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

Fixes: undefined behavior

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

1 files changed, 6 insertions, 2 deletions

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 ++;
     }
 }