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/*
* Copyright (C) 2015 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#ifndef ANDROID_AUDIO_FIFO_H
#define ANDROID_AUDIO_FIFO_H
#include <stdlib.h>
// FIXME use atomic_int_least32_t and new atomic operations instead of legacy Android ones
// #include <stdatomic.h>
#ifdef __cplusplus
extern "C" {
#endif
// Single writer, single reader non-blocking FIFO.
// Writer and reader must be in same process.
// No user-serviceable parts within.
struct audio_utils_fifo {
// These fields are const after initialization
size_t mFrameCount; // max number of significant frames to be stored in the FIFO > 0
size_t mFrameCountP2; // roundup(mFrameCount)
size_t mFudgeFactor; // mFrameCountP2 - mFrameCount, the number of "wasted" frames after
// the end of mBuffer. Only the indices are wasted, not any memory.
size_t mFrameSize; // size of each frame in bytes
void *mBuffer; // pointer to caller-allocated buffer of size mFrameCount frames
volatile int32_t mFront; // frame index of first frame slot available to read, or read index
volatile int32_t mRear; // frame index of next frame slot available to write, or write index
};
// Initialize a FIFO object.
// Input parameters:
// fifo Pointer to the FIFO object.
// frameCount Max number of significant frames to be stored in the FIFO > 0.
// If writes and reads always use the same count, and that count is a divisor of
// frameCount, then the writes and reads will never do a partial transfer.
// frameSize Size of each frame in bytes.
// buffer Pointer to a caller-allocated buffer of frameCount frames.
void audio_utils_fifo_init(struct audio_utils_fifo *fifo, size_t frameCount, size_t frameSize,
void *buffer);
// De-initialize a FIFO object.
// Input parameters:
// fifo Pointer to the FIFO object.
void audio_utils_fifo_deinit(struct audio_utils_fifo *fifo);
// Write to FIFO.
// Input parameters:
// fifo Pointer to the FIFO object.
// buffer Pointer to source buffer containing 'count' frames of data.
// Returns actual number of frames written <= count.
// The actual transfer count may be zero if the FIFO is full,
// or partial if the FIFO was almost full.
// A negative return value indicates an error. Currently there are no errors defined.
ssize_t audio_utils_fifo_write(struct audio_utils_fifo *fifo, const void *buffer, size_t count);
// Read from FIFO.
// Input parameters:
// fifo Pointer to the FIFO object.
// buffer Pointer to destination buffer to be filled with up to 'count' frames of data.
// Returns actual number of frames read <= count.
// The actual transfer count may be zero if the FIFO is empty,
// or partial if the FIFO was almost empty.
// A negative return value indicates an error. Currently there are no errors defined.
ssize_t audio_utils_fifo_read(struct audio_utils_fifo *fifo, void *buffer, size_t count);
#ifdef __cplusplus
}
#endif
#endif // !ANDROID_AUDIO_FIFO_H
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