hashmap.hpp

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// Copyright (c) 2021 MIT Digital Currency Initiative,
//                    Federal Reserve Bank of Boston
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
#ifndef OPENCBDC_TX_SRC_COMMON_HASHMAP_H_
#define OPENCBDC_TX_SRC_COMMON_HASHMAP_H_
 
#include "buffer.hpp"
#include "crypto/siphash.h"
#include "hash.hpp"
 
#include <array>
#include <cstring>
 
namespace cbdc::hashing {
    template<class T>
    struct const_sip_hash {
        static_assert(std::is_trivial_v<T>);
        auto operator()(T const& tx) const noexcept -> size_t {
            // TODO: pick the initialization key at random.
            static constexpr std::array<uint64_t, 2> siphash_key{0x1337,
                                                                 0x1337};
            CSipHasher hasher(siphash_key[0], siphash_key[1]);
            std::array<unsigned char, sizeof(tx)> tx_arr{};
            std::memcpy(tx_arr.data(), &tx, sizeof(tx));
            hasher.Write(tx_arr.data(), sizeof(tx));
            return hasher.Finalize();
        }
    };
 
    template<>
    struct const_sip_hash<buffer> {
        auto operator()(const buffer& buf) const noexcept -> size_t {
            // TODO: pick the initialization key at random.
            static constexpr std::array<uint64_t, 2> siphash_key{0x1337,
                                                                 0x1337};
            CSipHasher hasher(siphash_key[0], siphash_key[1]);
            std::vector<unsigned char> arr(buf.size());
            std::memcpy(arr.data(), buf.data(), buf.size());
            hasher.Write(arr.data(), arr.size());
            return hasher.Finalize();
        }
    };
 
    struct null {
        auto operator()(const hash_t& hash) const noexcept -> size_t;
    };
}
 
#endif // OPENCBDC_TX_SRC_COMMON_HASHMAP_H_