': // float
-            d = va_arg(argp, double); // float arguments are promoted to double in vararg lists
-            f = (float)d;
-            log(EVENT_FMT_FLOAT, &f, sizeof(f));
-            break;
-
-        case 'p': // pid
-            log(EVENT_FMT_PID, mPidTag, mPidTagSize);
-            break;
-
-        // the "%\0" case finishes parsing
-        case '\0':
-            --p;
-            break;
-
-        case '%':
-            break;
-
-        default:
-            ALOGW("NBLog Writer parsed invalid format specifier: %c", *p);
-            break;
-        }
-    }
-    Entry etr(EVENT_FMT_END, nullptr, 0);
-    log(etr, true);
-}
-
-void NBLog::Writer::log(Event event, const void *data, size_t length)
-{
-    if (!mEnabled) {
-        return;
-    }
-    if (data == NULL || length > Entry::kMaxLength) {
-        // TODO Perhaps it makes sense to display truncated data or at least a
-        //      message that the data is too long?  The current behavior can create
-        //      a confusion for a programmer debugging their code.
-        return;
-    }
-    // Ignore if invalid event
-    if (event == EVENT_RESERVED || event >= EVENT_UPPER_BOUND) {
-        return;
-    }
-    Entry etr(event, data, length);
-    log(etr, true /*trusted*/);
-}
-
-void NBLog::Writer::log(const NBLog::Entry &etr, bool trusted)
-{
-    if (!mEnabled) {
-        return;
-    }
-    if (!trusted) {
-        log(etr.mEvent, etr.mData, etr.mLength);
-        return;
-    }
-    const size_t need = etr.mLength + Entry::kOverhead; // mEvent, mLength, data[mLength], mLength
-                                                        // need = number of bytes written to FIFO
-
-    // FIXME optimize this using memcpy for the data part of the Entry.
-    // The Entry could have a method copyTo(ptr, offset, size) to optimize the copy.
-    // checks size of a single log Entry: type, length, data pointer and ending
-    uint8_t temp[Entry::kMaxLength + Entry::kOverhead];
-    // write this data to temp array
-    for (size_t i = 0; i < need; i++) {
-        temp[i] = etr.copyEntryDataAt(i);
-    }
-    // write to circular buffer
-    mFifoWriter->write(temp, need);
-}
-
-bool NBLog::Writer::isEnabled() const
-{
-    return mEnabled;
-}
-
-bool NBLog::Writer::setEnabled(bool enabled)
-{
-    bool old = mEnabled;
-    mEnabled = enabled && mShared != NULL;
-    return old;
-}
-
-// ---------------------------------------------------------------------------
-
-NBLog::LockedWriter::LockedWriter()
-    : Writer()
-{
-}
-
-NBLog::LockedWriter::LockedWriter(void *shared, size_t size)
-    : Writer(shared, size)
-{
-}
-
-bool NBLog::LockedWriter::isEnabled() const
-{
-    Mutex::Autolock _l(mLock);
-    return Writer::isEnabled();
-}
-
-bool NBLog::LockedWriter::setEnabled(bool enabled)
-{
-    Mutex::Autolock _l(mLock);
-    return Writer::setEnabled(enabled);
-}
-
-void NBLog::LockedWriter::log(const Entry &entry, bool trusted) {
-    Mutex::Autolock _l(mLock);
-    Writer::log(entry, trusted);
-}
-
-// ---------------------------------------------------------------------------
-
-// We make a set of the invalid types rather than the valid types when aligning
-// Snapshot EntryIterators to valid entries during log corruption checking.
-// This is done in order to avoid the maintenance overhead of adding a new NBLog::Event
-// type to the two sets below whenever a new NBLog::Event type is created, as it is
-// very likely that new types added will be valid types.
-// Currently, invalidBeginTypes and invalidEndTypes are used to handle the special
-// case of a Format Entry, which consists of a variable number of simple log entries.
-// If a new NBLog::Event is added that consists of a variable number of simple log entries,
-// then these sets need to be updated.
-
-// We want the beginning of a Snapshot to point to an entry that is not in
-// the middle of a formatted entry and not an FMT_END.
-const std::unordered_set<NBLog::Event> NBLog::Reader::invalidBeginTypes {
-    NBLog::Event::EVENT_FMT_TIMESTAMP,
-    NBLog::Event::EVENT_FMT_HASH,
-    NBLog::Event::EVENT_FMT_STRING,
-    NBLog::Event::EVENT_FMT_INTEGER,
-    NBLog::Event::EVENT_FMT_FLOAT,
-    NBLog::Event::EVENT_FMT_PID,
-    NBLog::Event::EVENT_FMT_AUTHOR,
-    NBLog::Event::EVENT_FMT_END
-};
-
-// We want the end of a Snapshot to point to an entry that is not in
-// the middle of a formatted entry and not a FMT_START.
-const std::unordered_set<NBLog::Event> NBLog::Reader::invalidEndTypes   {
-    NBLog::Event::EVENT_FMT_START,
-    NBLog::Event::EVENT_FMT_TIMESTAMP,
-    NBLog::Event::EVENT_FMT_HASH,
-    NBLog::Event::EVENT_FMT_STRING,
-    NBLog::Event::EVENT_FMT_INTEGER,
-    NBLog::Event::EVENT_FMT_FLOAT,
-    NBLog::Event::EVENT_FMT_PID,
-    NBLog::Event::EVENT_FMT_AUTHOR
-};
-
-NBLog::Reader::Reader(const void *shared, size_t size, const std::string &name)
-    : mName(name),
-      mShared((/*const*/ Shared *) shared), /*mIMemory*/
-      mFifo(mShared != NULL ?
-        new audio_utils_fifo(size, sizeof(uint8_t),
-            mShared->mBuffer, mShared->mRear, NULL /*throttlesFront*/) : NULL),
-      mFifoReader(mFifo != NULL ? new audio_utils_fifo_reader(*mFifo) : NULL)
-{
-}
-
-NBLog::Reader::Reader(const sp<IMemory>& iMemory, size_t size, const std::string &name)
-    : Reader(iMemory != 0 ? (Shared *) iMemory->pointer() : NULL, size, name)
-{
-    mIMemory = iMemory;
-}
-
-NBLog::Reader::~Reader()
-{
-    delete mFifoReader;
-    delete mFifo;
-}
-
-const uint8_t *NBLog::Reader::findLastValidEntry(const uint8_t *front, const uint8_t *back,
-                                            const std::unordered_set<Event> &invalidTypes) {
-    if (front == nullptr || back == nullptr) {
-        return nullptr;
-    }
-    while (back + Entry::kPreviousLengthOffset >= front) {
-        const uint8_t *prev = back - back[Entry::kPreviousLengthOffset] - Entry::kOverhead;
-        const Event type = (const Event)prev[offsetof(entry, type)];
-        if (prev < front
-                || prev + prev[offsetof(entry, length)] + Entry::kOverhead != back
-                || type <= NBLog::EVENT_RESERVED || type >= NBLog::EVENT_UPPER_BOUND) {
-            // prev points to an out of limits or inconsistent entry
-            return nullptr;
-        }
-        // if invalidTypes does not contain the type, then the type is valid.
-        if (invalidTypes.find(type) == invalidTypes.end()) {
-            return prev;
-        }
-        back = prev;
-    }
-    return nullptr; // no entry found
-}
-
-// Copies content of a Reader FIFO into its Snapshot
-// The Snapshot has the same raw data, but represented as a sequence of entries
-// and an EntryIterator making it possible to process the data.
-std::unique_ptr<NBLog::Snapshot> NBLog::Reader::getSnapshot()
-{
-    if (mFifoReader == NULL) {
-        return std::unique_ptr<Snapshot>(new Snapshot());
-    }
-
-    // This emulates the behaviour of audio_utils_fifo_reader::read, but without incrementing the
-    // reader index. The index is incremented after handling corruption, to after the last complete
-    // entry of the buffer
-    size_t lost = 0;
-    audio_utils_iovec iovec[2];
-    const size_t capacity = mFifo->capacity();
-    ssize_t availToRead;
-    // A call to audio_utils_fifo_reader::obtain() places the read pointer one buffer length
-    // before the writer's pointer (since mFifoReader was constructed with flush=false). The
-    // do while loop is an attempt to read all of the FIFO's contents regardless of how behind
-    // the reader is with respect to the writer. However, the following scheduling sequence is
-    // possible and can lead to a starvation situation:
-    // - Writer T1 writes, overrun with respect to Reader T2
-    // - T2 calls obtain() and gets EOVERFLOW, T2 ptr placed one buffer size behind T1 ptr
-    // - T1 write, overrun
-    // - T2 obtain(), EOVERFLOW (and so on...)
-    // To address this issue, we limit the number of tries for the reader to catch up with
-    // the writer.
-    int tries = 0;
-    size_t lostTemp;
-    do {
-        availToRead = mFifoReader->obtain(iovec, capacity, NULL /*timeout*/, &lostTemp);
-        lost += lostTemp;
-    } while (availToRead < 0 || ++tries <= kMaxObtainTries);
-
-    if (availToRead <= 0) {
-        ALOGW_IF(availToRead < 0, "NBLog Reader %s failed to catch up with Writer", mName.c_str());
-        return std::unique_ptr<Snapshot>(new Snapshot());
-    }
-
-    // Change to #if 1 for debugging. This statement is useful for checking buffer fullness levels
-    // (as seen by reader) and how much data was lost. If you find that the fullness level is
-    // getting close to full, or that data loss is happening to often, then you should
-    // probably try some of the following:
-    // - log less data
-    // - log less often
-    // - increase the initial shared memory allocation for the buffer
-#if 0
-    ALOGD("getSnapshot name=%s, availToRead=%zd, capacity=%zu, fullness=%.3f, lost=%zu",
-            name().c_str(), availToRead, capacity, (double)availToRead / (double)capacity, lost);
-#endif
-    std::unique_ptr<Snapshot> snapshot(new Snapshot(availToRead));
-    memcpy(snapshot->mData, (const char *) mFifo->buffer() + iovec[0].mOffset, iovec[0].mLength);
-    if (iovec[1].mLength > 0) {
-        memcpy(snapshot->mData + (iovec[0].mLength),
-                (const char *) mFifo->buffer() + iovec[1].mOffset, iovec[1].mLength);
-    }
-
-    // Handle corrupted buffer
-    // Potentially, a buffer has corrupted data on both beginning (due to overflow) and end
-    // (due to incomplete format entry). But even if the end format entry is incomplete,
-    // it ends in a complete entry (which is not an FMT_END). So is safe to traverse backwards.
-    // TODO: handle client corruption (in the middle of a buffer)
-
-    const uint8_t *back = snapshot->mData + availToRead;
-    const uint8_t *front = snapshot->mData;
-
-    // Find last FMT_END. <back> is sitting on an entry which might be the middle of a FormatEntry.
-    // We go backwards until we find an EVENT_FMT_END.
-    const uint8_t *lastEnd = findLastValidEntry(front, back, invalidEndTypes);
-    if (lastEnd == nullptr) {
-        snapshot->mEnd = snapshot->mBegin = EntryIterator(front);
-    } else {
-        // end of snapshot points to after last FMT_END entry
-        snapshot->mEnd = EntryIterator(lastEnd).next();
-        // find first FMT_START
-        const uint8_t *firstStart = nullptr;
-        const uint8_t *firstStartTmp = snapshot->mEnd;
-        while ((firstStartTmp = findLastValidEntry(front, firstStartTmp, invalidBeginTypes))
-                != nullptr) {
-            firstStart = firstStartTmp;
-        }
-        // firstStart is null if no FMT_START entry was found before lastEnd
-        if (firstStart == nullptr) {
-            snapshot->mBegin = snapshot->mEnd;
-        } else {
-            snapshot->mBegin = EntryIterator(firstStart);
-        }
-    }
-
-    // advance fifo reader index to after last entry read.
-    mFifoReader->release(snapshot->mEnd - front);
-
-    snapshot->mLost = lost;
-    return snapshot;
-}
-
-// TODO separate this method from the rest of NBLog
-// Takes raw content of the local merger FIFO, processes log entries, and
-// writes the data to a map of class PerformanceAnalysis, based on their thread ID.
-void NBLog::MergeReader::processSnapshot(NBLog::Snapshot &snapshot, int author)
-{
-    ReportPerformance::PerformanceData& data = mThreadPerformanceData[author];
-    // We don't do "auto it" because it reduces readability in this case.
-    for (EntryIterator it = snapshot.begin(); it != snapshot.end(); ++it) {
-        switch (it->type) {
-        case EVENT_HISTOGRAM_ENTRY_TS: {
-            const HistTsEntry payload = it.payload<HistTsEntry>();
-            // TODO: hash for histogram ts and audio state need to match
-            // and correspond to audio production source file location
-            mThreadPerformanceAnalysis[author][0 /*hash*/].logTsEntry(payload.ts);
-        } break;
-        case EVENT_AUDIO_STATE: {
-            mThreadPerformanceAnalysis[author][0 /*hash*/].handleStateChange();
-        } break;
-        case EVENT_THREAD_INFO: {
-            const thread_info_t info = it.payload<thread_info_t>();
-            // TODO make PerformanceData hold a type of thread_info_t.
-            // Currently, thread_info_t is defined in NBLog.h, which includes
-            // PerformanceAnalysis.h. PerformanceData is defined in PerformanceAnalysis.h,
-            // where including NBLog.h would result in circular includes. The organization
-            // of files will need to change to avoid this problem.
-            data.type = info.type;
-            data.frameCount = info.frameCount;
-            data.sampleRate = info.sampleRate;
-        } break;
-        case EVENT_LATENCY: {
-            const double latencyMs = it.payload<double>();
-            data.latencyHist.add(latencyMs);
-        } break;
-        case EVENT_WORK_TIME: {
-            const int64_t monotonicNs = it.payload<int64_t>();
-            const double monotonicMs = monotonicNs * 1e-6;
-            data.workHist.add(monotonicMs);
-            data.active += monotonicNs;
-        } break;
-        case EVENT_WARMUP_TIME: {
-            const double timeMs = it.payload<double>();
-            data.warmupHist.add(timeMs);
-        } break;
-        case EVENT_UNDERRUN:
-            data.underruns++;
-            break;
-        case EVENT_OVERRUN:
-            data.overruns++;
-            break;
-        case EVENT_RESERVED:
-        case EVENT_UPPER_BOUND:
-            ALOGW("warning: unexpected event %d", it->type);
-        default:
-            break;
-        }
