// metrohash128.h
//
// Copyright 2015-2018 J. Andrew Rogers
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#ifndef METROHASH_METROHASH_128_H
#define METROHASH_METROHASH_128_H

#include <stdint.h>
#include <utility>

typedef std::pair<uint64_t, uint64_t> _uint128_t;

class MetroHash128
{
public:
    static const uint32_t bits = 128;

    // Constructor initializes the same as Initialize()
    MetroHash128(const uint64_t seed=0);
    
    // Initializes internal state for new hash with optional seed
    void Initialize(const uint64_t seed=0);
    
    // Update the hash state with a string of bytes. If the length
    // is sufficiently long, the implementation switches to a bulk
    // hashing algorithm directly on the argument buffer for speed.
    void Update(const void* buffer, const uint64_t length) {
      Update(reinterpret_cast<const uint8_t*>(buffer), length);
    }
    void Update(const uint8_t* buffer, const uint64_t length);
    template <class T>
    void Update(const T& x) {
      Update(&x, sizeof(x));
    }
    
    // Constructs the final hash and writes it to the argument buffer.
    // After a hash is finalized, this instance must be Initialized()-ed
    // again or the behavior of Update() and Finalize() is undefined.
    void Finalize(uint8_t * const hash);
    
    // A non-incremental function implementation. This can be significantly
    // faster than the incremental implementation for some usage patterns.
    static void Hash(const uint8_t * buffer, const uint64_t length, uint8_t * const hash, const uint64_t seed=0);

    // Does implementation correctly execute test vectors?
    static bool ImplementationVerified();

    // test vectors -- Hash(test_string, seed=0) => test_seed_0
    static const char * test_string;
    static const uint8_t test_seed_0[16];
    static const uint8_t test_seed_1[16];

private:
    static const uint64_t k0 = 0xC83A91E1;
    static const uint64_t k1 = 0x8648DBDB;
    static const uint64_t k2 = 0x7BDEC03B;
    static const uint64_t k3 = 0x2F5870A5;
    
    struct { uint64_t v[4]; } state;
    struct { uint8_t b[32]; } input;
    uint64_t bytes;
};


// Legacy 128-bit hash functions -- do not use
void metrohash128_1(const uint8_t * key, uint64_t len, uint32_t seed, uint8_t * out);
void metrohash128_2(const uint8_t * key, uint64_t len, uint32_t seed, uint8_t * out);


#endif // #ifndef METROHASH_METROHASH_128_H