1 /* 2 * Copyright (C) 2015 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 #ifndef ANDROID_AUDIO_FIFO_H 18 #define ANDROID_AUDIO_FIFO_H 19 20 #include <stdlib.h> 21 22 // FIXME use atomic_int_least32_t and new atomic operations instead of legacy Android ones 23 // #include <stdatomic.h> 24 25 #ifdef __cplusplus 26 extern "C" { 27 #endif 28 29 // Single writer, single reader non-blocking FIFO. 30 // Writer and reader must be in same process. 31 32 // No user-serviceable parts within. 33 struct audio_utils_fifo { 34 // These fields are const after initialization 35 size_t mFrameCount; // max number of significant frames to be stored in the FIFO > 0 36 size_t mFrameCountP2; // roundup(mFrameCount) 37 size_t mFudgeFactor; // mFrameCountP2 - mFrameCount, the number of "wasted" frames after 38 // the end of mBuffer. Only the indices are wasted, not any memory. 39 size_t mFrameSize; // size of each frame in bytes 40 void *mBuffer; // pointer to caller-allocated buffer of size mFrameCount frames 41 42 volatile int32_t mFront; // frame index of first frame slot available to read, or read index 43 volatile int32_t mRear; // frame index of next frame slot available to write, or write index 44 }; 45 46 /** 47 * Initialize a FIFO object. 48 * 49 * \param fifo Pointer to the FIFO object. 50 * \param frameCount Max number of significant frames to be stored in the FIFO > 0. 51 * If writes and reads always use the same count, and that count is a divisor of 52 * frameCount, then the writes and reads will never do a partial transfer. 53 * \param frameSize Size of each frame in bytes. 54 * \param buffer Pointer to a caller-allocated buffer of frameCount frames. 55 */ 56 void audio_utils_fifo_init(struct audio_utils_fifo *fifo, size_t frameCount, size_t frameSize, 57 void *buffer); 58 59 /** 60 * De-initialize a FIFO object. 61 * 62 * \param fifo Pointer to the FIFO object. 63 */ 64 void audio_utils_fifo_deinit(struct audio_utils_fifo *fifo); 65 66 /** 67 * Write to FIFO. 68 * 69 * \param fifo Pointer to the FIFO object. 70 * \param buffer Pointer to source buffer containing 'count' frames of data. 71 * \param count Desired number of frames to write. 72 * 73 * \return actual number of frames written <= count. 74 * 75 * The actual transfer count may be zero if the FIFO is full, 76 * or partial if the FIFO was almost full. 77 * A negative return value indicates an error. Currently there are no errors defined. 78 */ 79 ssize_t audio_utils_fifo_write(struct audio_utils_fifo *fifo, const void *buffer, size_t count); 80 81 /** Read from FIFO. 82 * 83 * \param fifo Pointer to the FIFO object. 84 * \param buffer Pointer to destination buffer to be filled with up to 'count' frames of data. 85 * \param count Desired number of frames to read. 86 * 87 * \return actual number of frames read <= count. 88 * 89 * The actual transfer count may be zero if the FIFO is empty, 90 * or partial if the FIFO was almost empty. 91 * A negative return value indicates an error. Currently there are no errors defined. 92 */ 93 ssize_t audio_utils_fifo_read(struct audio_utils_fifo *fifo, void *buffer, size_t count); 94 95 #ifdef __cplusplus 96 } 97 #endif 98 99 #endif // !ANDROID_AUDIO_FIFO_H 100