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
|
/* ncmpc (Ncurses MPD Client)
* (c) 2004-2009 The Music Player Daemon Project
* Project homepage: http://musicpd.org
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
#include "str_pool.h"
#include <assert.h>
#include <stddef.h>
#include <stdlib.h>
#include <string.h>
#define NUM_SLOTS 4096
struct slot {
struct slot *next;
unsigned char ref;
char value[1];
} __attribute__((packed));
static struct slot *slots[NUM_SLOTS];
static inline unsigned
calc_hash(const char *p)
{
unsigned hash = 5381;
assert(p != NULL);
while (*p != 0)
hash = (hash << 5) + hash + *p++;
return hash;
}
static inline struct slot *
value_to_slot(char *value)
{
return (struct slot*)(value - offsetof(struct slot, value));
}
static struct slot *slot_alloc(struct slot *next, const char *value)
{
size_t length = strlen(value);
struct slot *slot = malloc(sizeof(*slot) + length);
if (slot == NULL)
abort(); /* XXX */
slot->next = next;
slot->ref = 1;
memcpy(slot->value, value, length + 1);
return slot;
}
char *str_pool_get(const char *value)
{
struct slot **slot_p, *slot;
slot_p = &slots[calc_hash(value) % NUM_SLOTS];
for (slot = *slot_p; slot != NULL; slot = slot->next) {
if (strcmp(value, slot->value) == 0 && slot->ref < 0xff) {
assert(slot->ref > 0);
++slot->ref;
return slot->value;
}
}
slot = slot_alloc(*slot_p, value);
*slot_p = slot;
return slot->value;
}
char *str_pool_dup(char *value)
{
struct slot *slot = value_to_slot(value);
assert(slot->ref > 0);
if (slot->ref < 0xff) {
++slot->ref;
return value;
} else {
/* the reference counter overflows above 0xff;
duplicate the value, and start with 1 */
struct slot **slot_p =
&slots[calc_hash(slot->value) % NUM_SLOTS];
slot = slot_alloc(*slot_p, slot->value);
*slot_p = slot;
return slot->value;
}
}
void str_pool_put(char *value)
{
struct slot **slot_p, *slot;
slot = value_to_slot(value);
assert(slot->ref > 0);
--slot->ref;
if (slot->ref > 0)
return;
for (slot_p = &slots[calc_hash(value) % NUM_SLOTS];
*slot_p != slot;
slot_p = &(*slot_p)->next) {
assert(*slot_p != NULL);
}
*slot_p = slot->next;
free(slot);
}
|
