87 lines
2.6 KiB
C++
87 lines
2.6 KiB
C++
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/*
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* Copyright (c) 2013 The WebRTC project authors. All Rights Reserved.
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*
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* Use of this source code is governed by a BSD-style license
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* that can be found in the LICENSE file in the root of the source
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* tree. An additional intellectual property rights grant can be found
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* in the file PATENTS. All contributing project authors may
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* be found in the AUTHORS file in the root of the source tree.
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*/
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#include "webrtc/modules/audio_device/android/single_rw_fifo.h"
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#if !defined(__ARMEL__)
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// ARM specific due to the implementation of MemoryBarrier.
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#error trying to compile ARM code for non-ARM target
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#endif
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static int UpdatePos(int pos, int capacity) {
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return (pos + 1) % capacity;
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}
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namespace webrtc {
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namespace subtle {
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// From http://src.chromium.org/viewvc/chrome/trunk/src/base/atomicops_internals_arm_gcc.h
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// Note that it is only the MemoryBarrier function that makes this class arm
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// specific. Borrowing other MemoryBarrier implementations, this class could
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// be extended to more platforms.
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inline void MemoryBarrier() {
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// Note: This is a function call, which is also an implicit compiler
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// barrier.
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typedef void (*KernelMemoryBarrierFunc)();
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((KernelMemoryBarrierFunc)0xffff0fa0)();
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}
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} // namespace subtle
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SingleRwFifo::SingleRwFifo(int capacity)
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: capacity_(capacity),
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size_(0),
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read_pos_(0),
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write_pos_(0) {
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queue_.reset(new int8_t*[capacity_]);
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}
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SingleRwFifo::~SingleRwFifo() {
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}
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void SingleRwFifo::Push(int8_t* mem) {
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assert(mem);
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// Ensure that there is space for the new data in the FIFO.
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// Note there is only one writer meaning that the other thread is guaranteed
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// only to decrease the size.
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const int free_slots = capacity() - size();
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if (free_slots <= 0) {
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// Size can be queried outside of the Push function. The caller is assumed
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// to ensure that Push will be successful before calling it.
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assert(false);
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return;
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}
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queue_[write_pos_] = mem;
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// Memory barrier ensures that |size_| is updated after the size has changed.
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subtle::MemoryBarrier();
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++size_;
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write_pos_ = UpdatePos(write_pos_, capacity());
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}
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int8_t* SingleRwFifo::Pop() {
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int8_t* ret_val = NULL;
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if (size() <= 0) {
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// Size can be queried outside of the Pop function. The caller is assumed
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// to ensure that Pop will be successfull before calling it.
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assert(false);
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return ret_val;
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}
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ret_val = queue_[read_pos_];
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// Memory barrier ensures that |size_| is updated after the size has changed.
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subtle::MemoryBarrier();
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--size_;
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read_pos_ = UpdatePos(read_pos_, capacity());
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return ret_val;
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}
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} // namespace webrtc
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