<html> <head> <title>Vorbisfile - function - ov_test_callbacks</title> <link rel=stylesheet href="style.css" type="text/css"> </head> <body bgcolor=white text=black link="#5555ff" alink="#5555ff" vlink="#5555ff"> <table border=0 width=100%> <tr> <td><p class=tiny>Vorbisfile documentation</p></td> <td align=right><p class=tiny>vorbisfile version 1.2.0 - 20070723</p></td> </tr> </table> <h1>ov_test_callbacks</h1> <p><i>declared in "vorbis/vorbisfile.h";</i></p> <p>This is an alternative function used to open and test an OggVorbis_File structure when using a data source other than a file, when its necessary to modify default file access behavior, or to test for Vorbis content from a <tt>FILE *</tt> pointer under Windows where <a href="ov_open.html">ov_test()</a> cannot be used. It allows the application to specify custom file manipulation routines and sets up all the related decoding structures. <p>Once this has been called, the same <tt>OggVorbis_File</tt> struct should be passed to all the libvorbisfile functions. <p> <br><br> <table border=0 color=black cellspacing=0 cellpadding=7> <tr bgcolor=#cccccc> <td> <pre><b> int ov_test_callbacks(void *datasource, <a href="OggVorbis_File.html">OggVorbis_File</a> *vf, char *initial, long ibytes, <a href="ov_callbacks.html">ov_callbacks</a> callbacks); </b></pre> </td> </tr> </table> <h3>Parameters</h3> <dl> <dt><i>f</i></dt> <dd>File pointer to an already opened file or pipe (it need not be seekable--though this obviously restricts what can be done with the bitstream).</dd> <dt><i>vf</i></dt> <dd>A pointer to the OggVorbis_File structure--this is used for ALL the externally visible libvorbisfile functions. Once this has been called, the same <tt>OggVorbis_File</tt> struct should be passed to all the libvorbisfile functions.</dd> <dt><i>initial</i></dt> <dd>Typically set to NULL. This parameter is useful if some data has already been read from the file and the stream is not seekable. It is used in conjunction with <tt>ibytes</tt>. In this case, <tt>initial</tt> should be a pointer to a buffer containing the data read.</dd> <dt><i>ibytes</i></dt> <dd>Typically set to 0. This parameter is useful if some data has already been read from the file and the stream is not seekable. In this case, <tt>ibytes</tt> should contain the length (in bytes) of the buffer. Used together with <tt>initial</tt>.</dd> <dt><i>callbacks</i></dt> <dd>A completed <a href="ov_callbacks.html">ov_callbacks</a> struct which indicates desired custom file manipulation routines. vorbisfile.h defines several preprovided callback sets; see <a href="ov_callbacks.html">ov_callbacks</a> for details.</dd> </dl> <h3>Return Values</h3> <blockquote> <li>0 for success</li> <li>less than zero for failure:</li> <ul> <li>OV_EREAD - A read from media returned an error.</li> <li>OV_ENOTVORBIS - Bitstream contains no Vorbis data.</li> <li>OV_EVERSION - Vorbis version mismatch.</li> <li>OV_EBADHEADER - Invalid Vorbis bitstream header.</li> <li>OV_EFAULT - Internal logic fault; indicates a bug or heap/stack corruption.</li> </ul> </blockquote> <p> <h3>Notes</h3> <dl> <dt><b>[a] Windows and use as an ov_test() substitute</b><p> Windows applications should not use <a href="ov_test.html">ov_test()</a> due to the likelihood of <a href="ov_open.html#winfoot">CRT linking mismatches and runtime protection faults [ov_open:a]</a>. ov_test_callbacks() is a safe substitute; specifically: <pre><tt>ov_test_callbacks(f, vf, initial, ibytes, OV_CALLBACKS_DEFAULT);</tt> </pre> ... provides exactly the same functionality as <a href="ov_test.html">ov_test()</a> but will always work correctly under Windows, regardless of linking setup details.<p> </dl> <br><br> <hr noshade> <table border=0 width=100%> <tr valign=top> <td><p class=tiny>copyright © 2007 Xiph.org</p></td> <td align=right><p class=tiny><a href="http://www.xiph.org/ogg/vorbis/">Ogg Vorbis</a></p></td> </tr><tr> <td><p class=tiny>Vorbisfile documentation</p></td> <td align=right><p class=tiny>vorbisfile version 1.2.0 - 20070723</p></td> </tr> </table> </body> </html>