Annotation of embedaddon/sqlite3/ext/fts1/ft_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 used in SQLite.
13: ** We've modified it slightly to serve as a standalone hash table
14: ** implementation for the full-text indexing module.
15: */
16: #include <assert.h>
17: #include <stdlib.h>
18: #include <string.h>
19:
20: #include "ft_hash.h"
21:
22: void *malloc_and_zero(int n){
23: void *p = malloc(n);
24: if( p ){
25: memset(p, 0, n);
26: }
27: return p;
28: }
29:
30: /* Turn bulk memory into a hash table object by initializing the
31: ** fields of the Hash structure.
32: **
33: ** "pNew" is a pointer to the hash table that is to be initialized.
34: ** keyClass is one of the constants HASH_INT, HASH_POINTER,
35: ** HASH_BINARY, or HASH_STRING. The value of keyClass
36: ** determines what kind of key the hash table will use. "copyKey" is
37: ** true if the hash table should make its own private copy of keys and
38: ** false if it should just use the supplied pointer. CopyKey only makes
39: ** sense for HASH_STRING and HASH_BINARY and is ignored
40: ** for other key classes.
41: */
42: void HashInit(Hash *pNew, int keyClass, int copyKey){
43: assert( pNew!=0 );
44: assert( keyClass>=HASH_STRING && keyClass<=HASH_BINARY );
45: pNew->keyClass = keyClass;
46: #if 0
47: if( keyClass==HASH_POINTER || keyClass==HASH_INT ) copyKey = 0;
48: #endif
49: pNew->copyKey = copyKey;
50: pNew->first = 0;
51: pNew->count = 0;
52: pNew->htsize = 0;
53: pNew->ht = 0;
54: pNew->xMalloc = malloc_and_zero;
55: pNew->xFree = free;
56: }
57:
58: /* Remove all entries from a hash table. Reclaim all memory.
59: ** Call this routine to delete a hash table or to reset a hash table
60: ** to the empty state.
61: */
62: void HashClear(Hash *pH){
63: HashElem *elem; /* For looping over all elements of the table */
64:
65: assert( pH!=0 );
66: elem = pH->first;
67: pH->first = 0;
68: if( pH->ht ) pH->xFree(pH->ht);
69: pH->ht = 0;
70: pH->htsize = 0;
71: while( elem ){
72: HashElem *next_elem = elem->next;
73: if( pH->copyKey && elem->pKey ){
74: pH->xFree(elem->pKey);
75: }
76: pH->xFree(elem);
77: elem = next_elem;
78: }
79: pH->count = 0;
80: }
81:
82: #if 0 /* NOT USED */
83: /*
84: ** Hash and comparison functions when the mode is HASH_INT
85: */
86: static int intHash(const void *pKey, int nKey){
87: return nKey ^ (nKey<<8) ^ (nKey>>8);
88: }
89: static int intCompare(const void *pKey1, int n1, const void *pKey2, int n2){
90: return n2 - n1;
91: }
92: #endif
93:
94: #if 0 /* NOT USED */
95: /*
96: ** Hash and comparison functions when the mode is HASH_POINTER
97: */
98: static int ptrHash(const void *pKey, int nKey){
99: uptr x = Addr(pKey);
100: return x ^ (x<<8) ^ (x>>8);
101: }
102: static int ptrCompare(const void *pKey1, int n1, const void *pKey2, int n2){
103: if( pKey1==pKey2 ) return 0;
104: if( pKey1<pKey2 ) return -1;
105: return 1;
106: }
107: #endif
108:
109: /*
110: ** Hash and comparison functions when the mode is HASH_STRING
111: */
112: static int strHash(const void *pKey, int nKey){
113: const char *z = (const char *)pKey;
114: int h = 0;
115: if( nKey<=0 ) nKey = (int) strlen(z);
116: while( nKey > 0 ){
117: h = (h<<3) ^ h ^ *z++;
118: nKey--;
119: }
120: return h & 0x7fffffff;
121: }
122: static int strCompare(const void *pKey1, int n1, const void *pKey2, int n2){
123: if( n1!=n2 ) return 1;
124: return strncmp((const char*)pKey1,(const char*)pKey2,n1);
125: }
126:
127: /*
128: ** Hash and comparison functions when the mode is HASH_BINARY
129: */
130: static int binHash(const void *pKey, int nKey){
131: int h = 0;
132: const char *z = (const char *)pKey;
133: while( nKey-- > 0 ){
134: h = (h<<3) ^ h ^ *(z++);
135: }
136: return h & 0x7fffffff;
137: }
138: static int binCompare(const void *pKey1, int n1, const void *pKey2, int n2){
139: if( n1!=n2 ) return 1;
140: return memcmp(pKey1,pKey2,n1);
141: }
142:
143: /*
144: ** Return a pointer to the appropriate hash function given the key class.
