SHA-1 in fully-portable C89?

[CBFalconer]

I believe the question was about an implementation of SHA-1, not
of C.

Yes, that would make a difference.

 

[Tor Rustad]

Might I ask where I can get my hands on the one you've been using?

You may, but I'm not allowed to disclose information about
code owned by my employer, even if the code was written by
me.

 

[Spoon]

And click on ciphers. There is an SHA1, SHA2 and SHA3 implementation

There is no SHA-3 yet.

http://csrc.nist.gov/groups/ST/hash/documents/FR_Notice_Nov07.pdf

 

[Szabolcs Nagy]

Might I ask where I can get my hands on the one you've been using?

you can try one of the several implementation in opensource highlevel
programming languages

eg python uses the reference nist implementation with minor
modifications to be more portable