Changeset c78cf00b in ffmpeg

Timestamp:

Jun 16, 2012, 10:47:46 AM (12 years ago)

Author:

Michael Niedermayer <michaelni@gmx.at>

Branches:

master

Children:

fd8def92

Parents:

c7bdfbe7

git-author:

Giorgio Vazzana <mywing81@gmail.com> (06/15/12 15:21:36)

git-committer:

Michael Niedermayer <michaelni@gmx.at> (06/16/12 10:47:46)

Message:

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@gmx.at>

(No files)