1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/src/hash_map.c Wed May 18 16:26:32 2022 +0200
1.3 @@ -0,0 +1,105 @@
1.4 +/*
1.5 + * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
1.6 + *
1.7 + * Copyright 2021 Mike Becker, Olaf Wintermann All rights reserved.
1.8 + *
1.9 + * Redistribution and use in source and binary forms, with or without
1.10 + * modification, are permitted provided that the following conditions are met:
1.11 + *
1.12 + * 1. Redistributions of source code must retain the above copyright
1.13 + * notice, this list of conditions and the following disclaimer.
1.14 + *
1.15 + * 2. Redistributions in binary form must reproduce the above copyright
1.16 + * notice, this list of conditions and the following disclaimer in the
1.17 + * documentation and/or other materials provided with the distribution.
1.18 + *
1.19 + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
1.20 + * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
1.21 + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
1.22 + * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
1.23 + * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
1.24 + * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
1.25 + * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
1.26 + * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
1.27 + * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
1.28 + * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
1.29 + * POSSIBILITY OF SUCH DAMAGE.
1.30 + */
1.31 +
1.32 +#include <string.h>
1.33 +#include "cx/hash_map.h"
1.34 +
1.35 +/**
1.36 + * Computes a murmur hash-2.
1.37 + *
1.38 + * @param data the data to hash
1.39 + * @param len the length of the data
1.40 + * @return the murmur hash-2 of the data
1.41 + */
1.42 +static unsigned cx_hash_map_murmur(
1.43 + unsigned char const *data,
1.44 + size_t len
1.45 +) {
1.46 + unsigned m = 0x5bd1e995;
1.47 + unsigned r = 24;
1.48 + unsigned h = 25 ^ len;
1.49 + unsigned i = 0;
1.50 + while (len >= 4) {
1.51 + unsigned k = data[i + 0] & 0xFF;
1.52 + k |= (data[i + 1] & 0xFF) << 8;
1.53 + k |= (data[i + 2] & 0xFF) << 16;
1.54 + k |= (data[i + 3] & 0xFF) << 24;
1.55 +
1.56 + k *= m;
1.57 + k ^= k >> r;
1.58 + k *= m;
1.59 +
1.60 + h *= m;
1.61 + h ^= k;
1.62 +
1.63 + i += 4;
1.64 + len -= 4;
1.65 + }
1.66 +
1.67 + switch (len) {
1.68 + case 3:
1.69 + h ^= (data[i + 2] & 0xFF) << 16;
1.70 + __attribute__((__fallthrough__));
1.71 + case 2:
1.72 + h ^= (data[i + 1] & 0xFF) << 8;
1.73 + __attribute__((__fallthrough__));
1.74 + case 1:
1.75 + h ^= (data[i + 0] & 0xFF);
1.76 + h *= m;
1.77 + __attribute__((__fallthrough__));
1.78 + default:
1.79 + /* do nothing */;
1.80 + }
1.81 +
1.82 + h ^= h >> 13;
1.83 + h *= m;
1.84 + h ^= h >> 15;
1.85 +
1.86 + return h;
1.87 +}
1.88 +
1.89 +
1.90 +/**
1.91 + * Creates a hash map key based on the given data.
1.92 + *
1.93 + * This function implicitly computes the hash.
1.94 + *
1.95 + * @attention The data will be copied to the key structure.
1.96 + *
1.97 + * @param data the data for the key
1.98 + * @return the computed key
1.99 + */
1.100 +static struct cx_hash_map_key_s cx_hash_map_key(CxDataPtr data) {
1.101 + unsigned char *target = malloc(data.len);
1.102 + memcpy(target, data.data, data.len);
1.103 + struct cx_hash_map_key_s key;
1.104 + key.data.data = target;
1.105 + key.data.len = data.len;
1.106 + key.hash = cx_hash_map_murmur(target, data.len);
1.107 + return key;
1.108 +}
