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Avoid av_memcpy_backptr hang without extra branch. 

This only happens for a "back" value of 0 which is invalid anyway,
but lcldec does not properly validate input.
Also extend the documentation to specify valid values.

Signed-off-by: Reimar Döffinger <Reimar.Doeffinger@gmx.de>
This commit is contained in:
Reimar Döffinger 2011-12-30 10:37:33 +01:00
parent b0143da806
commit 874da652b3
2 changed files with 7 additions and 4 deletions
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6
libavutil/lzo.c
View File

@ -112,7 +112,7 @@ static inline void memcpy_backptr(uint8_t *dst, int back, int cnt);
/**
* @brief Copies previously decoded bytes to current position.
* @param back how many bytes back we start
* @param back how many bytes back we start, must be > 0
* @param cnt number of bytes to copy, must be >= 0
*
* cnt > back is valid, this will copy the bytes we just copied,
@ -135,9 +135,9 @@ static inline void copy_backptr(LZOContext *c, int back, int cnt) {
static inline void memcpy_backptr(uint8_t *dst, int back, int cnt) {
const uint8_t *src = &dst[-back];
if (back == 1) {
if (back <= 1) {
memset(dst, *src, cnt);
} else if(back>0) {
} else {
#ifdef OUTBUF_PADDED
COPY2(dst, src);
COPY2(dst + 2, src + 2);

5
libavutil/lzo.h
View File

@ -62,11 +62,14 @@ int av_lzo1x_decode(void *out, int *outlen, const void *in, int *inlen);
/**
* @brief deliberately overlapping memcpy implementation
* @param dst destination buffer; must be padded with 12 additional bytes
* @param back how many bytes back we start (the initial size of the overlapping window)
* @param back how many bytes back we start (the initial size of the overlapping window), must be > 0
* @param cnt number of bytes to copy, must be >= 0
*
* cnt > back is valid, this will copy the bytes we just copied,
* thus creating a repeating pattern with a period length of back.
* Note that lcldec currently can set back == 0 - which is wrong and
* makes no sense, but the code should at least avoid crashing or hanging
* for this case.
*/
void av_memcpy_backptr(uint8_t *dst, int back, int cnt);