Annotation of embedaddon/php/ext/sqlite/libsqlite/src/hash.c, revision 1.1.1.1
1.1 misho 1: /*
2: ** 2001 September 22
3: **
4: ** The author disclaims copyright to this source code. In place of
5: ** a legal notice, here is a blessing:
6: **
7: ** May you do good and not evil.
8: ** May you find forgiveness for yourself and forgive others.
9: ** May you share freely, never taking more than you give.
10: **
11: *************************************************************************
12: ** This is the implementation of generic hash-tables
13: ** used in SQLite.
14: **
15: ** $Id: hash.c 195361 2005-09-07 15:11:33Z iliaa $
16: */
17: #include "sqliteInt.h"
18: #include <assert.h>
19:
20: /* Turn bulk memory into a hash table object by initializing the
21: ** fields of the Hash structure.
22: **
23: ** "new" is a pointer to the hash table that is to be initialized.
24: ** keyClass is one of the constants SQLITE_HASH_INT, SQLITE_HASH_POINTER,
25: ** SQLITE_HASH_BINARY, or SQLITE_HASH_STRING. The value of keyClass
26: ** determines what kind of key the hash table will use. "copyKey" is
27: ** true if the hash table should make its own private copy of keys and
28: ** false if it should just use the supplied pointer. CopyKey only makes
29: ** sense for SQLITE_HASH_STRING and SQLITE_HASH_BINARY and is ignored
30: ** for other key classes.
31: */
32: void sqliteHashInit(Hash *new, int keyClass, int copyKey){
33: assert( new!=0 );
34: assert( keyClass>=SQLITE_HASH_INT && keyClass<=SQLITE_HASH_BINARY );
35: new->keyClass = keyClass;
36: new->copyKey = copyKey &&
37: (keyClass==SQLITE_HASH_STRING || keyClass==SQLITE_HASH_BINARY);
38: new->first = 0;
39: new->count = 0;
40: new->htsize = 0;
41: new->ht = 0;
42: }
43:
44: /* Remove all entries from a hash table. Reclaim all memory.
45: ** Call this routine to delete a hash table or to reset a hash table
46: ** to the empty state.
47: */
48: void sqliteHashClear(Hash *pH){
49: HashElem *elem; /* For looping over all elements of the table */
50:
51: assert( pH!=0 );
52: elem = pH->first;
53: pH->first = 0;
54: if( pH->ht ) sqliteFree(pH->ht);
55: pH->ht = 0;
56: pH->htsize = 0;
57: while( elem ){
58: HashElem *next_elem = elem->next;
59: if( pH->copyKey && elem->pKey ){
60: sqliteFree(elem->pKey);
61: }
62: sqliteFree(elem);
63: elem = next_elem;
64: }
65: pH->count = 0;
66: }
67:
68: /*
69: ** Hash and comparison functions when the mode is SQLITE_HASH_INT
70: */
71: static int intHash(const void *pKey, int nKey){
72: return nKey ^ (nKey<<8) ^ (nKey>>8);
73: }
74: static int intCompare(const void *pKey1, int n1, const void *pKey2, int n2){
75: return n2 - n1;
76: }
77:
78: #if 0 /* NOT USED */
79: /*
80: ** Hash and comparison functions when the mode is SQLITE_HASH_POINTER
81: */
82: static int ptrHash(const void *pKey, int nKey){
83: uptr x = Addr(pKey);
84: return x ^ (x<<8) ^ (x>>8);
85: }
86: static int ptrCompare(const void *pKey1, int n1, const void *pKey2, int n2){
87: if( pKey1==pKey2 ) return 0;
88: if( pKey1<pKey2 ) return -1;
89: return 1;
90: }
91: #endif
92:
93: /*
94: ** Hash and comparison functions when the mode is SQLITE_HASH_STRING
95: */
96: static int strHash(const void *pKey, int nKey){
97: return sqliteHashNoCase((const char*)pKey, nKey);
98: }
99: static int strCompare(const void *pKey1, int n1, const void *pKey2, int n2){
100: if( n1!=n2 ) return n2-n1;
101: return sqliteStrNICmp((const char*)pKey1,(const char*)pKey2,n1);
102: }
103:
104: /*
105: ** Hash and comparison functions when the mode is SQLITE_HASH_BINARY
106: */
107: static int binHash(const void *pKey, int nKey){
108: int h = 0;
109: const char *z = (const char *)pKey;
110: while( nKey-- > 0 ){
111: h = (h<<3) ^ h ^ *(z++);
112: }
113: return h & 0x7fffffff;
114: }
115: static int binCompare(const void *pKey1, int n1, const void *pKey2, int n2){
116: if( n1!=n2 ) return n2-n1;
117: return memcmp(pKey1,pKey2,n1);
118: }
119:
120: /*
121: ** Return a pointer to the appropriate hash function given the key class.