-    }
-}
-
-void NBLog::MergeReader::getAndProcessSnapshot()
-{
-    // get a snapshot of each reader and process them
-    // TODO insert lock here
-    const size_t nLogs = mReaders.size();
-    std::vector<std::unique_ptr<Snapshot>> snapshots(nLogs);
-    for (size_t i = 0; i < nLogs; i++) {
-        snapshots[i] = mReaders[i]->getSnapshot();
-    }
-    // TODO unlock lock here
-    for (size_t i = 0; i < nLogs; i++) {
-        if (snapshots[i] != nullptr) {
-            processSnapshot(*(snapshots[i]), i);
-        }
-    }
-    checkPushToMediaMetrics();
-}
-
-void NBLog::MergeReader::checkPushToMediaMetrics()
-{
-    const nsecs_t now = systemTime();
-    for (auto& item : mThreadPerformanceData) {
-        ReportPerformance::PerformanceData& data = item.second;
-        if (now - data.start >= kPeriodicMediaMetricsPush) {
-            (void)ReportPerformance::sendToMediaMetrics(data);
-            data.reset();   // data is persistent per thread
-        }
-    }
-}
-
-void NBLog::MergeReader::dump(int fd, int indent)
-{
-    // TODO: add a mutex around media.log dump
-    ReportPerformance::dump(fd, indent, mThreadPerformanceAnalysis);
-    Json::Value root(Json::arrayValue);
-    for (const auto& item : mThreadPerformanceData) {
-        const ReportPerformance::PerformanceData& data = item.second;
-        std::unique_ptr<Json::Value> threadData = ReportPerformance::dumpToJson(data);
-        if (threadData == nullptr) {
-            continue;
-        }
-        (*threadData)["threadNum"] = item.first;
-        root.append(*threadData);
-    }
-    Json::StyledWriter writer;
-    std::string rootStr = writer.write(root);
-    dprintf(fd, "%s", rootStr.c_str());
-}
-
-// TODO for future compatibility, would prefer to have a dump() go to string, and then go
-// to fd only when invoked through binder.
-void NBLog::DumpReader::dump(int fd, size_t indent)
-{
-    if (fd < 0) return;
-    std::unique_ptr<Snapshot> snapshot = getSnapshot();
-    if (snapshot == nullptr) {
-        return;
-    }
-    String8 timestamp, body;
-
-    // TODO all logged types should have a printable format.
-    for (EntryIterator it = snapshot->begin(); it != snapshot->end(); ++it) {
-        switch (it->type) {
-        case EVENT_FMT_START:
-            it = handleFormat(FormatEntry(it), &timestamp, &body);
-            break;
-        case EVENT_WORK_TIME: {
-            const int64_t monotonicNs = it.payload<int64_t>();
-            body.appendFormat("Thread cycle: %ld ns", (long)monotonicNs);
-        } break;
-        case EVENT_LATENCY: {
-            const double latencyMs = it.payload<double>();
-            body.appendFormat("latency: %.3f ms", latencyMs);
-        } break;
-        case EVENT_WARMUP_TIME: {
-            const double timeMs = it.payload<double>();
-            body.appendFormat("warmup time: %.3f ms", timeMs);
-        } break;
-        case EVENT_UNDERRUN:
-            body.appendFormat("underrun");
-            break;
-        case EVENT_OVERRUN:
-            body.appendFormat("overrun");
-            break;
-        case EVENT_FMT_END:
-        case EVENT_RESERVED:
-        case EVENT_UPPER_BOUND:
-            body.appendFormat("warning: unexpected event %d", it->type);
-        default:
-            break;
-        }
-        if (!body.isEmpty()) {
-            dprintf(fd, "%.*s%s %s\n", (int)indent, "", timestamp.string(), body.string());
-            body.clear();
-        }
-        timestamp.clear();
-    }
-}
-
-bool NBLog::Reader::isIMemory(const sp<IMemory>& iMemory) const
-{
-    return iMemory != 0 && mIMemory != 0 && iMemory->pointer() == mIMemory->pointer();
-}
-
-void NBLog::DumpReader::appendTimestamp(String8 *body, const void *data)
-{
-    if (body == nullptr || data == nullptr) {
-        return;
-    }
-    int64_t ts;
-    memcpy(&ts, data, sizeof(ts));
-    body->appendFormat("[%d.%03d]", (int) (ts / (1000 * 1000 * 1000)),
-                    (int) ((ts / (1000 * 1000)) % 1000));
-}
-
-void NBLog::DumpReader::appendInt(String8 *body, const void *data)
-{
-    if (body == nullptr || data == nullptr) {
-        return;
-    }
-    int x = *((int*) data);
-    body->appendFormat("<%d>", x);
-}
-
-void NBLog::DumpReader::appendFloat(String8 *body, const void *data)
-{
-    if (body == nullptr || data == nullptr) {
-        return;
-    }
-    float f;
-    memcpy(&f, data, sizeof(f));
-    body->appendFormat("<%f>", f);
-}
-
-void NBLog::DumpReader::appendPID(String8 *body, const void* data, size_t length)
-{
-    if (body == nullptr || data == nullptr) {
-        return;
-    }
-    pid_t id = *((pid_t*) data);
-    char * name = &((char*) data)[sizeof(pid_t)];
-    body->appendFormat("<PID: %d, name: %.*s>", id, (int) (length - sizeof(pid_t)), name);
-}
-
-String8 NBLog::DumpReader::bufferDump(const uint8_t *buffer, size_t size)
-{
-    String8 str;
-    if (buffer == nullptr) {
-        return str;
-    }
-    str.append("[ ");
-    for(size_t i = 0; i < size; i++) {
-        str.appendFormat("%d ", buffer[i]);
-    }
-    str.append("]");
-    return str;
-}
-
-String8 NBLog::DumpReader::bufferDump(const EntryIterator &it)
-{
-    return bufferDump(it, it->length + Entry::kOverhead);
-}
-
-NBLog::EntryIterator NBLog::DumpReader::handleFormat(const FormatEntry &fmtEntry,
-                                                           String8 *timestamp,
-                                                           String8 *body)
-{
-    // log timestamp
-    const int64_t ts = fmtEntry.timestamp();
-    timestamp->clear();
-    timestamp->appendFormat("[%d.%03d]", (int) (ts / (1000 * 1000 * 1000)),
-                    (int) ((ts / (1000 * 1000)) % 1000));
-
-    // log unique hash
-    log_hash_t hash = fmtEntry.hash();
-    // print only lower 16bit of hash as hex and line as int to reduce spam in the log
-    body->appendFormat("%.4X-%d ", (int)(hash >> 16) & 0xFFFF, (int) hash & 0xFFFF);
-
-    // log author (if present)
-    handleAuthor(fmtEntry, body);
-
-    // log string
-    EntryIterator arg = fmtEntry.args();
-
-    const char* fmt = fmtEntry.formatString();
-    size_t fmt_length = fmtEntry.formatStringLength();
-
-    for (size_t fmt_offset = 0; fmt_offset < fmt_length; ++fmt_offset) {
-        if (fmt[fmt_offset] != '%') {
-            body->append(&fmt[fmt_offset], 1); // TODO optimize to write consecutive strings at once
-            continue;
-        }
-        // case "%%""
-        if (fmt[++fmt_offset] == '%') {
-            body->append("%");
-            continue;
-        }
-        // case "%\0"
-        if (fmt_offset == fmt_length) {
-            continue;
-        }
-
-        NBLog::Event event = (NBLog::Event) arg->type;
-        size_t length = arg->length;
-
-        // TODO check length for event type is correct
-
-        if (event == EVENT_FMT_END) {
-            break;
-        }
-
-        // TODO: implement more complex formatting such as %.3f
-        const uint8_t *datum = arg->data; // pointer to the current event args
-        switch(fmt[fmt_offset])
-        {
-        case 's': // string
-            ALOGW_IF(event != EVENT_FMT_STRING,
-                "NBLog Reader incompatible event for string specifier: %d", event);
-            body->append((const char*) datum, length);
-            break;
-
-        case 't': // timestamp
-            ALOGW_IF(event != EVENT_FMT_TIMESTAMP,
-                "NBLog Reader incompatible event for timestamp specifier: %d", event);
-            appendTimestamp(body, datum);
-            break;
-
-        case 'd': // integer
-            ALOGW_IF(event != EVENT_FMT_INTEGER,
-                "NBLog Reader incompatible event for integer specifier: %d", event);
-            appendInt(body, datum);
-            break;
-
-        case 'f': // float
-            ALOGW_IF(event != EVENT_FMT_FLOAT,
-                "NBLog Reader incompatible event for float specifier: %d", event);
-            appendFloat(body, datum);
-            break;
-
-        case 'p': // pid
-            ALOGW_IF(event != EVENT_FMT_PID,
-                "NBLog Reader incompatible event for pid specifier: %d", event);
-            appendPID(body, datum, length);
-            break;
-
-        default:
-            ALOGW("NBLog Reader encountered unknown character %c", fmt[fmt_offset]);
-        }
-        ++arg;
-    }
-    ALOGW_IF(arg->type != EVENT_FMT_END, "Expected end of format, got %d", arg->type);
-    return arg;
-}
-
-NBLog::Merger::Merger(const void *shared, size_t size):
-      mShared((Shared *) shared),
-      mFifo(mShared != NULL ?
-        new audio_utils_fifo(size, sizeof(uint8_t),
-            mShared->mBuffer, mShared->mRear, NULL /*throttlesFront*/) : NULL),
-      mFifoWriter(mFifo != NULL ? new audio_utils_fifo_writer(*mFifo) : NULL)
-{
-}
-
-void NBLog::Merger::addReader(const sp<NBLog::Reader> &reader)
-{
-    // FIXME This is called by binder thread in MediaLogService::registerWriter
-    //       but the access to shared variable mReaders is not yet protected by a lock.
-    mReaders.push_back(reader);
-}
-
-// items placed in priority queue during merge
-// composed by a timestamp and the index of the snapshot where the timestamp came from
-struct MergeItem
-{
-    int64_t ts;
-    int index;
-    MergeItem(int64_t ts, int index): ts(ts), index(index) {}
-};
-
-bool operator>(const struct MergeItem &i1, const struct MergeItem &i2)
-{
-    return i1.ts > i2.ts || (i1.ts == i2.ts && i1.index > i2.index);
-}
-
-// Merge registered readers, sorted by timestamp, and write data to a single FIFO in local memory
-void NBLog::Merger::merge()
-{
-    if (true) return; // Merging is not necessary at the moment, so this is to disable it
-                      // and bypass compiler warnings about member variables not being used.
-    const int nLogs = mReaders.size();
-    std::vector<std::unique_ptr<Snapshot>> snapshots(nLogs);
-    std::vector<EntryIterator> offsets;
-    offsets.reserve(nLogs);
-    for (int i = 0; i < nLogs; ++i) {
-        snapshots[i] = mReaders[i]->getSnapshot();
-        offsets.push_back(snapshots[i]->begin());
-    }
-    // initialize offsets
-    // TODO custom heap implementation could allow to update top, improving performance
-    // for bursty buffers
-    std::priority_queue<MergeItem, std::vector<MergeItem>, std::greater<MergeItem>> timestamps;
-    for (int i = 0; i < nLogs; ++i)
-    {
-        if (offsets[i] != snapshots[i]->end()) {
-            std::unique_ptr<AbstractEntry> abstractEntry = AbstractEntry::buildEntry(offsets[i]);
-            if (abstractEntry == nullptr) {
-                continue;
-            }
-            timestamps.emplace(abstractEntry->timestamp(), i);
-        }
-    }
-
-    while (!timestamps.empty()) {
-        int index = timestamps.top().index;     // find minimum timestamp
-        // copy it to the log, increasing offset
-        offsets[index] = AbstractEntry::buildEntry(offsets[index])->
-            copyWithAuthor(mFifoWriter, index);
-        // update data structures
-        timestamps.pop();
-        if (offsets[index] != snapshots[index]->end()) {
-            int64_t ts = AbstractEntry::buildEntry(offsets[index])->timestamp();
-            timestamps.emplace(ts, index);
-        }
-    }
-}
-
-const std::vector<sp<NBLog::Reader>>& NBLog::Merger::getReaders() const
-{
-    //AutoMutex _l(mLock);
-    return mReaders;
-}
-
-// ---------------------------------------------------------------------------
-
-NBLog::MergeReader::MergeReader(const void *shared, size_t size, Merger &merger)
-    : Reader(shared, size, "MergeReader"), mReaders(merger.getReaders())
-{
-}
-
-void NBLog::MergeReader::handleAuthor(const NBLog::AbstractEntry &entry, String8 *body)
-{
-    int author = entry.author();
-    if (author == -1) {
-        return;
-    }
-    // FIXME Needs a lock
-    const char* name = mReaders[author]->name().c_str();
-    body->appendFormat("%s: ", name);
-}
-
-// ---------------------------------------------------------------------------
-
-NBLog::MergeThread::MergeThread(NBLog::Merger &merger, NBLog::MergeReader &mergeReader)
-    : mMerger(merger),
-      mMergeReader(mergeReader),
-      mTimeoutUs(0)
-{
-}
-
-NBLog::MergeThread::~MergeThread()
-{
-    // set exit flag, set timeout to 0 to force threadLoop to exit and wait for the thread to join
-    requestExit();
-    setTimeoutUs(0);
-    join();
-}
-
-bool NBLog::MergeThread::threadLoop()
-{
-    bool doMerge;
-    {
-        AutoMutex _l(mMutex);
-        // If mTimeoutUs is negative, wait on the condition variable until it's positive.
-        // If it's positive, merge. The minimum period between waking the condition variable
-        // is handled in AudioFlinger::MediaLogNotifier::threadLoop().
-        mCond.wait(mMutex);
-        doMerge = mTimeoutUs > 0;
-        mTimeoutUs -= kThreadSleepPeriodUs;
-    }
-    if (doMerge) {
-        // Merge data from all the readers
-        mMerger.merge();
-        // Process the data collected by mMerger and write it to PerformanceAnalysis
-        // FIXME: decide whether to call getAndProcessSnapshot every time
-        // or whether to have a separate thread that calls it with a lower frequency
-        mMergeReader.getAndProcessSnapshot();
-    }
-    return true;
-}
-
-void NBLog::MergeThread::wakeup()
-{
-    setTimeoutUs(kThreadWakeupPeriodUs);
-}
-
-void NBLog::MergeThread::setTimeoutUs(int time)
-{
-    AutoMutex _l(mMutex);
-    mTimeoutUs = time;
-    mCond.signal();
-}
-
-}   // namespace android
diff --git a/media/libnblog/PerformanceAnalysis.cpp b/media/libnblog/PerformanceAnalysis.cpp
index 94ad114..46912d3 100644
--- a/media/libnblog/PerformanceAnalysis.cpp
+++ b/media/libnblog/PerformanceAnalysis.cpp
@@ -47,7 +47,6 @@
 #include <utility>
 
