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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