From 45e3c163a95cc006e6dceefef4fe7b720adf7f6e Mon Sep 17 00:00:00 2001 From: Reimar Döffinger Date: Mon, 20 Aug 2007 16:54:47 +0000 Subject: Additional documentation for CRC functions Originally committed as revision 10151 to svn://svn.ffmpeg.org/ffmpeg/trunk --- libavutil/crc.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) (limited to 'libavutil') diff --git a/libavutil/crc.c b/libavutil/crc.c index b519ac43de..91257d2b8c 100644 --- a/libavutil/crc.c +++ b/libavutil/crc.c @@ -37,6 +37,15 @@ AVCRC av_crc07 [257]; * Inits a crc table. * @param ctx must be an array of sizeof(AVCRC)*257 or sizeof(AVCRC)*1024 * @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 */ 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; } +/** + * 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){ const uint8_t *end= buffer+length; -- cgit v1.2.3