/*

   SipHash reference C implementation

   Copyright (c) 2012-2014 Jean-Philippe Aumasson

   <jeanphilippe.aumasson@gmail.com>

   Copyright (c) 2012-2014 Daniel J. Bernstein <djb@cr.yp.to>

   To the extent possible under law, the author(s) have dedicated all copyright

   and related and neighboring rights to this software to the public domain

   worldwide. This software is distributed without any warranty.

   You should have received a copy of the CC0 Public Domain Dedication along

   with

   this software. If not, see

   <http://creativecommons.org/publicdomain/zero/1.0/>.

 */

#include <stdint.h>

#include <stdio.h>

#include <string.h>

/* default: SipHash-2-4 */

#define cROUNDS 2

#define dROUNDS 4

#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

#define TRACE                                                                  \

  do {                                                                         \

    printf("(%3d) v0 %08x %08x\n", (int)inlen, (uint32_t)(v0 >> 32),           \

           (uint32_t)v0);                                                      \

    printf("(%3d) v1 %08x %08x\n", (int)inlen, (uint32_t)(v1 >> 32),           \

           (uint32_t)v1);                                                      \

    printf("(%3d) v2 %08x %08x\n", (int)inlen, (uint32_t)(v2 >> 32),           \

           (uint32_t)v2);                                                      \

    printf("(%3d) v3 %08x %08x\n", (int)inlen, (uint32_t)(v3 >> 32),           \

           (uint32_t)v3);                                                      \

  } while (0)

#else

#define TRACE

#endif

int siphash(uint8_t *out, const uint8_t *in, uint64_t inlen, const uint8_t *k) {

  /* "somepseudorandomlygeneratedbytes" */

  uint64_t v0 = 0x736f6d6570736575ULL;

  uint64_t v1 = 0x646f72616e646f6dULL;

  uint64_t v2 = 0x6c7967656e657261ULL;

  uint64_t v3 = 0x7465646279746573ULL;

  uint64_t b;

  uint64_t k0 = U8TO64_LE(k);

  uint64_t k1 = U8TO64_LE(k + 8);

  uint64_t m;

  int i;

  const uint8_t *end = in + inlen - (inlen % sizeof(uint64_t));

  const int left = inlen & 7;

  b = ((uint64_t)inlen) << 56;

  v3 ^= k1;

  v2 ^= k0;

  v1 ^= k1;

  v0 ^= k0;

#ifdef DOUBLE

  v1 ^= 0xee;

#endif

  for (; in != end; 
in += 819.4M
) {

    m = U8TO64_LE(in);

    v3 ^= m;

    TRACE;

    for (i = 0; i < cROUNDS; 
++i38.8M
)

      SIPROUND;

    v0 ^= m;

  }

  switch (left) {

  case 7:

    b |= ((uint64_t)in[6]) << 48;

  case 6:

    b |= ((uint64_t)in[5]) << 40;

  case 5:

    b |= ((uint64_t)in[4]) << 32;

  case 4:

    b |= ((uint64_t)in[3]) << 24;

  case 3:

    b |= ((uint64_t)in[2]) << 16;

  case 2:

    b |= ((uint64_t)in[1]) << 8;

  case 1:

    b |= ((uint64_t)in[0]);

    break;

  case 0:

    break;

  }

  v3 ^= b;

  TRACE;

  for (i = 0; i < cROUNDS; 
++i12.4M
)

    SIPROUND;

  v0 ^= b;

#ifndef DOUBLE

  v2 ^= 0xff;

#else

  v2 ^= 0xee;

#endif

  TRACE;

  for (i = 0; i < dROUNDS; 
++i24.9M
)

    SIPROUND;

  b = v0 ^ v1 ^ v2 ^ v3;

  U64TO8_LE(out, b);

#ifdef DOUBLE

  v1 ^= 0xdd;

  TRACE;

  for (i = 0; i < dROUNDS; ++i)

    SIPROUND;

  b = v0 ^ v1 ^ v2 ^ v3;

  U64TO8_LE(out + 8, b);

#endif

  return 0;

}