Repository navigation
Expand file tree
/
Copy pathhash.c
More file actions
281 lines (263 loc) · 7.97 KB
/
Copy pathhash.c
File metadata and controls
281 lines (263 loc) · 7.97 KB
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
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
/*
** 2001 September 22
**
** The author disclaims copyright to this source code. In place of
** a legal notice, here is a blessing:
**
** May you do good and not evil.
** May you find forgiveness for yourself and forgive others.
** May you share freely, never taking more than you give.
**
*************************************************************************
** This is the implementation of generic hash-tables
** used in SQLite.
*/
#include "sqliteInt.h"
#include <assert.h>
/* Turn bulk memory into a hash table object by initializing the
** fields of the Hash structure.
**
** "pNew" is a pointer to the hash table that is to be initialized.
*/
void sqlite3HashInit(Hash *pNew){
assert( pNew!=0 );
pNew->first = 0;
pNew->count = 0;
pNew->htsize = 0;
pNew->ht = 0;
}
/* Remove all entries from a hash table. Reclaim all memory.
** Call this routine to delete a hash table or to reset a hash table
** to the empty state.
*/
void sqlite3HashClear(Hash *pH){
HashElem *elem; /* For looping over all elements of the table */
assert( pH!=0 );
elem = pH->first;
pH->first = 0;
sqlite3_free(pH->ht);
pH->ht = 0;
pH->htsize = 0;
while( elem ){
HashElem *next_elem = elem->next;
sqlite3_free(elem);
elem = next_elem;
}
pH->count = 0;
}
/*
** The hashing function.
*/
static unsigned int strHash(const char *z, int nKey){
int h = 0;
assert( nKey>=0 );
while( nKey > 0 ){
h = (h<<3) ^ h ^ sqlite3UpperToLower[(unsigned char)*z++];
nKey--;
}
return h;
}
/* Link pNew element into the hash table pH. If pEntry!=0 then also
** insert pNew into the pEntry hash bucket.
*/
static void insertElement(
Hash *pH, /* The complete hash table */
struct _ht *pEntry, /* The entry into which pNew is inserted */
HashElem *pNew /* The element to be inserted */
){
HashElem *pHead; /* First element already in pEntry */
if( pEntry ){
pHead = pEntry->count ? pEntry->chain : 0;
pEntry->count++;
pEntry->chain = pNew;
}else{
pHead = 0;
}
if( pHead ){
pNew->next = pHead;
pNew->prev = pHead->prev;
if( pHead->prev ){ pHead->prev->next = pNew; }
else { pH->first = pNew; }
pHead->prev = pNew;
}else{
pNew->next = pH->first;
if( pH->first ){ pH->first->prev = pNew; }
pNew->prev = 0;
pH->first = pNew;
}
}
/* Resize the hash table so that it cantains "new_size" buckets.
**
** The hash table might fail to resize if sqlite3_malloc() fails or
** if the new size is the same as the prior size.
** Return TRUE if the resize occurs and false if not.
*/
static int rehash(Hash *pH, unsigned int new_size){
struct _ht *new_ht; /* The new hash table */
HashElem *elem, *next_elem; /* For looping over existing elements */
#if SQLITE_MALLOC_SOFT_LIMIT>0
if( new_size*sizeof(struct _ht)>SQLITE_MALLOC_SOFT_LIMIT ){
new_size = SQLITE_MALLOC_SOFT_LIMIT/sizeof(struct _ht);
}
if( new_size==pH->htsize ) return 0;
#endif
/* The inability to allocates space for a larger hash table is
** a performance hit but it is not a fatal error. So mark the
** allocation as a benign. Use sqlite3Malloc()/memset(0) instead of
** sqlite3MallocZero() to make the allocation, as sqlite3MallocZero()
** only zeroes the requested number of bytes whereas this module will
** use the actual amount of space allocated for the hash table (which
** may be larger than the requested amount).
*/
sqlite3BeginBenignMalloc();
new_ht = (struct _ht *)sqlite3Malloc( new_size*sizeof(struct _ht) );
sqlite3EndBenignMalloc();
if( new_ht==0 ) return 0;
sqlite3_free(pH->ht);
pH->ht = new_ht;
pH->htsize = new_size = sqlite3MallocSize(new_ht)/sizeof(struct _ht);
memset(new_ht, 0, new_size*sizeof(struct _ht));
for(elem=pH->first, pH->first=0; elem; elem = next_elem){
unsigned int h = strHash(elem->pKey, elem->nKey) % new_size;
next_elem = elem->next;
insertElement(pH, &new_ht[h], elem);
}
return 1;
