-
-
Notifications
You must be signed in to change notification settings - Fork 249
/
cache.c
190 lines (165 loc) · 4.25 KB
/
cache.c
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
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
// Copyright (c) 2011, 2021 Peter Ohler. All rights reserved.
// Licensed under the MIT License. See LICENSE file in the project root for license details.
#include "cache.h"
#define REHASH_LIMIT 64
#define MIN_SHIFT 8
typedef struct _slot {
struct _slot *next;
VALUE val;
uint32_t hash;
uint8_t klen;
char key[CACHE_MAX_KEY];
} * Slot;
typedef struct _cache {
Slot * slots;
size_t cnt;
VALUE (*form)(const char *str, size_t len);
uint32_t size;
uint32_t mask;
bool mark;
} * Cache;
// almost the Murmur hash algorithm
#define M 0x5bd1e995
#define C1 0xCC9E2D51
#define C2 0x1B873593
#define N 0xE6546B64
void cache_set_form(Cache c, VALUE (*form)(const char *str, size_t len)) {
c->form = form;
}
#if 0
// For debugging only.
static void cache_print(Cache c) {
for (uint32_t i = 0; i < c->size; i++) {
printf("%4d:", i);
for (Slot s = c->slots[i]; NULL != s; s = s->next) {
char buf[40];
strncpy(buf, s->key, s->klen);
buf[s->klen] = '\0';
printf(" %s", buf);
}
printf("\n");
}
}
#endif
static uint32_t hash_calc(const uint8_t *key, size_t len) {
const uint8_t *end = key + len;
const uint8_t *endless = key + (len & 0xFFFFFFFC);
uint32_t h = (uint32_t)len;
uint32_t k;
while (key < endless) {
k = (uint32_t)*key++;
k |= (uint32_t)*key++ << 8;
k |= (uint32_t)*key++ << 16;
k |= (uint32_t)*key++ << 24;
k *= M;
k ^= k >> 24;
h *= M;
h ^= k * M;
}
if (1 < end - key) {
uint16_t k16 = (uint16_t)*key++;
k16 |= (uint16_t)*key++ << 8;
h ^= k16 << 8;
}
if (key < end) {
h ^= *key;
}
h *= M;
h ^= h >> 13;
h *= M;
h ^= h >> 15;
return h;
}
Cache cache_create(size_t size, VALUE (*form)(const char *str, size_t len), bool mark) {
Cache c = ALLOC(struct _cache);
int shift = 0;
for (; REHASH_LIMIT < size; size /= 2, shift++) {
}
if (shift < MIN_SHIFT) {
shift = MIN_SHIFT;
}
c->size = 1 << shift;
c->mask = c->size - 1;
c->slots = ALLOC_N(Slot, c->size);
memset(c->slots, 0, sizeof(Slot) * c->size);
c->form = form;
c->cnt = 0;
c->mark = mark;
return c;
}
static void rehash(Cache c) {
uint32_t osize = c->size;
Slot * end = c->slots + osize;
Slot * sp;
c->size = osize * 4;
c->mask = c->size - 1;
REALLOC_N(c->slots, Slot, c->size);
memset(c->slots + osize, 0, sizeof(Slot) * osize * 3);
for (sp = c->slots; sp < end; sp++) {
Slot s = *sp;
Slot next = NULL;
*sp = NULL;
for (; NULL != s; s = next) {
uint32_t h = s->hash & c->mask;
Slot * bucket = c->slots + h;
next = s->next;
s->next = *bucket;
*bucket = s;
}
}
}
void cache_free(Cache c) {
for (uint32_t i = 0; i < c->size; i++) {
Slot next;
Slot s;
for (s = c->slots[i]; NULL != s; s = next) {
next = s->next;
xfree(s);
}
}
xfree(c->slots);
xfree(c);
}
void cache_mark(Cache c) {
if (c->mark) {
uint32_t i;
for (i = 0; i < c->size; i++) {
for (Slot s = c->slots[i]; NULL != s; s = s->next) {
rb_gc_mark(s->val);
}
}
}
}
VALUE
cache_intern(Cache c, const char *key, size_t len) {
if (CACHE_MAX_KEY < len) {
return c->form(key, len);
}
uint32_t h = hash_calc((const uint8_t *)key, len);
Slot * bucket = c->slots + (h & c->mask);
Slot b;
Slot tail = NULL;
for (b = *bucket; NULL != b; b = b->next) {
if ((uint8_t)len == b->klen && 0 == strncmp(b->key, key, len)) {
return b->val;
}
tail = b;
}
b = ALLOC(struct _slot);
b->hash = h;
b->next = NULL;
memcpy(b->key, key, len);
b->klen = (uint8_t)len;
b->key[len] = '\0';
b->val = c->form(key, len);
if (NULL == tail) {
*bucket = b;
} else {
tail->next = b;
}
c->cnt++;
if (REHASH_LIMIT < c->cnt / c->size) {
rehash(c);
}
return b->val;
}