diff options
| -rw-r--r-- | libavutil/lzo.c | 24 | ||||
| -rw-r--r-- | libavutil/lzo.h | 2 |
2 files changed, 23 insertions, 3 deletions
diff --git a/libavutil/lzo.c b/libavutil/lzo.c index d5d11867f8..12d3b894b5 100644 --- a/libavutil/lzo.c +++ b/libavutil/lzo.c @@ -106,6 +106,8 @@ static inline void copy(LZOContext *c, int cnt) { c->out = dst + cnt; } +static inline void memcpy_backptr(uint8_t *dst, int back, int cnt); + /** * \brief copy previously decoded bytes to current position * \param back how many bytes back we start @@ -125,9 +127,14 @@ static inline void copy_backptr(LZOContext *c, int back, int cnt) { cnt = FFMAX(c->out_end - dst, 0); c->error |= LZO_OUTPUT_FULL; } + memcpy_backptr(dst, back, cnt); + c->out = dst + cnt; +} + +static inline void memcpy_backptr(uint8_t *dst, int back, int cnt) { + const uint8_t *src = &dst[-back]; if (back == 1) { memset(dst, *src, cnt); - dst += cnt; } else { #ifdef OUTBUF_PADDED COPY2(dst, src); @@ -155,9 +162,20 @@ static inline void copy_backptr(LZOContext *c, int back, int cnt) { } memcpy(dst, src, cnt); } - dst += cnt; } - c->out = dst; +} + +/** + * \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 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. + */ +void av_memcpy_backptr(uint8_t *dst, int back, int cnt) { + memcpy_backptr(dst, back, cnt); } /** diff --git a/libavutil/lzo.h b/libavutil/lzo.h index e7795f7718..6c5e5a31bc 100644 --- a/libavutil/lzo.h +++ b/libavutil/lzo.h @@ -32,4 +32,6 @@ int lzo1x_decode(void *out, int *outlen, const void *in, int *inlen); +void av_memcpy_backptr(uint8_t *dst, int back, int cnt); + #endif /* FFMPEG_LZO_H */ |