Add template class StateQueue
Change-Id: Iccc5eb42bc295a22b2e429a4551f083cd7b6831a
diff --git a/services/audioflinger/StateQueue.cpp b/services/audioflinger/StateQueue.cpp
new file mode 100644
index 0000000..ae263f5
--- /dev/null
+++ b/services/audioflinger/StateQueue.cpp
@@ -0,0 +1,133 @@
+/*
+ * Copyright (C) 2012 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 "StateQueue"
+//#define LOG_NDEBUG 0
+
+#include <time.h>
+#include <cutils/atomic.h>
+#include <utils/Log.h>
+#include "StateQueue.h"
+
+namespace android {
+
+// Constructor and destructor
+
+template<typename T> StateQueue<T>::StateQueue() :
+ mNext(NULL), mAck(NULL), mCurrent(NULL),
+ mMutating(&mStates[0]), mExpecting(NULL),
+ mInMutation(false), mIsDirty(false), mIsInitialized(false)
+{
+}
+
+template<typename T> StateQueue<T>::~StateQueue()
+{
+}
+
+// Observer APIs
+
+template<typename T> const T* StateQueue<T>::poll()
+{
+ const T *next = (const T *) android_atomic_acquire_load((volatile int32_t *) &mNext);
+ if (next != mCurrent) {
+ mAck = next; // no additional barrier needed
+ mCurrent = next;
+ }
+ return next;
+}
+
+// Mutator APIs
+
+template<typename T> T* StateQueue<T>::begin()
+{
+ ALOG_ASSERT(!mInMutation, "begin() called when in a mutation");
+ mInMutation = true;
+ return mMutating;
+}
+
+template<typename T> void StateQueue<T>::end(bool didModify)
+{
+ ALOG_ASSERT(mInMutation, "end() called when not in a mutation");
+ ALOG_ASSERT(mIsInitialized || didModify, "first end() must modify for initialization");
+ if (didModify) {
+ mIsDirty = true;
+ mIsInitialized = true;
+ }
+ mInMutation = false;
+}
+
+template<typename T> bool StateQueue<T>::push(StateQueue<T>::block_t block)
+{
+#define PUSH_BLOCK_ACK_NS 3000000L // 3 ms: time between checks for ack in push()
+ // FIXME should be configurable
+ static const struct timespec req = {0, PUSH_BLOCK_ACK_NS};
+
+ ALOG_ASSERT(!mInMutation, "push() called when in a mutation");
+
+ if (mIsDirty) {
+
+ // wait for prior push to be acknowledged
+ if (mExpecting != NULL) {
+ for (;;) {
+ const T *ack = (const T *) mAck; // no additional barrier needed
+ if (ack == mExpecting) {
+ // unnecessary as we're about to rewrite
+ //mExpecting = NULL;
+ break;
+ }
+ if (block == BLOCK_NEVER) {
+ return false;
+ }
+ nanosleep(&req, NULL);
+ }
+ }
+
+ // publish
+ android_atomic_release_store((int32_t) mMutating, (volatile int32_t *) &mNext);
+ mExpecting = mMutating;
+
+ // copy with circular wraparound
+ if (++mMutating >= &mStates[kN]) {
+ mMutating = &mStates[0];
+ }
+ *mMutating = *mExpecting;
+ mIsDirty = false;
+
+ }
+
+ // optionally wait for this push or a prior push to be acknowledged
+ if (block == BLOCK_UNTIL_ACKED) {
+ if (mExpecting != NULL) {
+ for (;;) {
+ const T *ack = (const T *) mAck; // no additional barrier needed
+ if (ack == mExpecting) {
+ mExpecting = NULL;
+ break;
+ }
+ nanosleep(&req, NULL);
+ }
+ }
+ }
+
+ return true;
+}
+
+} // namespace android
+
+// hack for gcc
+#ifdef STATE_QUEUE_INSTANTIATIONS
+#include STATE_QUEUE_INSTANTIATIONS
+#endif