// Copyright 2005 Google Inc.

//

// Licensed to the Apache Software Foundation (ASF) under one

// or more contributor license agreements.  See the NOTICE file

// distributed with this work for additional information

// regarding copyright ownership.  The ASF licenses this file

// to you 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.

//

// ---

//

//

// Utility functions that depend on bytesex. We define htonll and ntohll,

// as well as "Google" versions of all the standards: ghtonl, ghtons, and

// so on. These functions do exactly the same as their standard variants,

// but don't require including the dangerous netinet/in.h.

//

// Buffer routines will copy to and from buffers without causing

// a bus error when the architecture requires different byte alignments

#pragma once

#include <assert.h>

#include "gutil/integral_types.h"

#include "gutil/port.h"

#include "vec/core/wide_integer.h"

inline uint64 gbswap_64(uint64 host_int) {

#if defined(__GNUC__) && defined(__x86_64__) && !defined(__APPLE__)

    // Adapted from /usr/include/byteswap.h.  Not available on Mac.

    if (__builtin_constant_p(host_int)) {

        return __bswap_constant_64(host_int);

    } else {

        uint64 result;

        __asm__("bswap %0" : "=r"(result) : "0"(host_int));

        return result;

    }

#elif defined(bswap_64)

    return bswap_64(host_int);

#else

    return static_cast<uint64>(bswap_32(static_cast<uint32>(host_int >> 32))) |

           (static_cast<uint64>(bswap_32(static_cast<uint32>(host_int))) << 32);

#endif // bswap_64

}

inline unsigned __int128 gbswap_128(unsigned __int128 host_int) {

    return static_cast<unsigned __int128>(bswap_64(static_cast<uint64>(host_int >> 64))) |

           (static_cast<unsigned __int128>(bswap_64(static_cast<uint64>(host_int))) << 64);

}

inline wide::UInt256 gbswap_256(wide::UInt256 host_int) {

    wide::UInt256 result {gbswap_64(host_int.items[3]), gbswap_64(host_int.items[2]),

                          gbswap_64(host_int.items[1]), gbswap_64(host_int.items[0])};

    return result;

}

// Swap bytes of a 24-bit value.

inline uint32_t bswap_24(uint32_t x) {

    return ((x & 0x0000ffULL) << 16) | ((x & 0x00ff00ULL)) | ((x & 0xff0000ULL) >> 16);

}

#ifdef IS_LITTLE_ENDIAN

// Definitions for ntohl etc. that don't require us to include

// netinet/in.h. We wrap bswap_32 and bswap_16 in functions rather

// than just #defining them because in debug mode, gcc doesn't

// correctly handle the (rather involved) definitions of bswap_32.

// gcc guarantees that inline functions are as fast as macros, so

// this isn't a performance hit.

inline uint16 ghtons(uint16 x) {

    return bswap_16(x);

}

inline uint32 ghtonl(uint32 x) {

    return bswap_32(x);

}

inline uint64 ghtonll(uint64 x) {

    return gbswap_64(x);

}

#elif defined IS_BIG_ENDIAN

// These definitions are simpler on big-endian machines

// These are functions instead of macros to avoid self-assignment warnings

// on calls such as "i = ghtnol(i);".  This also provides type checking.

inline uint16 ghtons(uint16 x) {

    return x;

}

inline uint32 ghtonl(uint32 x) {

    return x;

}

inline uint64 ghtonll(uint64 x) {

    return x;

}

#else

#error "Unsupported bytesex: Either IS_BIG_ENDIAN or IS_LITTLE_ENDIAN must be defined"  // NOLINT

#endif // bytesex

// ntoh* and hton* are the same thing for any size and bytesex,

// since the function is an involution, i.e., its own inverse.

#if !defined(__APPLE__)

// This one is safe to take as it's an extension

#define htonll(x) ghtonll(x)

#define ntohll(x) htonll(x)

#endif

// Utilities to convert numbers between the current hosts's native byte

// order and little-endian byte order

//

// Load/Store methods are alignment safe

class LittleEndian {

public:

    // Conversion functions.

