// Copyright (C) 2023 RozK
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.

#ifndef RK_ENGINE_CMP_MEMCPY_H
#define RK_ENGINE_CMP_MEMCPY_H

#include "types.hpp"

template<typename _type>
bool _rk_cmp_memcpy_small(
    void * const __restrict _dst,
    void const * const __restrict _src,
    unsigned const size) {
    unsigned count = (size / sizeof(_type));
    _type * dst = reinterpret_cast<_type *>(_dst);
    _type const * src = reinterpret_cast<_type const *>(_src);
    _type cmp = 0;
    do {
        cmp |= *dst ^ *src;
        *dst++ = *src++;
    } while(--count > 0);
    return (cmp != 0);
}

template<typename _big, typename _small>
bool _rk_cmp_memcpy_big(
    void * const __restrict _dst,
    void const * const __restrict _src,
    unsigned const size) {
    unsigned count = size / sizeof(_big);
    unsigned const remain = size % sizeof(_big);
    _big * dst = reinterpret_cast<_big *>(_dst);
    _big const * src = reinterpret_cast<_big const *>(_src);
    _big cmp = 0;
    do {
        cmp |= *dst ^ *src;
        *dst++ = *src++;
    } while(--count > 0);
    bool modified = (cmp != 0);
    if (remain) {
        modified |= _rk_cmp_memcpy_small<_small>(dst, src, remain);
    }
    return modified;
}

#ifdef RK_CMP_MEMCPY_UNALIGNED
#define _rk_size_and_alignment(_t) (size >= sizeof(_t))
#else
#define _rk_size_and_alignment(_t) (size >= sizeof(_t) && !(alignment & (sizeof(_t) - 1)))
#endif

template<unsigned _s>
bool rk_cmp_memcpy(
    void * const __restrict _dst,
    void const * const __restrict _src,
    unsigned const size);

template<>
bool rk_cmp_memcpy<sizeof(rk_ubyte)>(
    void * const __restrict _dst,
    void const * const __restrict _src,
    unsigned const size) {
#ifndef RK_CMP_MEMCPY_UNALIGNED
    unsigned const alignment = reinterpret_cast<uintptr_t>(_dst) | reinterpret_cast<uintptr_t const>(_src);
#endif
    if (_rk_size_and_alignment(rk_ullong)) {
        return _rk_cmp_memcpy_big<rk_ullong, rk_ubyte>(_dst, _src, size);
    }
    if (_rk_size_and_alignment(rk_ulong)) {
        return _rk_cmp_memcpy_big<rk_ulong, rk_ubyte>(_dst, _src, size);
    }
    if (_rk_size_and_alignment(rk_uint)) {
        return _rk_cmp_memcpy_big<rk_uint, rk_ubyte>(_dst, _src, size);
    }
    if (_rk_size_and_alignment(rk_ushort)) {
        return _rk_cmp_memcpy_big<rk_ushort, rk_ubyte>(_dst, _src, size);
    }
    if (size > 0) {
        return _rk_cmp_memcpy_small<rk_ubyte>(_dst, _src, size);
    }
    return false;
}

template<>
bool rk_cmp_memcpy<sizeof(rk_ushort)>(
    void * const __restrict _dst,
    void const * const __restrict _src,
    unsigned const size) {
#ifndef RK_CMP_MEMCPY_UNALIGNED
    unsigned const alignment = reinterpret_cast<uintptr_t>(_dst) | reinterpret_cast<uintptr_t const>(_src);
#endif
    if (_rk_size_and_alignment(rk_ullong)) {
        return _rk_cmp_memcpy_big<rk_ullong, rk_ushort>(_dst, _src, size);
    }
    if (_rk_size_and_alignment(rk_ulong)) {
        return _rk_cmp_memcpy_big<rk_ulong, rk_ushort>(_dst, _src, size);
    }
    if (_rk_size_and_alignment(rk_uint)) {
        return _rk_cmp_memcpy_big<rk_uint, rk_ushort>(_dst, _src, size);
    }
    if (size > 0) {
        return _rk_cmp_memcpy_small<rk_ushort>(_dst, _src, size);
    }
    return false;
}

template<>
bool rk_cmp_memcpy<sizeof(rk_uint)>(
    void * const __restrict _dst,
    void const * const __restrict _src,
    unsigned const size) {
#ifndef RK_CMP_MEMCPY_UNALIGNED
    unsigned const alignment = reinterpret_cast<uintptr_t>(_dst) | reinterpret_cast<uintptr_t const>(_src);
#endif
    if (_rk_size_and_alignment(rk_ullong)) {
        return _rk_cmp_memcpy_big<rk_ullong, rk_uint>(_dst, _src, size);
    }
    if (_rk_size_and_alignment(rk_ulong)) {
        return _rk_cmp_memcpy_big<rk_ulong, rk_uint>(_dst, _src, size);
    }
    if (size > 0) {
        return _rk_cmp_memcpy_small<rk_uint>(_dst, _src, size);
    }
    return false;
}

template<>
bool rk_cmp_memcpy<sizeof(rk_ulong)>(
    void * const __restrict _dst,
    void const * const __restrict _src,
    unsigned const size) {
#ifndef RK_CMP_MEMCPY_UNALIGNED
    unsigned const alignment = reinterpret_cast<uintptr_t>(_dst) | reinterpret_cast<uintptr_t const>(_src);
#endif
    if (_rk_size_and_alignment(rk_ullong)) {
        return _rk_cmp_memcpy_big<rk_ullong, rk_ulong>(_dst, _src, size);
    }
    if (size > 0) {
        return _rk_cmp_memcpy_small<rk_ulong>(_dst, _src, size);
    }
    return false;
}

template<>
bool rk_cmp_memcpy<sizeof(rk_ullong)>(
    void * const __restrict _dst,
    void const * const __restrict _src,
    unsigned const size) {
    if (size > 0) {
        return _rk_cmp_memcpy_small<rk_ullong>(_dst, _src, size);
    }
    return false;
}

#undef _rk_size_and_alignment

#endif // RK_ENGINE_CMP_MEMCPY_H