BufferQueue class to hide audio data micromanagement from scaling algorithms. May be useful in other contexts.

BUG=16011
TEST=src/media/base/buffer_queue_unittest.cc
Review URL: http://codereview.chromium.org/155193

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@20211 0039d316-1c4b-4281-b951-d872f2087c98

4 files changed, 290 insertions, 0 deletions

diff --git a/media/base/buffer_queue.cc b/media/base/buffer_queue.cc
new file mode 100644
index 0000000..18b30d50
--- /dev/null
+++ b/media/base/buffer_queue.cc
@@ -0,0 +1,99 @@
+// Copyright (c) 2009 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 "media/base/buffer_queue.h"
+
+#include "media/base/buffers.h"
+
+namespace media {
+
+BufferQueue::BufferQueue()
+    : data_offset_(0),
+      size_in_bytes_(0) {
+}
+
+BufferQueue::~BufferQueue() {
+}
+
+void BufferQueue::Consume(size_t bytes_to_be_consumed) {
+  // Make sure user isn't trying to consume more than we have.
+  DCHECK(size_in_bytes_ >= bytes_to_be_consumed);
+
+  // As we have enough data to consume, adjust |size_in_bytes_|.
+  size_in_bytes_ -= bytes_to_be_consumed;
+
+  // Now consume them.
+  while (bytes_to_be_consumed > 0) {
+    // Calculate number of usable bytes in the front of the |queue_|.
+    size_t front_remaining = queue_.front()->GetDataSize() - data_offset_;
+
+    // If there is enough data in our first buffer to advance into it, do so.
+    // Otherwise, advance into the queue.
+    if (front_remaining > bytes_to_be_consumed) {
+      data_offset_ += bytes_to_be_consumed;
+      bytes_to_be_consumed = 0;
+    } else {
+      data_offset_ = 0;
+      queue_.pop_front();
+      bytes_to_be_consumed -= front_remaining;
+    }
+  }
+}
+
+size_t BufferQueue::Copy(uint8* dest, size_t bytes) {
+  if (bytes == 0)
+    return 0;
+
+  DCHECK(!queue_.empty());
+
+  size_t current_remaining = 0;
+  const uint8* current = NULL;
+  size_t copied = 0;
+
+  for (size_t i = 0; i < queue_.size() && bytes > 0; ++i) {
+    // Calculate number of usable bytes in the front of the |queue_|. Special
+    // case for front due to |data_offset_|.
+    if (i == 0) {
+      current_remaining = queue_.front()->GetDataSize() - data_offset_;
+      current = queue_.front()->GetData() + data_offset_;
+    } else {
+      current_remaining = queue_[i]->GetDataSize();
+      current = queue_[i]->GetData();
+    }
+
+    // Prevent writing over the end of the buffer.
+    if (current_remaining > bytes)
+      current_remaining = bytes;
+
+    memcpy(dest + copied, current, current_remaining);
+
+    // Modify counts and pointers.
+    copied += current_remaining;
+    bytes -= current_remaining;
+  }
+  return copied;
+}
+
+void BufferQueue::Enqueue(Buffer* buffer_in) {
+  queue_.push_back(buffer_in);
+  size_in_bytes_ += buffer_in->GetDataSize();
+}
+
+void BufferQueue::Clear() {
+  queue_.clear();
+  size_in_bytes_ = 0;
+  data_offset_ = 0;
+}
+
+bool BufferQueue::IsEmpty() {
+  // Since we keep track of the number of bytes, this is easier than calling
+  // into |queue_|.
+  return size_in_bytes_ == 0;
+}
+
+size_t BufferQueue::SizeInBytes() {
+  return size_in_bytes_;
+}
+
+}  // namespace media
diff --git a/media/base/buffer_queue.h b/media/base/buffer_queue.h
new file mode 100644
index 0000000..363b136
--- /dev/null
+++ b/media/base/buffer_queue.h
@@ -0,0 +1,62 @@
+// Copyright (c) 2009 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.
