filesha1 Function

filesha1 is a variant of sha1 that hashes the contents of a given file rather than a literal string.

This is similar to sha1(file(filename)), but because file accepts only UTF-8 text it cannot be used to create hashes for binary files.

Collision attacks have been successfully performed against this hashing function. Before using this function for anything security-sensitive, review relevant literature to understand the security implications.