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avcodec/scpr: Factor some indexes out in decode_run_i() 

This improves the speed of decode_run_i()

After:  clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_SCPR_fuzzer-5656821117747200 in 13516 ms
Before: clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_SCPR_fuzzer-5656821117747200 in 14018 ms

Improves: 11270/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_SCPR_fuzzer-5656821117747200

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
This commit is contained in:
Michael Niedermayer 2018-12-27 02:21:00 +01:00
parent 609e2e64f6
commit 20564d23fd
1 changed files with 12 additions and 10 deletions
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22
libavcodec/scpr.h
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@ -140,26 +140,28 @@ static int decode_run_i(AVCodecContext *avctx, uint32_t ptype, int run,
case 4:
while (run-- > 0) {
uint8_t *odst = (uint8_t *)dst;
int off1 = (ly * linesize + lx) * 4;
int off2 = ((y * linesize + x) + off) * 4;
if (y < 1 || y >= avctx->height ||
(y == 1 && x == 0))
return AVERROR_INVALIDDATA;
if (x == 0) {
z = backstep;
z = backstep * 4;
} else {
z = 0;
}
r = odst[(ly * linesize + lx) * 4] +
odst[((y * linesize + x) + off) * 4 + 4] -
odst[((y * linesize + x) + off - z) * 4];
g = odst[(ly * linesize + lx) * 4 + 1] +
odst[((y * linesize + x) + off) * 4 + 5] -
odst[((y * linesize + x) + off - z) * 4 + 1];
b = odst[(ly * linesize + lx) * 4 + 2] +
odst[((y * linesize + x) + off) * 4 + 6] -
odst[((y * linesize + x) + off - z) * 4 + 2];
r = odst[off1] +
odst[off2 + 4] -
odst[off2 - z ];
g = odst[off1 + 1] +
odst[off2 + 5] -
odst[off2 - z + 1];
b = odst[off1 + 2] +
odst[off2 + 6] -
odst[off2 - z + 2];
clr = ((b & 0xFF) << 16) + ((g & 0xFF) << 8) + (r & 0xFF);
dst[y * linesize + x] = clr;
lx = x;