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Take advantage of available input padding to optimize mszh_decomp

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Originally committed as revision 19059 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Reimar Döffinger 2009-05-31 11:32:03 +00:00
parent a5d2745d8e
commit 7a15b25827
1 changed files with 7 additions and 8 deletions
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15
libavcodec/lcldec.c
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@ -73,7 +73,7 @@ typedef struct LclDecContext {
/** /**
* \param srcptr compressed source buffer, must be padded with at least 4 extra bytes * \param srcptr compressed source buffer, must be padded with at least 5 extra bytes
* \param destptr must be padded sufficiently for av_memcpy_backptr * \param destptr must be padded sufficiently for av_memcpy_backptr
*/ */
static unsigned int mszh_decomp(const unsigned char * srcptr, int srclen, unsigned char * destptr, unsigned int destsize) static unsigned int mszh_decomp(const unsigned char * srcptr, int srclen, unsigned char * destptr, unsigned int destsize)
@ -81,16 +81,11 @@ static unsigned int mszh_decomp(const unsigned char * srcptr, int srclen, unsign
unsigned char *destptr_bak = destptr; unsigned char *destptr_bak = destptr;
unsigned char *destptr_end = destptr + destsize; unsigned char *destptr_end = destptr + destsize;
const unsigned char *srcptr_end = srcptr + srclen; const unsigned char *srcptr_end = srcptr + srclen;
unsigned char mask = 0; unsigned char mask = *srcptr++;
unsigned char maskbit = 0; unsigned char maskbit = 0x80;
unsigned int ofs, cnt; unsigned int ofs, cnt;
while (srcptr < srcptr_end && destptr < destptr_end) { while (srcptr < srcptr_end && destptr < destptr_end) {
if (maskbit == 0) {
mask = *srcptr++;
maskbit = 0x80;
continue;
}
if (!(mask & maskbit)) { if (!(mask & maskbit)) {
memcpy(destptr, srcptr, 4); memcpy(destptr, srcptr, 4);
destptr += 4; destptr += 4;
@ -105,6 +100,10 @@ static unsigned int mszh_decomp(const unsigned char * srcptr, int srclen, unsign
destptr += cnt; destptr += cnt;
} }
maskbit >>= 1; maskbit >>= 1;
if (!maskbit) {
mask = *srcptr++;
maskbit = 0x80;
}
} }
return destptr - destptr_bak; return destptr - destptr_bak;