+
+// BufferQueue is a simple Buffer manager that handles requests for data
+// while hiding Buffer boundaries, treating its internal queue of Buffers
+// as a contiguous region.
+//
+// This class is not threadsafe and requires external locking.
+
+#ifndef MEDIA_BASE_BUFFER_QUEUE_H_
+#define MEDIA_BASE_BUFFER_QUEUE_H_
+
+#include <deque>
+
+#include "base/ref_counted.h"
+
+namespace media {
+
+class Buffer;
+
+class BufferQueue {
+ public:
+  BufferQueue();
+  ~BufferQueue();
+
+  // Clears |queue_|.
+  void Clear();
+
+  // Advances front pointer |bytes_to_be_consumed| bytes and discards
+  // "consumed" buffers.
+  void Consume(size_t bytes_to_be_consumed);
+
+  // Tries to copy |bytes| bytes from our data to |dest|. Returns the number
+  // of bytes successfully copied.
+  size_t Copy(uint8* dest, size_t bytes);
+
+  // Enqueues |buffer_in| and adds a reference.
+  void Enqueue(Buffer* buffer_in);
+
+  // Returns true if the |queue_| is empty.
+  bool IsEmpty();
+
+  // Returns the number of bytes in the |queue_|.
+  size_t SizeInBytes();
+
+ private:
+  // Queued audio data.
+  std::deque< scoped_refptr<Buffer> > queue_;
+
+  // Remembers the amount of remaining audio data in the front buffer.
+  size_t data_offset_;
+
+  // Keeps track of the |queue_| size in bytes.
+  size_t size_in_bytes_;
+
+  DISALLOW_COPY_AND_ASSIGN(BufferQueue);
+};
+
+}  // namespace media
+
+#endif  // MEDIA_BASE_BUFFER_QUEUE_H_
diff --git a/media/base/buffer_queue_unittest.cc b/media/base/buffer_queue_unittest.cc
new file mode 100644
index 0000000..7f64b43
--- /dev/null
+++ b/media/base/buffer_queue_unittest.cc
@@ -0,0 +1,126 @@
+// Copyright (c) 2009 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/scoped_ptr.h"
+#include "base/string_util.h"
+#include "media/base/buffer_queue.h"
+#include "media/base/data_buffer.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace media {
+
+class BufferQueueTest : public testing::Test {
+ protected:
+  BufferQueueTest() {
+    buffer1 = new DataBuffer();
+    data1 = buffer1->GetWritableData(kDataSize);
+
+    buffer2 = new DataBuffer();
+    data2 = buffer2->GetWritableData(kNewDataSize);
+
+    bufferBig = new DataBuffer();
+    dataBig = bufferBig->GetWritableData(2 * (kDataSize + kNewDataSize));
+
+    memcpy(data1, kData, kDataSize);
+    memcpy(data2, kNewData, kNewDataSize);
+  }
+
+  BufferQueue queue_;
+
+  static const char kData[];
+  static const size_t kDataSize;
+  static const char kNewData[];
+  static const size_t kNewDataSize;
+  scoped_refptr<DataBuffer> buffer1;
+  scoped_refptr<DataBuffer> buffer2;
+  scoped_refptr<DataBuffer> bufferBig;
+  uint8* data1;
+  uint8* data2;
+  uint8* dataBig;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(BufferQueueTest);
+};
+
+const char BufferQueueTest::kData[] = "hello";
+const size_t BufferQueueTest::kDataSize = arraysize(BufferQueueTest::kData);
+const char BufferQueueTest::kNewData[] = "chromium";
