callback.h (7057B)
1 /* libFLAC - Free Lossless Audio Codec library 2 * Copyright (C) 2004,2005 Josh Coalson 3 * 4 * Redistribution and use in source and binary forms, with or without 5 * modification, are permitted provided that the following conditions 6 * are met: 7 * 8 * - Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 11 * - Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 15 * - Neither the name of the Xiph.org Foundation nor the names of its 16 * contributors may be used to endorse or promote products derived from 17 * this software without specific prior written permission. 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 20 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 21 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 22 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR 23 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, 24 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, 25 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR 26 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF 27 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING 28 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS 29 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 30 */ 31 32 #ifndef FLAC__CALLBACK_H 33 #define FLAC__CALLBACK_H 34 35 #include "ordinals.h" 36 #include <stdlib.h> /* for size_t */ 37 38 /** \file include/FLAC/callback.h 39 * 40 * \brief 41 * This module defines the structures for describing I/O callbacks 42 * to the other FLAC interfaces. 43 * 44 * See the detailed documentation for callbacks in the 45 * \link flac_callbacks callbacks \endlink module. 46 */ 47 48 /** \defgroup flac_callbacks FLAC/callback.h: I/O callback structures 49 * \ingroup flac 50 * 51 * \brief 52 * This module defines the structures for describing I/O callbacks 53 * to the other FLAC interfaces. 54 * 55 * The purpose of the I/O callback functions is to create a common way 56 * for the metadata interfaces to handle I/O. 57 * 58 * Originally the metadata interfaces required filenames as the way of 59 * specifying FLAC files to operate on. This is problematic in some 60 * environments so there is an additional option to specify a set of 61 * callbacks for doing I/O on the FLAC file, instead of the filename. 62 * 63 * In addition to the callbacks, a FLAC__IOHandle type is defined as an 64 * opaque structure for a data source. 65 * 66 * The callback function prototypes are similar (but not identical) to the 67 * stdio functions fread, fwrite, fseek, ftell, feof, and fclose. If you use 68 * stdio streams to implement the callbacks, you can pass fread, fwrite, and 69 * fclose anywhere a FLAC__IOCallback_Read, FLAC__IOCallback_Write, or 70 * FLAC__IOCallback_Close is required, and a FILE* anywhere a FLAC__IOHandle 71 * is required. \warning You generally can NOT directly use fseek or ftell 72 * for FLAC__IOCallback_Seek or FLAC__IOCallback_Tell since on most systems 73 * these use 32-bit offsets and FLAC requires 64-bit offsets to deal with 74 * large files. You will have to find an equivalent function (e.g. ftello), 75 * or write a wrapper. The same is true for feof() since this is usually 76 * implemented as a macro, not as a function whose address can be taken. 77 * 78 * \{ 79 */ 80 81 #ifdef __cplusplus 82 extern "C" { 83 #endif 84 85 typedef void* FLAC__IOHandle; 86 87 /** Signature for the read callback. 88 * The signature and semantics match POSIX fread() implementations 89 * and can generally be used interchangeably. 90 * 91 * \param ptr The address of the read buffer. 92 * \param size The size of the records to be read. 93 * \param nmemb The number of records to be read. 94 * \param handle The handle to the data source. 95 * \retval size_t 96 * The number of records read. 97 */ 98 typedef size_t (*FLAC__IOCallback_Read) (void *ptr, size_t size, size_t nmemb, FLAC__IOHandle handle); 99 100 /** Signature for the write callback. 101 * The signature and semantics match POSIX fwrite() implementations 102 * and can generally be used interchangeably. 103 * 104 * \param ptr The address of the write buffer. 105 * \param size The size of the records to be written. 106 * \param nmemb The number of records to be written. 107 * \param handle The handle to the data source. 108 * \retval size_t 109 * The number of records written. 110 */ 111 typedef size_t (*FLAC__IOCallback_Write) (const void *ptr, size_t size, size_t nmemb, FLAC__IOHandle handle); 112 113 /** Signature for the seek callback. 114 * The signature and semantics mostly match POSIX fseek() WITH ONE IMPORTANT 115 * EXCEPTION: the offset is a 64-bit type whereas fseek() is generally 'long' 116 * and 32-bits wide. 117 * 118 * \param handle The handle to the data source. 119 * \param offset The new position, relative to \a whence 120 * \param whence \c SEEK_SET, \c SEEK_CUR, or \c SEEK_END 121 * \retval int 122 * \c 0 on success, \c -1 on error. 123 */ 124 typedef int (*FLAC__IOCallback_Seek) (FLAC__IOHandle handle, FLAC__int64 offset, int whence); 125 126 /** Signature for the tell callback. 127 * The signature and semantics mostly match POSIX ftell() WITH ONE IMPORTANT 128 * EXCEPTION: the offset is a 64-bit type whereas ftell() is generally 'long' 129 * and 32-bits wide. 130 * 131 * \param handle The handle to the data source. 132 * \retval FLAC__int64 133 * The current position on success, \c -1 on error. 134 */ 135 typedef FLAC__int64 (*FLAC__IOCallback_Tell) (FLAC__IOHandle handle); 136 137 /** Signature for the EOF callback. 138 * The signature and semantics mostly match POSIX feof() but WATCHOUT: 139 * on many systems, feof() is a macro, so in this case a wrapper function 140 * must be provided instead. 141 * 142 * \param handle The handle to the data source. 143 * \retval int 144 * \c 0 if not at end of file, nonzero if at end of file. 145 */ 146 typedef int (*FLAC__IOCallback_Eof) (FLAC__IOHandle handle); 147 148 /** Signature for the close callback. 149 * The signature and semantics match POSIX fclose() implementations 150 * and can generally be used interchangeably. 151 * 152 * \param handle The handle to the data source. 153 * \retval int 154 * \c 0 on success, \c EOF on error. 155 */ 156 typedef int (*FLAC__IOCallback_Close) (FLAC__IOHandle handle); 157 158 /** A structure for holding a set of callbacks. 159 * Each FLAC interface that requires a FLAC__IOCallbacks structure will 160 * describe which of the callbacks are required. The ones that are not 161 * required may be set to NULL. 162 * 163 * If the seek requirement for an interface is optional, you can signify that 164 * a data sorce is not seekable by setting the \a seek field to \c NULL. 165 */ 166 typedef struct { 167 FLAC__IOCallback_Read read; 168 FLAC__IOCallback_Write write; 169 FLAC__IOCallback_Seek seek; 170 FLAC__IOCallback_Tell tell; 171 FLAC__IOCallback_Eof eof; 172 FLAC__IOCallback_Close close; 173 } FLAC__IOCallbacks; 174 175 /* \} */ 176 177 #ifdef __cplusplus 178 } 179 #endif 180 181 #endif