1 /* libFLAC - Free Lossless Audio Codec library 2 * Copyright (C) 2004-2009 Josh Coalson 3 * Copyright (C) 2011-2016 Xiph.Org Foundation 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 9 * - Redistributions of source code must retain the above copyright 10 * notice, this list of conditions and the following disclaimer. 11 * 12 * - Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 16 * - Neither the name of the Xiph.org Foundation nor the names of its 17 * contributors may be used to endorse or promote products derived from 18 * this software without specific prior written permission. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 21 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 22 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 23 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR 24 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, 25 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, 26 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR 27 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF 28 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING 29 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS 30 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 31 */ 32 33 #ifndef FLAC__CALLBACK_H 34 #define FLAC__CALLBACK_H 35 36 #include "ordinals.h" 37 #include <stdlib.h> /* for size_t */ 38 39 /** \file include/FLAC/callback.h 40 * 41 * \brief 42 * This module defines the structures for describing I/O callbacks 43 * to the other FLAC interfaces. 44 * 45 * See the detailed documentation for callbacks in the 46 * \link flac_callbacks callbacks \endlink module. 47 */ 48 49 /** \defgroup flac_callbacks FLAC/callback.h: I/O callback structures 50 * \ingroup flac 51 * 52 * \brief 53 * This module defines the structures for describing I/O callbacks 54 * to the other FLAC interfaces. 55 * 56 * The purpose of the I/O callback functions is to create a common way 57 * for the metadata interfaces to handle I/O. 58 * 59 * Originally the metadata interfaces required filenames as the way of 60 * specifying FLAC files to operate on. This is problematic in some 61 * environments so there is an additional option to specify a set of 62 * callbacks for doing I/O on the FLAC file, instead of the filename. 63 * 64 * In addition to the callbacks, a FLAC__IOHandle type is defined as an 65 * opaque structure for a data source. 66 * 67 * The callback function prototypes are similar (but not identical) to the 68 * stdio functions fread, fwrite, fseek, ftell, feof, and fclose. If you use 69 * stdio streams to implement the callbacks, you can pass fread, fwrite, and 70 * fclose anywhere a FLAC__IOCallback_Read, FLAC__IOCallback_Write, or 71 * FLAC__IOCallback_Close is required, and a FILE* anywhere a FLAC__IOHandle 72 * is required. \warning You generally CANNOT directly use fseek or ftell 73 * for FLAC__IOCallback_Seek or FLAC__IOCallback_Tell since on most systems 74 * these use 32-bit offsets and FLAC requires 64-bit offsets to deal with 75 * large files. You will have to find an equivalent function (e.g. ftello), 76 * or write a wrapper. The same is true for feof() since this is usually 77 * implemented as a macro, not as a function whose address can be taken. 78 * 79 * \{ 80 */ 81 82 #ifdef __cplusplus 83 extern "C" { 84 #endif 85 86 /** This is the opaque handle type used by the callbacks. Typically 87 * this is a \c FILE* or address of a file descriptor. 88 */ 89 typedef void* FLAC__IOHandle; 90 91 /** Signature for the read callback. 92 * The signature and semantics match POSIX fread() implementations 93 * and can generally be used interchangeably. 94 * 95 * \param ptr The address of the read buffer. 96 * \param size The size of the records to be read. 97 * \param nmemb The number of records to be read. 98 * \param handle The handle to the data source. 99 * \retval size_t 100 * The number of records read. 101 */ 102 typedef size_t (*FLAC__IOCallback_Read) (void *ptr, size_t size, size_t nmemb, FLAC__IOHandle handle); 103 104 /** Signature for the write callback. 105 * The signature and semantics match POSIX fwrite() implementations 106 * and can generally be used interchangeably. 107 * 108 * \param ptr The address of the write buffer. 109 * \param size The size of the records to be written. 110 * \param nmemb The number of records to be written. 111 * \param handle The handle to the data source. 112 * \retval size_t 113 * The number of records written. 114 */ 115 typedef size_t (*FLAC__IOCallback_Write) (const void *ptr, size_t size, size_t nmemb, FLAC__IOHandle handle); 116 117 /** Signature for the seek callback. 118 * The signature and semantics mostly match POSIX fseek() WITH ONE IMPORTANT 119 * EXCEPTION: the offset is a 64-bit type whereas fseek() is generally 'long' 120 * and 32-bits wide. 121 * 122 * \param handle The handle to the data source. 123 * \param offset The new position, relative to \a whence 124 * \param whence \c SEEK_SET, \c SEEK_CUR, or \c SEEK_END 125 * \retval int 126 * \c 0 on success, \c -1 on error. 127 */ 128 typedef int (*FLAC__IOCallback_Seek) (FLAC__IOHandle handle, FLAC__int64 offset, int whence); 129 130 /** Signature for the tell callback. 131 * The signature and semantics mostly match POSIX ftell() WITH ONE IMPORTANT 132 * EXCEPTION: the offset is a 64-bit type whereas ftell() is generally 'long' 133 * and 32-bits wide. 134 * 135 * \param handle The handle to the data source. 136 * \retval FLAC__int64 137 * The current position on success, \c -1 on error. 138 */ 139 typedef FLAC__int64 (*FLAC__IOCallback_Tell) (FLAC__IOHandle handle); 140 141 /** Signature for the EOF callback. 142 * The signature and semantics mostly match POSIX feof() but WATCHOUT: 143 * on many systems, feof() is a macro, so in this case a wrapper function 144 * must be provided instead. 145 * 146 * \param handle The handle to the data source. 147 * \retval int 148 * \c 0 if not at end of file, nonzero if at end of file. 149 */ 150 typedef int (*FLAC__IOCallback_Eof) (FLAC__IOHandle handle); 151 152 /** Signature for the close callback. 153 * The signature and semantics match POSIX fclose() implementations 154 * and can generally be used interchangeably. 155 * 156 * \param handle The handle to the data source. 157 * \retval int 158 * \c 0 on success, \c EOF on error. 159 */ 160 typedef int (*FLAC__IOCallback_Close) (FLAC__IOHandle handle); 161 162 /** A structure for holding a set of callbacks. 163 * Each FLAC interface that requires a FLAC__IOCallbacks structure will 164 * describe which of the callbacks are required. The ones that are not 165 * required may be set to NULL. 166 * 167 * If the seek requirement for an interface is optional, you can signify that 168 * a data sorce is not seekable by setting the \a seek field to \c NULL. 169 */ 170 typedef struct { 171 FLAC__IOCallback_Read read; 172 FLAC__IOCallback_Write write; 173 FLAC__IOCallback_Seek seek; 174 FLAC__IOCallback_Tell tell; 175 FLAC__IOCallback_Eof eof; 176 FLAC__IOCallback_Close close; 177 } FLAC__IOCallbacks; 178 179 /* \} */ 180 181 #ifdef __cplusplus 182 } 183 #endif 184 185 #endif 186