1 /* libFLAC - Free Lossless Audio Codec library
2 * Copyright (C) 2004,2005,2006,2007,2008,2009 Josh Coalson
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
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9 * notice, this list of conditions and the following disclaimer.
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12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution.
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16 * contributors may be used to endorse or promote products derived from
17 * this software without specific prior written permission.
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20 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
21 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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32 #ifndef FLAC__CALLBACK_H
33 #define FLAC__CALLBACK_H
36 #include <stdlib.h> /* for size_t */
38 /** \file include/FLAC/callback.h
41 * This module defines the structures for describing I/O callbacks
42 * to the other FLAC interfaces.
44 * See the detailed documentation for callbacks in the
45 * \link flac_callbacks callbacks \endlink module.
48 /** \defgroup flac_callbacks FLAC/callback.h: I/O callback structures
52 * This module defines the structures for describing I/O callbacks
53 * to the other FLAC interfaces.
55 * The purpose of the I/O callback functions is to create a common way
56 * for the metadata interfaces to handle I/O.
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.
63 * In addition to the callbacks, a FLAC__IOHandle type is defined as an
64 * opaque structure for a data source.
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 CANNOT 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.
85 /** This is the opaque handle type used by the callbacks. Typically
86 * this is a \c FILE* or address of a file descriptor.
88 typedef void* FLAC__IOHandle;
90 /** Signature for the read callback.
91 * The signature and semantics match POSIX fread() implementations
92 * and can generally be used interchangeably.
94 * \param ptr The address of the read buffer.
95 * \param size The size of the records to be read.
96 * \param nmemb The number of records to be read.
97 * \param handle The handle to the data source.
99 * The number of records read.
101 typedef size_t (*FLAC__IOCallback_Read) (void *ptr, size_t size, size_t nmemb, FLAC__IOHandle handle);
103 /** Signature for the write callback.
104 * The signature and semantics match POSIX fwrite() implementations
105 * and can generally be used interchangeably.
107 * \param ptr The address of the write buffer.
108 * \param size The size of the records to be written.
109 * \param nmemb The number of records to be written.
110 * \param handle The handle to the data source.
112 * The number of records written.
114 typedef size_t (*FLAC__IOCallback_Write) (const void *ptr, size_t size, size_t nmemb, FLAC__IOHandle handle);
116 /** Signature for the seek callback.
117 * The signature and semantics mostly match POSIX fseek() WITH ONE IMPORTANT
118 * EXCEPTION: the offset is a 64-bit type whereas fseek() is generally 'long'
121 * \param handle The handle to the data source.
122 * \param offset The new position, relative to \a whence
123 * \param whence \c SEEK_SET, \c SEEK_CUR, or \c SEEK_END
125 * \c 0 on success, \c -1 on error.
127 typedef int (*FLAC__IOCallback_Seek) (FLAC__IOHandle handle, FLAC__int64 offset, int whence);
129 /** Signature for the tell callback.
130 * The signature and semantics mostly match POSIX ftell() WITH ONE IMPORTANT
131 * EXCEPTION: the offset is a 64-bit type whereas ftell() is generally 'long'
134 * \param handle The handle to the data source.
135 * \retval FLAC__int64
136 * The current position on success, \c -1 on error.
138 typedef FLAC__int64 (*FLAC__IOCallback_Tell) (FLAC__IOHandle handle);
140 /** Signature for the EOF callback.
141 * The signature and semantics mostly match POSIX feof() but WATCHOUT:
142 * on many systems, feof() is a macro, so in this case a wrapper function
143 * must be provided instead.
145 * \param handle The handle to the data source.
147 * \c 0 if not at end of file, nonzero if at end of file.
149 typedef int (*FLAC__IOCallback_Eof) (FLAC__IOHandle handle);
151 /** Signature for the close callback.
152 * The signature and semantics match POSIX fclose() implementations
153 * and can generally be used interchangeably.
155 * \param handle The handle to the data source.
157 * \c 0 on success, \c EOF on error.
159 typedef int (*FLAC__IOCallback_Close) (FLAC__IOHandle handle);
161 /** A structure for holding a set of callbacks.
162 * Each FLAC interface that requires a FLAC__IOCallbacks structure will
163 * describe which of the callbacks are required. The ones that are not
164 * required may be set to NULL.
166 * If the seek requirement for an interface is optional, you can signify that
167 * a data sorce is not seekable by setting the \a seek field to \c NULL.
170 FLAC__IOCallback_Read read;
171 FLAC__IOCallback_Write write;
172 FLAC__IOCallback_Seek seek;
173 FLAC__IOCallback_Tell tell;
174 FLAC__IOCallback_Eof eof;
175 FLAC__IOCallback_Close close;