generic_common_impl.h

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/**********************************************************************
 * Copyright (c) 2018 Pieter Wuille, Greg Maxwell, Gleb Naumenko      *
 * Distributed under the MIT software license, see the accompanying   *
 * file LICENSE or http://www.opensource.org/licenses/mit-license.php.*
 **********************************************************************/
 
#ifndef _MINISKETCH_FIELDS_GENERIC_COMMON_IMPL_H_
#define _MINISKETCH_FIELDS_GENERIC_COMMON_IMPL_H_ 1
 
#include <stdint.h>
 
#include "../int_utils.h"
#include "../lintrans.h"
 
namespace {

template<typename I, int B, uint32_t MOD, typename F, typename T, const F* SQR, const F* QRT> class Field
{
    typedef BitsInt<I, B> O;
    typedef LFSR<O, MOD> L;
 
public:
    typedef I Elem;
    constexpr int Bits() const { return B; }
 
    constexpr inline Elem Mul2(Elem val) const { return L::Call(val); }
 
    class Multiplier
    {
        T table;
    public:
        explicit Multiplier(const Field&, Elem a) { table.template Build<L::Call>(a); }
        constexpr inline Elem operator()(Elem a) const { return table.template Map<O>(a); }
    };
 
    Elem Mul(Elem a, Elem b) const { return GFMul<I, B, L, O>(a, b); }

    inline constexpr Elem Sqr(Elem a) const { return SQR->template Map<O>(a); }

    inline constexpr Elem Qrt(Elem a) const { return QRT->template Map<O>(a); }

    Elem Inv(Elem a) const { return InvExtGCD<I, O, B, MOD>(a); }

    Elem FromSeed(uint64_t seed) const {
        uint64_t k0 = 0x496e744669656c64ull; // "IntField"
        uint64_t k1 = seed;
        uint64_t count = ((uint64_t)B) << 32;
        Elem ret;
        do {
            ret = O::Mask(I(SipHash(k0, k1, count++)));
        } while(ret == 0);
        return ret;
    }
 
    Elem Deserialize(BitReader& in) const { return in.template Read<B, I>(); }
 
    void Serialize(BitWriter& out, Elem val) const { out.template Write<B, I>(val); }
 
    constexpr Elem FromUint64(uint64_t x) const { return O::Mask(I(x)); }
    constexpr uint64_t ToUint64(Elem val) const { return uint64_t(val); }
};
 
}
 
#endif