 namespace android {
-
 namespace ReportPerformance {
 
 void Histogram::add(double value)
@@ -367,5 +366,4 @@
 }
 
 } // namespace ReportPerformance
-
 }   // namespace android
diff --git a/media/libnblog/Reader.cpp b/media/libnblog/Reader.cpp
new file mode 100644
index 0000000..f86bb99
--- /dev/null
+++ b/media/libnblog/Reader.cpp
@@ -0,0 +1,421 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#define LOG_TAG "NBLog"
+//#define LOG_NDEBUG 0
+
+#include <memory>
+#include <stddef.h>
+#include <string>
+#include <unordered_set>
+
+#include <audio_utils/fifo.h>
+#include <binder/IMemory.h>
+#include <media/nblog/Entry.h>
+#include <media/nblog/Events.h>
+#include <media/nblog/Reader.h>
+#include <media/nblog/Timeline.h>
+#include <utils/Log.h>
+#include <utils/String8.h>
+
+namespace android {
+namespace NBLog {
+
+Reader::Reader(const void *shared, size_t size, const std::string &name)
+    : mName(name),
+      mShared((/*const*/ Shared *) shared), /*mIMemory*/
+      mFifo(mShared != NULL ?
+        new audio_utils_fifo(size, sizeof(uint8_t),
+            mShared->mBuffer, mShared->mRear, NULL /*throttlesFront*/) : NULL),
+      mFifoReader(mFifo != NULL ? new audio_utils_fifo_reader(*mFifo) : NULL)
+{
+}
+
+Reader::Reader(const sp<IMemory>& iMemory, size_t size, const std::string &name)
+    : Reader(iMemory != 0 ? (Shared *) iMemory->pointer() : NULL, size, name)
+{
+    mIMemory = iMemory;
+}
+
+Reader::~Reader()
+{
+    delete mFifoReader;
+    delete mFifo;
+}
+
+// Copies content of a Reader FIFO into its Snapshot
+// The Snapshot has the same raw data, but represented as a sequence of entries
+// and an EntryIterator making it possible to process the data.
+std::unique_ptr<Snapshot> Reader::getSnapshot()
+{
+    if (mFifoReader == NULL) {
+        return std::unique_ptr<Snapshot>(new Snapshot());
+    }
+
+    // This emulates the behaviour of audio_utils_fifo_reader::read, but without incrementing the
+    // reader index. The index is incremented after handling corruption, to after the last complete
+    // entry of the buffer
+    size_t lost = 0;
+    audio_utils_iovec iovec[2];
+    const size_t capacity = mFifo->capacity();
+    ssize_t availToRead;
+    // A call to audio_utils_fifo_reader::obtain() places the read pointer one buffer length
+    // before the writer's pointer (since mFifoReader was constructed with flush=false). The
+    // do while loop is an attempt to read all of the FIFO's contents regardless of how behind
+    // the reader is with respect to the writer. However, the following scheduling sequence is
+    // possible and can lead to a starvation situation:
+    // - Writer T1 writes, overrun with respect to Reader T2
+    // - T2 calls obtain() and gets EOVERFLOW, T2 ptr placed one buffer size behind T1 ptr
+    // - T1 write, overrun
+    // - T2 obtain(), EOVERFLOW (and so on...)
+    // To address this issue, we limit the number of tries for the reader to catch up with
+    // the writer.
+    int tries = 0;
+    size_t lostTemp;
+    do {
+        availToRead = mFifoReader->obtain(iovec, capacity, NULL /*timeout*/, &lostTemp);
+        lost += lostTemp;
+    } while (availToRead < 0 || ++tries <= kMaxObtainTries);
+
+    if (availToRead <= 0) {
+        ALOGW_IF(availToRead < 0, "NBLog Reader %s failed to catch up with Writer", mName.c_str());
+        return std::unique_ptr<Snapshot>(new Snapshot());
+    }
+
+    // Change to #if 1 for debugging. This statement is useful for checking buffer fullness levels
+    // (as seen by reader) and how much data was lost. If you find that the fullness level is
+    // getting close to full, or that data loss is happening to often, then you should
+    // probably try some of the following:
+    // - log less data
+    // - log less often
+    // - increase the initial shared memory allocation for the buffer
+#if 0
+    ALOGD("getSnapshot name=%s, availToRead=%zd, capacity=%zu, fullness=%.3f, lost=%zu",
+            name().c_str(), availToRead, capacity, (double)availToRead / (double)capacity, lost);
+#endif
+    std::unique_ptr<Snapshot> snapshot(new Snapshot(availToRead));
+    memcpy(snapshot->mData, (const char *) mFifo->buffer() + iovec[0].mOffset, iovec[0].mLength);
+    if (iovec[1].mLength > 0) {
+        memcpy(snapshot->mData + (iovec[0].mLength),
+                (const char *) mFifo->buffer() + iovec[1].mOffset, iovec[1].mLength);
+    }
+
+    // Handle corrupted buffer
+    // Potentially, a buffer has corrupted data on both beginning (due to overflow) and end
+    // (due to incomplete format entry). But even if the end format entry is incomplete,
+    // it ends in a complete entry (which is not an FMT_END). So is safe to traverse backwards.
+    // TODO: handle client corruption (in the middle of a buffer)
+
+    const uint8_t *back = snapshot->mData + availToRead;
+    const uint8_t *front = snapshot->mData;
+
+    // Find last FMT_END. <back> is sitting on an entry which might be the middle of a FormatEntry.
+    // We go backwards until we find an EVENT_FMT_END.
+    const uint8_t *lastEnd = findLastValidEntry(front, back, invalidEndTypes);
+    if (lastEnd == nullptr) {
+        snapshot->mEnd = snapshot->mBegin = EntryIterator(front);
+    } else {
+        // end of snapshot points to after last FMT_END entry
+        snapshot->mEnd = EntryIterator(lastEnd).next();
+        // find first FMT_START
+        const uint8_t *firstStart = nullptr;
+        const uint8_t *firstStartTmp = snapshot->mEnd;
+        while ((firstStartTmp = findLastValidEntry(front, firstStartTmp, invalidBeginTypes))
+                != nullptr) {
+            firstStart = firstStartTmp;
+        }
+        // firstStart is null if no FMT_START entry was found before lastEnd
+        if (firstStart == nullptr) {
+            snapshot->mBegin = snapshot->mEnd;
+        } else {
+            snapshot->mBegin = EntryIterator(firstStart);
+        }
+    }
+
+    // advance fifo reader index to after last entry read.
+    mFifoReader->release(snapshot->mEnd - front);
+
+    snapshot->mLost = lost;
+    return snapshot;
+}
+
+bool Reader::isIMemory(const sp<IMemory>& iMemory) const
+{
+    return iMemory != 0 && mIMemory != 0 && iMemory->pointer() == mIMemory->pointer();
+}
+
+// We make a set of the invalid types rather than the valid types when aligning
+// Snapshot EntryIterators to valid entries during log corruption checking.
+// This is done in order to avoid the maintenance overhead of adding a new Event
+// type to the two sets below whenever a new Event type is created, as it is
+// very likely that new types added will be valid types.
+// Currently, invalidBeginTypes and invalidEndTypes are used to handle the special
+// case of a Format Entry, which consists of a variable number of simple log entries.
+// If a new Event is added that consists of a variable number of simple log entries,
+// then these sets need to be updated.
+
+// We want the beginning of a Snapshot to point to an entry that is not in
+// the middle of a formatted entry and not an FMT_END.
+const std::unordered_set<Event> Reader::invalidBeginTypes {
+    EVENT_FMT_AUTHOR,
+    EVENT_FMT_END,
+    EVENT_FMT_FLOAT,
+    EVENT_FMT_HASH,
+    EVENT_FMT_INTEGER,
+    EVENT_FMT_PID,
+    EVENT_FMT_STRING,
+    EVENT_FMT_TIMESTAMP,
+};
+
+// We want the end of a Snapshot to point to an entry that is not in
+// the middle of a formatted entry and not a FMT_START.
+const std::unordered_set<Event> Reader::invalidEndTypes {
+    EVENT_FMT_AUTHOR,
+    EVENT_FMT_FLOAT,
+    EVENT_FMT_HASH,
+    EVENT_FMT_INTEGER,
+    EVENT_FMT_PID,
+    EVENT_FMT_START,
+    EVENT_FMT_STRING,
+    EVENT_FMT_TIMESTAMP,
+};
+
+const uint8_t *Reader::findLastValidEntry(const uint8_t *front, const uint8_t *back,
+                                          const std::unordered_set<Event> &invalidTypes) {
+    if (front == nullptr || back == nullptr) {
+        return nullptr;
+    }
+    while (back + Entry::kPreviousLengthOffset >= front) {
+        const uint8_t *prev = back - back[Entry::kPreviousLengthOffset] - Entry::kOverhead;
+        const Event type = (const Event)prev[offsetof(entry, type)];
+        if (prev < front
+                || prev + prev[offsetof(entry, length)] + Entry::kOverhead != back
+                || type <= EVENT_RESERVED || type >= EVENT_UPPER_BOUND) {
+            // prev points to an out of limits or inconsistent entry
+            return nullptr;
+        }
+        // if invalidTypes does not contain the type, then the type is valid.
+        if (invalidTypes.find(type) == invalidTypes.end()) {
+            return prev;
+        }
+        back = prev;
+    }
+    return nullptr; // no entry found
+}
+
+// TODO for future compatibility, would prefer to have a dump() go to string, and then go
+// to fd only when invoked through binder.
+void DumpReader::dump(int fd, size_t indent)
+{
+    if (fd < 0) return;
+    std::unique_ptr<Snapshot> snapshot = getSnapshot();
+    if (snapshot == nullptr) {
+        return;
+    }
+    String8 timestamp, body;
+
+    // TODO all logged types should have a printable format.
+    for (EntryIterator it = snapshot->begin(); it != snapshot->end(); ++it) {
+        switch (it->type) {
+        case EVENT_FMT_START:
+            it = handleFormat(FormatEntry(it), &timestamp, &body);
+            break;
+        case EVENT_WORK_TIME: {
+            const int64_t monotonicNs = it.payload<int64_t>();
+            body.appendFormat("Thread cycle: %ld ns", (long)monotonicNs);
+        } break;
+        case EVENT_LATENCY: {
+            const double latencyMs = it.payload<double>();
+            body.appendFormat("latency: %.3f ms", latencyMs);
+        } break;
+        case EVENT_WARMUP_TIME: {
+            const double timeMs = it.payload<double>();
+            body.appendFormat("warmup time: %.3f ms", timeMs);
+        } break;
+        case EVENT_UNDERRUN:
+            body.appendFormat("underrun");
+            break;
+        case EVENT_OVERRUN:
+            body.appendFormat("overrun");
+            break;
+        case EVENT_FMT_END:
+        case EVENT_RESERVED:
+        case EVENT_UPPER_BOUND:
+            body.appendFormat("warning: unexpected event %d", it->type);
+        default:
+            break;
+        }
+        if (!body.isEmpty()) {
+            dprintf(fd, "%.*s%s %s\n", (int)indent, "", timestamp.string(), body.string());
+            body.clear();
+        }
+        timestamp.clear();
+    }
+}
+
+EntryIterator DumpReader::handleFormat(const FormatEntry &fmtEntry,
+        String8 *timestamp, String8 *body)
+{
+    // log timestamp
+    const int64_t ts = fmtEntry.timestamp();
+    timestamp->clear();
+    timestamp->appendFormat("[%d.%03d]", (int) (ts / (1000 * 1000 * 1000)),
+                    (int) ((ts / (1000 * 1000)) % 1000));
+
+    // log unique hash
+    log_hash_t hash = fmtEntry.hash();
+    // print only lower 16bit of hash as hex and line as int to reduce spam in the log
+    body->appendFormat("%.4X-%d ", (int)(hash >> 16) & 0xFFFF, (int) hash & 0xFFFF);
+
+    // log author (if present)
+    handleAuthor(fmtEntry, body);
+
+    // log string
+    EntryIterator arg = fmtEntry.args();
+
+    const char* fmt = fmtEntry.formatString();
+    size_t fmt_length = fmtEntry.formatStringLength();
+
+    for (size_t fmt_offset = 0; fmt_offset < fmt_length; ++fmt_offset) {
+        if (fmt[fmt_offset] != '%') {
+            body->append(&fmt[fmt_offset], 1); // TODO optimize to write consecutive strings at once
+            continue;
+        }
+        // case "%%""
+        if (fmt[++fmt_offset] == '%') {
+            body->append("%");
+            continue;
+        }
+        // case "%\0"
+        if (fmt_offset == fmt_length) {
+            continue;
+        }
+
+        Event event = (Event) arg->type;
+        size_t length = arg->length;
+
+        // TODO check length for event type is correct
+
+        if (event == EVENT_FMT_END) {
+            break;
+        }
+
+        // TODO: implement more complex formatting such as %.3f
+        const uint8_t *datum = arg->data; // pointer to the current event args
+        switch(fmt[fmt_offset])
+        {
+        case 's': // string
+            ALOGW_IF(event != EVENT_FMT_STRING,
+                "NBLog Reader incompatible event for string specifier: %d", event);
+            body->append((const char*) datum, length);
+            break;
+
+        case 't': // timestamp
+            ALOGW_IF(event != EVENT_FMT_TIMESTAMP,
+                "NBLog Reader incompatible event for timestamp specifier: %d", event);
+            appendTimestamp(body, datum);
+            break;
+
+        case 'd': // integer
+            ALOGW_IF(event != EVENT_FMT_INTEGER,
+                "NBLog Reader incompatible event for integer specifier: %d", event);
+            appendInt(body, datum);
+            break;
+
+        case 'f': // float
+            ALOGW_IF(event != EVENT_FMT_FLOAT,
+                "NBLog Reader incompatible event for float specifier: %d", event);
+            appendFloat(body, datum);
+            break;
+
+        case 'p': // pid
+            ALOGW_IF(event != EVENT_FMT_PID,
+                "NBLog Reader incompatible event for pid specifier: %d", event);
+            appendPID(body, datum, length);
+            break;
+
+        default:
+            ALOGW("NBLog Reader encountered unknown character %c", fmt[fmt_offset]);
+        }
+        ++arg;
+    }
+    ALOGW_IF(arg->type != EVENT_FMT_END, "Expected end of format, got %d", arg->type);
+    return arg;
+}
+
+void DumpReader::appendInt(String8 *body, const void *data)
+{
+    if (body == nullptr || data == nullptr) {
+        return;
+    }
+    //int x = *((int*) data);
+    int x;
+    memcpy(&x, data, sizeof(x));
+    body->appendFormat("<%d>", x);
+}
+
+void DumpReader::appendFloat(String8 *body, const void *data)
+{
+    if (body == nullptr || data == nullptr) {
+        return;
+    }
+    float f;
+    memcpy(&f, data, sizeof(f));
+    body->appendFormat("<%f>", f);
+}
+
+void DumpReader::appendPID(String8 *body, const void* data, size_t length)
+{
+    if (body == nullptr || data == nullptr) {
+        return;
+    }
+    pid_t id = *((pid_t*) data);
+    char * name = &((char*) data)[sizeof(pid_t)];
+    body->appendFormat("<PID: %d, name: %.*s>", id, (int) (length - sizeof(pid_t)), name);
+}
+
+void DumpReader::appendTimestamp(String8 *body, const void *data)
+{
+    if (body == nullptr || data == nullptr) {
+        return;
+    }
+    int64_t ts;
+    memcpy(&ts, data, sizeof(ts));
+    body->appendFormat("[%d.%03d]", (int) (ts / (1000 * 1000 * 1000)),
+                    (int) ((ts / (1000 * 1000)) % 1000));
+}
+
+String8 DumpReader::bufferDump(const uint8_t *buffer, size_t size)
+{
+    String8 str;
+    if (buffer == nullptr) {
+        return str;
+    }
+    str.append("[ ");
+    for(size_t i = 0; i < size; i++) {
+        str.appendFormat("%d ", buffer[i]);
+    }
+    str.append("]");
+    return str;
+}
+
+String8 DumpReader::bufferDump(const EntryIterator &it)
+{
+    return bufferDump(it, it->length + Entry::kOverhead);
+}
+
+}   // namespace NBLog
+}   // namespace android
diff --git a/media/libnblog/ReportPerformance.cpp b/media/libnblog/ReportPerformance.cpp
index aab67c6..bf8a1dc 100644
--- a/media/libnblog/ReportPerformance.cpp
+++ b/media/libnblog/ReportPerformance.cpp
@@ -15,6 +15,7 @@
  */
 
