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<title>vorbisfile - datatype - ov_callbacks</title>
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<td><p class=tiny>vorbisfile documentation</p></td>
<td align=right><p class=tiny>vorbisfile version 1.25 - 20000615</p></td>
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<h1>ov_callbacks</h1>

<p><i>declared in "vorbis/codec.h"</i></p>

<p>
The ov_callbacks structure contains file manipulation function prototypes necessary for opening, closing, seeking, and location.
<p>
The ov_callbacks structure does not need to be user-defined if you are working with a standard file.  The typical <a href="ov_open.html">ov_open()</a> call will fill ov_callbacks for you.  However, ov_callbacks should be defined if you are using other data sources.  In this situation, use <a href="ov_open_callbacks.html">ov_open_callbacks()</a> instead of <a href="ov_open.html">ov_open()</a>.
<p>

<p>
The callbacks are designed following the stdio functions fread, fseek, fclose,
and ftell. Except where otherwise noted below, they should work the same as
these functions do.
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<pre><b>typedef struct {
  size_t (*read_func)  (void *ptr, size_t size, size_t nmemb, void *datasource);
  int    (*seek_func)  (void *datasource, int64_t offset, int whence);
  int    (*close_func) (void *datasource);
  long   (*tell_func)  (void *datasource);
} ov_callbacks;</b></pre>
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<h3>Relevant Struct Members</h3>
<dl>
<dt><i>read_func</i></dt>
<dd>Pointer to custom data reading function. Read up to size*nmemb bytes from
the source into the buffer at ptr. Return the number of bytes read successfully.
Must return 0 if nothing can be read. Should also set errno if an error occurs,
in order to distinguish between error and EOF.</dd>
<dt><i>seek_func</i></dt>
<dd>Pointer to custom data seeking function. If your data source does not support
seeking, you <em>must</em> return -1. Returns 0 on success. Seeks to a position <em>offset</em> bytes from a position defined by <em>whence</em>. If whence is SEEK_SET, seek relative to the file start. If SEEK_CUR, seek is relative to current file position. If SEEK_END, relative to end of file.</dd>
<dt><i>close_func</i></dt>
<dd>Pointer to custom data source closure function. This should clear any
resources used by the data source, such as open files or network sockets. Returns 0.</dd>
<dt><i>tell_func</i></dt>
<dd>Pointer to custom data location function. Returns the current offset (from the start) of the data stream. If your source is non-seekable, this need not be
implemented.</dd>
</dl>


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<td><p class=tiny>copyright &copy; 2000 vorbis team</p></td>
<td align=right><p class=tiny><a href="http://www.xiph.org/ogg/vorbis/index.html">Ogg Vorbis</a><br><a href="mailto:team@vorbis.org">team@vorbis.org</a></p></td>
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<td><p class=tiny>vorbisfile documentation</p></td>
<td align=right><p class=tiny>vorbisfile version 1.25 - 20000615</p></td>
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