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md5: consistently use uint32_t instead of unsigned int

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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@gmx.at>
This commit is contained in:
Giorgio Vazzana 2012-06-15 17:21:36 +02:00 committed by Michael Niedermayer
parent c7bdfbe79f
commit c78cf00bd8
1 changed files with 5 additions and 5 deletions
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10
libavutil/md5.c
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@ -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++)