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..c54f38c883c7084a1ec97a74112ef4bdafade868
--- /dev/null
+++ b/third_party/WebKit/Source/platform/audio/PushPullFIFO.cpp
@@ -0,0 +1,138 @@
+// Copyright 2017 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 "platform/audio/AudioUtilities.h"
+#include "wtf/PtrUtil.h"
+#include <memory>
+
+namespace blink {
+
+// Suppress the warning log if over/underflow happens more than 100 times.
+const unsigned kMaxMessagesToLog = 100;

[o1ka, 2017/02/02 16:30:24]

Put it into an unnamed namespace?

[hongchan, 2017/02/02 19:55:23]

Done.

+
+PushPullFIFO::PushPullFIFO(unsigned numberOfChannels, size_t fifoLength)
+    : m_fifoLength(fifoLength),
+      m_framesAvailable(0),
+      m_indexRead(0),
+      m_indexWrite(0),
+      m_overflowCount(0),
+      m_underflowCount(0) {
+  CHECK_LE(m_fifoLength, kMaxFIFOLength);
+  m_fifoBus = AudioBus::create(numberOfChannels, m_fifoLength);
+}
+
+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) {
+  CHECK(inputBus);
+  CHECK_EQ(inputBus->length(), AudioUtilities::kRenderQuantumFrames);
+  SECURITY_CHECK(inputBus->length() <= m_fifoLength);
+  SECURITY_CHECK(m_indexWrite < m_fifoLength);
+
+  const size_t inputBusLength = inputBus->length();
+  const size_t remainder = m_fifoLength - m_indexWrite;
+
+  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 |indexRead| to the updated |indexWrite| to
+  // avoid reading overwritten frames by the next pull.
+  if (inputBusLength > m_fifoLength - m_framesAvailable) {
+    m_indexRead = m_indexWrite;
+    if (++m_overflowCount < kMaxMessagesToLog) {
+      DVLOG(1) << "PushPullFIFO: overflow while pushing ("
+               << "overflowCount=" << m_overflowCount
+               << ", availableFrames=" << m_framesAvailable
+               << ", inputFrames=" << inputBusLength
+               << ", fifoLength=" << m_fifoLength << ")";
+    }
+  }
+
+  // Update the number of frames available in FIFO.
+  m_framesAvailable =
+      std::min(m_framesAvailable + inputBusLength, m_fifoLength);

[o1ka, 2017/02/02 16:30:24]

DCHECK that relations between m_indexRead, m_indexWrite and m_framesAvailable
are correct (one can be calculated from another two)

[hongchan, 2017/02/02 19:55:23]

This doesn't seem to possible because of the heuristic for under/overflow.

Purely based on two indexes, we cannot tell if the FIFO is empty or full when
they are at the same position. That's why we use m_framesAvailable - to keep
track of actual available frames.

If you have a better idea please do suggest.

[o1ka, 2017/02/03 10:41:17]

How about DCHECK_EQ((m_indexRead + m_framesAvailable) % m_fifoLength,
m_indexWrite)?

m_indexWrite is deductible, right?

[hongchan, 2017/02/03 17:20:11]

Well, I thought you wanted the verification purely based on m_indexRead and
m_indexWrite.

Done.

+}
+
+// Pull the data out of FIFO to |outputBus|. If remaining frame in the FIFO
+// is less than the frames to pull, provides remaining frame plus the silence.
+void PushPullFIFO::pull(AudioBus* outputBus, size_t framesRequested) {
+  CHECK(outputBus);
+  SECURITY_CHECK(framesRequested <= outputBus->length());
+  SECURITY_CHECK(framesRequested <= m_fifoLength);
+  SECURITY_CHECK(m_indexRead < m_fifoLength);
+
+  const size_t remainder = m_fifoLength - m_indexRead;
+  const size_t framesToFill = std::min(m_framesAvailable, framesRequested);
+
+  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 (framesRequested > framesToFill) {
+      memset(outputBusChannel + framesToFill, 0,
+             (framesRequested - 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 |indexWrite| to the updated |indexRead|.
+  if (framesRequested > framesToFill) {
+    m_indexWrite = m_indexRead;
+    if (m_underflowCount++ < kMaxMessagesToLog) {
+      DVLOG(1) << "PushPullFIFO: underflow while pulling ("
+               << "underflowCount=" << m_underflowCount
+               << ", availableFrames=" << m_framesAvailable
+               << ", requestedFrames=" << framesRequested
+               << ", fifoLength=" << m_fifoLength << ")";
+    }
+  }
+
+  // Update the number of frames in FIFO.
+  m_framesAvailable -= framesToFill;

[o1ka, 2017/02/02 16:30:24]

Same here: DCHECK the relations

[hongchan, 2017/02/02 19:55:23]

Ditto.

[o1ka, 2017/02/03 10:41:17]

Ditto :)

[hongchan, 2017/02/03 17:20:12]

Done.

+}
+
+const PushPullFIFOStateForTest PushPullFIFO::getStateForTest() const {
+  return {length(),     numberOfChannels(), framesAvailable(), m_indexRead,
+          m_indexWrite, m_overflowCount,    m_underflowCount};
+}
+
+}  // namespace blink