}
/* This function (for internal use only) locates an element in an
** hash table that matches the given key. The hash for this key has
** already been computed and is passed as the 4th parameter.
*/
static HashElem *findElementGivenHash(
const Hash *pH, /* The pH to be searched */
const char *pKey, /* The key we are searching for */
int nKey, /* Bytes in key (not counting zero terminator) */
unsigned int h /* The hash for this key. */
){
HashElem *elem; /* Used to loop thru the element list */
int count; /* Number of elements left to test */
if( pH->ht ){
struct _ht *pEntry = &pH->ht[h];
elem = pEntry->chain;
count = pEntry->count;
}else{
elem = pH->first;
count = pH->count;
}
while( count-- && ALWAYS(elem) ){
if( elem->nKey==nKey && sqlite3StrNICmp(elem->pKey,pKey,nKey)==0 ){
return elem;
}
elem = elem->next;
}
return 0;
}
/* Remove a single entry from the hash table given a pointer to that
** element and a hash on the element's key.
*/
static void removeElementGivenHash(
Hash *pH, /* The pH containing "elem" */
HashElem* elem, /* The element to be removed from the pH */
unsigned int h /* Hash value for the element */
){
struct _ht *pEntry;
if( elem->prev ){
elem->prev->next = elem->next;
}else{
pH->first = elem->next;
}
if( elem->next ){
elem->next->prev = elem->prev;
}
if( pH->ht ){
pEntry = &pH->ht[h];
if( pEntry->chain==elem ){
pEntry->chain = elem->next;
}
pEntry->count--;
assert( pEntry->count>=0 );
}
sqlite3_free( elem );
pH->count--;
if( pH->count==0 ){
assert( pH->first==0 );
assert( pH->count==0 );
sqlite3HashClear(pH);
}
}
/* Attempt to locate an element of the hash table pH with a key
** that matches pKey,nKey. Return the data for this element if it is
** found, or NULL if there is no match.
*/
void *sqlite3HashFind(const Hash *pH, const char *pKey, int nKey){
HashElem *elem; /* The element that matches key */
unsigned int h; /* A hash on key */
assert( pH!=0 );
assert( pKey!=0 );
assert( nKey>=0 );
if( pH->ht ){
h = strHash(pKey, nKey) % pH->htsize;
}else{
h = 0;
}
elem = findElementGivenHash(pH, pKey, nKey, h);
return elem ? elem->data : 0;
}
/* Insert an element into the hash table pH. The key is pKey,nKey
** and the data is "data".
**
** If no element exists with a matching key, then a new
** element is created and NULL is returned.
**
** If another element already exists with the same key, then the
** new data replaces the old data and the old data is returned.
** The key is not copied in this instance. If a malloc fails, then
** the new data is returned and the hash table is unchanged.
**
** If the "data" parameter to this function is NULL, then the
** element corresponding to "key" is removed from the hash table.
*/
void *sqlite3HashInsert(Hash *pH, const char *pKey, int nKey, void *data){
unsigned int h; /* the hash of the key modulo hash table size */
HashElem *elem; /* Used to loop thru the element list */
HashElem *new_elem; /* New element added to the pH */
assert( pH!=0 );
assert( pKey!=0 );
assert( nKey>=0 );
if( pH->htsize ){
h = strHash(pKey, nKey) % pH->htsize;
}else{
h = 0;
}
elem = findElementGivenHash(pH,pKey,nKey,h);
if( elem ){
void *old_data = elem->data;
if( data==0 ){
removeElementGivenHash(pH,elem,h);
}else{
elem->data = data;
elem->pKey = pKey;
assert(nKey==elem->nKey);
}
return old_data;
}
if( data==0 ) return 0;
new_elem = (HashElem*)sqlite3Malloc( sizeof(HashElem) );
if( new_elem==0 ) return data;
new_elem->pKey = pKey;
new_elem->nKey = nKey;
new_elem->data = data;
pH->count++;
if( pH->count>=10 && pH->count > 2*pH->htsize ){
if( rehash(pH, pH->count*2) ){
assert( pH->htsize>0 );
h = strHash(pKey, nKey) % pH->htsize;
}
}
if( pH->ht ){
insertElement(pH, &pH->ht[h], new_elem);
}else{
insertElement(pH, 0, new_elem);
}
return 0;
}