122: **
123: ** The C syntax in this function definition may be unfamilar to some
124: ** programmers, so we provide the following additional explanation:
125: **
126: ** The name of the function is "hashFunction". The function takes a
127: ** single parameter "keyClass". The return value of hashFunction()
128: ** is a pointer to another function. Specifically, the return value
129: ** of hashFunction() is a pointer to a function that takes two parameters
130: ** with types "const void*" and "int" and returns an "int".
131: */
132: static int (*hashFunction(int keyClass))(const void*,int){
133: switch( keyClass ){
134: case SQLITE_HASH_INT: return &intHash;
135: /* case SQLITE_HASH_POINTER: return &ptrHash; // NOT USED */
136: case SQLITE_HASH_STRING: return &strHash;
137: case SQLITE_HASH_BINARY: return &binHash;;
138: default: break;
139: }
140: return 0;
141: }
142:
143: /*
144: ** Return a pointer to the appropriate hash function given the key class.
145: **
146: ** For help in interpreted the obscure C code in the function definition,
147: ** see the header comment on the previous function.
148: */
149: static int (*compareFunction(int keyClass))(const void*,int,const void*,int){
150: switch( keyClass ){
151: case SQLITE_HASH_INT: return &intCompare;
152: /* case SQLITE_HASH_POINTER: return &ptrCompare; // NOT USED */
153: case SQLITE_HASH_STRING: return &strCompare;
154: case SQLITE_HASH_BINARY: return &binCompare;
155: default: break;
156: }
157: return 0;
158: }
159:
160:
161: /* Resize the hash table so that it cantains "new_size" buckets.
162: ** "new_size" must be a power of 2. The hash table might fail
163: ** to resize if sqliteMalloc() fails.
164: */
165: static void rehash(Hash *pH, int new_size){
166: struct _ht *new_ht; /* The new hash table */
167: HashElem *elem, *next_elem; /* For looping over existing elements */
168: HashElem *x; /* Element being copied to new hash table */
169: int (*xHash)(const void*,int); /* The hash function */
170:
171: assert( (new_size & (new_size-1))==0 );
172: new_ht = (struct _ht *)sqliteMalloc( new_size*sizeof(struct _ht) );
173: if( new_ht==0 ) return;
174: if( pH->ht ) sqliteFree(pH->ht);
175: pH->ht = new_ht;
176: pH->htsize = new_size;
177: xHash = hashFunction(pH->keyClass);
178: for(elem=pH->first, pH->first=0; elem; elem = next_elem){
179: int h = (*xHash)(elem->pKey, elem->nKey) & (new_size-1);
180: next_elem = elem->next;
181: x = new_ht[h].chain;
182: if( x ){
183: elem->next = x;
184: elem->prev = x->prev;
185: if( x->prev ) x->prev->next = elem;
186: else pH->first = elem;
187: x->prev = elem;
188: }else{
189: elem->next = pH->first;
190: if( pH->first ) pH->first->prev = elem;
191: elem->prev = 0;
192: pH->first = elem;
193: }
194: new_ht[h].chain = elem;
195: new_ht[h].count++;
196: }
197: }
198:
199: /* This function (for internal use only) locates an element in an
200: ** hash table that matches the given key. The hash for this key has
201: ** already been computed and is passed as the 4th parameter.
202: */
203: static HashElem *findElementGivenHash(
204: const Hash *pH, /* The pH to be searched */
205: const void *pKey, /* The key we are searching for */
206: int nKey,
207: int h /* The hash for this key. */
208: ){
209: HashElem *elem; /* Used to loop thru the element list */
210: int count; /* Number of elements left to test */
211: int (*xCompare)(const void*,int,const void*,int); /* comparison function */
212:
213: if( pH->ht ){
214: elem = pH->ht[h].chain;
215: count = pH->ht[h].count;
216: xCompare = compareFunction(pH->keyClass);
217: while( count-- && elem ){
218: if( (*xCompare)(elem->pKey,elem->nKey,pKey,nKey)==0 ){
219: return elem;
220: }
221: elem = elem->next;
222: }
223: }
224: return 0;
225: }
226:
227: /* Remove a single entry from the hash table given a pointer to that
228: ** element and a hash on the element's key.