 #define LOG_TAG "ReportPerformance"
+//#define LOG_NDEBUG 0
 
 #include <fstream>
 #include <iostream>
@@ -30,23 +31,22 @@
 #include <utility>
 #include <json/json.h>
 #include <media/MediaAnalyticsItem.h>
-#include <media/nblog/NBLog.h>
+#include <media/nblog/Events.h>
 #include <media/nblog/PerformanceAnalysis.h>
 #include <media/nblog/ReportPerformance.h>
 #include <utils/Log.h>
 #include <utils/String8.h>
 
 namespace android {
-
 namespace ReportPerformance {
 
 std::unique_ptr<Json::Value> dumpToJson(const PerformanceData& data)
 {
     std::unique_ptr<Json::Value> rootPtr = std::make_unique<Json::Value>(Json::objectValue);
     Json::Value& root = *rootPtr;
-    root["type"] = data.type;
-    root["frameCount"] = (Json::Value::Int)data.frameCount;
-    root["sampleRate"] = (Json::Value::Int)data.sampleRate;
+    root["type"] = (Json::Value::Int)data.threadInfo.type;
+    root["frameCount"] = (Json::Value::Int)data.threadInfo.frameCount;
+    root["sampleRate"] = (Json::Value::Int)data.threadInfo.sampleRate;
     root["workMsHist"] = data.workHist.toString();
     root["latencyMsHist"] = data.latencyHist.toString();
     root["warmupMsHist"] = data.warmupHist.toString();
@@ -102,15 +102,10 @@
     // we want to send them only if there are performance metrics to send.
     if (item->count() > 0) {
         // Add thread info fields.
-        const int type = data.type;
-        // TODO have a int-to-string mapping defined somewhere else for other thread types.
-        if (type == 2) {
-            item->setCString(kThreadType, "FASTMIXER");
-        } else {
-            item->setCString(kThreadType, "UNKNOWN");
-        }
-        item->setInt32(kThreadFrameCount, data.frameCount);
-        item->setInt32(kThreadSampleRate, data.sampleRate);
+        const char * const typeString = NBLog::threadTypeToString(data.threadInfo.type);
+        item->setCString(kThreadType, typeString);
+        item->setInt32(kThreadFrameCount, data.threadInfo.frameCount);
+        item->setInt32(kThreadSampleRate, data.threadInfo.sampleRate);
         // Add time info fields.
         item->setInt64(kThreadActive, data.active / 1000000);
         item->setInt64(kThreadDuration, (systemTime() - data.start) / 1000000);
@@ -211,6 +206,5 @@
     pfs.close();
 }
 
