/*
 * Copyright (C) 2015-present ScyllaDB
 */

/*
 * SPDX-License-Identifier: LicenseRef-ScyllaDB-Source-Available-1.0
 *
 */

#pragma once

#include <cstdint>
#include <seastar/net/byteorder.hh>
#include <seastar/core/byteorder.hh>

#if defined(__x86_64__) || defined(__i386__)
#include <smmintrin.h>
#elif defined(__aarch64__)
#include <arm_acle.h>
/* Implement x86-64 intrinsics with according aarch64 ones */
inline uint32_t _mm_crc32_u8(uint32_t crc, uint8_t in)
{
    return __crc32cb(crc, in);
}
inline uint32_t _mm_crc32_u16(uint32_t crc, uint16_t in)
{
    return __crc32ch(crc, in);
}
inline uint32_t _mm_crc32_u32(uint32_t crc, uint32_t in)
{
    return __crc32cw(crc, in);
}
inline uint32_t _mm_crc32_u64(uint32_t crc, uint64_t in)
{
    return __crc32cd(crc, in);
}
#endif

#include "utils/clmul.hh"
#include "utils/fragment_range.hh"

namespace utils {

class crc32 {
    uint32_t _r = 0;
public:
    // All process() functions assume input is in
    // host byte order (i.e. equivalent to storing
    // the value in a buffer and crcing the buffer).
    // On x86 use the crc32 instruction added in SSE 4.2.
#if defined(__x86_64__) || defined(__i386__) || defined(__aarch64__)
    void process_le(int8_t in) {
        _r = _mm_crc32_u8(_r, in);
    }
    void process_le(uint8_t in) {
        _r = _mm_crc32_u8(_r, in);
    }
    void process_le(int16_t in) {
        _r = _mm_crc32_u16(_r, in);
    }
    void process_le(uint16_t in) {
        _r = _mm_crc32_u16(_r, in);
    }
    void process_le(int32_t in) {
        _r = _mm_crc32_u32(_r, in);
    }
    void process_le(uint32_t in) {
        _r = _mm_crc32_u32(_r, in);
    }
    void process_le(int64_t in) {
        _r = _mm_crc32_u64(_r, in);
    }
    void process_le(uint64_t in) {
        _r = _mm_crc32_u64(_r, in);
    }

    template <typename T>
    void process_be(T in) {
        in = seastar::net::hton(in);
        process_le(in);
    }

#endif
    void process(const uint8_t* in, size_t size) {
        if ((reinterpret_cast<uintptr_t>(in) & 1) && size >= 1) {
            process_le(*in);
            ++in;
            --size;
        }
        if ((reinterpret_cast<uintptr_t>(in) & 3) && size >= 2) {
            process_le(seastar::read_le<uint16_t>(reinterpret_cast<const char*>(in)));
            in += 2;
            size -= 2;
        }
        if ((reinterpret_cast<uintptr_t>(in) & 7) && size >= 4) {
            process_le(seastar::read_le<uint32_t>(reinterpret_cast<const char*>(in)));
            in += 4;
            size -= 4;
        }

        // do in three parallel loops
        while (size >= 1024) {
            uint32_t crc0 = _r, crc1 = 0, crc2 = 0;

            // calculate three blocks in parallel
            // - crc0: in64[ 0,  1, ...,  41]
            // - crc1: in64[42, 43, ...,  83]
            // - crc2: in64[84, 85, ..., 125]
            for (int i = 0; i < 42; ++i, in += 8) {
                crc0 = _mm_crc32_u64(crc0, seastar::read_le<uint64_t>((const char*)in));
                crc1 = _mm_crc32_u64(crc1, seastar::read_le<uint64_t>((const char*)in + 42*8));
                crc2 = _mm_crc32_u64(crc2, seastar::read_le<uint64_t>((const char*)in + 42*2*8));
            }
            in += 42*2*8;

            // combine three blocks' crc and last two u64
            // - CRC32(crc0 * CRC32(x^(42*64*2)))
            crc0 = _mm_crc32_u64(0, clmul_u32(crc0, 0xe417f38a));
            // - CRC32(crc1 * CRC32(x^(42*64)))
            crc1 = _mm_crc32_u64(0, clmul_u32(crc1, 0x8f158014));
            // - CRC32(crc2 * x^32 + u64[-2])
            crc2 = _mm_crc32_u64(crc2, seastar::read_le<uint64_t>((const char*)in));
            in += 8;
            // - Last u64
            _r = _mm_crc32_u64(crc0^crc1^crc2, seastar::read_le<uint64_t>((const char*)in));
            in += 8;

            size -= 1024;
        }

        while (size >= 8) {
            process_le(seastar::read_le<uint64_t>(reinterpret_cast<const char*>(in)));
            in += 8;
            size -= 8;
        }
        if (size >= 4) {
            process_le(seastar::read_le<uint32_t>(reinterpret_cast<const char*>(in)));
            in += 4;
            size -= 4;
        }
        if (size >= 2) {
            process_le(seastar::read_le<uint16_t>(reinterpret_cast<const char*>(in)));
            in += 2;
            size -= 2;
        }
        if (size >= 1) {
            process_le(*in);
        }
    }

    template<typename FragmentedBuffer>
    requires FragmentRange<FragmentedBuffer>
    void process_fragmented(const FragmentedBuffer& buffer) {
        for (bytes_view bv : buffer) {
            process(reinterpret_cast<const uint8_t*>(bv.data()), bv.size());
        }
    }

    uint32_t get() const {
        return _r;
    }
};

}