Split MoveReadPosition into Forward and Backward versions.

This makes the interface consistent in its use of size_t, and will
reduce casts in callers as they shift to size_t, e.g. this CL:
https://codereview.webrtc.org/1227203003/

Review URL: https://codereview.webrtc.org/1252943007

Cr-Commit-Position: refs/heads/master@{#9646}

webrtc/common_audio/audio_ring_buffer.cc

@@ -18,6 +18,7 @@
 namespace webrtc {
 
 AudioRingBuffer::AudioRingBuffer(size_t channels, size_t max_frames) {
+  buffers_.reserve(channels);
   for (size_t i = 0; i < channels; ++i)
     buffers_.push_back(WebRtc_CreateBuffer(max_frames, sizeof(float)));
 }
@@ -31,7 +32,7 @@ void AudioRingBuffer::Write(const float* const* data, size_t channels,
                             size_t frames) {
   DCHECK_EQ(buffers_.size(), channels);
   for (size_t i = 0; i < channels; ++i) {
-    size_t written = WebRtc_WriteBuffer(buffers_[i], data[i], frames);
+    const size_t written = WebRtc_WriteBuffer(buffers_[i], data[i], frames);
     CHECK_EQ(written, frames);
   }
 }
@@ -39,7 +40,8 @@ void AudioRingBuffer::Write(const float* const* data, size_t channels,
 void AudioRingBuffer::Read(float* const* data, size_t channels, size_t frames) {
   DCHECK_EQ(buffers_.size(), channels);
   for (size_t i = 0; i < channels; ++i) {
-    size_t read = WebRtc_ReadBuffer(buffers_[i], nullptr, data[i], frames);
+    const size_t read =
+        WebRtc_ReadBuffer(buffers_[i], nullptr, data[i], frames);
     CHECK_EQ(read, frames);
   }
 }
@@ -54,9 +56,18 @@ size_t AudioRingBuffer::WriteFramesAvailable() const {
   return WebRtc_available_write(buffers_[0]);
 }
 
-void AudioRingBuffer::MoveReadPosition(int frames) {
+void AudioRingBuffer::MoveReadPositionForward(size_t frames) {
   for (auto buf : buffers_) {
-    int moved = WebRtc_MoveReadPtr(buf, frames);
+    const size_t moved =
+        static_cast<size_t>(WebRtc_MoveReadPtr(buf, static_cast<int>(frames)));
+    CHECK_EQ(moved, frames);
+  }
+}
+
+void AudioRingBuffer::MoveReadPositionBackward(size_t frames) {
+  for (auto buf : buffers_) {
+    const size_t moved = static_cast<size_t>(
+        -WebRtc_MoveReadPtr(buf, -static_cast<int>(frames)));
     CHECK_EQ(moved, frames);
   }
 }

webrtc/common_audio/audio_ring_buffer.h

@@ -27,20 +27,23 @@ class AudioRingBuffer final {
   AudioRingBuffer(size_t channels, size_t max_frames);
   ~AudioRingBuffer();
 
-  // Copy |data| to the buffer and advance the write pointer. |channels| must
+  // Copies |data| to the buffer and advances the write pointer. |channels| must
   // be the same as at creation time.
   void Write(const float* const* data, size_t channels, size_t frames);
 
-  // Copy from the buffer to |data| and advance the read pointer. |channels|
+  // Copies from the buffer to |data| and advances the read pointer. |channels|
   // must be the same as at creation time.
   void Read(float* const* data, size_t channels, size_t frames);
 
   size_t ReadFramesAvailable() const;
   size_t WriteFramesAvailable() const;
 
-  // Positive values advance the read pointer and negative values withdraw
-  // the read pointer (i.e. flush and stuff the buffer respectively.)
-  void MoveReadPosition(int frames);
+  // Moves the read position. The forward version advances the read pointer
+  // towards the write pointer and the backward verison withdraws the read
+  // pointer away from the write pointer (i.e. flushing and stuffing the buffer
+  // respectively.)
+  void MoveReadPositionForward(size_t frames);
+  void MoveReadPositionBackward(size_t frames);
 
  private:
   // We don't use a ScopedVector because it doesn't support a specialized

webrtc/common_audio/audio_ring_buffer_unittest.cc

@@ -98,11 +98,11 @@ TEST_F(AudioRingBufferTest, MoveReadPosition) {
   AudioRingBuffer buf(kNumChannels, kNumFrames);
   buf.Write(input.channels(), kNumChannels, kNumFrames);
 
-  buf.MoveReadPosition(3);
+  buf.MoveReadPositionForward(3);
   ChannelBuffer<float> output(1, kNumChannels);
   buf.Read(output.channels(), kNumChannels, 1);
   EXPECT_EQ(4, output.channels()[0][0]);
-  buf.MoveReadPosition(-3);
+  buf.MoveReadPositionBackward(3);
   buf.Read(output.channels(), kNumChannels, 1);
   EXPECT_EQ(2, output.channels()[0][0]);
 }

webrtc/common_audio/blocker.cc

@@ -119,10 +119,10 @@ Blocker::Blocker(int chunk_size,
       shift_amount_(shift_amount),
       callback_(callback) {
   CHECK_LE(num_output_channels_, num_input_channels_);
-  CHECK(window);
+  CHECK_LE(shift_amount_, block_size_);
 
   memcpy(window_.get(), window, block_size_ * sizeof(*window_.get()));
-  input_buffer_.MoveReadPosition(-initial_delay_);
+  input_buffer_.MoveReadPositionBackward(initial_delay_);
 }
 
 // When block_size < chunk_size the input and output buffers look like this:
@@ -180,7 +180,7 @@ void Blocker::ProcessChunk(const float* const* input,
   while (first_frame_in_block < chunk_size_) {
     input_buffer_.Read(input_block_.channels(), num_input_channels,
                        block_size_);
-    input_buffer_.MoveReadPosition(-block_size_ + shift_amount_);
+    input_buffer_.MoveReadPositionBackward(block_size_ - shift_amount_);
 
     ApplyWindow(window_.get(),
                 block_size_,