On Sun, Jan 24, 2021 at 02:05:17PM +0100, Anton Khirnov wrote: > Quoting Michael Niedermayer (2021-01-23 23:34:19) > > On Sat, Jan 23, 2021 at 03:29:38PM +0100, Anton Khirnov wrote: > > > Quoting Michael Niedermayer (2021-01-22 15:09:47) > > > > Fixes: Timeout (too long -> 241ms) > > > > Fixes: > > > > 29083/clusterfuzz-testcase-minimized-ffmpeg_dem_SWF_fuzzer-6273684478230528 > > > > > > > > Found-by: continuous fuzzing process > > > > https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg > > > > Signed-off-by: Michael Niedermayer <mich...@niedermayer.cc> > > > > --- > > > > libavformat/swfdec.c | 3 +++ > > > > 1 file changed, 3 insertions(+) > > > > > > > > diff --git a/libavformat/swfdec.c b/libavformat/swfdec.c > > > > index 1463f0ad4d..aa4be88f91 100644 > > > > --- a/libavformat/swfdec.c > > > > +++ b/libavformat/swfdec.c > > > > @@ -367,6 +367,9 @@ static int swf_read_packet(AVFormatContext *s, > > > > AVPacket *pkt) > > > > ff_dlog(s, "bitmap: ch=%d fmt=%d %dx%d (linesize=%d) > > > > len=%d->%ld pal=%d\n", > > > > ch_id, bmp_fmt, width, height, linesize, len, > > > > out_len, colormapsize); > > > > > > > > + if (len * 17373LL < out_len) > > > > > > Where does the magic number come from? > > > > A very quick simulation of the best case compression for "compress" > > below is not nice written code as i did not expect I or anyone else > > would ever see it again > > > > I would have preferred some nicer expression or course, but thats > > what it seems to be asymptotically. For smaller amounts of data a > > tighter bound is possible but i saw no nice way to consider that > > and it seems also overkill to try to do it more fine grained for > > just this > > > > main(){ > > int64_t bits = 0; > > int bank = 256; > > int bitbank = 8; > > for(unsigned i = 0; i<1024*1024*1024*4U-100000;) { > > int word_size = bank-255; > > i += word_size; > > bits += bitbank; > > > > if (!(bank & (bank-1))) > > bitbank ++; > > bank++; > > if (bitbank > 16) { > > printf("BEST %f \n", 8.0 * i / bits ); > > bank = 256; > > bitbank = 8; > > } > > } > > } > > > > above assumes i remembered correctly how the algorithm works but the > > value was close to what actual compession of zeros gave > > People who read this code in the future will be interested in all this. > So the content of your reply should be added to the commit message > and/or the code itself.
will apply with the message in the commit message thx [...] -- Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB If you fake or manipulate statistics in a paper in physics you will never get a job again. If you fake or manipulate statistics in a paper in medicin you will get a job for life at the pharma industry.
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