/* Copyright (c) 2019, Google Inc.

 *

 * Permission to use, copy, modify, and/or distribute this software for any

 * purpose with or without fee is hereby granted, provided that the above

 * copyright notice and this permission notice appear in all copies.

 *

 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES

 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF

 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY

 * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES

 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION

 * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN

 * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */

#include <stdint.h>

#include <string.h>

#include <openssl/siphash.h>

#include "../internal.h"

static void siphash_round(uint64_t v[4]) {

  v[0] += v[1];

  v[2] += v[3];

  v[1] = CRYPTO_rotl_u64(v[1], 13);

  v[3] = CRYPTO_rotl_u64(v[3], 16);

  v[1] ^= v[0];

  v[3] ^= v[2];

  v[0] = CRYPTO_rotl_u64(v[0], 32);

  v[2] += v[1];

  v[0] += v[3];

  v[1] = CRYPTO_rotl_u64(v[1], 17);

  v[3] = CRYPTO_rotl_u64(v[3], 21);

  v[1] ^= v[2];

  v[3] ^= v[0];

  v[2] = CRYPTO_rotl_u64(v[2], 32);

}

uint64_t SIPHASH_24(const uint64_t key[2], const uint8_t *input,

                    size_t input_len) {

  const size_t orig_input_len = input_len;

  uint64_t v[4];

  v[0] = key[0] ^ UINT64_C(0x736f6d6570736575);

  v[1] = key[1] ^ UINT64_C(0x646f72616e646f6d);

  v[2] = key[0] ^ UINT64_C(0x6c7967656e657261);

  v[3] = key[1] ^ UINT64_C(0x7465646279746573);

  while (input_len >= sizeof(uint64_t)) {

    uint64_t m = CRYPTO_load_u64_le(input);

    v[3] ^= m;

    siphash_round(v);

    siphash_round(v);

    v[0] ^= m;

    input += sizeof(uint64_t);

    input_len -= sizeof(uint64_t);

  }

  uint8_t last_block[8];

  OPENSSL_memset(last_block, 0, sizeof(last_block));

  OPENSSL_memcpy(last_block, input, input_len);

  last_block[7] = orig_input_len & 0xff;

  uint64_t last_block_word = CRYPTO_load_u64_le(last_block);

  v[3] ^= last_block_word;

  siphash_round(v);

  siphash_round(v);

  v[0] ^= last_block_word;

  v[2] ^= 0xff;

  siphash_round(v);

  siphash_round(v);

  siphash_round(v);

  siphash_round(v);

  return v[0] ^ v[1] ^ v[2] ^ v[3];

}