/* Copyright (c) INRIA and Microsoft Corporation. All rights reserved.
   Licensed under the Apache 2.0 and MIT Licenses. */

#ifndef KRML_HEADER_LOWSTAR_ENDIANNESS_H
#define KRML_HEADER_LOWSTAR_ENDIANNESS_H

#include <string.h>
#include <inttypes.h>

/******************************************************************************/
/* Implementing C.fst (part 2: endian-ness macros)                            */
/******************************************************************************/

/* ... for Linux */
#if defined(__linux__) || defined(__CYGWIN__) || defined(__USE_SYSTEM_ENDIAN_H__) || defined(__GLIBC__)
#include <endian.h>

/* ... for OSX */
#elif defined(__APPLE__)
#include <libkern/OSByteOrder.h>
#define htole64(x) OSSwapHostToLittleInt64(x)
#define le64toh(x) OSSwapLittleToHostInt64(x)
#define htobe64(x) OSSwapHostToBigInt64(x)
#define be64toh(x) OSSwapBigToHostInt64(x)

#define htole16(x) OSSwapHostToLittleInt16(x)
#define le16toh(x) OSSwapLittleToHostInt16(x)
#define htobe16(x) OSSwapHostToBigInt16(x)
#define be16toh(x) OSSwapBigToHostInt16(x)

#define htole32(x) OSSwapHostToLittleInt32(x)
#define le32toh(x) OSSwapLittleToHostInt32(x)
#define htobe32(x) OSSwapHostToBigInt32(x)
#define be32toh(x) OSSwapBigToHostInt32(x)

/* ... for Solaris */
#elif defined(__sun__)
#include <sys/byteorder.h>
#define htole64(x) LE_64(x)
#define le64toh(x) LE_64(x)
#define htobe64(x) BE_64(x)
#define be64toh(x) BE_64(x)

#define htole16(x) LE_16(x)
#define le16toh(x) LE_16(x)
#define htobe16(x) BE_16(x)
#define be16toh(x) BE_16(x)

#define htole32(x) LE_32(x)
#define le32toh(x) LE_32(x)
#define htobe32(x) BE_32(x)
#define be32toh(x) BE_32(x)

/* ... for the BSDs */
#elif defined(__FreeBSD__) || defined(__NetBSD__) || defined(__DragonFly__)
#include <sys/endian.h>
#elif defined(__OpenBSD__)
#include <endian.h>

/* ... for Windows (MSVC)... not targeting XBOX 360! */
#elif defined(_MSC_VER)

#include <stdlib.h>
#define htobe16(x) _byteswap_ushort(x)
#define htole16(x) (x)
#define be16toh(x) _byteswap_ushort(x)
#define le16toh(x) (x)

#define htobe32(x) _byteswap_ulong(x)
#define htole32(x) (x)
#define be32toh(x) _byteswap_ulong(x)
#define le32toh(x) (x)

#define htobe64(x) _byteswap_uint64(x)
#define htole64(x) (x)
#define be64toh(x) _byteswap_uint64(x)
#define le64toh(x) (x)

/* ... for Windows (GCC-like, e.g. mingw or clang) */
#elif (defined(_WIN32) || defined(_WIN64) || defined(__EMSCRIPTEN__)) && \
    (defined(__GNUC__) || defined(__clang__))

#define htobe16(x) __builtin_bswap16(x)
#define htole16(x) (x)
#define be16toh(x) __builtin_bswap16(x)
#define le16toh(x) (x)

#define htobe32(x) __builtin_bswap32(x)
#define htole32(x) (x)
#define be32toh(x) __builtin_bswap32(x)
#define le32toh(x) (x)

#define htobe64(x) __builtin_bswap64(x)
#define htole64(x) (x)
#define be64toh(x) __builtin_bswap64(x)
#define le64toh(x) (x)

/* ... generic big-endian fallback code */
/* ... AIX doesn't have __BYTE_ORDER__ (with XLC compiler) & is always big-endian */
#elif (defined(__BYTE_ORDER__) && __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__) || defined(_AIX)

/* byte swapping code inspired by:
 * https://github.com/rweather/arduinolibs/blob/master/libraries/Crypto/utility/EndianUtil.h
 * */