#ifdef IS_LITTLE_ENDIAN

    static uint16 FromHost16(uint16 x) { return x; }

    static uint16 ToHost16(uint16 x) { return x; }

    static uint32 FromHost32(uint32 x) { return x; }

    static uint32 ToHost32(uint32 x) { return x; }

    static uint64 FromHost64(uint64 x) { return x; }

    static uint64 ToHost64(uint64 x) { return x; }

    static unsigned __int128 FromHost128(unsigned __int128 x) { return x; }

    static unsigned __int128 ToHost128(unsigned __int128 x) { return x; }

    static wide::UInt256 FromHost256(wide::UInt256 x) { return x; }

    static wide::UInt256 ToHost256(wide::UInt256 x) { return x; }

    static bool IsLittleEndian() { return true; }

#elif defined IS_BIG_ENDIAN

    static uint16 FromHost16(uint16 x) { return bswap_16(x); }

    static uint16 ToHost16(uint16 x) { return bswap_16(x); }

    static uint32 FromHost32(uint32 x) { return bswap_32(x); }

    static uint32 ToHost32(uint32 x) { return bswap_32(x); }

    static uint64 FromHost64(uint64 x) { return gbswap_64(x); }

    static uint64 ToHost64(uint64 x) { return gbswap_64(x); }

    static unsigned __int128 FromHost128(unsigned __int128 x) { return gbswap_128(x); }

    static unsigned __int128 ToHost128(unsigned __int128 x) { return gbswap_128(x); }

    static wide::UInt256 FromHost256(wide::UInt256 x) { return gbswap_256(x); }

    static wide::UInt256 ToHost256(wide::UInt256 x) { return gbswap_256(x); }

    static bool IsLittleEndian() { return false; }

#endif /* ENDIAN */

    // Functions to do unaligned loads and stores in little-endian order.

    static uint16 Load16(const void* p) { return ToHost16(UNALIGNED_LOAD16(p)); }

    static void Store16(void* p, uint16 v) { UNALIGNED_STORE16(p, FromHost16(v)); }

    static uint32 Load32(const void* p) { return ToHost32(UNALIGNED_LOAD32(p)); }

    static void Store32(void* p, uint32 v) { UNALIGNED_STORE32(p, FromHost32(v)); }

    static uint64 Load64(const void* p) { return ToHost64(UNALIGNED_LOAD64(p)); }

    // Build a uint64 from 1-8 bytes.

    // 8 * len least significant bits are loaded from the memory with

    // LittleEndian order. The 64 - 8 * len most significant bits are

    // set all to 0.

    // In latex-friendly words, this function returns:

    //     $\sum_{i=0}^{len-1} p[i] 256^{i}$, where p[i] is unsigned.

    //

    // This function is equivalent with:

    // uint64 val = 0;

    // memcpy(&val, p, len);

    // return ToHost64(val);

    // TODO(user): write a small benchmark and benchmark the speed

    // of a memcpy based approach.

    //

    // For speed reasons this function does not work for len == 0.

    // The caller needs to guarantee that 1 <= len <= 8.

    static uint64 Load64VariableLength(const void* const p, int len) {

        assert(len >= 1 && len <= 8);

        const char* const buf = static_cast<const char*>(p);

        uint64 val = 0;

        --len;

        do {

            val = (val << 8) | buf[len];

            // (--len >= 0) is about 10 % faster than (len--) in some benchmarks.

        } while (--len >= 0);

        // No ToHost64(...) needed. The bytes are accessed in little-endian manner

        // on every architecture.

        return val;

    }

    static void Store64(void* p, uint64 v) { UNALIGNED_STORE64(p, FromHost64(v)); }

    // Load & Store in machine's word size.

    static uword_t LoadUnsignedWord(const void* p) {

        if (sizeof(uword_t) == 8)

            return Load64(p);

        else

            return Load32(p);

    }

    static void StoreUnsignedWord(void* p, uword_t v) {

        if (sizeof(v) == 8)

            Store64(p, v);

        else

            Store32(p, v);

    }

};

// Utilities to convert numbers between the current hosts's native byte

// order and big-endian byte order (same as network byte order)

//

// Load/Store methods are alignment safe

class BigEndian {

public:

