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 // Initialize a FIFO object. 47 // Input parameters: 48 // fifo Pointer to the FIFO object. 49 // frameCount Max number of significant frames to be stored in the FIFO > 0. 50 // If writes and reads always use the same count, and that count is a divisor of 51 // frameCount, then the writes and reads will never do a partial transfer. 52 // frameSize Size of each frame in bytes. 53 // buffer Pointer to a caller-allocated buffer of frameCount frames. 54 void audio_utils_fifo_init(struct audio_utils_fifo *fifo, size_t frameCount, size_t frameSize, 55 void *buffer); 56 57 // De-initialize a FIFO object. 58 // Input parameters: 59 // fifo Pointer to the FIFO object. 60 void audio_utils_fifo_deinit(struct audio_utils_fifo *fifo); 61 62 // Write to FIFO. 63 // Input parameters: 64 // fifo Pointer to the FIFO object. 65 // buffer Pointer to source buffer containing 'count' frames of data. 66 // Returns actual number of frames written <= count. 67 // The actual transfer count may be zero if the FIFO is full, 68 // or partial if the FIFO was almost full. 69 // A negative return value indicates an error. Currently there are no errors defined. 70 ssize_t audio_utils_fifo_write(struct audio_utils_fifo *fifo, const void *buffer, size_t count); 71 72 // Read from FIFO. 73 // Input parameters: 74 // fifo Pointer to the FIFO object. 75 // buffer Pointer to destination buffer to be filled with up to 'count' frames of data. 76 // Returns actual number of frames read <= count. 77 // The actual transfer count may be zero if the FIFO is empty, 78 // or partial if the FIFO was almost empty. 79 // A negative return value indicates an error. Currently there are no errors defined. 80 ssize_t audio_utils_fifo_read(struct audio_utils_fifo *fifo, void *buffer, size_t count); 81 82 #ifdef __cplusplus 83 } 84 #endif 85 86 #endif // !ANDROID_AUDIO_FIFO_H 87
