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avcodec/rangecoder: Do not increase the pointer beyond the buffer 

Fixes: undefined behavior

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
This commit is contained in:
Michael Niedermayer 2017-08-14 00:15:54 +02:00
parent f4544163b2
commit c359c51947
2 changed files with 7 additions and 2 deletions
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1
libavcodec/rangecoder.c
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@ -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;

8
libavcodec/rangecoder.h
View File

@ -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 ++;
}
}