[FFmpeg-devel] [PATCH 3/5] startcode: Stop overreading

[Andreas Rheinhardt]

Up until now ff_startcode_find_candidate_c could overread; it relied on
zero-padding after the buffer in order to function correctly. This has
been changed: No overreads occur any more.
The ultimate goal behind all this is to create a high-performance
function for searching of startcodes that can be applied even in
scenarios where the buffer is not padded.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt at gmail.com>
---
 libavcodec/startcode.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/libavcodec/startcode.c b/libavcodec/startcode.c
index 373572365b..b027c191c0 100644
--- a/libavcodec/startcode.c
+++ b/libavcodec/startcode.c
@@ -41,10 +41,7 @@ int ff_startcode_find_candidate_c(const uint8_t *buf, int size)
 
 #define READ(bitness) AV_RN ## bitness ## A
 #define MAIN_LOOP(bitness, mask1, mask2) do {                              \
-        /* we check p < end instead of p + 3 / 7 because it is
-         * simpler and there must be AV_INPUT_BUFFER_PADDING_SIZE
-         * bytes at the end. */                                            \
-        for (; buf < end; buf += bitness / 8)                              \
+        for (; buf <= end - bitness / 8; buf += bitness / 8)               \
             if ((~READ(bitness)(buf) & (READ(bitness)(buf) - mask1))       \
                                      & mask2)                              \
                 break;                                                     \
-- 
2.21.0