Motown in-proc streaming framework used to implement media services.

services/media/framework/models/lpcm_frames.h

+// 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.
+
+#ifndef MOJO_MEDIA_MODELS_LPCM_FRAMES_H_
+#define MOJO_MEDIA_MODELS_LPCM_FRAMES_H_
+
+#include <cstdint>
+
+#include "base/logging.h"
+#include "services/media/framework/packet.h"
+
+namespace mojo {
+namespace media {
+
+// References an LPCM frame buffer and implements advancement through it.
+class LpcmFrames {
+ public:
+  LpcmFrames() :
+      bytes_per_frame_(0),
+      remaining_buffer_(nullptr),
+      remaining_frame_count_(0) {}
+
+  void set_bytes_per_frame(uint32_t bytes_per_frame) {
+    bytes_per_frame_ = bytes_per_frame;
+  }
+
+  uint32_t bytes_per_frame() {
+    return bytes_per_frame_;
+  }
+
+  // The remaining frame buffer.
+  void* buffer() {
+    return remaining_buffer_;
+  }
+
+  // The remaining number of frames accommodated by the frame buffer.
+  uint64_t frame_count() {
+    return remaining_frame_count_;
+  }
+
+  // Resets the buffer and frame.
+  void reset() {
+    remaining_buffer_ = nullptr;
+    remaining_frame_count_ = 0;
+    reset_when_exhausted_ = nullptr;
+  }
+
+  // Sets the buffer and frame count.
+  void set(void* buffer, uint64_t frame_count) {
+    remaining_buffer_ = buffer;
+    remaining_frame_count_ = frame_count;
+    reset_when_exhausted_ = nullptr;
+  }
+
+  void set(PacketPtr* packet) {
+    DCHECK(packet);
+    DCHECK(*packet);
+    remaining_buffer_ = (*packet)->payload();
+    remaining_frame_count_ = (*packet)->duration();
+    if (remaining_frame_count_ == 0) {
+      packet->reset();
+      reset_when_exhausted_ = nullptr;
+    } else {
+      reset_when_exhausted_ = packet;
+    }
+  }
+
+  // Updates buffer and frame_count to reflect use of the buffer.
+  void advance(uint64_t frame_count) {
+    DCHECK(remaining_buffer_);
+    DCHECK(frame_count <= remaining_frame_count_);
+    remaining_buffer_ = reinterpret_cast<uint8_t*>(remaining_buffer_) +
+        (frame_count * bytes_per_frame_);
+    remaining_frame_count_ -= frame_count;
+    if (remaining_frame_count_ == 0 && reset_when_exhausted_ != nullptr) {
+      (*reset_when_exhausted_).reset();
+    }
+  }
+
+ private:
+  uint32_t bytes_per_frame_;
+  void* remaining_buffer_;
+  uint64_t remaining_frame_count_;
+  PacketPtr* reset_when_exhausted_;
+};
+
+}  // namespace media
+}  // namespace mojo
+
+#endif // MOJO_MEDIA_MODELS_LPCM_FRAMES_H_