#define htobe32(x) (x)
#define be32toh(x) (x)
#define htole32(x)                                                      \
    (__extension__({                                                    \
        uint32_t _temp = (x);                                           \
        ((_temp >> 24) & 0x000000FF) | ((_temp >> 8) & 0x0000FF00) |    \
            ((_temp << 8) & 0x00FF0000) | ((_temp << 24) & 0xFF000000); \
    }))
#define le32toh(x) (htole32((x)))

#define htobe64(x) (x)
#define be64toh(x) (x)
#define htole64(x)                                           \
    (__extension__({                                         \
        uint64_t __temp = (x);                               \
        uint32_t __low = htobe32((uint32_t)__temp);          \
        uint32_t __high = htobe32((uint32_t)(__temp >> 32)); \
        (((uint64_t)__low) << 32) | __high;                  \
    }))
#define le64toh(x) (htole64((x)))

/* ... generic little-endian fallback code */
#elif defined(__BYTE_ORDER__) && __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__

#define htole32(x) (x)
#define le32toh(x) (x)
#define htobe32(x)                                                      \
    (__extension__({                                                    \
        uint32_t _temp = (x);                                           \
        ((_temp >> 24) & 0x000000FF) | ((_temp >> 8) & 0x0000FF00) |    \
            ((_temp << 8) & 0x00FF0000) | ((_temp << 24) & 0xFF000000); \
    }))
#define be32toh(x) (htobe32((x)))

#define htole64(x) (x)
#define le64toh(x) (x)
#define htobe64(x)                                           \
    (__extension__({                                         \
        uint64_t __temp = (x);                               \
        uint32_t __low = htobe32((uint32_t)__temp);          \
        uint32_t __high = htobe32((uint32_t)(__temp >> 32)); \
        (((uint64_t)__low) << 32) | __high;                  \
    }))
#define be64toh(x) (htobe64((x)))

/* ... couldn't determine endian-ness of the target platform */
#else
#error "Please define __BYTE_ORDER__!"

#endif /* defined(__linux__) || ... */

/* Loads and stores. These avoid undefined behavior due to unaligned memory
 * accesses, via memcpy. */

inline static uint16_t
load16(uint8_t *b)
{
    uint16_t x;
    memcpy(&x, b, 2);
    return x;
}

inline static uint32_t
load32(uint8_t *b)
{
    uint32_t x;
    memcpy(&x, b, 4);
    return x;
}

inline static uint64_t
load64(uint8_t *b)
{
    uint64_t x;
    memcpy(&x, b, 8);
    return x;
}

inline static void
store16(uint8_t *b, uint16_t i)
{
    memcpy(b, &i, 2);
}

inline static void
store32(uint8_t *b, uint32_t i)
{
    memcpy(b, &i, 4);
}

inline static void
store64(uint8_t *b, uint64_t i)
{
    memcpy(b, &i, 8);
}

/* Legacy accessors so that this header can serve as an implementation of
 * C.Endianness */
#define load16_le(b) (le16toh(load16(b)))
#define store16_le(b, i) (store16(b, htole16(i)))
#define load16_be(b) (be16toh(load16(b)))
#define store16_be(b, i) (store16(b, htobe16(i)))

#define load32_le(b) (le32toh(load32(b)))
#define store32_le(b, i) (store32(b, htole32(i)))
#define load32_be(b) (be32toh(load32(b)))
#define store32_be(b, i) (store32(b, htobe32(i)))

#define load64_le(b) (le64toh(load64(b)))
#define store64_le(b, i) (store64(b, htole64(i)))
#define load64_be(b) (be64toh(load64(b)))
#define store64_be(b, i) (store64(b, htobe64(i)))

/* Co-existence of LowStar.Endianness and FStar.Endianness generates name
 * conflicts, because of course both insist on having no prefixes. Until a
 * prefix is added, or until we truly retire FStar.Endianness, solve this issue
 * in an elegant way. */
#define load16_le0 load16_le
#define store16_le0 store16_le
#define load16_be0 load16_be
#define store16_be0 store16_be

#define load32_le0 load32_le
#define store32_le0 store32_le
#define load32_be0 load32_be
#define store32_be0 store32_be

#define load64_le0 load64_le
#define store64_le0 store64_le
#define load64_be0 load64_be
#define store64_be0 store64_be

#define load128_le0 load128_le
#define store128_le0 store128_le
#define load128_be0 load128_be
#define store128_be0 store128_be

#endif /* KRML_HEADER_LOWSTAR_ENDIANNESS_H */
