pa_ringbuffer.h (8848B)
1 #ifndef PA_RINGBUFFER_H 2 #define PA_RINGBUFFER_H 3 /* 4 * $Id$ 5 * Portable Audio I/O Library 6 * Ring Buffer utility. 7 * 8 * Author: Phil Burk, http://www.softsynth.com 9 * modified for SMP safety on OS X by Bjorn Roche. 10 * also allowed for const where possible. 11 * modified for multiple-byte-sized data elements by Sven Fischer 12 * 13 * Note that this is safe only for a single-thread reader 14 * and a single-thread writer. 15 * 16 * This program is distributed with the PortAudio Portable Audio Library. 17 * For more information see: http://www.portaudio.com 18 * Copyright (c) 1999-2000 Ross Bencina and Phil Burk 19 * 20 * Permission is hereby granted, free of charge, to any person obtaining 21 * a copy of this software and associated documentation files 22 * (the "Software"), to deal in the Software without restriction, 23 * including without limitation the rights to use, copy, modify, merge, 24 * publish, distribute, sublicense, and/or sell copies of the Software, 25 * and to permit persons to whom the Software is furnished to do so, 26 * subject to the following conditions: 27 * 28 * The above copyright notice and this permission notice shall be 29 * included in all copies or substantial portions of the Software. 30 * 31 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, 32 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF 33 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. 34 * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR 35 * ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF 36 * CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION 37 * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. 38 */ 39 40 /* 41 * The text above constitutes the entire PortAudio license; however, 42 * the PortAudio community also makes the following non-binding requests: 43 * 44 * Any person wishing to distribute modifications to the Software is 45 * requested to send the modifications to the original developer so that 46 * they can be incorporated into the canonical version. It is also 47 * requested that these non-binding requests be included along with the 48 * license above. 49 */ 50 51 /** @file 52 @ingroup common_src 53 @brief Single-reader single-writer lock-free ring buffer 54 55 PaUtilRingBuffer is a ring buffer used to transport samples between 56 different execution contexts (threads, OS callbacks, interrupt handlers) 57 without requiring the use of any locks. This only works when there is 58 a single reader and a single writer (ie. one thread or callback writes 59 to the ring buffer, another thread or callback reads from it). 60 61 The PaUtilRingBuffer structure manages a ring buffer containing N 62 elements, where N must be a power of two. An element may be any size 63 (specified in bytes). 64 65 The memory area used to store the buffer elements must be allocated by 66 the client prior to calling PaUtil_InitializeRingBuffer() and must outlive 67 the use of the ring buffer. 68 69 @note The ring buffer functions are not normally exposed in the PortAudio libraries. 70 If you want to call them then you will need to add pa_ringbuffer.c to your application source code. 71 */ 72 73 #if defined(__APPLE__) 74 #include <sys/types.h> 75 typedef int32_t ring_buffer_size_t; 76 #elif defined( __GNUC__ ) 77 typedef long ring_buffer_size_t; 78 #elif (_MSC_VER >= 1400) 79 typedef long ring_buffer_size_t; 80 #elif defined(_MSC_VER) || defined(__BORLANDC__) 81 typedef long ring_buffer_size_t; 82 #else 83 typedef long ring_buffer_size_t; 84 #endif 85 86 87 88 #ifdef __cplusplus 89 extern "C" 90 { 91 #endif /* __cplusplus */ 92 93 typedef struct PaUtilRingBuffer 94 { 95 ring_buffer_size_t bufferSize; /**< Number of elements in FIFO. Power of 2. Set by PaUtil_InitRingBuffer. */ 96 volatile ring_buffer_size_t writeIndex; /**< Index of next writable element. Set by PaUtil_AdvanceRingBufferWriteIndex. */ 97 volatile ring_buffer_size_t readIndex; /**< Index of next readable element. Set by PaUtil_AdvanceRingBufferReadIndex. */ 98 ring_buffer_size_t bigMask; /**< Used for wrapping indices with extra bit to distinguish full/empty. */ 99 ring_buffer_size_t smallMask; /**< Used for fitting indices to buffer. */ 100 ring_buffer_size_t elementSizeBytes; /**< Number of bytes per element. */ 101 char *buffer; /**< Pointer to the buffer containing the actual data. */ 102 }PaUtilRingBuffer; 103 104 /** Initialize Ring Buffer to empty state ready to have elements written to it. 105 106 @param rbuf The ring buffer. 107 108 @param elementSizeBytes The size of a single data element in bytes. 