#ifdef IS_LITTLE_ENDIAN

    static uint16 FromHost16(uint16 x) { return bswap_16(x); }

    static uint16 ToHost16(uint16 x) { return bswap_16(x); }

    static uint32 FromHost24(uint32 x) { return bswap_24(x); }

    static uint32 ToHost24(uint32 x) { return bswap_24(x); }

    static uint32 FromHost32(uint32 x) { return bswap_32(x); }

    static uint32 ToHost32(uint32 x) { return bswap_32(x); }

    static uint64 FromHost64(uint64 x) { return gbswap_64(x); }

    static uint64 ToHost64(uint64 x) { return gbswap_64(x); }

    static unsigned __int128 FromHost128(unsigned __int128 x) { return gbswap_128(x); }

    static unsigned __int128 ToHost128(unsigned __int128 x) { return gbswap_128(x); }

    static wide::UInt256 FromHost256(wide::UInt256 x) { return gbswap_256(x); }

    static wide::UInt256 ToHost256(wide::UInt256 x) { return gbswap_256(x); }

    static bool IsLittleEndian() { return true; }

#elif defined IS_BIG_ENDIAN

    static uint16 FromHost16(uint16 x) { return x; }

    static uint16 ToHost16(uint16 x) { return x; }

    static uint32 FromHost24(uint32 x) { return x; }

    static uint32 ToHost24(uint32 x) { return x; }

    static uint32 FromHost32(uint32 x) { return x; }

    static uint32 ToHost32(uint32 x) { return x; }

    static uint64 FromHost64(uint64 x) { return x; }

    static uint64 ToHost64(uint64 x) { return x; }

    static wide::UInt256 FromHost256(wide::UInt256 x) { return x; }

    static wide::UInt256 ToHost256(wide::UInt256 x) { return x; }

    static bool IsLittleEndian() { return false; }

#endif /* ENDIAN */

    // Functions to do unaligned loads and stores in little-endian order.

    static uint16 Load16(const void* p) { return ToHost16(UNALIGNED_LOAD16(p)); }

    static void Store16(void* p, uint16 v) { UNALIGNED_STORE16(p, FromHost16(v)); }

    static uint32 Load32(const void* p) { return ToHost32(UNALIGNED_LOAD32(p)); }

    static void Store32(void* p, uint32 v) { UNALIGNED_STORE32(p, FromHost32(v)); }

    static uint64 Load64(const void* p) { return ToHost64(UNALIGNED_LOAD64(p)); }

    // Build a uint64 from 1-8 bytes.

    // 8 * len least significant bits are loaded from the memory with

    // BigEndian order. The 64 - 8 * len most significant bits are

    // set all to 0.

    // In latex-friendly words, this function returns:

    //     $\sum_{i=0}^{len-1} p[i] 256^{i}$, where p[i] is unsigned.

    //

    // This function is equivalent with:

    // uint64 val = 0;

    // memcpy(&val, p, len);

    // return ToHost64(val);

    // TODO(user): write a small benchmark and benchmark the speed

    // of a memcpy based approach.

    //

    // For speed reasons this function does not work for len == 0.

    // The caller needs to guarantee that 1 <= len <= 8.

    static uint64 Load64VariableLength(const void* const p, int len) {

        assert(len >= 1 && len <= 8);

        uint64 val = Load64(p);

        uint64 mask = 0;

        --len;

        do {

            mask = (mask << 8) | 0xff;

            // (--len >= 0) is about 10 % faster than (len--) in some benchmarks.

        } while (--len >= 0);

        return val & mask;

    }

    static void Store64(void* p, uint64 v) { UNALIGNED_STORE64(p, FromHost64(v)); }

    // Load & Store in machine's word size.

    static uword_t LoadUnsignedWord(const void* p) {

        if (sizeof(uword_t) == 8)

            return Load64(p);

        else

            return Load32(p);

    }

    static void StoreUnsignedWord(void* p, uword_t v) {

        if (sizeof(uword_t) == 8)

            Store64(p, v);

        else

            Store32(p, v);

    }

}; // BigEndian

// Network byte order is big-endian

typedef BigEndian NetworkByteOrder;