Hash2, a hash function library

This library contains an extensible framework for implementing hashing algorithms that can support user-defined types, based on the paper "Types don't know #" by Howard Hinnant, Vinnie Falco and John Bytheway.

It also contains implementations of several popular hashing algorithms:

• FNV-1a
• MurmurHash 3
• xxHash
• SpookyHash v2
• SipHash
• MD5
• SHA-1
• HMAC-MD5 and HMAC-SHA1

The hashing algorithms conform to the following concept:

struct HashAlgorithm
{
    typedef /*integral or array<unsigned char, N>*/ result_type; // result type
    typedef /*unsigned integral*/ size_type; // how is container.size() hashed

    HashAlgorithm(); // default-constructible
    explicit HashAlgorithm( uint64_t seed ); // seed-constructible
    HashAlgorithm( unsigned char const* seed, size_t n ); // seed-constructible

    HashAlgorithm( HashAlgorithm const& r ); // copy-constructible
    HashAlgorithm& operator=( HashAlgorithm const& r ); // assignable

    void update( void const* data, size_t n ); // feed bytes

    result_type result(); // obtain result; also advances state,
                          // and can be called multiple times
};

Supported compilers

The library requires C++11. The following compilers:

• g++ 4.8 or later
• clang++ 3.9 or later
• Visual Studio 2015 and above

are being tested on Github Actions and Appveyor.

Documentation

None yet.

Planned Additions

• Documentation (obv.)
• SHA2-256, 384, 512
• Support for endian-independent hashing
• A std::hash-compatible adaptor
• A type-erased hash_function
• A hash2sum example

License

Distributed under the Boost Software License, Version 1.0.