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Additional documentation for CRC functions 

Originally committed as revision 10151 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Reimar Döffinger 2007-08-20 16:54:47 +00:00
parent 6d1ba1ac83
commit 45e3c163a9
1 changed files with 16 additions and 0 deletions
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16
libavutil/crc.c
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@ -37,6 +37,15 @@ AVCRC av_crc07 [257];
* Inits a crc table. * Inits a crc table.
* @param ctx must be an array of sizeof(AVCRC)*257 or sizeof(AVCRC)*1024 * @param ctx must be an array of sizeof(AVCRC)*257 or sizeof(AVCRC)*1024
* @param cts_size size of ctx in bytes * @param cts_size size of ctx in bytes
* @param le if 1, lowest bit represents coefficient for highest exponent
* of corresponding polynomial (both for poly and actual CRC).
* If 0, you must swap the crc parameter and the result of av_crc
* if you need the standard representation (can be simplified in
* most cases to e.g. bswap16):
* bswap_32(crc << (32-bits))
* @param bits number of bits for the CRC
* @param poly generator polynomial without the x**bits coefficient, in the
* representation as specified by le
* @return <0 on failure * @return <0 on failure
*/ */
int av_crc_init(AVCRC *ctx, int le, int bits, uint32_t poly, int ctx_size){ int av_crc_init(AVCRC *ctx, int le, int bits, uint32_t poly, int ctx_size){
@ -70,6 +79,13 @@ int av_crc_init(AVCRC *ctx, int le, int bits, uint32_t poly, int ctx_size){
return 0; return 0;
} }
/**
* Calculate the CRC of a block
* @param crc CRC of previous blocks if any or initial value for CRC.
* @return CRC updated with the data from the given block
*
* @see av_crc_init() "le" parameter
*/
uint32_t av_crc(const AVCRC *ctx, uint32_t crc, const uint8_t *buffer, size_t length){ uint32_t av_crc(const AVCRC *ctx, uint32_t crc, const uint8_t *buffer, size_t length){
const uint8_t *end= buffer+length; const uint8_t *end= buffer+length;