diff options
| author | Jonathan Campbell <jonathan@castus.tv> | 2016-09-03 03:29:29 -0700 |
|---|---|---|
| committer | Michael Niedermayer <michael@niedermayer.cc> | 2017-01-22 02:28:53 +0100 |
| commit | 76c5a69e26afbfdfc5b6f538594ea12efa31fc9a (patch) | |
| tree | 0cef85bf008e1670513082029c727a5b38cc3979 | |
| parent | 0a5add45c7527bbe627899be744f962588e5b2fa (diff) | |
| download | ffmpeg-76c5a69e26afbfdfc5b6f538594ea12efa31fc9a.tar.gz | |
libavutil: add av_lfg_init_from_data() function
seeds an AVLFG from binary data.
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
| -rw-r--r-- | doc/APIchanges | 3 | ||||
| -rw-r--r-- | libavutil/lfg.c | 27 | ||||
| -rw-r--r-- | libavutil/lfg.h | 9 | ||||
| -rw-r--r-- | libavutil/version.h | 2 |
4 files changed, 40 insertions, 1 deletions
diff --git a/doc/APIchanges b/doc/APIchanges index 98f8076f47..f5f7e0c07f 100644 --- a/doc/APIchanges +++ b/doc/APIchanges @@ -15,6 +15,9 @@ libavutil: 2015-08-28 API changes, most recent first: +2017-01-22 - xxxxxxx - lavu 55.44.100 - lfg.h + Add av_lfg_init_from_data(). + 2017-01-xx - xxxxxxx - lavc 57.74.100 - vaapi.h Deprecate struct vaapi_context and the vaapi.h installed header. Callers should set AVCodecContext.hw_frames_ctx instead. diff --git a/libavutil/lfg.c b/libavutil/lfg.c index 08a4f678e2..46b04d2403 100644 --- a/libavutil/lfg.c +++ b/libavutil/lfg.c @@ -23,7 +23,9 @@ #include <limits.h> #include <math.h> #include "lfg.h" +#include "crc.h" #include "md5.h" +#include "error.h" #include "intreadwrite.h" #include "attributes.h" @@ -58,3 +60,28 @@ void av_bmg_get(AVLFG *lfg, double out[2]) out[0] = x1 * w; out[1] = x2 * w; } + +int av_lfg_init_from_data(AVLFG *c, const uint8_t *data, unsigned int length) { + unsigned int beg, end, segm; + const AVCRC *avcrc; + uint32_t crc = 1; + + /* avoid integer overflow in the loop below. */ + if (length > (UINT_MAX / 128U)) return AVERROR(EINVAL); + + c->index = 0; + avcrc = av_crc_get_table(AV_CRC_32_IEEE); /* This can't fail. It's a well-defined table in crc.c */ + + /* across 64 segments of the incoming data, + * do a running crc of each segment and store the crc as the state for that slot. + * this works even if the length of the segment is 0 bytes. */ + beg = 0; + for (segm = 0;segm < 64;segm++) { + end = (((segm + 1) * length) / 64); + crc = av_crc(avcrc, crc, data + beg, end - beg); + c->state[segm] = (unsigned int)crc; + beg = end; + } + + return 0; +} diff --git a/libavutil/lfg.h b/libavutil/lfg.h index ec90562cf2..03f779ad8a 100644 --- a/libavutil/lfg.h +++ b/libavutil/lfg.h @@ -22,6 +22,8 @@ #ifndef AVUTIL_LFG_H #define AVUTIL_LFG_H +#include <stdint.h> + typedef struct AVLFG { unsigned int state[64]; int index; @@ -30,6 +32,13 @@ typedef struct AVLFG { void av_lfg_init(AVLFG *c, unsigned int seed); /** + * Seed the state of the ALFG using binary data. + * + * Return value: 0 on success, negative value (AVERROR) on failure. + */ +int av_lfg_init_from_data(AVLFG *c, const uint8_t *data, unsigned int length); + +/** * Get the next random unsigned 32-bit number using an ALFG. * * Please also consider a simple LCG like state= state*1664525+1013904223, diff --git a/libavutil/version.h b/libavutil/version.h index 9f8c4c2364..2e83ef279e 100644 --- a/libavutil/version.h +++ b/libavutil/version.h @@ -79,7 +79,7 @@ */ #define LIBAVUTIL_VERSION_MAJOR 55 -#define LIBAVUTIL_VERSION_MINOR 43 +#define LIBAVUTIL_VERSION_MINOR 44 #define LIBAVUTIL_VERSION_MICRO 100 #define LIBAVUTIL_VERSION_INT AV_VERSION_INT(LIBAVUTIL_VERSION_MAJOR, \ |