From 74f4b1bc3b627ba4c7e03498234d88cacdfbe97b Mon Sep 17 00:00:00 2001 From: Aki Date: Wed, 29 Sep 2021 22:52:49 +0200 Subject: Squashed 'vorbis/' content from commit d22c3ab5f git-subtree-dir: vorbis git-subtree-split: d22c3ab5f633460abc2532feee60ca0892134cbf --- doc/vorbisfile/callbacks.html | 121 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 121 insertions(+) create mode 100644 doc/vorbisfile/callbacks.html (limited to 'doc/vorbisfile/callbacks.html') diff --git a/doc/vorbisfile/callbacks.html b/doc/vorbisfile/callbacks.html new file mode 100644 index 0000000..20ae55a --- /dev/null +++ b/doc/vorbisfile/callbacks.html @@ -0,0 +1,121 @@ + + + +Vorbisfile - Callbacks and non-stdio I/O + + + + + + + + + +

Vorbisfile documentation

vorbisfile version 1.3.2 - 20101101

+ +

Callbacks and non-stdio I/O

+ +Although stdio is convenient and nearly universally implemented as per +ANSI C, it is not suited to all or even most potential uses of Vorbis. +For additional flexibility, embedded applications may provide their +own I/O functions for use with Vorbisfile when stdio is unavailable or not +suitable. One common example is decoding a Vorbis stream from a +memory buffer.

+ +Use custom I/O functions by populating an ov_callbacks structure and calling ov_open_callbacks() or ov_test_callbacks() rather than the +typical ov_open() or ov_test(). Past the open call, use of +libvorbisfile is identical to using it with stdio. + +

Read function

+ +The read-like function provided in the read_func field is +used to fetch the requested amount of data. It expects the fetch +operation to function similar to file-access, that is, a multiple read +operations will retrieve contiguous sequential pieces of data, +advancing a position cursor after each read.

+ +The following behaviors are also expected:

a return of '0' indicates end-of-data (if the by-thread errno is unset) +
short reads mean nothing special (short reads are not treated as error conditions) +
a return of zero with the by-thread errno set to nonzero indicates a read error +

+ +

Seek function

+ +The seek-like function provided in the seek_func field is +used to request non-sequential data access by libvorbisfile, moving +the access cursor to the requested position. The seek function is +optional; if callbacks are only to handle non-seeking (streaming) data +or the application wishes to force streaming behavior, +seek_func and tell_func should be set to NULL. If +the seek function is non-NULL, libvorbisfile mandates the following +behavior: + +

The seek function must always return -1 (failure) if the given +data abstraction is not seekable. It may choose to always return -1 +if the application desires libvorbisfile to treat the Vorbis data +strictly as a stream (which makes for a less expensive open +operation).
+ +
If the seek function initially indicates seekability, it must +always succeed upon being given a valid seek request.
+ +
The seek function must implement all of SEEK_SET, SEEK_CUR and +SEEK_END. The implementation of SEEK_END should set the access cursor +one past the last byte of accessible data, as would stdio +fseek()
+

+ +

Close function

+ +The close function should deallocate any access state used by the +passed in instance of the data access abstraction and invalidate the +instance handle. The close function is assumed to succeed; its return +code is not checked.

+ +The close_func may be set to NULL to indicate that libvorbis +should not attempt to close the file/data handle in ov_clear but allow the application to handle +file/data access cleanup itself. For example, by passing the normal +stdio calls as callback functions, but passing a close_func +that is NULL or does nothing (as in the case of OV_CALLBACKS_NOCLOSE), an +application may call ov_clear() and then +later fclose() the file originally passed to libvorbisfile. + +

Tell function

+ +The tell function is intended to mimic the +behavior of ftell() and must return the byte position of the +next data byte that would be read. If the data access cursor is at +the end of the 'file' (pointing to one past the last byte of data, as +it would be after calling fseek(file,SEEK_END,0)), the tell +function must return the data position (and thus the total file size), +not an error.

+ +The tell function need not be provided if the data IO abstraction is +not seekable, or the application wishes to force streaming +behavior. In this case, the tell_func and seek_func +fields should be set to NULL.

+ +

+

+ + + + + + + + +

copyright © 2000-2010 Xiph.Org	Ogg Vorbis
Vorbisfile documentation	vorbisfile version 1.3.2 - 20101101

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