How does the MD5 function work?

I'd like to implent a function for SuperFastHash that is compatible so openssl's MD5 function. MD5 is declared in md5.h as:

unsigned char *MD5(const unsigned char *d, size_t n, unsigned char *md);

But I can't find it's definition in the headers and the sourcecode.

So how does it work exactly? The function not the algorithm开发者_StackOverflow社区.

https://www.rfc-editor.org/rfc/rfc1321

In addition to the answer that was given you, I'd like to point out that openssl implementation if md5 can be found in openssl tarball that is available from here http://www.openssl.org/source/

You are after crypto\md5\asm folder inside it.