Introduce PushPullFIFO class and remove other FIFOs

third_party/WebKit/Source/platform/audio/PushPullFIFO.cpp

Index: third_party/WebKit/Source/platform/audio/PushPullFIFO.cpp
diff --git a/third_party/WebKit/Source/platform/audio/PushPullFIFO.cpp b/third_party/WebKit/Source/platform/audio/PushPullFIFO.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..3ec86e1733d6a713ef94ee694d8d4943e9f016a8
--- /dev/null
+++ b/third_party/WebKit/Source/platform/audio/PushPullFIFO.cpp
@@ -0,0 +1,139 @@
+// 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 "platform/audio/PushPullFIFO.h"
+
+#include "wtf/PtrUtil.h"
+#include <memory>
+
+namespace blink {
+
+// Suppress the warning log if over/underflow happens more than 100 times.
+const int kLogCapOverUnderflow = 100;
+
+PushPullFIFO::PushPullFIFO(unsigned numberOfChannels, size_t fifoLength)
+    : m_fifoBus(AudioBus::create(numberOfChannels, fifoLength)),
+      m_fifoLength(static_cast<int>(fifoLength)),
+      m_framesAvailable(0),
+      m_indexRead(0),
+      m_indexWrite(0),
+      m_overflowCount(0),
+      m_underflowCount(0) {}
+
+PushPullFIFO::~PushPullFIFO() {}
+
+// Push the data from |inputBus| to FIFO. The size of push is determined by
+// the length of |inputBus|.
+void PushPullFIFO::push(const AudioBus* inputBus) {
+  DCHECK(inputBus);
+  if (!inputBus)
+    return;
+
+  const int inputBusLength = static_cast<int>(inputBus->length());
+  const int remainder = m_fifoLength - m_indexWrite;
+  SECURITY_CHECK(inputBusLength < m_fifoLength);
+  SECURITY_CHECK(m_indexWrite < m_fifoLength);
+
+  for (unsigned i = 0; i < m_fifoBus->numberOfChannels(); ++i) {
+    float* fifoBusChannel = m_fifoBus->channel(i)->mutableData();
+    const float* inputBusChannel = inputBus->channel(i)->data();
+    if (remainder >= inputBusLength) {
+      // The remainder is big enough for the input data.
+      memcpy(fifoBusChannel + m_indexWrite, inputBusChannel,
+             inputBusLength * sizeof(*fifoBusChannel));
+    } else {
+      // The input data overflows the remainder size. Wrap around the index.
+      memcpy(fifoBusChannel + m_indexWrite, inputBusChannel,
+             remainder * sizeof(*fifoBusChannel));
+      memcpy(fifoBusChannel, inputBusChannel + remainder,
+             (inputBusLength - remainder) * sizeof(*fifoBusChannel));
+    }
+  }
+
+  // Update the write index; wrap it around if necessary.
+  m_indexWrite = (m_indexWrite + inputBusLength) % m_fifoLength;
+
+  // In case of overflow, move the read index to the updated write index.
+  if (m_fifoLength < inputBusLength + m_framesAvailable) {
+    m_indexRead = m_indexWrite;
+    if (++m_overflowCount < kLogCapOverUnderflow) {
+      LOG(WARNING) << "PushPullFIFO::pushing overflown. "
+                   << "(count = " << m_overflowCount << ") \n"
+                   << "in-FIFO frames = " << m_framesAvailable
+                   << ", input frames = " << inputBusLength
+                   << ", FIFO size = " << m_fifoLength;
+    }
+  }
+
+  // Update the number of frames available in FIFO.
+  m_framesAvailable =
+      std::min(m_fifoLength, m_framesAvailable + inputBusLength);
+}
+
+// Pull the data out of FIFO to |outputBus|. If the remaining frames in the FIFO
+// is less than the frames to pull, provides the remaining frames plus the
+// silence.
+void PushPullFIFO::pull(AudioBus* outputBus, size_t framesRequested) {
+  DCHECK(outputBus);
+  SECURITY_CHECK(framesRequested <= outputBus->length());
+  if (!outputBus)
+    return;
+
+  // TODO(hongchan): add a mutex here for this operation when two threads are
+  // introduced. Pulling operation has a higher priority to ensure the audio
+  // device callback to be uninterrupted.
+
+  const int remainder = m_fifoLength - m_indexRead;
+  const int framesToProvide = static_cast<int>(framesRequested);
+  SECURITY_CHECK(framesToProvide < m_fifoLength);
+  SECURITY_CHECK(m_indexRead < m_fifoLength);
+
+  const int framesToFill = std::min(m_framesAvailable, framesToProvide);
+
+  for (unsigned i = 0; i < m_fifoBus->numberOfChannels(); ++i) {
+    const float* fifoBusChannel = m_fifoBus->channel(i)->data();
+    float* outputBusChannel = outputBus->channel(i)->mutableData();
+
+    // Fill up the output bus with the available frames first.
+    if (remainder >= framesToFill) {
+      // The remainder is big enough for the frames to pull.
+      memcpy(outputBusChannel, fifoBusChannel + m_indexRead,
+             framesToFill * sizeof(*fifoBusChannel));
+    } else {
+      // The frames to pull is bigger than the remainder size.
+      // Wrap around the index.
+      memcpy(outputBusChannel, fifoBusChannel + m_indexRead,
+             remainder * sizeof(*fifoBusChannel));
+      memcpy(outputBusChannel + remainder, fifoBusChannel,
+             (framesToFill - remainder) * sizeof(*fifoBusChannel));
+    }
+
+    // The frames available was not enough to fulfill the requested frames. Fill
+    // the rest of the channel with silence.
+    if (framesToProvide > framesToFill) {
+      memset(outputBusChannel + framesToFill, 0,
+             (framesToProvide - framesToFill) * sizeof(*outputBusChannel));
+    }
+  }
+
+  // Update the read index; wrap it around if necessary.
+  m_indexRead = (m_indexRead + framesToFill) % m_fifoLength;
+
+  // In case of underflow, move the write index to the updated read index.
+  if (framesToProvide > framesToFill) {
+    m_indexWrite = m_indexRead;
+    if (m_underflowCount++ < kLogCapOverUnderflow) {
+      LOG(WARNING) << "PushPullFIFO::pulling underflown. "
+                   << "(count = " << m_underflowCount << ") \n"
+                   << "in-FIFO frames = " << m_framesAvailable
+                   << ", requested frames = " << framesToProvide
+                   << ", FIFO size = " << m_fifoLength << ")";
+    }
+  }
+
+  // Update the number of frames in FIFO.
+  m_framesAvailable = std::max(0, m_framesAvailable - framesToFill);
+}
+
+}  // namespace blink