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.

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

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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.