Where to find a C++ hash code function for text files ?

[for.fun]

Hi everybody,

I need to calculate the hash code of a text file (in order to uniquely
identify a file)
My program has to run under Windows and under Unix (Solaris)

That's why I am looking for a Standard C++ function which would
calculate the hash value.

Does anyone knows if such a function exist ?

Under Windows, I looked in the STL and found the "hash_value(const char
*)" function but unfortunately, it returns the same value for strings
which have a few differences.

Please tell me if there is a standard and reliable C++ hash function.
If not, please send me a link or another forum where I can get the
answer.

Thanks in advance.

 

[mlimber]

I need to calculate the hash code of a text file (in order to uniquely
identify a file)
My program has to run under Windows and under Unix (Solaris)

That's why I am looking for a Standard C++ function which would
calculate the hash value.

Does anyone knows if such a function exist ?

Under Windows, I looked in the STL and found the "hash_value(const char
*)" function but unfortunately, it returns the same value for strings
which have a few differences.

Please tell me if there is a standard and reliable C++ hash function.
If not, please send me a link or another forum where I can get the
answer.

There is no standard hash function (yet), and the one you found is
likely a part of the STL that was developed by SGI but didn't make it
into the standard library and is thus considered a non-standard
extension. In any case, I think if you want to consider a relatively
large file, a checksum or something of that sort would probably be
better. Google for it.

Cheers! --M

 

[for.fun]

mlimber a écrit :

There is no standard hash function (yet), and the one you found is
likely a part of the STL that was developed by SGI but didn't make it
into the standard library and is thus considered a non-standard
extension. In any case, I think if you want to consider a relatively
large file, a checksum or something of that sort would probably be
better. Google for it.

Thanks for your help and for orienting me to checksums.

 

[sergejusz]

Look for "message digest" - maybe it will help you.

Serge
http://www.sergejusz.com

 

[Roland Pibinger]

I need to calculate the hash code of a text file (in order to uniquely
identify a file)

Start here:
http://en.wikipedia.org/wiki/Cryptographic_hash_function

 

[for.fun]

I cut/paste the C code from the RFC 1321 (http://tools.ietf.org/html/
rfc1321) and it works fine.
Thanks for the links.