+const size_t BufferQueueTest::kNewDataSize =
+    arraysize(BufferQueueTest::kNewData);
+
+TEST_F(BufferQueueTest, ValidTestData) {
+  ASSERT_TRUE(kNewDataSize > kDataSize);
+  ASSERT_TRUE(buffer1.get());
+  ASSERT_TRUE(data1);
+  ASSERT_TRUE(buffer2.get());
+  ASSERT_TRUE(data2);
+  ASSERT_TRUE(bufferBig.get());
+  ASSERT_TRUE(dataBig);
+}
+
+TEST_F(BufferQueueTest, Ctor) {
+  EXPECT_TRUE(queue_.IsEmpty());
+  EXPECT_EQ(0u, queue_.SizeInBytes());
+}
+
+TEST_F(BufferQueueTest, Enqueue) {
+  queue_.Enqueue(buffer1.get());
+  EXPECT_FALSE(queue_.IsEmpty());
+  EXPECT_EQ(kDataSize, queue_.SizeInBytes());
+}
+
+TEST_F(BufferQueueTest, CopyWithOneBuffer) {
+  queue_.Enqueue(buffer1.get());
+
+  EXPECT_EQ(kDataSize, queue_.Copy(data2, kDataSize));
+  EXPECT_EQ(0, memcmp(data2, kData, kDataSize));
+}
+
+TEST_F(BufferQueueTest, Clear) {
+  queue_.Enqueue(buffer1.get());
+
+  queue_.Clear();
+  EXPECT_TRUE(queue_.IsEmpty());
+  EXPECT_EQ(0u, queue_.SizeInBytes());
+}
+
+TEST_F(BufferQueueTest, MultipleEnqueues) {
+  queue_.Enqueue(buffer2.get());
+  queue_.Enqueue(buffer1.get());
+  EXPECT_EQ(kDataSize + kNewDataSize, queue_.SizeInBytes());
+}
+
+TEST_F(BufferQueueTest, CopyWithMultipleBuffers) {
+  queue_.Enqueue(buffer2.get());
+  queue_.Enqueue(buffer1.get());
+
+  EXPECT_EQ(kDataSize + kNewDataSize,
+            queue_.Copy(dataBig, kDataSize + kNewDataSize));
+  EXPECT_EQ(0, memcmp(dataBig, kNewData, kNewDataSize));
+  dataBig += kNewDataSize;
+  EXPECT_EQ(0, memcmp(dataBig, kData, kDataSize));
+}
+
+TEST_F(BufferQueueTest, Consume) {
+  queue_.Enqueue(buffer2.get());
+  queue_.Enqueue(buffer1.get());
+
+  queue_.Consume(kDataSize);
+  EXPECT_EQ(kNewDataSize, queue_.SizeInBytes());
+}
+
+TEST_F(BufferQueueTest, CopyFromMiddleOfBuffer) {
+  queue_.Enqueue(buffer2.get());
+  queue_.Enqueue(buffer1.get());
+  queue_.Consume(kDataSize);
+
+  EXPECT_EQ(kNewDataSize, queue_.Copy(dataBig, kNewDataSize));
+  EXPECT_EQ(0, memcmp(dataBig,
+                      kNewData + kDataSize,
+                      kNewDataSize - kDataSize));
+  dataBig += (kNewDataSize - kDataSize);
+  EXPECT_EQ(0, memcmp(dataBig, kData, kDataSize));
+}
+
+}  // namespace media
diff --git a/media/media.gyp b/media/media.gyp
index 669f08e..2e149cb 100644
--- a/media/media.gyp
+++ b/media/media.gyp
@@ -44,6 +44,8 @@
         'audio/win/audio_output_win.cc',
         'audio/win/waveout_output_win.cc',
         'audio/win/waveout_output_win.h',
+        'base/buffer_queue.h',
+        'base/buffer_queue.cc',
         'base/buffers.h',
         'base/data_buffer.cc',
         'base/data_buffer.h',
@@ -150,6 +152,7 @@
         'audio/win/audio_output_win_unittest.cc',
         'audio/mac/audio_output_mac_unittest.cc',
         'audio/simple_sources_unittest.cc',
+        'base/buffer_queue_unittest.cc',
         'base/data_buffer_unittest.cc',
         'base/mock_ffmpeg.cc',
         'base/mock_ffmpeg.h',