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
151
152
153
154
155
|
/*
* Copyright (C) 2003-2013 The Music Player Daemon Project
* http://www.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 "config.h"
#include "TagPool.hxx"
#include "Tag.hxx"
#include <glib.h>
#include <assert.h>
#include <string.h>
Mutex tag_pool_lock;
#define NUM_SLOTS 4096
struct slot {
struct slot *next;
unsigned char ref;
TagItem item;
} mpd_packed;
static struct slot *slots[NUM_SLOTS];
static inline unsigned
calc_hash_n(enum tag_type type, const char *p, size_t length)
{
unsigned hash = 5381;
assert(p != nullptr);
while (length-- > 0)
hash = (hash << 5) + hash + *p++;
return hash ^ type;
}
static inline unsigned
calc_hash(enum tag_type type, const char *p)
{
unsigned hash = 5381;
assert(p != nullptr);
while (*p != 0)
hash = (hash << 5) + hash + *p++;
return hash ^ type;
}
static inline struct slot *
tag_item_to_slot(TagItem *item)
{
return (struct slot*)(((char*)item) - offsetof(struct slot, item));
}
static struct slot *slot_alloc(struct slot *next,
enum tag_type type,
const char *value, int length)
{
struct slot *slot;
slot = (struct slot *)
g_malloc(sizeof(*slot) - sizeof(slot->item.value) + length + 1);
slot->next = next;
slot->ref = 1;
slot->item.type = type;
memcpy(slot->item.value, value, length);
slot->item.value[length] = 0;
return slot;
}
TagItem *
tag_pool_get_item(enum tag_type type, const char *value, size_t length)
{
struct slot **slot_p, *slot;
slot_p = &slots[calc_hash_n(type, value, length) % NUM_SLOTS];
for (slot = *slot_p; slot != nullptr; slot = slot->next) {
if (slot->item.type == type &&
length == strlen(slot->item.value) &&
memcmp(value, slot->item.value, length) == 0 &&
slot->ref < 0xff) {
assert(slot->ref > 0);
++slot->ref;
return &slot->item;
}
}
slot = slot_alloc(*slot_p, type, value, length);
*slot_p = slot;
return &slot->item;
}
TagItem *
tag_pool_dup_item(TagItem *item)
{
struct slot *slot = tag_item_to_slot(item);
assert(slot->ref > 0);
if (slot->ref < 0xff) {
++slot->ref;
return item;
} else {
/* the reference counter overflows above 0xff;
duplicate the item, and start with 1 */
size_t length = strlen(item->value);
struct slot **slot_p =
&slots[calc_hash_n(item->type, item->value,
length) % NUM_SLOTS];
slot = slot_alloc(*slot_p, item->type,
item->value, strlen(item->value));
*slot_p = slot;
return &slot->item;
}
}
void
tag_pool_put_item(TagItem *item)
{
struct slot **slot_p, *slot;
slot = tag_item_to_slot(item);
assert(slot->ref > 0);
--slot->ref;
if (slot->ref > 0)
return;
for (slot_p = &slots[calc_hash(item->type, item->value) % NUM_SLOTS];
*slot_p != slot;
slot_p = &(*slot_p)->next) {
assert(*slot_p != nullptr);
}
*slot_p = slot->next;
g_free(slot);
}
|