-} // namespace ReportPerformance
-
+}   // namespace ReportPerformance
 }   // namespace android
diff --git a/media/libnblog/Timeline.cpp b/media/libnblog/Timeline.cpp
new file mode 100644
index 0000000..c09b03b
--- /dev/null
+++ b/media/libnblog/Timeline.cpp
@@ -0,0 +1,50 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <stddef.h>
+
+#include <audio_utils/roundup.h>
+#include <media/nblog/Timeline.h>
+
+namespace android {
+namespace NBLog {
+
+#if 0   // FIXME see note in Timeline.h
+NBLog::Timeline::Timeline(size_t size, void *shared)
+    : mSize(roundup(size)), mOwn(shared == NULL),
+      mShared((Shared *) (mOwn ? new char[sharedSize(size)] : shared))
+{
+    new (mShared) Shared;
+}
+
+NBLog::Timeline::~Timeline()
+{
+    mShared->~Shared();
+    if (mOwn) {
+        delete[] (char *) mShared;
+    }
+}
+#endif
+
+/*static*/
+size_t Timeline::sharedSize(size_t size)
+{
+    // TODO fifo now supports non-power-of-2 buffer sizes, so could remove the roundup
+    return sizeof(Shared) + roundup(size);
+}
+
+}   // namespace NBLog
+}   // namespace android
diff --git a/media/libnblog/Writer.cpp b/media/libnblog/Writer.cpp
new file mode 100644
index 0000000..da3bd52
--- /dev/null
+++ b/media/libnblog/Writer.cpp
@@ -0,0 +1,320 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#define LOG_TAG "NBLog"
+//#define LOG_NDEBUG 0
+
+#include <stdarg.h>
+#include <stddef.h>
+#include <sys/prctl.h>
+
+#include <audio_utils/fifo.h>
+#include <binder/IMemory.h>
+#include <media/nblog/Entry.h>
+#include <media/nblog/Events.h>
+#include <media/nblog/Timeline.h>
+#include <media/nblog/Writer.h>
+#include <utils/Log.h>
+#include <utils/Mutex.h>
+
+namespace android {
+namespace NBLog {
+
+Writer::Writer(void *shared, size_t size)
+    : mShared((Shared *) shared),
+      mFifo(mShared != NULL ?
+        new audio_utils_fifo(size, sizeof(uint8_t),
+            mShared->mBuffer, mShared->mRear, NULL /*throttlesFront*/) : NULL),
+      mFifoWriter(mFifo != NULL ? new audio_utils_fifo_writer(*mFifo) : NULL),
+      mEnabled(mFifoWriter != NULL)
+{
+    // caching pid and process name
+    pid_t id = ::getpid();
+    char procName[16];
+    int status = prctl(PR_GET_NAME, procName);
+    if (status) {  // error getting process name
+        procName[0] = '\0';
+    }
+    size_t length = strlen(procName);
+    mPidTagSize = length + sizeof(pid_t);
+    mPidTag = new char[mPidTagSize];
+    memcpy(mPidTag, &id, sizeof(pid_t));
+    memcpy(mPidTag + sizeof(pid_t), procName, length);
+}
+
+Writer::Writer(const sp<IMemory>& iMemory, size_t size)
+    : Writer(iMemory != 0 ? (Shared *) iMemory->pointer() : NULL, size)
+{
+    mIMemory = iMemory;
+}
+
+Writer::~Writer()
+{
+    delete mFifoWriter;
+    delete mFifo;
+    delete[] mPidTag;
+}
+
+void Writer::log(const char *string)
+{
+    if (!mEnabled) {
+        return;
+    }
+    LOG_ALWAYS_FATAL_IF(string == NULL, "Attempted to log NULL string");
+    size_t length = strlen(string);
+    if (length > Entry::kMaxLength) {
+        length = Entry::kMaxLength;
+    }
+    log(EVENT_STRING, string, length);
+}
+
+void Writer::logf(const char *fmt, ...)
+{
+    if (!mEnabled) {
+        return;
+    }
+    va_list ap;
+    va_start(ap, fmt);
+    Writer::logvf(fmt, ap);     // the Writer:: is needed to avoid virtual dispatch for LockedWriter
+    va_end(ap);
+}
+
+void Writer::logTimestamp()
+{
+    if (!mEnabled) {
+        return;
+    }
+    struct timespec ts;
+    if (!clock_gettime(CLOCK_MONOTONIC, &ts)) {
+        log(EVENT_TIMESTAMP, &ts, sizeof(ts));
+    }
+}
+
+void Writer::logFormat(const char *fmt, log_hash_t hash, ...)
+{
+    if (!mEnabled) {
+        return;
+    }
+    va_list ap;
+    va_start(ap, hash);
+    Writer::logVFormat(fmt, hash, ap);
+    va_end(ap);
+}
+
+void Writer::logEventHistTs(Event event, log_hash_t hash)
+{
+    if (!mEnabled) {
+        return;
+    }
+    HistTsEntry data;
+    data.hash = hash;
+    data.ts = systemTime();
+    if (data.ts > 0) {
+        log(event, &data, sizeof(data));
+    } else {
+        ALOGE("Failed to get timestamp");
+    }
+}
+
+bool Writer::isEnabled() const
+{
+    return mEnabled;
+}
+
+bool Writer::setEnabled(bool enabled)
+{
+    bool old = mEnabled;
+    mEnabled = enabled && mShared != NULL;
+    return old;
+}
+
+void Writer::log(const Entry &etr, bool trusted)
+{
+    if (!mEnabled) {
+        return;
+    }
+    if (!trusted) {
+        log(etr.mEvent, etr.mData, etr.mLength);
+        return;
+    }
+    const size_t need = etr.mLength + Entry::kOverhead; // mEvent, mLength, data[mLength], mLength
+                                                        // need = number of bytes written to FIFO
+
+    // FIXME optimize this using memcpy for the data part of the Entry.
+    // The Entry could have a method copyTo(ptr, offset, size) to optimize the copy.
+    // checks size of a single log Entry: type, length, data pointer and ending
+    uint8_t temp[Entry::kMaxLength + Entry::kOverhead];
+    // write this data to temp array
+    for (size_t i = 0; i < need; i++) {
+        temp[i] = etr.copyEntryDataAt(i);
+    }
+    // write to circular buffer
+    mFifoWriter->write(temp, need);
+}
+
+void Writer::log(Event event, const void *data, size_t length)
+{
+    if (!mEnabled) {
+        return;
+    }
+    if (data == NULL || length > Entry::kMaxLength) {
+        // TODO Perhaps it makes sense to display truncated data or at least a
+        //      message that the data is too long?  The current behavior can create
+        //      a confusion for a programmer debugging their code.
+        return;
+    }
+    // Ignore if invalid event
+    if (event == EVENT_RESERVED || event >= EVENT_UPPER_BOUND) {
+        return;
+    }
+    Entry etr(event, data, length);
+    log(etr, true /*trusted*/);
+}
+
+void Writer::logvf(const char *fmt, va_list ap)
+{
+    if (!mEnabled) {
+        return;
+    }
+    char buffer[Entry::kMaxLength + 1 /*NUL*/];
+    int length = vsnprintf(buffer, sizeof(buffer), fmt, ap);
+    if (length >= (int) sizeof(buffer)) {
+        length = sizeof(buffer) - 1;
+        // NUL termination is not required
+        // buffer[length] = '\0';
+    }
+    if (length >= 0) {
+        log(EVENT_STRING, buffer, length);
+    }
+}
+
+void Writer::logStart(const char *fmt)
+{
+    if (!mEnabled) {
+        return;
+    }
+    size_t length = strlen(fmt);
+    if (length > Entry::kMaxLength) {
+        length = Entry::kMaxLength;
+    }
+    log(EVENT_FMT_START, fmt, length);
+}
+
+void Writer::logTimestampFormat()
+{
+    if (!mEnabled) {
+        return;
+    }
+    const nsecs_t ts = systemTime();
+    if (ts > 0) {
+        log(EVENT_FMT_TIMESTAMP, &ts, sizeof(ts));
+    } else {
+        ALOGE("Failed to get timestamp");
+    }
+}
+
+void Writer::logVFormat(const char *fmt, log_hash_t hash, va_list argp)
+{
+    if (!mEnabled) {
+        return;
+    }
+    Writer::logStart(fmt);
+    int i;
+    double d;
+    float f;
+    char* s;
+    size_t length;
+    int64_t t;
+    Writer::logTimestampFormat();
+    log(EVENT_FMT_HASH, &hash, sizeof(hash));
+    for (const char *p = fmt; *p != '\0'; p++) {
+        // TODO: implement more complex formatting such as %.3f
+        if (*p != '%') {
+            continue;
+        }
+        switch(*++p) {
+        case 's': // string
+            s = va_arg(argp, char *);
+            length = strlen(s);
+            if (length > Entry::kMaxLength) {
+                length = Entry::kMaxLength;
+            }
+            log(EVENT_FMT_STRING, s, length);
+            break;
+
+        case 't': // timestamp
+            t = va_arg(argp, int64_t);
+            log(EVENT_FMT_TIMESTAMP, &t, sizeof(t));
+            break;
+
+        case 'd': // integer
+            i = va_arg(argp, int);
+            log(EVENT_FMT_INTEGER, &i, sizeof(i));
+            break;
+
+        case 'f': // float
+            d = va_arg(argp, double); // float arguments are promoted to double in vararg lists
+            f = (float)d;
+            log(EVENT_FMT_FLOAT, &f, sizeof(f));
+            break;
+
+        case 'p': // pid
+            log(EVENT_FMT_PID, mPidTag, mPidTagSize);
+            break;
+
+        // the "%\0" case finishes parsing
+        case '\0':
+            --p;
+            break;
+
+        case '%':
+            break;
+
+        default:
+            ALOGW("NBLog Writer parsed invalid format specifier: %c", *p);
+            break;
+        }
+    }
+    Entry etr(EVENT_FMT_END, nullptr, 0);
+    log(etr, true);
+}
+
+// ---------------------------------------------------------------------------
+
+LockedWriter::LockedWriter(void *shared, size_t size)
+    : Writer(shared, size)
+{
+}
+
+bool LockedWriter::isEnabled() const
+{
+    Mutex::Autolock _l(mLock);
+    return Writer::isEnabled();
+}
+
+bool LockedWriter::setEnabled(bool enabled)
+{
+    Mutex::Autolock _l(mLock);
+    return Writer::setEnabled(enabled);
+}
+
+void LockedWriter::log(const Entry &entry, bool trusted) {
+    Mutex::Autolock _l(mLock);
+    Writer::log(entry, trusted);
+}
+
+}   // namespace NBLog
+}   // namespace android
diff --git a/media/libnblog/include/media/nblog/Entry.h b/media/libnblog/include/media/nblog/Entry.h
new file mode 100644
index 0000000..53f00b6
--- /dev/null
+++ b/media/libnblog/include/media/nblog/Entry.h
@@ -0,0 +1,232 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef ANDROID_MEDIA_NBLOG_ENTRY_H
+#define ANDROID_MEDIA_NBLOG_ENTRY_H
+
+#include <memory>
+#include <stddef.h>
+#include <stdint.h>
+#include <type_traits>
+
+#include <media/nblog/Events.h>
+
+class audio_utils_fifo_writer;
+
+namespace android {
+namespace NBLog {
+
+// entry representation in memory
+struct entry {
+    const uint8_t type;
+    const uint8_t length;
+    const uint8_t data[0];
+};
+
+// entry tail representation (after data)
+struct ending {
+    uint8_t length;
+    uint8_t next[0];
+};
+
+// representation of a single log entry in shared memory
+//  byte[0]             mEvent
+//  byte[1]             mLength
+//  byte[2]             mData[0]
+//  ...
+//  byte[2+i]           mData[i]
+//  ...
+//  byte[2+mLength-1]   mData[mLength-1]
+//  byte[2+mLength]     duplicate copy of mLength to permit reverse scan
+//  byte[3+mLength]     start of next log entry
+class Entry {
+public:
+    Entry(Event event, const void *data, size_t length)
+        : mEvent(event), mLength(length), mData(data) {}
+    ~Entry() {}
+
+    // used during writing to format Entry information as follows:
+    // [type][length][data ... ][length]
+    int     copyEntryDataAt(size_t offset) const;
+
+private:
+    friend class Writer;
+    Event       mEvent;     // event type
+    uint8_t     mLength;    // length of additional data, 0 <= mLength <= kMaxLength
+    const void *mData;      // event type-specific data
+    static const size_t kMaxLength = 255;
+public:
+    // mEvent, mLength, mData[...], duplicate mLength
+    static const size_t kOverhead = sizeof(entry) + sizeof(ending);
+    // endind length of previous entry
+    static const ssize_t kPreviousLengthOffset = - sizeof(ending) +
+        offsetof(ending, length);
+};
+
+// entry iterator
+class EntryIterator {
+public:
+    // Used for dummy initialization. Performing operations on a default-constructed
+    // EntryIterator other than assigning it to another valid EntryIterator
+    // is undefined behavior.
+    EntryIterator();
+    // Caller's responsibility to make sure entry is not nullptr.
+    // Passing in nullptr can result in undefined behavior.
+    explicit EntryIterator(const uint8_t *entry);
+    EntryIterator(const EntryIterator &other);
+
+    // dereference underlying entry
+    const entry&    operator*() const;
+    const entry*    operator->() const;
+    // advance to next entry
+    EntryIterator&  operator++(); // ++i
+    // back to previous entry
+    EntryIterator&  operator--(); // --i
+    // returns an EntryIterator corresponding to the next entry
+    EntryIterator   next() const;
+    // returns an EntryIterator corresponding to the previous entry
+    EntryIterator   prev() const;
+    bool            operator!=(const EntryIterator &other) const;
+    int             operator-(const EntryIterator &other) const;
+
+    bool            hasConsistentLength() const;
+    void            copyTo(std::unique_ptr<audio_utils_fifo_writer> &dst) const;
+    void            copyData(uint8_t *dst) const;
+
+    // memcpy preferred to reinterpret_cast to avoid potentially unsupported
+    // unaligned memory access.
+#if 0
+    template<typename T>
+    inline const T& payload() {
+        return *reinterpret_cast<const T *>(mPtr + offsetof(entry, data));
+    }
+#else
+    template<typename T>
+    inline T payload() const {
+        static_assert(std::is_trivially_copyable<T>::value
+                && !std::is_pointer<T>::value,
+                "NBLog::EntryIterator payload must be trivially copyable, non-pointer type.");
+        T payload;
+        memcpy(&payload, mPtr + offsetof(entry, data), sizeof(payload));
+        return payload;
+    }
+#endif
+
+    inline operator const uint8_t*() const {
+        return mPtr;
+    }
+
+private:
+    const uint8_t  *mPtr;   // Should not be nullptr except for dummy initialization
+};
+
+// ---------------------------------------------------------------------------
+// The following classes are used for merging into the Merger's buffer.
+
+class AbstractEntry {
+public:
+    virtual ~AbstractEntry() {}
+
+    // build concrete entry of appropriate class from ptr.
