[FFmpeg-cvslog] atrac3: avoid oversized shifting in decode_bytes()

[Xi Wang]

ffmpeg | branch: release/0.7 | Xi Wang <xi.wang at gmail.com> | Fri Mar 15 06:31:21 2013 -0400| [78889be3fb4b78a980de283a80a6eabb307db882] | committer: Reinhard Tartler

atrac3: avoid oversized shifting in decode_bytes()

When `off' is 0, `0x537F6103 << 32' in the following expression invokes
undefined behavior, the result of which is not necessarily 0.

    (0x537F6103 >> (off * 8)) | (0x537F6103 << (32 - (off * 8)))

Avoid oversized shifting.

CC: libav-stable at libav.org

Signed-off-by: Xi Wang <xi.wang at gmail.com>
Signed-off-by: Luca Barbato <lu_zero at gentoo.org>

(cherry picked from commit eba1ff31304e407db3cefd7532108408f364367b)

Conflicts:
	libavcodec/atrac3.c

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=78889be3fb4b78a980de283a80a6eabb307db882
---

 libavcodec/atrac3.c |    7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/libavcodec/atrac3.c b/libavcodec/atrac3.c
index 914998e..7831225 100644
--- a/libavcodec/atrac3.c
+++ b/libavcodec/atrac3.c
@@ -179,8 +179,11 @@ static int decode_bytes(const uint8_t* inbuffer, uint8_t* out, int bytes){
     uint32_t* obuf = (uint32_t*) out;
 
     off = (intptr_t)inbuffer & 3;
-    buf = (const uint32_t*) (inbuffer - off);
-    c = av_be2ne32((0x537F6103 >> (off*8)) | (0x537F6103 << (32-(off*8))));
+    buf = (const uint32_t *)(inbuffer - off);
+    if (off)
+        c = av_be2ne32((0x537F6103U >> (off * 8)) | (0x537F6103U << (32 - (off * 8))));
+    else
+        c = av_be2ne32(0x537F6103U);
     bytes += 3 + off;
     for (i = 0; i < bytes/4; i++)
         obuf[i] = c ^ buf[i];