1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
|
/*-
* Copyright (c) 2015 Nuxi, https://nuxi.nl/
*
* 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 AUTHOR 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 AUTHOR 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.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include <errno.h>
#include <limits.h>
#include <search.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include "hsearch.h"
/*
* Look up an unused entry in the hash table for a given hash. For this
* implementation we use quadratic probing. Quadratic probing has the
* advantage of preventing primary clustering.
*/
static ENTRY *
hsearch_lookup_free(struct __hsearch *hsearch, size_t hash)
{
size_t index, i;
for (index = hash, i = 0;; index += ++i) {
ENTRY *entry = &hsearch->entries[index & hsearch->index_mask];
if (entry->key == NULL)
return (entry);
}
}
/*
* Computes an FNV-1a hash of the key. Depending on the pointer size, this
* either uses the 32- or 64-bit FNV prime.
*/
static size_t
hsearch_hash(size_t offset_basis, const char *str)
{
size_t hash;
hash = offset_basis;
while (*str != '\0') {
hash ^= (uint8_t)*str++;
if (sizeof(size_t) * CHAR_BIT <= 32)
hash *= UINT32_C(16777619);
else
hash *= UINT64_C(1099511628211);
}
return (hash);
}
int
hsearch_r(ENTRY item, ACTION action, ENTRY **retval, struct hsearch_data *htab)
{
struct __hsearch *hsearch;
ENTRY *entry, *old_entries, *new_entries;
size_t hash, index, i, old_hash, old_count, new_count;
hsearch = htab->__hsearch;
hash = hsearch_hash(hsearch->offset_basis, item.key);
/*
* Search the hash table for an existing entry for this key.
* Stop searching if we run into an unused hash table entry.
*/
for (index = hash, i = 0;; index += ++i) {
entry = &hsearch->entries[index & hsearch->index_mask];
if (entry->key == NULL)
break;
if (strcmp(entry->key, item.key) == 0) {
*retval = entry;
return (1);
}
}
/* Only perform the insertion if action is set to ENTER. */
if (action == FIND) {
errno = ESRCH;
return (0);
}
if (hsearch->entries_used * 2 >= hsearch->index_mask) {
/* Preserve the old hash table entries. */
old_count = hsearch->index_mask + 1;
old_entries = hsearch->entries;
/*
* Allocate and install a new table if insertion would
* yield a hash table that is more than 50% used. By
* using 50% as a threshold, a lookup will only take up
* to two steps on average.
*/
new_count = (hsearch->index_mask + 1) * 2;
new_entries = calloc(new_count, sizeof(ENTRY));
if (new_entries == NULL)
return (0);
hsearch->entries = new_entries;
hsearch->index_mask = new_count - 1;
/* Copy over the entries from the old table to the new table. */
for (i = 0; i < old_count; ++i) {
entry = &old_entries[i];
if (entry->key != NULL) {
old_hash = hsearch_hash(hsearch->offset_basis,
entry->key);
*hsearch_lookup_free(hsearch, old_hash) =
*entry;
}
}
/* Destroy the old hash table entries. */
free(old_entries);
/*
* Perform a new lookup for a free table entry, so that
* we insert the entry into the new hash table.
*/
hsearch = htab->__hsearch;
entry = hsearch_lookup_free(hsearch, hash);
}
/* Insert the new entry into the hash table. */
*entry = item;
++hsearch->entries_used;
*retval = entry;
return (1);
}
|
