[FFmpeg-cvslog] md5: consistently use uint32_t instead of unsigned int
Giorgio Vazzana
git at videolan.org
Sat Jun 16 13:03:30 CEST 2012
ffmpeg | branch: master | Giorgio Vazzana <mywing81 at gmail.com> | Fri Jun 15 17:21:36 2012 +0200| [c78cf00bd8329dd339d2f73d1b43c366d0f46837] | committer: Michael Niedermayer
md5: consistently use uint32_t instead of unsigned int
Basically to make code clearer and adherent to the
standard. RFC 1321, on page 2 states
Let the symbol "+" denote addition of words (i.e., modulo-2^32
addition). Let X <<< s denote the 32-bit value obtained by circularly
shifting (rotating) X left by s bit positions.
on page 3, section 3.3 states:
A four-word buffer (A,B,C,D) is used to compute the message digest.
Here each of A, B, C, D is a 32-bit register.
so the algorithm needs to work with integers that are exactly 32bits
in length. And indeed in struct AVMD5 the MD buffer is declared as
"uint32_t ABCD[4];", while in the function that performs the block
transformation the state variables were "unsigned int"s. On
architectures where sizeof(unsigned int) != sizeof(uint32_t) this
could be a problem, although I can't name such an architecture from
the top of my head.
On a side note, both the reference implementation in RFC 1321 and the
gnulib implementation (used by md5sum program on GNU systems) use
uint32_t in the transform function.
Signed-off-by: Michael Niedermayer <michaelni at gmx.at>
> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=c78cf00bd8329dd339d2f73d1b43c366d0f46837
---
libavutil/md5.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)
diff --git a/libavutil/md5.c b/libavutil/md5.c
index 471a510..00447f9 100644
--- a/libavutil/md5.c
+++ b/libavutil/md5.c
@@ -88,12 +88,12 @@ static const uint32_t T[64] = { // T[i]= fabs(sin(i+1)<<32)
static void body(uint32_t ABCD[4], uint32_t X[16])
{
- int t;
int i av_unused;
- unsigned int a = ABCD[3];
- unsigned int b = ABCD[2];
- unsigned int c = ABCD[1];
- unsigned int d = ABCD[0];
+ uint32_t t;
+ uint32_t a = ABCD[3];
+ uint32_t b = ABCD[2];
+ uint32_t c = ABCD[1];
+ uint32_t d = ABCD[0];
#if HAVE_BIGENDIAN
for (i = 0; i < 16; i++)
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