145: **
146: ** The C syntax in this function definition may be unfamilar to some
147: ** programmers, so we provide the following additional explanation:
148: **
149: ** The name of the function is "hashFunction". The function takes a
150: ** single parameter "keyClass". The return value of hashFunction()
151: ** is a pointer to another function. Specifically, the return value
152: ** of hashFunction() is a pointer to a function that takes two parameters
153: ** with types "const void*" and "int" and returns an "int".
154: */
155: static int (*hashFunction(int keyClass))(const void*,int){
156: #if 0 /* HASH_INT and HASH_POINTER are never used */
157: switch( keyClass ){
158: case HASH_INT: return &intHash;
159: case HASH_POINTER: return &ptrHash;
160: case HASH_STRING: return &strHash;
161: case HASH_BINARY: return &binHash;;
162: default: break;
163: }
164: return 0;
165: #else
166: if( keyClass==HASH_STRING ){
167: return &strHash;
168: }else{
169: assert( keyClass==HASH_BINARY );
170: return &binHash;
171: }
172: #endif
173: }
174:
175: /*
176: ** Return a pointer to the appropriate hash function given the key class.
177: **
178: ** For help in interpreted the obscure C code in the function definition,
179: ** see the header comment on the previous function.
180: */
181: static int (*compareFunction(int keyClass))(const void*,int,const void*,int){
182: #if 0 /* HASH_INT and HASH_POINTER are never used */
183: switch( keyClass ){
184: case HASH_INT: return &intCompare;
185: case HASH_POINTER: return &ptrCompare;
186: case HASH_STRING: return &strCompare;
187: case HASH_BINARY: return &binCompare;
188: default: break;
189: }
190: return 0;
191: #else
192: if( keyClass==HASH_STRING ){
193: return &strCompare;
194: }else{
195: assert( keyClass==HASH_BINARY );
196: return &binCompare;
197: }
198: #endif
199: }
200:
201: /* Link an element into the hash table
202: */
203: static void insertElement(
204: Hash *pH, /* The complete hash table */
205: struct _ht *pEntry, /* The entry into which pNew is inserted */
206: HashElem *pNew /* The element to be inserted */
207: ){
208: HashElem *pHead; /* First element already in pEntry */
209: pHead = pEntry->chain;
210: if( pHead ){
211: pNew->next = pHead;
212: pNew->prev = pHead->prev;
213: if( pHead->prev ){ pHead->prev->next = pNew; }
214: else { pH->first = pNew; }
215: pHead->prev = pNew;
216: }else{
217: pNew->next = pH->first;
218: if( pH->first ){ pH->first->prev = pNew; }
219: pNew->prev = 0;
220: pH->first = pNew;
221: }
222: pEntry->count++;
223: pEntry->chain = pNew;
224: }
225:
226:
227: /* Resize the hash table so that it cantains "new_size" buckets.
228: ** "new_size" must be a power of 2. The hash table might fail
229: ** to resize if sqliteMalloc() fails.
230: */
231: static void rehash(Hash *pH, int new_size){
232: struct _ht *new_ht; /* The new hash table */
233: HashElem *elem, *next_elem; /* For looping over existing elements */
234: int (*xHash)(const void*,int); /* The hash function */
235:
236: assert( (new_size & (new_size-1))==0 );
237: new_ht = (struct _ht *)pH->xMalloc( new_size*sizeof(struct _ht) );
238: if( new_ht==0 ) return;
239: if( pH->ht ) pH->xFree(pH->ht);
240: pH->ht = new_ht;
241: pH->htsize = new_size;
242: xHash = hashFunction(pH->keyClass);
243: for(elem=pH->first, pH->first=0; elem; elem = next_elem){
244: int h = (*xHash)(elem->pKey, elem->nKey) & (new_size-1);
245: next_elem = elem->next;
246: insertElement(pH, &new_ht[h], elem);
247: }
248: }
249:
250: /* This function (for internal use only) locates an element in an
251: ** hash table that matches the given key. The hash for this key has
252: ** already been computed and is passed as the 4th parameter.
253: */
254: static HashElem *findElementGivenHash(
255: const Hash *pH, /* The pH to be searched */
256: const void *pKey, /* The key we are searching for */
257: int nKey,
258: int h /* The hash for this key. */
259: ){
260: HashElem *elem; /* Used to loop thru the element list */
261: int count; /* Number of elements left to test */
262: int (*xCompare)(const void*,int,const void*,int); /* comparison function */
263:
264: if( pH->ht ){
265: struct _ht *pEntry = &pH->ht[h];
266: elem = pEntry->chain;
267: count = pEntry->count;
268: xCompare = compareFunction(pH->keyClass);
269: while( count-- && elem ){
270: if( (*xCompare)(elem->pKey,elem->nKey,pKey,nKey)==0 ){
271: return elem;
272: }
273: elem = elem->next;
274: }
275: }
276: return 0;
277: }
278:
279: /* Remove a single entry from the hash table given a pointer to that
280: ** element and a hash on the element's key.
