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| 1 // Copyright 2017 The Chromium Authors. All rights reserved. |
| 2 // Use of this source code is governed by a BSD-style license that can be |
| 3 // found in the LICENSE file. |
| 4 |
| 5 #ifndef PushPullFIFO_h |
| 6 #define PushPullFIFO_h |
| 7 |
| 8 #include "platform/audio/AudioBus.h" |
| 9 #include "public/platform/WebCommon.h" |
| 10 #include "wtf/Allocator.h" |
| 11 |
| 12 namespace blink { |
| 13 |
| 14 // A configuration data container for PushPullFIFO unit test. |
| 15 struct PushPullFIFOStateForTest { |
| 16 const size_t fifoLength; |
| 17 const unsigned numberOfChannels; |
| 18 const size_t framesAvailable; |
| 19 const size_t indexRead; |
| 20 const size_t indexWrite; |
| 21 const unsigned overflowCount; |
| 22 const unsigned underflowCount; |
| 23 }; |
| 24 |
| 25 // PushPullFIFO class is an intermediate audio sample storage between |
| 26 // Blink-WebAudio and the renderer. The renderer's hardware callback buffer size |
| 27 // varies on the platform, but the WebAudio always renders 128 frames (render |
| 28 // quantum, RQ) thus FIFO is needed to handle the general case. |
| 29 class BLINK_PLATFORM_EXPORT PushPullFIFO { |
| 30 USING_FAST_MALLOC(PushPullFIFO); |
| 31 WTF_MAKE_NONCOPYABLE(PushPullFIFO); |
| 32 |
| 33 public: |
| 34 // Maximum FIFO length. (512 render quanta) |
| 35 static const size_t kMaxFIFOLength; |
| 36 |
| 37 // |fifoLength| cannot exceed |kMaxFIFOLength|. Otherwise it crashes. |
| 38 explicit PushPullFIFO(unsigned numberOfChannels, size_t fifoLength); |
| 39 ~PushPullFIFO(); |
| 40 |
| 41 // Pushes the rendered frames by WebAudio engine. |
| 42 // - The |inputBus| length is 128 frames (1 render quantum), fixed. |
| 43 // - In case of overflow (FIFO full while push), the existing frames in FIFO |
| 44 // will be overwritten and |indexRead| will be forcibly moved to |
| 45 // |indexWrite| to avoid reading overwritten frames. |
| 46 void push(const AudioBus* inputBus); |
| 47 |
| 48 // Pulling |framesRequested| by the audio device thread. |
| 49 // - If |framesRequested| is bigger than the length of |outputBus|, it |
| 50 // violates SECURITY_CHECK(). |
| 51 // - If |framesRequested| is bigger than FIFO length, it violates |
| 52 // SECURITY_CHECK(). |
| 53 // - In case of underflow (FIFO empty while pull), the remaining space in the |
| 54 // requested output bus will be filled with silence. Thus it will fulfill |
| 55 // the request from the consumer without causing error, but with a glitch. |
| 56 void pull(AudioBus* outputBus, size_t framesRequested); |
| 57 |
| 58 size_t framesAvailable() const { return m_framesAvailable; } |
| 59 size_t length() const { return m_fifoLength; } |
| 60 unsigned numberOfChannels() const { return m_fifoBus->numberOfChannels(); } |
| 61 AudioBus* bus() const { return m_fifoBus.get(); } |
| 62 |
| 63 // For unit test. Get the current configuration that consists of FIFO length, |
| 64 // number of channels, read/write index position and under/overflow count. |
| 65 const PushPullFIFOStateForTest getStateForTest() const; |
| 66 |
| 67 private: |
| 68 // The size of the FIFO. |
| 69 const size_t m_fifoLength = 0; |
| 70 |
| 71 RefPtr<AudioBus> m_fifoBus; |
| 72 |
| 73 // The number of frames in the FIFO actually available for pulling. |
| 74 size_t m_framesAvailable; |
| 75 |
| 76 size_t m_indexRead; |
| 77 size_t m_indexWrite; |
| 78 |
| 79 unsigned m_overflowCount; |
| 80 unsigned m_underflowCount; |
| 81 }; |
| 82 |
| 83 } // namespace blink |
| 84 |
| 85 #endif // PushPullFIFO_h |
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