On Sun, Aug 13, 2017 at 07:18:11PM -0300, James Almer wrote:
> On 8/13/2017 7:15 PM, Michael Niedermayer wrote:
> > Fixes: undefined behavior
> >
> > Signed-off-by: Michael Niedermayer <mich...@niedermayer.cc>
> > ---
> > libavcodec/rangecoder.c | 1 +
> > libavcodec/rangecoder.h | 8 ++++++--
> > 2 files changed, 7 insertions(+), 2 deletions(-)
> >
> > diff --git a/libavcodec/rangecoder.c b/libavcodec/rangecoder.c
> > index 0bb79c880e..0d53bef076 100644
> > --- a/libavcodec/rangecoder.c
> > +++ b/libavcodec/rangecoder.c
> > @@ -58,6 +58,7 @@ av_cold void ff_init_range_decoder(RangeCoder *c, const
> > uint8_t *buf,
> >
> > c->low = AV_RB16(c->bytestream);
> > c->bytestream += 2;
> > + c->overread = 0;
> > if (c->low >= 0xFF00) {
> > c->low = 0xFF00;
> > c->bytestream_end = c->bytestream;
> > diff --git a/libavcodec/rangecoder.h b/libavcodec/rangecoder.h
> > index c3e81d0dcb..44af88b8f5 100644
> > --- a/libavcodec/rangecoder.h
> > +++ b/libavcodec/rangecoder.h
> > @@ -42,6 +42,8 @@ typedef struct RangeCoder {
> > uint8_t *bytestream_start;
> > uint8_t *bytestream;
> > uint8_t *bytestream_end;
> > + int overread;
> > +#define MAX_OVERREAD 2
> > } RangeCoder;
> >
> > void ff_init_range_encoder(RangeCoder *c, uint8_t *buf, int buf_size);
> > @@ -106,9 +108,11 @@ static inline void refill(RangeCoder *c)
> > if (c->range < 0x100) {
> > c->range <<= 8;
> > c->low <<= 8;
> > - if (c->bytestream < c->bytestream_end)
> > + if (c->bytestream < c->bytestream_end) {
> > c->low += c->bytestream[0];
> > - c->bytestream++;
> > + c->bytestream++;
> > + } else
> > + c->overread ++;
> > }
> > }
>
> Wouldn't it be better to port this to the bytestream2 reading api?this is speed relevant code, i am not sure bytestream2 wouldnt add overhead. In fact i wasnt entirely sure keeping track of the overread bytes is a great idea. But i didnt see an easy way to avoid that. [...] -- Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB Take away the freedom of one citizen and you will be jailed, take away the freedom of all citizens and you will be congratulated by your peers in Parliament.
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