+    static std::unique_ptr<AbstractEntry> buildEntry(const uint8_t *ptr);
+
+    // get format entry timestamp
+    virtual int64_t       timestamp() const = 0;
+
+    // get format entry's unique id
+    virtual log_hash_t    hash() const = 0;
+
+    // entry's author index (-1 if none present)
+    // a Merger has a vector of Readers, author simply points to the index of the
+    // Reader that originated the entry
+    // TODO consider changing to uint32_t
+    virtual int           author() const = 0;
+
+    // copy entry, adding author before timestamp, returns iterator to end of entry
+    virtual EntryIterator copyWithAuthor(std::unique_ptr<audio_utils_fifo_writer> &dst,
+                                            int author) const = 0;
+
+protected:
+    // Entry starting in the given pointer, which shall not be nullptr.
+    explicit AbstractEntry(const uint8_t *entry) : mEntry(entry) {}
+    // copies ordinary entry from src to dst, and returns length of entry
+    // size_t      copyEntry(audio_utils_fifo_writer *dst, const iterator &it);
+    const uint8_t * const mEntry;
+};
+
+// API for handling format entry operations
+
+// a formatted entry has the following structure:
+//    * FMT_START entry, containing the format string
+//    * TIMESTAMP entry
+//    * HASH entry
+//    * author entry of the thread that generated it (optional, present in merged log)
+//    * format arg1
+//    * format arg2
+//    * ...
+//    * FMT_END entry
+class FormatEntry : public AbstractEntry {
+public:
+    // explicit FormatEntry(const EntryIterator &it);
+    explicit FormatEntry(const uint8_t *ptr) : AbstractEntry(ptr) {}
+    ~FormatEntry() override = default;
+
+    EntryIterator begin() const;
+
+    // Entry's format string
+    const char*   formatString() const;
+
+    // Enrty's format string length
+    size_t        formatStringLength() const;
+
+    // Format arguments (excluding format string, timestamp and author)
+    EntryIterator args() const;
+
+    // get format entry timestamp
+    int64_t       timestamp() const override;
+
+    // get format entry's unique id
+    log_hash_t    hash() const override;
+
+    // entry's author index (-1 if none present)
+    // a Merger has a vector of Readers, author simply points to the index of the
+    // Reader that originated the entry
+    int           author() const override;
+
+    // copy entry, adding author before timestamp, returns size of original entry
+    EntryIterator copyWithAuthor(std::unique_ptr<audio_utils_fifo_writer> &dst,
+                                 int author) const override;
+};
+
+class HistogramEntry : public AbstractEntry {
+public:
+    explicit HistogramEntry(const uint8_t *ptr) : AbstractEntry(ptr) {}
+    ~HistogramEntry() override = default;
+
+    int64_t       timestamp() const override;
+
+    log_hash_t    hash() const override;
+
+    int           author() const override;
+
+    EntryIterator copyWithAuthor(std::unique_ptr<audio_utils_fifo_writer> &dst,
+                                 int author) const override;
+};
+
+}   // namespace NBLog
+}   // namespace android
+
+#endif  // ANDROID_MEDIA_NBLOG_ENTRY_H
diff --git a/media/libnblog/include/media/nblog/Events.h b/media/libnblog/include/media/nblog/Events.h
new file mode 100644
index 0000000..9212ce4
--- /dev/null
+++ b/media/libnblog/include/media/nblog/Events.h
@@ -0,0 +1,142 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef ANDROID_MEDIA_NBLOG_EVENTS_H
+#define ANDROID_MEDIA_NBLOG_EVENTS_H
+
+#include <stddef.h>
+#include <stdint.h>
+#include <type_traits>
+
+namespace android {
+namespace NBLog {
+
+// TODO have a comment somewhere explaining the whole process for adding a new EVENT_
+
+// NBLog Event types. The Events are named to provide contextual meaning for what is logged.
+// If adding a new standalone Event here, update the event-to-type mapping by adding a
+// MAP_EVENT_TO_TYPE statement below.
+// XXX Note that as of the current design, Events should not be renumbered (i.e. reordered)
+// if they ever leave memory (for example, written to file, uploaded to cloud, etc.).
+// TODO make some sort of interface to keep these "contract" constants.
+enum Event : uint8_t {
+    EVENT_RESERVED,
+    EVENT_STRING,               // ASCII string, not NUL-terminated
+                                // TODO: make timestamp optional
+    EVENT_TIMESTAMP,            // clock_gettime(CLOCK_MONOTONIC)
+
+    // Types for Format Entry, i.e. formatted entry
+    EVENT_FMT_START,            // logFormat start event: entry includes format string,
+                                // following entries contain format arguments
+    // format arguments
+    EVENT_FMT_AUTHOR,           // author index (present in merged logs) tracks entry's
+                                // original log
+    EVENT_FMT_FLOAT,            // floating point value entry
+    EVENT_FMT_HASH,             // unique HASH of log origin, originates from hash of file name
+                                // and line number
+    EVENT_FMT_INTEGER,          // integer value entry
+    EVENT_FMT_PID,              // process ID and process name
+    EVENT_FMT_STRING,           // string value entry
+    EVENT_FMT_TIMESTAMP,        // timestamp value entry
+    // end of format arguments
+    EVENT_FMT_END,              // end of logFormat argument list
+
+    // Types for wakeup timestamp histograms
+    EVENT_AUDIO_STATE,          // audio on/off event: logged on FastMixer::onStateChange call
+    EVENT_HISTOGRAM_ENTRY_TS,   // single datum for timestamp histogram
+
+    // Types representing audio performance metrics
+    EVENT_LATENCY,              // difference between frames presented by HAL and frames
+                                // written to HAL output sink, divided by sample rate.
+    EVENT_OVERRUN,              // predicted thread overrun event timestamp
+    EVENT_THREAD_INFO,          // thread type, frameCount and sampleRate, which give context
+                                // for the metrics below.
+    EVENT_UNDERRUN,             // predicted thread underrun event timestamp
+    EVENT_WARMUP_TIME,          // thread warmup time
+    EVENT_WORK_TIME,            // the time a thread takes to do work, e.g. read, write, etc.
+
+    EVENT_UPPER_BOUND,          // to check for invalid events
+};
+
+// NBLog custom-defined structs. Some NBLog Event types map to these structs.
+
+using log_hash_t = uint64_t;
+
+// used for EVENT_HISTOGRAM_ENTRY_TS (not mapped)
+struct HistTsEntry {
+    log_hash_t hash;
+    int64_t ts;
+}; //TODO __attribute__((packed));
+
+// used for EVENT_HISTOGRAM_ENTRY_TS (not mapped)
+struct HistTsEntryWithAuthor {
+    log_hash_t hash;
+    int64_t ts;
+    int author;
+}; //TODO __attribute__((packed));
+
+enum ThreadType {
+    UNKNOWN,
+    MIXER,
+    CAPTURE,
+    FASTMIXER,
+    FASTCAPTURE,
+};
+
+inline const char *threadTypeToString(ThreadType type) {
+    switch (type) {
+    case MIXER:
+        return "MIXER";
+    case CAPTURE:
+        return "CAPTURE";
+    case FASTMIXER:
+        return "FASTMIXER";
+    case FASTCAPTURE:
+        return "FASTCAPTURE";
+    case UNKNOWN:
+    default:
+        return "UNKNOWN";
+    }
+}
+
+// mapped from EVENT_THREAD_INFO
+struct thread_info_t {
+    ThreadType type;
+    size_t frameCount;      // number of frames per read or write buffer
+    unsigned sampleRate;    // in frames per second
+};
+
+template <Event E> struct get_mapped;
+#define MAP_EVENT_TO_TYPE(E, T) \
+template<> struct get_mapped<E> { \
+    static_assert(std::is_trivially_copyable<T>::value \
+            && !std::is_pointer<T>::value, \
+            "NBLog::Event must map to trivially copyable, non-pointer type."); \
+    typedef T type; \
+}
+
+// Maps an NBLog Event type to a C++ POD type.
+MAP_EVENT_TO_TYPE(EVENT_LATENCY, double);
+MAP_EVENT_TO_TYPE(EVENT_OVERRUN, int64_t);
+MAP_EVENT_TO_TYPE(EVENT_THREAD_INFO, thread_info_t);
+MAP_EVENT_TO_TYPE(EVENT_UNDERRUN, int64_t);
+MAP_EVENT_TO_TYPE(EVENT_WARMUP_TIME, double);
+MAP_EVENT_TO_TYPE(EVENT_WORK_TIME, int64_t);
+
+}   // namespace NBLog
+}   // namespace android
+
+#endif  // ANDROID_MEDIA_NBLOG_EVENTS_H
diff --git a/media/libnblog/include/media/nblog/Merger.h b/media/libnblog/include/media/nblog/Merger.h
new file mode 100644
index 0000000..ac63a7e
--- /dev/null
+++ b/media/libnblog/include/media/nblog/Merger.h
@@ -0,0 +1,154 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef ANDROID_MEDIA_NBLOG_MERGER_H
+#define ANDROID_MEDIA_NBLOG_MERGER_H
+
+#include <memory>
+#include <stddef.h>
+#include <stdint.h>
+#include <vector>
+
+#include <audio_utils/fifo.h>
+#include <media/nblog/PerformanceAnalysis.h>
+#include <media/nblog/Reader.h>
+#include <utils/Condition.h>
+#include <utils/Mutex.h>
+#include <utils/RefBase.h>
+#include <utils/Thread.h>
+
+namespace android {
+
+class String8;
+
+namespace NBLog {
+
+struct Shared;
+
+// TODO update comments to reflect current functionalities
+
+// This class is used to read data from each thread's individual FIFO in shared memory
+// and write it to a single FIFO in local memory.
+class Merger : public RefBase {
+public:
+    Merger(const void *shared, size_t size);
+
+    ~Merger() override = default;
+
+    void addReader(const sp<NBLog::Reader> &reader);
+    // TODO add removeReader
+    void merge();
+
+    // FIXME This is returning a reference to a shared variable that needs a lock
+    const std::vector<sp<Reader>>& getReaders() const;
+
+private:
+    // vector of the readers the merger is supposed to merge from.
+    // every reader reads from a writer's buffer
+    // FIXME Needs to be protected by a lock
+    std::vector<sp<Reader>> mReaders;
+
+    Shared * const mShared; // raw pointer to shared memory
+    std::unique_ptr<audio_utils_fifo> mFifo; // FIFO itself
+    std::unique_ptr<audio_utils_fifo_writer> mFifoWriter; // used to write to FIFO
+};
+
+// This class has a pointer to the FIFO in local memory which stores the merged
+// data collected by NBLog::Merger from all Readers. It is used to process
+// this data and write the result to PerformanceAnalysis.
+class MergeReader : public Reader {
+public:
+    MergeReader(const void *shared, size_t size, Merger &merger);
+
+    // process a particular snapshot of the reader
+    void processSnapshot(Snapshot &snap, int author);
+
+    // call getSnapshot of the content of the reader's buffer and process the data
+    void getAndProcessSnapshot();
+
+    // check for periodic push of performance data to media metrics, and perform
+    // the send if it is time to do so.
+    void checkPushToMediaMetrics();
+
+    void dump(int fd, int indent = 0);
+
+private:
+    // FIXME Needs to be protected by a lock,
+    //       because even though our use of it is read-only there may be asynchronous updates
+    // The object is owned by the Merger class.
+    const std::vector<sp<Reader>>& mReaders;
+
+    // analyzes, compresses and stores the merged data
+    // contains a separate instance for every author (thread), and for every source file
+    // location within each author
+    ReportPerformance::PerformanceAnalysisMap mThreadPerformanceAnalysis;
+
+    // compresses and stores audio performance data from each thread's buffers.
+    // first parameter is author, i.e. thread index.
+    std::map<int, ReportPerformance::PerformanceData> mThreadPerformanceData;
+
+    // how often to push data to Media Metrics
+    static constexpr nsecs_t kPeriodicMediaMetricsPush = s2ns((nsecs_t)2 * 60 * 60); // 2 hours
+
+    // handle author entry by looking up the author's name and appending it to the body
+    // returns number of bytes read from fmtEntry
+    void handleAuthor(const AbstractEntry &fmtEntry, String8 *body);
+};
+
+// MergeThread is a thread that contains a Merger. It works as a retriggerable one-shot:
+// when triggered, it awakes for a lapse of time, during which it periodically merges; if
+// retriggered, the timeout is reset.
+// The thread is triggered on AudioFlinger binder activity.
+class MergeThread : public Thread {
+public:
+    MergeThread(Merger &merger, MergeReader &mergeReader);
+    ~MergeThread() override;
+
+    // Reset timeout and activate thread to merge periodically if it's idle
+    void wakeup();
+
+    // Set timeout period until the merging thread goes idle again
+    void setTimeoutUs(int time);
+
+private:
+    bool threadLoop() override;
+
+    // the merger who actually does the work of merging the logs
+    Merger&      mMerger;
+
+    // the mergereader used to process data merged by mMerger
+    MergeReader& mMergeReader;
+
+    // mutex for the condition variable
+    Mutex        mMutex;
+
+    // condition variable to activate merging on timeout >= 0
+    Condition    mCond;
+
+    // time left until the thread blocks again (in microseconds)
+    int          mTimeoutUs;
+
+    // merging period when the thread is awake
+    static const int  kThreadSleepPeriodUs = 1000000 /*1s*/;
+
+    // initial timeout value when triggered
+    static const int  kThreadWakeupPeriodUs = 3000000 /*3s*/;
+};
+
+}   // namespace NBLog
+}   // namespace android
+
+#endif  // ANDROID_MEDIA_NBLOG_MERGER_H
diff --git a/media/libnblog/include/media/nblog/NBLog.h b/media/libnblog/include/media/nblog/NBLog.h
index e43b026..fd73538 100644
--- a/media/libnblog/include/media/nblog/NBLog.h
+++ b/media/libnblog/include/media/nblog/NBLog.h
@@ -19,670 +19,10 @@
 #ifndef ANDROID_MEDIA_NBLOG_H
 #define ANDROID_MEDIA_NBLOG_H
 