281: */
282: static void removeElementGivenHash(
283: Hash *pH, /* The pH containing "elem" */
284: HashElem* elem, /* The element to be removed from the pH */
285: int h /* Hash value for the element */
286: ){
287: struct _ht *pEntry;
288: if( elem->prev ){
289: elem->prev->next = elem->next;
290: }else{
291: pH->first = elem->next;
292: }
293: if( elem->next ){
294: elem->next->prev = elem->prev;
295: }
296: pEntry = &pH->ht[h];
297: if( pEntry->chain==elem ){
298: pEntry->chain = elem->next;
299: }
300: pEntry->count--;
301: if( pEntry->count<=0 ){
302: pEntry->chain = 0;
303: }
304: if( pH->copyKey && elem->pKey ){
305: pH->xFree(elem->pKey);
306: }
307: pH->xFree( elem );
308: pH->count--;
309: if( pH->count<=0 ){
310: assert( pH->first==0 );
311: assert( pH->count==0 );
312: HashClear(pH);
313: }
314: }
315:
316: /* Attempt to locate an element of the hash table pH with a key
317: ** that matches pKey,nKey. Return the data for this element if it is
318: ** found, or NULL if there is no match.
319: */
320: void *HashFind(const Hash *pH, const void *pKey, int nKey){
321: int h; /* A hash on key */
322: HashElem *elem; /* The element that matches key */
323: int (*xHash)(const void*,int); /* The hash function */
324:
325: if( pH==0 || pH->ht==0 ) return 0;
326: xHash = hashFunction(pH->keyClass);
327: assert( xHash!=0 );
328: h = (*xHash)(pKey,nKey);
329: assert( (pH->htsize & (pH->htsize-1))==0 );
330: elem = findElementGivenHash(pH,pKey,nKey, h & (pH->htsize-1));
331: return elem ? elem->data : 0;
332: }
333:
334: /* Insert an element into the hash table pH. The key is pKey,nKey
335: ** and the data is "data".
336: **
337: ** If no element exists with a matching key, then a new
338: ** element is created. A copy of the key is made if the copyKey
339: ** flag is set. NULL is returned.
340: **
341: ** If another element already exists with the same key, then the
342: ** new data replaces the old data and the old data is returned.
343: ** The key is not copied in this instance. If a malloc fails, then
344: ** the new data is returned and the hash table is unchanged.
345: **
346: ** If the "data" parameter to this function is NULL, then the
347: ** element corresponding to "key" is removed from the hash table.
348: */
349: void *HashInsert(Hash *pH, const void *pKey, int nKey, void *data){
350: int hraw; /* Raw hash value of the key */
351: int h; /* the hash of the key modulo hash table size */
352: HashElem *elem; /* Used to loop thru the element list */
353: HashElem *new_elem; /* New element added to the pH */
354: int (*xHash)(const void*,int); /* The hash function */
355:
356: assert( pH!=0 );
357: xHash = hashFunction(pH->keyClass);
358: assert( xHash!=0 );
359: hraw = (*xHash)(pKey, nKey);
360: assert( (pH->htsize & (pH->htsize-1))==0 );
361: h = hraw & (pH->htsize-1);
362: elem = findElementGivenHash(pH,pKey,nKey,h);
363: if( elem ){
364: void *old_data = elem->data;
365: if( data==0 ){
366: removeElementGivenHash(pH,elem,h);
367: }else{
368: elem->data = data;
369: }
370: return old_data;
371: }
372: if( data==0 ) return 0;
373: new_elem = (HashElem*)pH->xMalloc( sizeof(HashElem) );
374: if( new_elem==0 ) return data;
375: if( pH->copyKey && pKey!=0 ){
376: new_elem->pKey = pH->xMalloc( nKey );
377: if( new_elem->pKey==0 ){
378: pH->xFree(new_elem);
379: return data;
380: }
381: memcpy((void*)new_elem->pKey, pKey, nKey);
382: }else{
383: new_elem->pKey = (void*)pKey;
384: }
385: new_elem->nKey = nKey;
386: pH->count++;
387: if( pH->htsize==0 ){
388: rehash(pH,8);
389: if( pH->htsize==0 ){
390: pH->count = 0;
391: pH->xFree(new_elem);
392: return data;
393: }
394: }
395: if( pH->count > pH->htsize ){
396: rehash(pH,pH->htsize*2);
397: }
398: assert( pH->htsize>0 );
399: assert( (pH->htsize & (pH->htsize-1))==0 );
400: h = hraw & (pH->htsize-1);
401: insertElement(pH, &pH->ht[h], new_elem);
402: new_elem->data = data;
403: return 0;
404: }
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