/*	$NetBSD: mi_vector_hash.c,v 1.1 2013/12/11 01:24:08 joerg Exp $	*/
/*-
 * Copyright (c) 2009 The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * This code is derived from software contributed to The NetBSD Foundation
 * by Joerg Sonnenberger.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

/*
 * See http://burtleburtle.net/bob/hash/doobs.html for the full description
 * and the original version of the code.  This version differs by exposing
 * the full internal state and avoiding byte operations in the inner loop
 * if the key is aligned correctly.
 */

#include <sys/cdefs.h>
#include <sys/endian.h>
#include <stdint.h>
#include <stdlib.h>

#define mix(a, b, c)                                                           \
  do {                                                                         \
    a -= b;                                                                    \
    a -= c;                                                                    \
    a ^= (c >> 13);                                                            \
    b -= c;                                                                    \
    b -= a;                                                                    \
    b ^= (a << 8);                                                             \
    c -= a;                                                                    \
    c -= b;                                                                    \
    c ^= (b >> 13);                                                            \
    a -= b;                                                                    \
    a -= c;                                                                    \
    a ^= (c >> 12);                                                            \
    b -= c;                                                                    \
    b -= a;                                                                    \
    b ^= (a << 16);                                                            \
    c -= a;                                                                    \
    c -= b;                                                                    \
    c ^= (b >> 5);                                                             \
    a -= b;                                                                    \
    a -= c;                                                                    \
    a ^= (c >> 3);                                                             \
    b -= c;                                                                    \
    b -= a;                                                                    \
    b ^= (a << 10);                                                            \
    c -= a;                                                                    \
    c -= b;                                                                    \
    c ^= (b >> 15);                                                            \
  } while (/* CONSTCOND */ 0)

#define FIXED_SEED 0x9e3779b9 /* Golden ratio, arbitrary constant */

void mi_vector_hash(const void *__restrict key, size_t len, uint32_t seed,
                    uint32_t hashes[3]) {
  static const uint32_t mask[4] = {0x000000ff, 0x0000ffff, 0x00ffffff,
                                   0xffffffff};
  uint32_t orig_len, a, b, c;
  const uint8_t *k;

  orig_len = (uint32_t)len;

  a = b = FIXED_SEED;
  c = seed;

  if ((uintptr_t)key & 3) {
    k = key;
    while (len >= 12) {
      a += le32dec(k);
      b += le32dec(k + 4);
      c += le32dec(k + 8);
      mix(a, b, c);
      k += 12;
      len -= 12;
    }
    c += orig_len;

    if (len > 8) {
      switch (len) {
        case 11:
          c += (uint32_t)k[10] << 24;
          /* FALLTHROUGH */
        case 10:
          c += (uint32_t)k[9] << 16;
          /* FALLTHROUGH */
        case 9:
          c += (uint32_t)k[8] << 8;
          /* FALLTHROUGH */
      }
      b += le32dec(k + 4);
      a += le32dec(k);
    } else if (len > 4) {
      switch (len) {
        case 8:
          b += (uint32_t)k[7] << 24;
          /* FALLTHROUGH */
        case 7:
          b += (uint32_t)k[6] << 16;
          /* FALLTHROUGH */
        case 6:
          b += (uint32_t)k[5] << 8;
          /* FALLTHROUGH */
        case 5:
          b += k[4];
          /* FALLTHROUGH */
      }
      a += le32dec(k);
    } else if (len) {
      switch (len) {
        case 4:
          a += (uint32_t)k[3] << 24;
          /* FALLTHROUGH */
        case 3:
          a += (uint32_t)k[2] << 16;
          /* FALLTHROUGH */
        case 2:
          a += (uint32_t)k[1] << 8;
          /* FALLTHROUGH */
        case 1:
          a += k[0];
          /* FALLTHROUGH */
      }
    }
  } else {
    const uint32_t *key32 = key;
    while (len >= 12) {
      a += le32toh(key32[0]);
      b += le32toh(key32[1]);
      c += le32toh(key32[2]);
      mix(a, b, c);
      key32 += 3;
      len -= 12;
    }
    c += orig_len;

    if (len > 8) {
      c += (le32toh(key32[2]) & mask[len - 9]) << 8;
      b += le32toh(key32[1]);
      a += le32toh(key32[0]);
    } else if (len > 4) {
      b += le32toh(key32[1]) & mask[len - 5];
      a += le32toh(key32[0]);
    } else if (len)
      a += le32toh(key32[0]) & mask[len - 1];
  }
  mix(a, b, c);
  hashes[0] = a;
  hashes[1] = b;
  hashes[2] = c;
}