-#include <map>
-#include <memory>
-#include <type_traits>
-#include <unordered_set>
-#include <vector>
-
-#include <audio_utils/fifo.h>
-#include <binder/IMemory.h>
-#include <media/nblog/PerformanceAnalysis.h>
-#include <media/nblog/ReportPerformance.h>
-#include <utils/Mutex.h>
-#include <utils/threads.h>
-#include <utils/Timers.h>
-
-namespace android {
-
-class String8;
-
-class NBLog {
-
-public:
-
-    using log_hash_t = uint64_t;
-
-    // FIXME Everything needed for client (writer API and registration) should be isolated
-    //       from the rest of the implementation.
-    class Writer;
-    class Reader;
-
-    // TODO have a comment somewhere explaining the whole process for adding a new EVENT_
-
-    // NBLog Event types. The Events are named to provide contextual meaning for what is logged.
-    // If adding a new standalone Event here, update the event-to-type mapping by adding a
-    // MAP_EVENT_TO_TYPE statement below.
-    enum Event : uint8_t {
-        EVENT_RESERVED,
-        EVENT_STRING,               // ASCII string, not NUL-terminated
-                                    // TODO: make timestamp optional
-        EVENT_TIMESTAMP,            // clock_gettime(CLOCK_MONOTONIC)
-
-        // Types for Format Entry, i.e. formatted entry
-        EVENT_FMT_START,            // logFormat start event: entry includes format string,
-                                    // following entries contain format arguments
-        // format arguments
-        EVENT_FMT_TIMESTAMP,        // timestamp value entry
-        EVENT_FMT_HASH,             // unique HASH of log origin, originates from hash of file name
-                                    // and line number
-        EVENT_FMT_STRING,           // string value entry
-        EVENT_FMT_INTEGER,          // integer value entry
-        EVENT_FMT_FLOAT,            // floating point value entry
-        EVENT_FMT_PID,              // process ID and process name
-        EVENT_FMT_AUTHOR,           // author index (present in merged logs) tracks entry's
-                                    // original log
-        // end of format arguments
-        EVENT_FMT_END,              // end of logFormat argument list
-
-        // Types for wakeup timestamp histograms
-        EVENT_HISTOGRAM_ENTRY_TS,   // single datum for timestamp histogram
-        EVENT_AUDIO_STATE,          // audio on/off event: logged on FastMixer::onStateChange call
-
-        // Types representing audio performance metrics
-        EVENT_THREAD_INFO,          // thread type, frameCount and sampleRate, which give context
-                                    // for the metrics below.
-        EVENT_LATENCY,              // difference between frames presented by HAL and frames
-                                    // written to HAL output sink, divided by sample rate.
-        EVENT_WORK_TIME,            // the time a thread takes to do work, e.g. read, write, etc.
-        EVENT_WARMUP_TIME,          // thread warmup time
-        EVENT_UNDERRUN,             // predicted thread underrun event timestamp
-        EVENT_OVERRUN,              // predicted thread overrun event timestamp
-
-        EVENT_UPPER_BOUND,          // to check for invalid events
-    };
-
-    // NBLog custom-defined structs. Some NBLog Event types map to these structs.
-
-    // mapped from EVENT_THREAD_INFO
-    struct thread_info_t {
-        // TODO make type an enum
-        int type;               // Thread type: 0 for MIXER, 1 for CAPTURE,
-                                // 2 for FASTMIXER, 3 for FASTCAPTURE
-        size_t frameCount;      // number of frames per read or write buffer
-        unsigned sampleRate;    // in frames per second
-    };
-
-    template <Event E> struct get_mapped;
-#define MAP_EVENT_TO_TYPE(E, T) \
-    template<> struct get_mapped<E> { \
-        static_assert(std::is_trivially_copyable<T>::value \
-                && !std::is_pointer<T>::value, \
-                "NBLog::Event must map to trivially copyable, non-pointer type."); \
-        typedef T type; \
-    }
-
-    // Maps an NBLog Event type to a C++ POD type.
-    MAP_EVENT_TO_TYPE(EVENT_THREAD_INFO, thread_info_t);
-    MAP_EVENT_TO_TYPE(EVENT_LATENCY, double);
-    MAP_EVENT_TO_TYPE(EVENT_WORK_TIME, int64_t);
-    MAP_EVENT_TO_TYPE(EVENT_WARMUP_TIME, double);
-    MAP_EVENT_TO_TYPE(EVENT_UNDERRUN, int64_t);
-    MAP_EVENT_TO_TYPE(EVENT_OVERRUN, int64_t);
-
-private:
-
-    // ---------------------------------------------------------------------------
-
-    // entry representation in memory
-    struct entry {
-        const uint8_t type;
-        const uint8_t length;
-        const uint8_t data[0];
-    };
-
-    // entry tail representation (after data)
-    struct ending {
-        uint8_t length;
-        uint8_t next[0];
-    };
-
-    // entry iterator
-    class EntryIterator {
-    public:
-        // Used for dummy initialization. Performing operations on a default-constructed
-        // EntryIterator other than assigning it to another valid EntryIterator
-        // is undefined behavior.
-        EntryIterator();
-        // Caller's responsibility to make sure entry is not nullptr.
-        // Passing in nullptr can result in undefined behavior.
-        explicit EntryIterator(const uint8_t *entry);
-        EntryIterator(const EntryIterator &other);
-
-        // dereference underlying entry
-        const entry&    operator*() const;
-        const entry*    operator->() const;
-        // advance to next entry
-        EntryIterator&       operator++(); // ++i
-        // back to previous entry
-        EntryIterator&       operator--(); // --i
-        // returns an EntryIterator corresponding to the next entry
-        EntryIterator        next() const;
-        // returns an EntryIterator corresponding to the previous entry
-        EntryIterator        prev() const;
-        bool            operator!=(const EntryIterator &other) const;
-        int             operator-(const EntryIterator &other) const;
-
-        bool            hasConsistentLength() const;
-        void            copyTo(std::unique_ptr<audio_utils_fifo_writer> &dst) const;
-        void            copyData(uint8_t *dst) const;
-
-        // memcpy preferred to reinterpret_cast to avoid potentially unsupported
-        // unaligned memory access.
-#if 0
-        template<typename T>
-        inline const T& payload() {
-            return *reinterpret_cast<const T *>(mPtr + offsetof(entry, data));
-        }
-#else
-        template<typename T>
-        inline T payload() const {
-            static_assert(std::is_trivially_copyable<T>::value
-                    && !std::is_pointer<T>::value,
-                    "NBLog::EntryIterator payload must be trivially copyable, non-pointer type.");
-            T payload;
-            memcpy(&payload, mPtr + offsetof(entry, data), sizeof(payload));
-            return payload;
-        }
-#endif
-
-        inline operator const uint8_t*() const {
-            return mPtr;
-        }
-
-    private:
-        const uint8_t  *mPtr;   // Should not be nullptr except for dummy initialization
-    };
-
-    // ---------------------------------------------------------------------------
-    // The following classes are used for merging into the Merger's buffer.
-
-    class AbstractEntry {
-    public:
-        virtual ~AbstractEntry() {}
-
-        // build concrete entry of appropriate class from ptr.
-        static std::unique_ptr<AbstractEntry> buildEntry(const uint8_t *ptr);
-
-        // get format entry timestamp
-        virtual int64_t      timestamp() const = 0;
-
-        // get format entry's unique id
-        virtual log_hash_t   hash() const = 0;
-
-        // entry's author index (-1 if none present)
-        // a Merger has a vector of Readers, author simply points to the index of the
-        // Reader that originated the entry
-        // TODO consider changing to uint32_t
-        virtual int          author() const = 0;
-
-        // copy entry, adding author before timestamp, returns iterator to end of entry
-        virtual EntryIterator    copyWithAuthor(std::unique_ptr<audio_utils_fifo_writer> &dst,
-                                                int author) const = 0;
-
-    protected:
-        // Entry starting in the given pointer, which shall not be nullptr.
-        explicit AbstractEntry(const uint8_t *entry);
-        // copies ordinary entry from src to dst, and returns length of entry
-        // size_t      copyEntry(audio_utils_fifo_writer *dst, const iterator &it);
-        const uint8_t  *mEntry;
-    };
-
-    // API for handling format entry operations
-
-    // a formatted entry has the following structure:
-    //    * FMT_START entry, containing the format string
-    //    * TIMESTAMP entry
-    //    * HASH entry
-    //    * author entry of the thread that generated it (optional, present in merged log)
-    //    * format arg1
-    //    * format arg2
-    //    * ...
-    //    * FMT_END entry
-    class FormatEntry : public AbstractEntry {
-    public:
-        // explicit FormatEntry(const EntryIterator &it);
-        explicit FormatEntry(const uint8_t *ptr) : AbstractEntry(ptr) {}
-        virtual ~FormatEntry() {}
-
-        EntryIterator begin() const;
-
-        // Entry's format string
-        const   char* formatString() const;
-
-        // Enrty's format string length
-        size_t      formatStringLength() const;
-
-        // Format arguments (excluding format string, timestamp and author)
-        EntryIterator    args() const;
-
-        // get format entry timestamp
-        virtual int64_t     timestamp() const override;
-
-        // get format entry's unique id
-        virtual log_hash_t  hash() const override;
-
-        // entry's author index (-1 if none present)
-        // a Merger has a vector of Readers, author simply points to the index of the
-        // Reader that originated the entry
-        virtual int         author() const override;
-
-        // copy entry, adding author before timestamp, returns size of original entry
-        virtual EntryIterator    copyWithAuthor(std::unique_ptr<audio_utils_fifo_writer> &dst,
-                                                int author) const override;
-    };
-
-    class HistogramEntry : public AbstractEntry {
-    public:
-        explicit HistogramEntry(const uint8_t *ptr) : AbstractEntry(ptr) {
-        }
-        virtual ~HistogramEntry() {}
-
-        virtual int64_t     timestamp() const override;
-
-        virtual log_hash_t  hash() const override;
-
-        virtual int         author() const override;
-
-        virtual EntryIterator    copyWithAuthor(std::unique_ptr<audio_utils_fifo_writer> &dst,
-                                                int author) const override;
-    };
-
-    // ---------------------------------------------------------------------------
-
-    // representation of a single log entry in shared memory
-    //  byte[0]             mEvent
-    //  byte[1]             mLength
-    //  byte[2]             mData[0]
-    //  ...
-    //  byte[2+i]           mData[i]
-    //  ...
-    //  byte[2+mLength-1]   mData[mLength-1]
-    //  byte[2+mLength]     duplicate copy of mLength to permit reverse scan
-    //  byte[3+mLength]     start of next log entry
-    class Entry {
-    public:
-        Entry(Event event, const void *data, size_t length)
-            : mEvent(event), mLength(length), mData(data) { }
-        /*virtual*/ ~Entry() { }
-
-        // used during writing to format Entry information as follows:
-        // [type][length][data ... ][length]
-        int     copyEntryDataAt(size_t offset) const;
-
-    private:
-        friend class Writer;
-        Event       mEvent;     // event type
-        uint8_t     mLength;    // length of additional data, 0 <= mLength <= kMaxLength
-        const void *mData;      // event type-specific data
-        static const size_t kMaxLength = 255;
-    public:
-        // mEvent, mLength, mData[...], duplicate mLength
-        static const size_t kOverhead = sizeof(entry) + sizeof(ending);
-        // endind length of previous entry
-        static const ssize_t kPreviousLengthOffset = - sizeof(ending) +
-            offsetof(ending, length);
-    };
-
-    // TODO move these somewhere else
-    struct HistTsEntry {
-        log_hash_t hash;
-        int64_t ts;
-    }; //TODO __attribute__((packed));
-
-    struct HistTsEntryWithAuthor {
-        log_hash_t hash;
-        int64_t ts;
-        int author;
-    }; //TODO __attribute__((packed));
-
-    struct HistIntEntry {
-        log_hash_t hash;
-        int value;
-    }; //TODO __attribute__((packed));
-
-public:
-
-    // Located in shared memory, must be POD.
-    // Exactly one process must explicitly call the constructor or use placement new.
-    // Since this is a POD, the destructor is empty and unnecessary to call it explicitly.
-    struct Shared {
-        Shared() /* mRear initialized via default constructor */ { }
-        /*virtual*/ ~Shared() { }
-
-        audio_utils_fifo_index  mRear;  // index one byte past the end of most recent Entry
-        char    mBuffer[0];             // circular buffer for entries
-    };
-
-public:
-
-    // ---------------------------------------------------------------------------
-
-    // FIXME Timeline was intended to wrap Writer and Reader, but isn't actually used yet.
-    // For now it is just a namespace for sharedSize().
-    class Timeline : public RefBase {
-    public:
-#if 0
-        Timeline(size_t size, void *shared = NULL);
-        virtual ~Timeline();
-#endif
-
-        // Input parameter 'size' is the desired size of the timeline in byte units.
-        // Returns the size rounded up to a power-of-2, plus the constant size overhead for indices.
-        static size_t sharedSize(size_t size);
-
-#if 0
-    private:
-        friend class    Writer;
-        friend class    Reader;
-
-        const size_t    mSize;      // circular buffer size in bytes, must be a power of 2
-        bool            mOwn;       // whether I own the memory at mShared
-        Shared* const   mShared;    // pointer to shared memory
-#endif
-    };
-
-    // ---------------------------------------------------------------------------
-    // NBLog Writer API
-    // ---------------------------------------------------------------------------
-
-    // Writer is thread-safe with respect to Reader, but not with respect to multiple threads
-    // calling Writer methods.  If you need multi-thread safety for writing, use LockedWriter.
-    class Writer : public RefBase {
-    public:
-        Writer();                   // dummy nop implementation without shared memory
-
-        // Input parameter 'size' is the desired size of the timeline in byte units.
-        // The size of the shared memory must be at least Timeline::sharedSize(size).
-        Writer(void *shared, size_t size);
-        Writer(const sp<IMemory>& iMemory, size_t size);
-
-        virtual ~Writer();
-
-        // FIXME needs comments, and some should be private
-        void    log(const char *string);
-        void    logf(const char *fmt, ...) __attribute__ ((format (printf, 2, 3)));
-        void    logTimestamp();
-        void    logFormat(const char *fmt, log_hash_t hash, ...);
-        void    logEventHistTs(Event event, log_hash_t hash);
-
-        // Log data related to Event E. See the event-to-type mapping for the type of data
-        // corresponding to the event. For example, if you see a mapping statement:
-        //     MAP_TYPE_TO_EVENT(E, T);
-        // then the usage of this method would be:
-        //     T data = doComputation();
-        //     tlNBLogWriter->log<NBLog::E>(data);
-        template<Event E>
-        void    log(typename get_mapped<E>::type data) {
-            log(E, &data, sizeof(data));
-        }
-
-        virtual bool    isEnabled() const;
-
-        // return value for all of these is the previous isEnabled()
-        virtual bool    setEnabled(bool enabled);   // but won't enable if no shared memory
-        bool    enable()    { return setEnabled(true); }
-        bool    disable()   { return setEnabled(false); }
-
-        sp<IMemory>     getIMemory() const  { return mIMemory; }
-
-        // Public logging function implementations should always use one of the
-        // two log() function calls below to write to shared memory.
-    protected:
-        // Writes a single Entry to the FIFO if the writer is enabled.
-        // This is protected and virtual because LockedWriter uses a lock to protect
-        // writing to the FIFO before writing to this function.
-        virtual void log(const Entry &entry, bool trusted = false);
-
-    private:
-        // 0 <= length <= kMaxLength
-        // Log a single Entry with corresponding event, data, and length.
-        void    log(Event event, const void *data, size_t length);
-
-        void    logvf(const char *fmt, va_list ap);
-
-        // helper functions for logging parts of a formatted entry
-        void    logStart(const char *fmt);
-        void    logTimestampFormat();
-        void    logVFormat(const char *fmt, log_hash_t hash, va_list ap);
-
-        Shared* const   mShared;    // raw pointer to shared memory
-        sp<IMemory>     mIMemory;   // ref-counted version, initialized in constructor
-                                    // and then const
-        audio_utils_fifo * const mFifo;                 // FIFO itself, non-NULL
-                                                        // unless constructor fails
-        audio_utils_fifo_writer * const mFifoWriter;    // used to write to FIFO, non-NULL
-                                                        // unless dummy constructor used
-        bool            mEnabled;   // whether to actually log
-
-        // cached pid and process name to use in %p format specifier
-        // total tag length is mPidTagSize and process name is not zero terminated
-        char   *mPidTag;
-        size_t  mPidTagSize;
-    };
-
-    // ---------------------------------------------------------------------------
-
-    // Similar to Writer, but safe for multiple threads to call concurrently
-    class LockedWriter : public Writer {
-    public:
-        LockedWriter();
-        LockedWriter(void *shared, size_t size);
-
-        bool    isEnabled() const override;
-        bool    setEnabled(bool enabled) override;
-
-    private:
-        // Lock needs to be obtained before writing to FIFO.
-        void log(const Entry &entry, bool trusted = false) override;
-        mutable Mutex   mLock;
-    };
-
-    // ---------------------------------------------------------------------------
-    // NBLog Reader API
-    // ---------------------------------------------------------------------------
-
-    class Snapshot;     // Forward declaration needed for Reader::getSnapshot()
-
-    class Reader : public RefBase {
-    public:
-        // Input parameter 'size' is the desired size of the timeline in byte units.
-        // The size of the shared memory must be at least Timeline::sharedSize(size).
-        Reader(const void *shared, size_t size, const std::string &name);
-        Reader(const sp<IMemory>& iMemory, size_t size, const std::string &name);
-        virtual ~Reader();
-
-        // get snapshot of readers fifo buffer, effectively consuming the buffer
-        std::unique_ptr<Snapshot> getSnapshot();
-        bool     isIMemory(const sp<IMemory>& iMemory) const;
-        const std::string &name() const { return mName; }
-
-    private:
-        // Amount of tries for reader to catch up with writer in getSnapshot().
-        static constexpr int kMaxObtainTries = 3;
-
-        // invalidBeginTypes and invalidEndTypes are used to align the Snapshot::begin() and
-        // Snapshot::end() EntryIterators to valid entries.
-        static const std::unordered_set<Event> invalidBeginTypes;
-        static const std::unordered_set<Event> invalidEndTypes;
-
-        // declared as const because audio_utils_fifo() constructor
-        sp<IMemory> mIMemory;       // ref-counted version, assigned only in constructor
-
-        const std::string mName;            // name of reader (actually name of writer)
-        /*const*/ Shared* const mShared;    // raw pointer to shared memory, actually const but not
-        audio_utils_fifo * const mFifo;                 // FIFO itself,
-                                                        // non-NULL unless constructor fails
-        audio_utils_fifo_reader * const mFifoReader;    // used to read from FIFO,
-                                                        // non-NULL unless constructor fails
-
-        // Searches for the last valid entry in the range [front, back)
-        // back has to be entry-aligned. Returns nullptr if none enconuntered.
-        static const uint8_t *findLastValidEntry(const uint8_t *front, const uint8_t *back,
-                                                   const std::unordered_set<Event> &invalidTypes);
-    };
-
-    // A snapshot of a readers buffer
-    // This is raw data. No analysis has been done on it
-    class Snapshot {
-    public:
-        ~Snapshot() { delete[] mData; }
-
-        // amount of data lost (given by audio_utils_fifo_reader)
-        size_t   lost() const { return mLost; }
-
-        // iterator to beginning of readable segment of snapshot
-        // data between begin and end has valid entries
-        EntryIterator begin() const { return mBegin; }
-
-        // iterator to end of readable segment of snapshot
-        EntryIterator end() const { return mEnd; }
-
-    private:
-        Snapshot() = default;
-        explicit Snapshot(size_t bufferSize) : mData(new uint8_t[bufferSize]) {}
-        friend std::unique_ptr<Snapshot> Reader::getSnapshot();
-        uint8_t * const       mData = nullptr;
-        size_t                mLost = 0;
-        EntryIterator mBegin;
-        EntryIterator mEnd;
-    };
-
-    // TODO move this to MediaLogService?
-    class DumpReader : public Reader {
-    public:
-        DumpReader(const void *shared, size_t size, const std::string &name)
-            : Reader(shared, size, name) {}
-        DumpReader(const sp<IMemory>& iMemory, size_t size, const std::string &name)
-            : Reader(iMemory, size, name) {}
-        void dump(int fd, size_t indent = 0);
-    private:
-        void handleAuthor(const AbstractEntry& fmtEntry __unused, String8* body __unused) {}
-        EntryIterator handleFormat(const FormatEntry &fmtEntry, String8 *timestamp, String8 *body);
-
-        static void    appendInt(String8 *body, const void *data);
-        static void    appendFloat(String8 *body, const void *data);
-        static void    appendPID(String8 *body, const void *data, size_t length);
-        static void    appendTimestamp(String8 *body, const void *data);
-
-        // The bufferDump functions are used for debugging only.
-        static String8 bufferDump(const uint8_t *buffer, size_t size);
-        static String8 bufferDump(const EntryIterator &it);
-    };
-
-    // ---------------------------------------------------------------------------
-    // TODO move Merger, MergeReader, and MergeThread to a separate file.
-
-    // This class is used to read data from each thread's individual FIFO in shared memory
-    // and write it to a single FIFO in local memory.
-    class Merger : public RefBase {
-    public:
-        Merger(const void *shared, size_t size);
-
-        virtual ~Merger() {}
-
-        void addReader(const sp<NBLog::Reader> &reader);
-        // TODO add removeReader
-        void merge();
-
-        // FIXME This is returning a reference to a shared variable that needs a lock
-        const std::vector<sp<Reader>>& getReaders() const;
-
-    private:
-        // vector of the readers the merger is supposed to merge from.
-        // every reader reads from a writer's buffer
-        // FIXME Needs to be protected by a lock
-        std::vector<sp<Reader>> mReaders;
-
-        Shared * const mShared; // raw pointer to shared memory
-        std::unique_ptr<audio_utils_fifo> mFifo; // FIFO itself
-        std::unique_ptr<audio_utils_fifo_writer> mFifoWriter; // used to write to FIFO
-    };
-
-    // This class has a pointer to the FIFO in local memory which stores the merged
-    // data collected by NBLog::Merger from all Readers. It is used to process
-    // this data and write the result to PerformanceAnalysis.
-    class MergeReader : public Reader {
-    public:
-        MergeReader(const void *shared, size_t size, Merger &merger);
-
-        void dump(int fd, int indent = 0);
-
-        // process a particular snapshot of the reader
-        void processSnapshot(Snapshot &snap, int author);
-
-        // call getSnapshot of the content of the reader's buffer and process the data
-        void getAndProcessSnapshot();
-
-        // check for periodic push of performance data to media metrics, and perform
-        // the send if it is time to do so.
-        void checkPushToMediaMetrics();
-
-    private:
-        // FIXME Needs to be protected by a lock,
-        //       because even though our use of it is read-only there may be asynchronous updates
-        // The object is owned by the Merger class.
-        const std::vector<sp<Reader>>& mReaders;
-
-        // analyzes, compresses and stores the merged data
-        // contains a separate instance for every author (thread), and for every source file
-        // location within each author
-        ReportPerformance::PerformanceAnalysisMap mThreadPerformanceAnalysis;
-
-        // compresses and stores audio performance data from each thread's buffers.
-        // first parameter is author, i.e. thread index.
-        std::map<int, ReportPerformance::PerformanceData> mThreadPerformanceData;
-
-        // how often to push data to Media Metrics
-        static constexpr nsecs_t kPeriodicMediaMetricsPush = s2ns((nsecs_t)2 * 60 * 60); // 2 hours
-
-        // handle author entry by looking up the author's name and appending it to the body
-        // returns number of bytes read from fmtEntry
-        void handleAuthor(const AbstractEntry &fmtEntry, String8 *body);
-    };
-
-    // MergeThread is a thread that contains a Merger. It works as a retriggerable one-shot:
-    // when triggered, it awakes for a lapse of time, during which it periodically merges; if
-    // retriggered, the timeout is reset.
-    // The thread is triggered on AudioFlinger binder activity.
-    class MergeThread : public Thread {
-    public:
-        MergeThread(Merger &merger, MergeReader &mergeReader);
-        virtual ~MergeThread() override;
-
-        // Reset timeout and activate thread to merge periodically if it's idle
-        void wakeup();
-
-        // Set timeout period until the merging thread goes idle again
-        void setTimeoutUs(int time);
-
-    private:
-        virtual bool threadLoop() override;
-
-        // the merger who actually does the work of merging the logs
-        Merger&     mMerger;
-
-        // the mergereader used to process data merged by mMerger
-        MergeReader& mMergeReader;
-
-        // mutex for the condition variable
-        Mutex       mMutex;
-
-        // condition variable to activate merging on timeout >= 0
-        Condition   mCond;
-
-        // time left until the thread blocks again (in microseconds)
-        int         mTimeoutUs;
-
-        // merging period when the thread is awake
-        static const int  kThreadSleepPeriodUs = 1000000 /*1s*/;
-
-        // initial timeout value when triggered
-        static const int  kThreadWakeupPeriodUs = 3000000 /*3s*/;
-    };
-
-};  // class NBLog
-
-}   // namespace android
+#include <media/nblog/Entry.h>
+#include <media/nblog/Events.h>
+#include <media/nblog/Reader.h>
+#include <media/nblog/Timeline.h>
+#include <media/nblog/Writer.h>
 
