Motown: ffmpeg implementations of framework 'parts'

services/media/framework_ffmpeg/ffmpeg_io.cc

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/logging.h"
+#include "services/media/framework/parts/reader.h"
+#include "services/media/framework_ffmpeg/ffmpeg_init.h"
+#include "services/media/framework_ffmpeg/ffmpeg_io.h"
+extern "C" {
+#include "third_party/ffmpeg/libavformat/avio.h"
+}
+
+namespace mojo {
+namespace media {
+
+static int AvioRead(void* opaque, uint8_t* buf, int buf_size);
+static int64_t AvioSeek(void* opaque, int64_t offset, int whence);
+
+AvioContextPtr CreateAvioContext(Reader* reader) {
+  // Internal buffer size used by AVIO for reading.
+  const int kBufferSize = 32 * 1024;
+
+  InitFfmpeg();
+
+  AVIOContext* result = avio_alloc_context(
+      static_cast<unsigned char*>(av_malloc(kBufferSize)),
+      kBufferSize,
+      0, // write_flag
+      reader, // opaque
+      &AvioRead,
+      nullptr,
+      &AvioSeek);
+
+  // Ensure FFmpeg only tries to seek when we know how.
+  result->seekable = reader->CanSeek() ? AVIO_SEEKABLE_NORMAL : 0;
+
+  // Ensure writing is disabled.
+  result->write_flag = 0;
+
+  return AvioContextPtr(result);
+}
+
+// Performs a read operation using the signature required for avio.
+static int AvioRead(void* opaque, uint8_t* buf, int buf_size) {
+  Reader* reader = reinterpret_cast<Reader*>(opaque);
+  int result = reader->Read(buf, buf_size);
+  if (result < 0) {
+    result = AVERROR(EIO);
+  }
+  return result;
+}
+
+// Performs a seek operation using the signature required for avio.
+static int64_t AvioSeek(void* opaque, int64_t offset, int whence) {
+  Reader* reader = reinterpret_cast<Reader*>(opaque);
+
+  if (whence == AVSEEK_SIZE) {
+    int64_t result = reader->GetSize();
+    if (result == -1) {
+      return AVERROR(EIO);
+    }
+    return result;
+  }
+
+  int64_t base;
+  switch (whence) {
+    case SEEK_SET:
+      base = 0;
+      break;
+
+    case SEEK_CUR:
+      base = reader->GetPosition();
+      if (base == -1) {
+        return AVERROR(EIO);
+      }
+      break;
+
+    case SEEK_END:
+      base = reader->GetSize();
+      if (base == -1) {
+        return AVERROR(EIO);
+      }
+      break;
+
+    default:
+      NOTREACHED();
+      return AVERROR(EIO);
+  }
+
+  int64_t result = reader->SetPosition(base + offset);
+  if (result == -1) {
+    return AVERROR(EIO);
+  }
+
+  return result;
+}
+
+} // namespace media
+} // namespace mojo