lib/hash.c

   1 /*
   2  * Copyright (c) 2008, 2009, 2010, 2012, 2013 Nicira, Inc.
   3  *
   4  * Licensed under the Apache License, Version 2.0 (the "License");
   5  * you may not use this file except in compliance with the License.
   6  * You may obtain a copy of the License at:
   7  *
   8  *     http://www.apache.org/licenses/LICENSE-2.0
   9  *
  10  * Unless required by applicable law or agreed to in writing, software
  11  * distributed under the License is distributed on an "AS IS" BASIS,
  12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13  * See the License for the specific language governing permissions and
  14  * limitations under the License.
  15  */
  16 #include <config.h>
  17 #include "hash.h"
  18 #include <string.h>
  19 #include "unaligned.h"
  20
  21 /* Returns the hash of 'a', 'b', and 'c'. */
  22 uint32_t
  23 hash_3words(uint32_t a, uint32_t b, uint32_t c)
  24 {
  25     return hash_finish(hash_add(hash_add(hash_add(a, 0), b), c), 12);
  26 }
  27
  28 /* Returns the hash of the 'n' bytes at 'p', starting from 'basis'. */
  29 uint32_t
  30 hash_bytes(const void *p_, size_t n, uint32_t basis)
  31 {
  32     const uint32_t *p = p_;
  33     size_t orig_n = n;
  34     uint32_t hash;
  35
  36     hash = basis;
  37     while (n >= 4) {
  38         hash = hash_add(hash, get_unaligned_u32(p));
  39         n -= 4;
  40         p += 1;
  41     }
  42
  43     if (n) {
  44         uint32_t tmp = 0;
  45
  46         memcpy(&tmp, p, n);
  47         hash = hash_add(hash, tmp);
  48     }
  49
  50     return hash_finish(hash, orig_n);
  51 }
  52
  53 uint32_t
  54 hash_double(double x, uint32_t basis)
  55 {
  56     uint32_t value[2];
  57     BUILD_ASSERT_DECL(sizeof x == sizeof value);
  58
  59     memcpy(value, &x, sizeof value);
  60     return hash_3words(value[0], value[1], basis);
  61 }
  62
  63 uint32_t
  64 hash_words__(const uint32_t p[], size_t n_words, uint32_t basis)
  65 {
  66     return hash_words_inline(p, n_words, basis);
  67 }
  68
  69 uint32_t
  70 hash_words64__(const uint64_t p[], size_t n_words, uint64_t basis)
  71 {
  72     return hash_words64_inline(p, n_words, basis);
  73 }