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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>
FFmpeg README ------------- 1) Documentation ---------------- * Read the documentation in the doc/ directory in git. You can also view it online at http://ffmpeg.org/documentation.html 2) Licensing ------------ * See the LICENSE file. 3) Build and Install -------------------- * See the INSTALL file.