C-ify DataSource

Add a C API for DataSource/Base, and a helper so extractors
can continue using a C++ API.

Bug: 111407253
Test: build, boot, play some files

Change-Id: I1c8b2990e17d18eee53c9abf7ebef2ced0e8b7fd
diff --git a/media/libmedia/MidiIoWrapper.cpp b/media/libmedia/MidiIoWrapper.cpp
index 5ca3b48..1150d61 100644
--- a/media/libmedia/MidiIoWrapper.cpp
+++ b/media/libmedia/MidiIoWrapper.cpp
@@ -23,6 +23,7 @@
 #include <fcntl.h>
 
 #include <media/MidiIoWrapper.h>
+#include <media/MediaExtractorPluginApi.h>
 
 static int readAt(void *handle, void *buffer, int pos, int size) {
     return ((android::MidiIoWrapper*)handle)->readAt(buffer, pos, size);
@@ -61,6 +62,51 @@
     }
 }
 
+class DataSourceUnwrapper : public DataSourceBase {
+
+public:
+    explicit DataSourceUnwrapper(CDataSource *csource) {
+        mSource = csource;
+    }
+    virtual status_t initCheck() const { return OK; }
+
+    // Returns the number of bytes read, or -1 on failure. It's not an error if
+    // this returns zero; it just means the given offset is equal to, or
+    // beyond, the end of the source.
+    virtual ssize_t readAt(off64_t offset, void *data, size_t size) {
+        return mSource->readAt(mSource->handle, offset, data, size);
+    }
+
+    // May return ERROR_UNSUPPORTED.
+    virtual status_t getSize(off64_t *size) {
+        return mSource->getSize(mSource->handle, size);
+    }
+
+    virtual bool getUri(char * /*uriString*/, size_t /*bufferSize*/) {
+        return false;
+    }
+
+    virtual uint32_t flags() {
+        return 0;
+    }
+
+    virtual void close() {};
+private:
+    CDataSource *mSource;
+};
+
+MidiIoWrapper::MidiIoWrapper(CDataSource *csource) {
+    ALOGV("MidiIoWrapper(CDataSource)");
+    mFd = -1;
+    mDataSource = new DataSourceUnwrapper(csource);
+    off64_t l;
+    if (mDataSource->getSize(&l) == OK) {
+        mLength = l;
+    } else {
+        mLength = 0;
+    }
+}
+
 MidiIoWrapper::~MidiIoWrapper() {
     ALOGV("~MidiIoWrapper");
     if (mFd >= 0) {