ucx: src/hash_key.c@edb9f875b7f9

     1 /*

     2  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.

     3  *

     4  * Copyright 2021 Mike Becker, Olaf Wintermann All rights reserved.

     5  *

     6  * Redistribution and use in source and binary forms, with or without

     7  * modification, are permitted provided that the following conditions are met:

     8  *

     9  *   1. Redistributions of source code must retain the above copyright

    10  *      notice, this list of conditions and the following disclaimer.

    11  *

    12  *   2. Redistributions in binary form must reproduce the above copyright

    13  *      notice, this list of conditions and the following disclaimer in the

    14  *      documentation and/or other materials provided with the distribution.

    15  *

    16  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"

    17  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE

    18  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE

    19  * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE

    20  * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR

    21  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF

    22  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS

    23  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN

    24  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)

    25  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE

    26  * POSSIBILITY OF SUCH DAMAGE.

    27  */

    29 #include "cx/hash_key.h"

    30 #include <string.h>

    32 void cx_hash_murmur(CxHashKey *key) {

    33     unsigned char const *data = key->data;

    34     if (data == NULL) {

    35         // extension: special value for NULL

    36         key->hash = 1574210520u;

    37         return;

    38     }

    39     size_t len = key->len;

    41     unsigned m = 0x5bd1e995;

    42     unsigned r = 24;

    43     unsigned h = 25 ^ len;

    44     unsigned i = 0;

    45     while (len >= 4) {

    46         unsigned k = data[i + 0] & 0xFF;

    47         k |= (data[i + 1] & 0xFF) << 8;

    48         k |= (data[i + 2] & 0xFF) << 16;

    49         k |= (data[i + 3] & 0xFF) << 24;

    51         k *= m;

    52         k ^= k >> r;

    53         k *= m;

    55         h *= m;

    56         h ^= k;

    58         i += 4;

    59         len -= 4;

    60     }

    62     switch (len) {

    63         case 3:

    64             h ^= (data[i + 2] & 0xFF) << 16;

    65                     __attribute__((__fallthrough__));

    66         case 2:

    67             h ^= (data[i + 1] & 0xFF) << 8;

    68                     __attribute__((__fallthrough__));

    69         case 1:

    70             h ^= (data[i + 0] & 0xFF);

    71             h *= m;

    72                     __attribute__((__fallthrough__));

    73         default: // do nothing

    74             ;

    75     }

    77     h ^= h >> 13;

    78     h *= m;

    79     h ^= h >> 15;

    81     key->hash = h;

    82 }

    84 CxHashKey cx_hash_key_str(char const *str) {

    85     CxHashKey key;

    86     key.data = str;

    87     key.len = str == NULL ? 0 : strlen(str);

    88     cx_hash_murmur(&key);

    89     return key;

    90 }

    92 CxHashKey cx_hash_key_bytes(

    93         unsigned char const *bytes,

    94         size_t len

    95 ) {

    96     CxHashKey key;

    97     key.data = bytes;

    98     key.len = len;

    99     cx_hash_murmur(&key);

   100     return key;

   101 }

   103 CxHashKey cx_hash_key(

   104         void const *obj,

   105         size_t len

   106 ) {

   107     CxHashKey key;

   108     key.data = obj;

   109     key.len = len;

   110     cx_hash_murmur(&key);

   111     return key;

   112 }

Mercurial > hg > ucx / file revision