Add basic resample support to WASAPIAudioInputStream.

media/base/audio_block_fifo.cc

Index: media/base/audio_block_fifo.cc
diff --git a/media/base/audio_block_fifo.cc b/media/base/audio_block_fifo.cc
index 4313cad7c75e9d891a600af0df552f082e094e59..be15fb11638729c914ba9293e092c9d5b0e140c7 100644
--- a/media/base/audio_block_fifo.cc
+++ b/media/base/audio_block_fifo.cc
@@ -27,38 +27,11 @@ AudioBlockFifo::~AudioBlockFifo() {}
 void AudioBlockFifo::Push(const void* source,
                           int frames,
                           int bytes_per_sample) {
-  DCHECK(source);
-  DCHECK_GT(frames, 0);
-  DCHECK_GT(bytes_per_sample, 0);
-  DCHECK_LT(available_blocks_, static_cast<int>(audio_blocks_.size()));
-  CHECK_LE(frames, GetUnfilledFrames());
-
-  const uint8_t* source_ptr = static_cast<const uint8_t*>(source);
-  int frames_to_push = frames;
-  while (frames_to_push) {
-    // Get the current write block.
-    AudioBus* current_block = audio_blocks_[write_block_];
-
-    // Figure out what segment sizes we need when adding the new content to
-    // the FIFO.
-    const int push_frames =
-        std::min(block_frames_ - write_pos_, frames_to_push);
-
-    // Deinterleave the content to the FIFO and update the |write_pos_|.
-    current_block->FromInterleavedPartial(
-        source_ptr, write_pos_, push_frames, bytes_per_sample);
-    write_pos_ = (write_pos_ + push_frames) % block_frames_;
-    if (!write_pos_) {
-      // The current block is completely filled, increment |write_block_| and
-      // |available_blocks_|.
-      write_block_ = (write_block_ + 1) % audio_blocks_.size();
-      ++available_blocks_;
-    }
+  PushInternal(source, frames, bytes_per_sample);
+}
 
-    source_ptr += push_frames * bytes_per_sample * channels_;
-    frames_to_push -= push_frames;
-    DCHECK_GE(frames_to_push, 0);
-  }
+void AudioBlockFifo::PushSilence(int frames) {
+  PushInternal(nullptr, frames, 0);
 }
 
 const AudioBus* AudioBlockFifo::Consume() {
@@ -103,8 +76,7 @@ void AudioBlockFifo::IncreaseCapacity(int blocks) {
     return;
 
   std::rotate(audio_blocks_.begin() + read_block_,
-              audio_blocks_.begin() + original_size,
-              audio_blocks_.end());
+              audio_blocks_.begin() + original_size, audio_blocks_.end());
 
   // Update the write pointer if it is on top of the new inserted blocks.
   if (write_block_ >= read_block_)
@@ -117,4 +89,47 @@ void AudioBlockFifo::IncreaseCapacity(int blocks) {
   DCHECK_LT(write_block_, static_cast<int>(audio_blocks_.size()));
 }
 
+void AudioBlockFifo::PushInternal(const void* source,
+                                  int frames,
+                                  int bytes_per_sample) {
+  // |source| may be nullptr if bytes_per_sample is 0. In that case,
+  // we inject silence.
+  DCHECK((source && bytes_per_sample > 0) || (!source && !bytes_per_sample));
+  DCHECK_GT(frames, 0);
+  DCHECK_LT(available_blocks_, static_cast<int>(audio_blocks_.size()));
+  CHECK_LE(frames, GetUnfilledFrames());
+
+  const uint8_t* source_ptr = static_cast<const uint8_t*>(source);
+  int frames_to_push = frames;
+  while (frames_to_push) {
+    // Get the current write block.
+    AudioBus* current_block = audio_blocks_[write_block_];
+
+    // Figure out what segment sizes we need when adding the new content to
+    // the FIFO.
+    const int push_frames =
+        std::min(block_frames_ - write_pos_, frames_to_push);
+
+    if (source) {
+      // Deinterleave the content to the FIFO and update the |write_pos_|.
+      current_block->FromInterleavedPartial(source_ptr, write_pos_, push_frames,
+                                            bytes_per_sample);
+    } else {
+      current_block->ZeroFramesPartial(write_pos_, push_frames);
+    }
+    write_pos_ = (write_pos_ + push_frames) % block_frames_;
+    if (!write_pos_) {
+      // The current block is completely filled, increment |write_block_| and
+      // |available_blocks_|.
+      write_block_ = (write_block_ + 1) % audio_blocks_.size();
+      ++available_blocks_;
+    }
+
+    if (source_ptr)
+      source_ptr += push_frames * bytes_per_sample * channels_;
+    frames_to_push -= push_frames;
+    DCHECK_GE(frames_to_push, 0);
+  }
+}
+
 }  // namespace media