/*
 * SipHash reference C implementation
 *
 * Copyright 2012-2024 JP Aumasson
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 *
 */

/* Note:  the reference implementation is also available under CC0 license
 * (dual licensed) we included the MIT license here since it is shorter */

#include "siphash.h"
#include <assert.h>
#include <stddef.h>
#include <stdint.h>

/* default: SipHash-2-4 */
#ifndef cROUNDS
#define cROUNDS 2
#endif
#ifndef dROUNDS
#define dROUNDS 4
#endif

#define ROTL(x, b) (uint64_t)(((x) << (b)) | ((x) >> (64 - (b))))

#define U32TO8_LE(p, v)            \
    (p)[0] = (uint8_t)((v));       \
    (p)[1] = (uint8_t)((v) >> 8);  \
    (p)[2] = (uint8_t)((v) >> 16); \
    (p)[3] = (uint8_t)((v) >> 24);

#define U64TO8_LE(p, v)              \
    U32TO8_LE((p), (uint32_t)((v))); \
    U32TO8_LE((p) + 4, (uint32_t)((v) >> 32));

#define U8TO64_LE(p)                                           \
    (((uint64_t)((p)[0])) | ((uint64_t)((p)[1]) << 8)          \
     | ((uint64_t)((p)[2]) << 16) | ((uint64_t)((p)[3]) << 24) \
     | ((uint64_t)((p)[4]) << 32) | ((uint64_t)((p)[5]) << 40) \
     | ((uint64_t)((p)[6]) << 48) | ((uint64_t)((p)[7]) << 56))

#define SIPROUND           \
    do                     \
    {                      \
        v0 += v1;          \
        v1 = ROTL(v1, 13); \
        v1 ^= v0;          \
        v0 = ROTL(v0, 32); \
        v2 += v3;          \
        v3 = ROTL(v3, 16); \
        v3 ^= v2;          \
        v0 += v3;          \
        v3 = ROTL(v3, 21); \
        v3 ^= v0;          \
        v2 += v1;          \
        v1 = ROTL(v1, 17); \
        v1 ^= v2;          \
        v2 = ROTL(v2, 32); \
    } while (0)

#ifdef DEBUG_SIPHASH
#include <stdio.h>

#define TRACE                                            \
    do                                                   \
    {                                                    \
        printf("(%3zu) v0 %016" PRIx64 "\n", inlen, v0); \
        printf("(%3zu) v1 %016" PRIx64 "\n", inlen, v1); \
        printf("(%3zu) v2 %016" PRIx64 "\n", inlen, v2); \
        printf("(%3zu) v3 %016" PRIx64 "\n", inlen, v3); \
    } while (0)
#else /* ifdef DEBUG_SIPHASH */
#define TRACE
#endif

/*
 *  Computes a SipHash value
 * in: pointer to input data (read-only)
 *  inlen: input data length in bytes (any size_t value)
 * k: pointer to the key data (read-only), must be 16 bytes
 * out: pointer to output data (write-only), outlen bytes must be allocated
 *  outlen: length of the output in bytes, must be 8 or 16
 */
int
siphash(const void *in, const size_t inlen, const void *k, uint8_t *out,
        const size_t outlen)
{
    const unsigned char *ni = (const unsigned char *)in;
    const unsigned char *kk = (const unsigned char *)k;

    assert((outlen == 8) || (outlen == 16));
    uint64_t v0 = UINT64_C(0x736f6d6570736575);
    uint64_t v1 = UINT64_C(0x646f72616e646f6d);
    uint64_t v2 = UINT64_C(0x6c7967656e657261);
    uint64_t v3 = UINT64_C(0x7465646279746573);
    uint64_t k0 = U8TO64_LE(kk);
    uint64_t k1 = U8TO64_LE(kk + 8);
    uint64_t m;
    int i;
    const unsigned char *end = ni + inlen - (inlen % sizeof(uint64_t));
    const int left = inlen & 7;
    uint64_t b = ((uint64_t)inlen) << 56;
    v3 ^= k1;
    v2 ^= k0;
    v1 ^= k1;
    v0 ^= k0;

    if (outlen == 16)
    {
        v1 ^= 0xee;
    }

    for (; ni != end; ni += 8)
    {
        m = U8TO64_LE(ni);
        v3 ^= m;

        TRACE;
        for (i = 0; i < cROUNDS; ++i)
        {
            SIPROUND;
        }

        v0 ^= m;
    }

    switch (left)
    {
        case 7:
            b |= ((uint64_t)ni[6]) << 48;

        /* FALLTHRU */
        case 6:
            b |= ((uint64_t)ni[5]) << 40;

        /* FALLTHRU */
        case 5:
            b |= ((uint64_t)ni[4]) << 32;

        /* FALLTHRU */
        case 4:
            b |= ((uint64_t)ni[3]) << 24;

        /* FALLTHRU */
        case 3:
            b |= ((uint64_t)ni[2]) << 16;

        /* FALLTHRU */
        case 2:
            b |= ((uint64_t)ni[1]) << 8;

        /* FALLTHRU */
        case 1:
            b |= ((uint64_t)ni[0]);
            break;

        case 0:
            break;
    }

    v3 ^= b;

    TRACE;
    for (i = 0; i < cROUNDS; ++i)
    {
        SIPROUND;
    }

    v0 ^= b;

    if (outlen == 16)
    {
        v2 ^= 0xee;
    }
    else
    {
        v2 ^= 0xff;
    }

    TRACE;
    for (i = 0; i < dROUNDS; ++i)
    {
        SIPROUND;
    }

    b = v0 ^ v1 ^ v2 ^ v3;
    U64TO8_LE(out, b);

    if (outlen == 8)
    {
        return 0;
    }

    v1 ^= 0xdd;

    TRACE;
    for (i = 0; i < dROUNDS; ++i)
    {
        SIPROUND;
    }

    b = v0 ^ v1 ^ v2 ^ v3;
    U64TO8_LE(out + 8, b);

    return 0;
}