229: */
230: static void removeElementGivenHash(
231: Hash *pH, /* The pH containing "elem" */
232: HashElem* elem, /* The element to be removed from the pH */
233: int h /* Hash value for the element */
234: ){
235: if( elem->prev ){
236: elem->prev->next = elem->next;
237: }else{
238: pH->first = elem->next;
239: }
240: if( elem->next ){
241: elem->next->prev = elem->prev;
242: }
243: if( pH->ht[h].chain==elem ){
244: pH->ht[h].chain = elem->next;
245: }
246: pH->ht[h].count--;
247: if( pH->ht[h].count<=0 ){
248: pH->ht[h].chain = 0;
249: }
250: if( pH->copyKey && elem->pKey ){
251: sqliteFree(elem->pKey);
252: }
253: sqliteFree( elem );
254: pH->count--;
255: }
256:
257: /* Attempt to locate an element of the hash table pH with a key
258: ** that matches pKey,nKey. Return the data for this element if it is
259: ** found, or NULL if there is no match.
260: */
261: void *sqliteHashFind(const Hash *pH, const void *pKey, int nKey){
262: int h; /* A hash on key */
263: HashElem *elem; /* The element that matches key */
264: int (*xHash)(const void*,int); /* The hash function */
265:
266: if( pH==0 || pH->ht==0 ) return 0;
267: xHash = hashFunction(pH->keyClass);
268: assert( xHash!=0 );
269: h = (*xHash)(pKey,nKey);
270: assert( (pH->htsize & (pH->htsize-1))==0 );
271: elem = findElementGivenHash(pH,pKey,nKey, h & (pH->htsize-1));
272: return elem ? elem->data : 0;
273: }
274:
275: /* Insert an element into the hash table pH. The key is pKey,nKey
276: ** and the data is "data".
277: **
278: ** If no element exists with a matching key, then a new
279: ** element is created. A copy of the key is made if the copyKey
280: ** flag is set. NULL is returned.
281: **
282: ** If another element already exists with the same key, then the
283: ** new data replaces the old data and the old data is returned.
284: ** The key is not copied in this instance. If a malloc fails, then
285: ** the new data is returned and the hash table is unchanged.
286: **
287: ** If the "data" parameter to this function is NULL, then the
288: ** element corresponding to "key" is removed from the hash table.
289: */
290: void *sqliteHashInsert(Hash *pH, const void *pKey, int nKey, void *data){
291: int hraw; /* Raw hash value of the key */
292: int h; /* the hash of the key modulo hash table size */
293: HashElem *elem; /* Used to loop thru the element list */
294: HashElem *new_elem; /* New element added to the pH */
295: int (*xHash)(const void*,int); /* The hash function */
296:
297: assert( pH!=0 );
298: xHash = hashFunction(pH->keyClass);
299: assert( xHash!=0 );
300: hraw = (*xHash)(pKey, nKey);
301: assert( (pH->htsize & (pH->htsize-1))==0 );
302: h = hraw & (pH->htsize-1);
303: elem = findElementGivenHash(pH,pKey,nKey,h);
304: if( elem ){
305: void *old_data = elem->data;
306: if( data==0 ){
307: removeElementGivenHash(pH,elem,h);
308: }else{
309: elem->data = data;
310: }
311: return old_data;
312: }
313: if( data==0 ) return 0;
314: new_elem = (HashElem*)sqliteMalloc( sizeof(HashElem) );
315: if( new_elem==0 ) return data;
316: if( pH->copyKey && pKey!=0 ){
317: new_elem->pKey = sqliteMallocRaw( nKey );
318: if( new_elem->pKey==0 ){
319: sqliteFree(new_elem);
320: return data;
321: }
322: memcpy((void*)new_elem->pKey, pKey, nKey);
323: }else{
324: new_elem->pKey = (void*)pKey;
325: }
326: new_elem->nKey = nKey;
327: pH->count++;
328: if( pH->htsize==0 ) rehash(pH,8);
329: if( pH->htsize==0 ){
330: pH->count = 0;
331: sqliteFree(new_elem);
332: return data;
333: }
334: if( pH->count > pH->htsize ){
335: rehash(pH,pH->htsize*2);
336: }
337: assert( (pH->htsize & (pH->htsize-1))==0 );
338: h = hraw & (pH->htsize-1);
339: elem = pH->ht[h].chain;
340: if( elem ){
341: new_elem->next = elem;
342: new_elem->prev = elem->prev;
343: if( elem->prev ){ elem->prev->next = new_elem; }
344: else { pH->first = new_elem; }
345: elem->prev = new_elem;
346: }else{
347: new_elem->next = pH->first;
348: new_elem->prev = 0;
349: if( pH->first ){ pH->first->prev = new_elem; }
350: pH->first = new_elem;
351: }
352: pH->ht[h].count++;
353: pH->ht[h].chain = new_elem;
354: new_elem->data = data;
355: return 0;
356: }
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