109 110 @param elementCount The number of elements in the buffer (must be a power of 2). 111 112 @param dataPtr A pointer to a previously allocated area where the data 113 will be maintained. It must be elementCount*elementSizeBytes long. 114 115 @return -1 if elementCount is not a power of 2, otherwise 0. 116 */ 117 ring_buffer_size_t PaUtil_InitializeRingBuffer( PaUtilRingBuffer *rbuf, ring_buffer_size_t elementSizeBytes, ring_buffer_size_t elementCount, void *dataPtr ); 118 119 /** Reset buffer to empty. Should only be called when buffer is NOT being read or written. 120 121 @param rbuf The ring buffer. 122 */ 123 void PaUtil_FlushRingBuffer( PaUtilRingBuffer *rbuf ); 124 125 /** Retrieve the number of elements available in the ring buffer for writing. 126 127 @param rbuf The ring buffer. 128 129 @return The number of elements available for writing. 130 */ 131 ring_buffer_size_t PaUtil_GetRingBufferWriteAvailable( const PaUtilRingBuffer *rbuf ); 132 133 /** Retrieve the number of elements available in the ring buffer for reading. 134 135 @param rbuf The ring buffer. 136 137 @return The number of elements available for reading. 138 */ 139 ring_buffer_size_t PaUtil_GetRingBufferReadAvailable( const PaUtilRingBuffer *rbuf ); 140 141 /** Write data to the ring buffer. 142 143 @param rbuf The ring buffer. 144 145 @param data The address of new data to write to the buffer. 146 147 @param elementCount The number of elements to be written. 148 149 @return The number of elements written. 150 */ 151 ring_buffer_size_t PaUtil_WriteRingBuffer( PaUtilRingBuffer *rbuf, const void *data, ring_buffer_size_t elementCount ); 152 153 /** Read data from the ring buffer. 154 155 @param rbuf The ring buffer. 156 157 @param data The address where the data should be stored. 158 159 @param elementCount The number of elements to be read. 160 161 @return The number of elements read. 162 */ 163 ring_buffer_size_t PaUtil_ReadRingBuffer( PaUtilRingBuffer *rbuf, void *data, ring_buffer_size_t elementCount ); 164 165 /** Get address of region(s) to which we can write data. 166 167 @param rbuf The ring buffer. 168 169 @param elementCount The number of elements desired. 170 171 @param dataPtr1 The address where the first (or only) region pointer will be 172 stored. 173 174 @param sizePtr1 The address where the first (or only) region length will be 175 stored. 176 177 @param dataPtr2 The address where the second region pointer will be stored if 178 the first region is too small to satisfy elementCount. 179 180 @param sizePtr2 The address where the second region length will be stored if 181 the first region is too small to satisfy elementCount. 182 183 @return The room available to be written or elementCount, whichever is smaller. 184 */ 185 ring_buffer_size_t PaUtil_GetRingBufferWriteRegions( PaUtilRingBuffer *rbuf, ring_buffer_size_t elementCount, 186 void **dataPtr1, ring_buffer_size_t *sizePtr1, 187 void **dataPtr2, ring_buffer_size_t *sizePtr2 ); 188 189 /** Advance the write index to the next location to be written. 190 191 @param rbuf The ring buffer. 192 193 @param elementCount The number of elements to advance. 194 195 @return The new position. 196 */ 197 ring_buffer_size_t PaUtil_AdvanceRingBufferWriteIndex( PaUtilRingBuffer *rbuf, ring_buffer_size_t elementCount ); 198 199 /** Get address of region(s) from which we can read data. 200 201 @param rbuf The ring buffer. 202 203 @param elementCount The number of elements desired. 204 205 @param dataPtr1 The address where the first (or only) region pointer will be 206 stored. 207 208 @param sizePtr1 The address where the first (or only) region length will be 209 stored. 210 211 @param dataPtr2 The address where the second region pointer will be stored if 212 the first region is too small to satisfy elementCount. 213 214 @param sizePtr2 The address where the second region length will be stored if 215 the first region is too small to satisfy elementCount. 216 217 @return The number of elements available for reading. 218 */ 219 ring_buffer_size_t PaUtil_GetRingBufferReadRegions( PaUtilRingBuffer *rbuf, ring_buffer_size_t elementCount, 220 void **dataPtr1, ring_buffer_size_t *sizePtr1, 221 void **dataPtr2, ring_buffer_size_t *sizePtr2 ); 222 223 /** Advance the read index to the next location to be read. 224 225 @param rbuf The ring buffer. 226 227 @param elementCount The number of elements to advance. 228 229 @return The new position. 230 */ 231 ring_buffer_size_t PaUtil_AdvanceRingBufferReadIndex( PaUtilRingBuffer *rbuf, ring_buffer_size_t elementCount ); 232 233 #ifdef __cplusplus 234 } 235 #endif /* __cplusplus */ 236 #endif /* PA_RINGBUFFER_H */