/*
 * Copyright (c) 2012-2014 Daniel J. Bernstein <djb@cr.yp.to>
 * Copyright (c) 2012-2022 Jean-Philippe Aumasson
 *
 * SPDX-License-Identifier: CC0-1.0
 */

#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
#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;
}