 #endif  // ANDROID_MEDIA_NBLOG_H
diff --git a/media/libnblog/include/media/nblog/PerformanceAnalysis.h b/media/libnblog/include/media/nblog/PerformanceAnalysis.h
index 6893fee..983b28a 100644
--- a/media/libnblog/include/media/nblog/PerformanceAnalysis.h
+++ b/media/libnblog/include/media/nblog/PerformanceAnalysis.h
@@ -22,6 +22,7 @@
 #include <utility>
 #include <vector>
 
+#include <media/nblog/Events.h>
 #include <media/nblog/ReportPerformance.h>
 #include <utils/Timers.h>
 
@@ -142,11 +143,9 @@
     static constexpr Histogram::Config kWarmupConfig = { 5., 10, 10.};
 
     // Thread Info
-    // TODO make type an enum
-    int type = -1;              // Thread type: 0 for MIXER, 1 for CAPTURE,
-                                // 2 for FASTMIXER, 3 for FASTCAPTURE
-    size_t frameCount = 0;
-    unsigned sampleRate = 0;
+    NBLog::thread_info_t threadInfo{
+        NBLog::UNKNOWN /*threadType*/, 0 /*frameCount*/, 0 /*sampleRate*/
+    };
 
     // Performance Data
     Histogram workHist{kWorkConfig};
@@ -265,8 +264,7 @@
 void dump(int fd, int indent, PerformanceAnalysisMap &threadPerformanceAnalysis);
 void dumpLine(int fd, int indent, const String8 &body);
 
-} // namespace ReportPerformance
-
+}   // namespace ReportPerformance
 }   // namespace android
 
 #endif  // ANDROID_MEDIA_PERFORMANCEANALYSIS_H
diff --git a/media/libnblog/include/media/nblog/Reader.h b/media/libnblog/include/media/nblog/Reader.h
new file mode 100644
index 0000000..bf1c321
--- /dev/null
+++ b/media/libnblog/include/media/nblog/Reader.h
@@ -0,0 +1,135 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef ANDROID_MEDIA_NBLOG_READER_H
+#define ANDROID_MEDIA_NBLOG_READER_H
+
+#include <memory>
+#include <stddef.h>
+#include <string>
+#include <unordered_set>
+
+#include <media/nblog/Entry.h>
+#include <media/nblog/Events.h>
+#include <utils/RefBase.h>
+
+class audio_utils_fifo;
+class audio_utils_fifo_reader;
+
+namespace android {
+
+class IMemory;
+class String8;
+
+namespace NBLog {
+
+struct Shared;
+
+// NBLog Reader API
+
+class Snapshot;     // Forward declaration needed for Reader::getSnapshot()
+
+class Reader : public RefBase {
+public:
+    // Input parameter 'size' is the desired size of the timeline in byte units.
+    // The size of the shared memory must be at least Timeline::sharedSize(size).
+    Reader(const void *shared, size_t size, const std::string &name);
+    Reader(const sp<IMemory>& iMemory, size_t size, const std::string &name);
+    ~Reader() override;
+
+    // get snapshot of readers fifo buffer, effectively consuming the buffer
+    std::unique_ptr<Snapshot> getSnapshot();
+    bool     isIMemory(const sp<IMemory>& iMemory) const;
+    const std::string &name() const { return mName; }
+
+private:
+    // Amount of tries for reader to catch up with writer in getSnapshot().
+    static constexpr int kMaxObtainTries = 3;
+
+    // invalidBeginTypes and invalidEndTypes are used to align the Snapshot::begin() and
+    // Snapshot::end() EntryIterators to valid entries.
+    static const std::unordered_set<Event> invalidBeginTypes;
+    static const std::unordered_set<Event> invalidEndTypes;
+
+    // declared as const because audio_utils_fifo() constructor
+    sp<IMemory> mIMemory;       // ref-counted version, assigned only in constructor
+
+    const std::string mName;            // name of reader (actually name of writer)
+    /*const*/ Shared* const mShared;    // raw pointer to shared memory, actually const but not
+    audio_utils_fifo * const mFifo;                 // FIFO itself,
+                                                    // non-NULL unless constructor fails
+    audio_utils_fifo_reader * const mFifoReader;    // used to read from FIFO,
+                                                    // non-NULL unless constructor fails
+
+    // Searches for the last valid entry in the range [front, back)
+    // back has to be entry-aligned. Returns nullptr if none enconuntered.
+    static const uint8_t *findLastValidEntry(const uint8_t *front, const uint8_t *back,
+                                               const std::unordered_set<Event> &invalidTypes);
+};
+
+// A snapshot of a readers buffer
+// This is raw data. No analysis has been done on it
+class Snapshot {
+public:
+    ~Snapshot() { delete[] mData; }
+
+    // amount of data lost (given by audio_utils_fifo_reader)
+    size_t lost() const { return mLost; }
+
+    // iterator to beginning of readable segment of snapshot
+    // data between begin and end has valid entries
+    EntryIterator begin() const { return mBegin; }
+
+    // iterator to end of readable segment of snapshot
+    EntryIterator end() const { return mEnd; }
+
+private:
+    Snapshot() = default;
+    explicit Snapshot(size_t bufferSize) : mData(new uint8_t[bufferSize]) {}
+    friend std::unique_ptr<Snapshot> Reader::getSnapshot();
+
+    uint8_t * const       mData = nullptr;
+    size_t                mLost = 0;
+    EntryIterator         mBegin;
+    EntryIterator         mEnd;
+};
+
+// TODO move this to MediaLogService?
+class DumpReader : public NBLog::Reader {
+public:
+    DumpReader(const void *shared, size_t size, const std::string &name)
+        : Reader(shared, size, name) {}
+    DumpReader(const sp<IMemory>& iMemory, size_t size, const std::string &name)
+        : Reader(iMemory, size, name) {}
+    void dump(int fd, size_t indent = 0);
+private:
+    void handleAuthor(const AbstractEntry& fmtEntry __unused, String8* body __unused) {}
+    EntryIterator handleFormat(const FormatEntry &fmtEntry, String8 *timestamp, String8 *body);
+
+    static void    appendInt(String8 *body, const void *data);
+    static void    appendFloat(String8 *body, const void *data);
+    static void    appendPID(String8 *body, const void *data, size_t length);
+    static void    appendTimestamp(String8 *body, const void *data);
+
+    // The bufferDump functions are used for debugging only.
+    static String8 bufferDump(const uint8_t *buffer, size_t size);
+    static String8 bufferDump(const EntryIterator &it);
+};
+
+}   // namespace NBLog
+}   // namespace android
+
+#endif  // ANDROID_MEDIA_NBLOG_READER_H
diff --git a/media/libnblog/include/media/nblog/ReportPerformance.h b/media/libnblog/include/media/nblog/ReportPerformance.h
index 09bb2a0..b69ed3b 100644
--- a/media/libnblog/include/media/nblog/ReportPerformance.h
+++ b/media/libnblog/include/media/nblog/ReportPerformance.h
@@ -27,7 +27,6 @@
 }
 
 namespace android {
-
 namespace ReportPerformance {
 
 struct PerformanceData;
@@ -78,8 +77,7 @@
                  const std::deque<timestamp> &peakTimestamps,
                  const char * kDirectory, bool append, int author, log_hash_t hash);
 
-} // namespace ReportPerformance
-
+}   // namespace ReportPerformance
 }   // namespace android
 
 #endif  // ANDROID_MEDIA_REPORTPERFORMANCE_H
diff --git a/media/libnblog/include/media/nblog/Timeline.h b/media/libnblog/include/media/nblog/Timeline.h
new file mode 100644
index 0000000..d4f0cff
--- /dev/null
+++ b/media/libnblog/include/media/nblog/Timeline.h
@@ -0,0 +1,66 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef ANDROID_MEDIA_NBLOG_TIMELINE_H
+#define ANDROID_MEDIA_NBLOG_TIMELINE_H
+
+#include <stddef.h>
+
+#include <audio_utils/fifo_index.h>
+#include <utils/RefBase.h>
+
+namespace android {
+namespace NBLog {
+
+// Located in shared memory, must be POD.
+// Exactly one process must explicitly call the constructor or use placement new.
+// Since this is a POD, the destructor is empty and unnecessary to call it explicitly.
+struct Shared {
+    Shared() /* mRear initialized via default constructor */ {}
+    ~Shared() {}
+
+    audio_utils_fifo_index  mRear;  // index one byte past the end of most recent Entry
+    char    mBuffer[0];             // circular buffer for entries
+};
+
+// FIXME Timeline was intended to wrap Writer and Reader, but isn't actually used yet.
+// For now it is just a namespace for sharedSize().
+class Timeline : public RefBase {
+public:
+#if 0
+    Timeline(size_t size, void *shared = NULL);
+    virtual ~Timeline();
+#endif
+
+    // Input parameter 'size' is the desired size of the timeline in byte units.
+    // Returns the size rounded up to a power-of-2, plus the constant size overhead for indices.
+    static size_t sharedSize(size_t size);
+
+#if 0
+private:
+    friend class    Writer;
+    friend class    Reader;
+
+    const size_t    mSize;      // circular buffer size in bytes, must be a power of 2
+    bool            mOwn;       // whether I own the memory at mShared
+    Shared* const   mShared;    // pointer to shared memory
+#endif
+};
+
+}   // namespace NBLog
+}   // namespace android
+
+#endif  // ANDROID_MEDIA_NBLOG_TIMELINE_H
diff --git a/media/libnblog/include/media/nblog/Writer.h b/media/libnblog/include/media/nblog/Writer.h
new file mode 100644
index 0000000..7fcd396
--- /dev/null
+++ b/media/libnblog/include/media/nblog/Writer.h
@@ -0,0 +1,139 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef ANDROID_MEDIA_NBLOG_WRITER_H
+#define ANDROID_MEDIA_NBLOG_WRITER_H
+
+#include <stdarg.h>
+#include <stddef.h>
+
+#include <binder/IMemory.h>
+#include <media/nblog/Events.h>
+#include <utils/Mutex.h>
+#include <utils/RefBase.h>
+
+class audio_utils_fifo;
+class audio_utils_fifo_writer;
+
+namespace android {
+
+class IMemory;
+
+namespace NBLog {
+
+class Entry;
+struct Shared;
+
+// NBLog Writer Interface
+
+// Writer is thread-safe with respect to Reader, but not with respect to multiple threads
+// calling Writer methods.  If you need multi-thread safety for writing, use LockedWriter.
+class Writer : public RefBase {
+public:
+    Writer() = default;         // dummy nop implementation without shared memory
+
+    // Input parameter 'size' is the desired size of the timeline in byte units.
+    // The size of the shared memory must be at least Timeline::sharedSize(size).
+    Writer(void *shared, size_t size);
+    Writer(const sp<IMemory>& iMemory, size_t size);
+
+    ~Writer() override;
+
+    // FIXME needs comments, and some should be private
+    void    log(const char *string);
+    void    logf(const char *fmt, ...) __attribute__ ((format (printf, 2, 3)));
+    void    logTimestamp();
+    void    logFormat(const char *fmt, log_hash_t hash, ...);
+    void    logEventHistTs(Event event, log_hash_t hash);
+
+    // Log data related to Event E. See the event-to-type mapping for the type of data
+    // corresponding to the event. For example, if you see a mapping statement:
+    //     MAP_TYPE_TO_EVENT(E, T);
+    // then the usage of this method would be:
+    //     T data = doComputation();
+    //     tlNBLogWriter->log<NBLog::E>(data);
+    template<Event E>
+    void    log(typename get_mapped<E>::type data) {
+        log(E, &data, sizeof(data));
+    }
+
+    virtual bool    isEnabled() const;
+
+    // return value for all of these is the previous isEnabled()
+    virtual bool    setEnabled(bool enabled);   // but won't enable if no shared memory
+    bool            enable()  { return setEnabled(true); }
+    bool            disable() { return setEnabled(false); }
+
+    sp<IMemory>     getIMemory() const { return mIMemory; }
+
+    // Public logging function implementations should always use one of the
+    // two log() function calls below to write to shared memory.
+protected:
+    // Writes a single Entry to the FIFO if the writer is enabled.
+    // This is protected and virtual because LockedWriter uses a lock to protect
+    // writing to the FIFO before writing to this function.
+    virtual void log(const Entry &entry, bool trusted = false);
+
+private:
+    // 0 <= length <= kMaxLength
+    // Log a single Entry with corresponding event, data, and length.
+    void    log(Event event, const void *data, size_t length);
+
+    void    logvf(const char *fmt, va_list ap);
+
+    // helper functions for logging parts of a formatted entry
+    void    logStart(const char *fmt);
+    void    logTimestampFormat();
+    void    logVFormat(const char *fmt, log_hash_t hash, va_list ap);
+
+    Shared* const   mShared{};          // raw pointer to shared memory
+    sp<IMemory>     mIMemory{};         // ref-counted version, initialized in constructor
+                                        // and then const
+    audio_utils_fifo * const mFifo{};               // FIFO itself, non-NULL
+                                                    // unless constructor fails
+                                                    // or dummy constructor used
+    audio_utils_fifo_writer * const mFifoWriter{};  // used to write to FIFO, non-NULL
+                                                    // unless dummy constructor used
+    bool            mEnabled = false;   // whether to actually log
+
+    // cached pid and process name to use in %p format specifier
+    // total tag length is mPidTagSize and process name is not zero terminated
+    char   *mPidTag{};
+    size_t  mPidTagSize = 0;
+};
+
+// ---------------------------------------------------------------------------
+
+// Similar to Writer, but safe for multiple threads to call concurrently
+class LockedWriter : public Writer {
+public:
+    LockedWriter() = default;
+    LockedWriter(void *shared, size_t size);
+
+    bool    isEnabled() const override;
+    bool    setEnabled(bool enabled) override;
+
+private:
+    // Lock needs to be obtained before writing to FIFO.
+    void log(const Entry &entry, bool trusted = false) override;
+
+    mutable Mutex   mLock;
+};
+
+}   // namespace NBLog
+}   // namespace android
+
+#endif  // ANDROID_MEDIA_NBLOG_WRITER_H
diff --git a/services/audioflinger/FastMixer.cpp b/services/audioflinger/FastMixer.cpp
index f650b66..d7b7fe8 100644
--- a/services/audioflinger/FastMixer.cpp
+++ b/services/audioflinger/FastMixer.cpp
@@ -195,8 +195,7 @@
             //       to avoid blocking here and to prevent possible priority inversion
             mMixer = new AudioMixer(frameCount, mSampleRate);
             // FIXME See the other FIXME at FastMixer::setNBLogWriter()
-            // TODO define an int to thread type mapping for the "2" below.
-            const NBLog::thread_info_t info = { 2 /*FastMixer*/, frameCount, mSampleRate };
+            const NBLog::thread_info_t info = { NBLog::FASTMIXER, frameCount, mSampleRate };
             LOG_THREAD_INFO(info);
             const size_t mixerFrameSize = mSinkChannelCount
                     * audio_bytes_per_sample(mMixerBufferFormat);
diff --git a/services/medialog/MediaLogService.cpp b/services/medialog/MediaLogService.cpp
index b23832e..0598ce7 100644
--- a/services/medialog/MediaLogService.cpp
+++ b/services/medialog/MediaLogService.cpp
@@ -20,6 +20,7 @@
 #include <sys/mman.h>
 #include <utils/Log.h>
 #include <binder/PermissionCache.h>
+#include <media/nblog/Merger.h>
 #include <media/nblog/NBLog.h>
 #include <mediautils/ServiceUtilities.h>
 #include "MediaLogService.h"
diff --git a/services/medialog/MediaLogService.h b/services/medialog/MediaLogService.h
index a1572f9..21df898 100644
--- a/services/medialog/MediaLogService.h
+++ b/services/medialog/MediaLogService.h
@@ -19,6 +19,7 @@
 
 #include <binder/BinderService.h>
 #include <media/IMediaLogService.h>
+#include <media/nblog/Merger.h>
 #include <media/nblog/NBLog.h>
 
 namespace android {