Annotation of embedaddon/sqlite3/ext/fts2/fts2_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:
17: /*
18: ** The code in this file is only compiled if:
19: **
20: ** * The FTS2 module is being built as an extension
21: ** (in which case SQLITE_CORE is not defined), or
22: **
23: ** * The FTS2 module is being built into the core of
24: ** SQLite (in which case SQLITE_ENABLE_FTS2 is defined).
25: */
26: #if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS2)
27:
28: #include <assert.h>
29: #include <stdlib.h>
30: #include <string.h>
31:
32: #include "sqlite3.h"
33: #include "fts2_hash.h"
34:
35: /*
36: ** Malloc and Free functions
37: */
38: static void *fts2HashMalloc(int n){
39: void *p = sqlite3_malloc(n);
40: if( p ){
41: memset(p, 0, n);
42: }
43: return p;
44: }
45: static void fts2HashFree(void *p){
46: sqlite3_free(p);
47: }
48:
49: /* Turn bulk memory into a hash table object by initializing the
50: ** fields of the Hash structure.
51: **
52: ** "pNew" is a pointer to the hash table that is to be initialized.
53: ** keyClass is one of the constants
54: ** FTS2_HASH_BINARY or FTS2_HASH_STRING. The value of keyClass
55: ** determines what kind of key the hash table will use. "copyKey" is
56: ** true if the hash table should make its own private copy of keys and
57: ** false if it should just use the supplied pointer.
58: */
59: void sqlite3Fts2HashInit(fts2Hash *pNew, int keyClass, int copyKey){
60: assert( pNew!=0 );
61: assert( keyClass>=FTS2_HASH_STRING && keyClass<=FTS2_HASH_BINARY );
62: pNew->keyClass = keyClass;
63: pNew->copyKey = copyKey;
64: pNew->first = 0;
65: pNew->count = 0;
66: pNew->htsize = 0;
67: pNew->ht = 0;
68: }
69:
70: /* Remove all entries from a hash table. Reclaim all memory.
71: ** Call this routine to delete a hash table or to reset a hash table
72: ** to the empty state.
73: */
74: void sqlite3Fts2HashClear(fts2Hash *pH){
75: fts2HashElem *elem; /* For looping over all elements of the table */
76:
77: assert( pH!=0 );
78: elem = pH->first;
79: pH->first = 0;
80: fts2HashFree(pH->ht);
81: pH->ht = 0;
82: pH->htsize = 0;
83: while( elem ){
84: fts2HashElem *next_elem = elem->next;
85: if( pH->copyKey && elem->pKey ){
86: fts2HashFree(elem->pKey);
87: }
88: fts2HashFree(elem);
89: elem = next_elem;
90: }
91: pH->count = 0;
92: }
93:
94: /*
95: ** Hash and comparison functions when the mode is FTS2_HASH_STRING
96: */
97: static int strHash(const void *pKey, int nKey){
98: const char *z = (const char *)pKey;
99: int h = 0;
100: if( nKey<=0 ) nKey = (int) strlen(z);
101: while( nKey > 0 ){
102: h = (h<<3) ^ h ^ *z++;
103: nKey--;
104: }
105: return h & 0x7fffffff;
106: }
107: static int strCompare(const void *pKey1, int n1, const void *pKey2, int n2){
108: if( n1!=n2 ) return 1;
109: return strncmp((const char*)pKey1,(const char*)pKey2,n1);
110: }
111:
112: /*
113: ** Hash and comparison functions when the mode is FTS2_HASH_BINARY
114: */
115: static int binHash(const void *pKey, int nKey){
116: int h = 0;
117: const char *z = (const char *)pKey;
118: while( nKey-- > 0 ){
119: h = (h<<3) ^ h ^ *(z++);
120: }
121: return h & 0x7fffffff;
122: }
123: static int binCompare(const void *pKey1, int n1, const void *pKey2, int n2){
124: if( n1!=n2 ) return 1;
125: return memcmp(pKey1,pKey2,n1);
126: }
127:
128: /*
129: ** Return a pointer to the appropriate hash function given the key class.
130: **
131: ** The C syntax in this function definition may be unfamilar to some
132: ** programmers, so we provide the following additional explanation:
133: **
134: ** The name of the function is "hashFunction". The function takes a
135: ** single parameter "keyClass". The return value of hashFunction()
136: ** is a pointer to another function. Specifically, the return value
137: ** of hashFunction() is a pointer to a function that takes two parameters
138: ** with types "const void*" and "int" and returns an "int".
139: */
140: static int (*hashFunction(int keyClass))(const void*,int){
141: if( keyClass==FTS2_HASH_STRING ){
142: return &strHash;
143: }else{
144: assert( keyClass==FTS2_HASH_BINARY );
145: return &binHash;
146: }
147: }
148:
149: /*
150: ** Return a pointer to the appropriate hash function given the key class.
151: **
152: ** For help in interpreted the obscure C code in the function definition,
153: ** see the header comment on the previous function.
154: */
155: static int (*compareFunction(int keyClass))(const void*,int,const void*,int){
156: if( keyClass==FTS2_HASH_STRING ){
157: return &strCompare;
158: }else{
159: assert( keyClass==FTS2_HASH_BINARY );
160: return &binCompare;
161: }
162: }
163:
164: /* Link an element into the hash table
165: */
166: static void insertElement(
167: fts2Hash *pH, /* The complete hash table */
168: struct _fts2ht *pEntry, /* The entry into which pNew is inserted */
169: fts2HashElem *pNew /* The element to be inserted */
170: ){
171: fts2HashElem *pHead; /* First element already in pEntry */
172: pHead = pEntry->chain;
173: if( pHead ){
174: pNew->next = pHead;
175: pNew->prev = pHead->prev;
176: if( pHead->prev ){ pHead->prev->next = pNew; }
177: else { pH->first = pNew; }
178: pHead->prev = pNew;
179: }else{
180: pNew->next = pH->first;
181: if( pH->first ){ pH->first->prev = pNew; }
182: pNew->prev = 0;
183: pH->first = pNew;
184: }
185: pEntry->count++;
186: pEntry->chain = pNew;
187: }
188:
189:
190: /* Resize the hash table so that it cantains "new_size" buckets.
191: ** "new_size" must be a power of 2. The hash table might fail
192: ** to resize if sqliteMalloc() fails.
193: */
194: static void rehash(fts2Hash *pH, int new_size){
195: struct _fts2ht *new_ht; /* The new hash table */
196: fts2HashElem *elem, *next_elem; /* For looping over existing elements */
197: int (*xHash)(const void*,int); /* The hash function */
198:
199: assert( (new_size & (new_size-1))==0 );
200: new_ht = (struct _fts2ht *)fts2HashMalloc( new_size*sizeof(struct _fts2ht) );
201: if( new_ht==0 ) return;
202: fts2HashFree(pH->ht);
203: pH->ht = new_ht;
204: pH->htsize = new_size;
205: xHash = hashFunction(pH->keyClass);
206: for(elem=pH->first, pH->first=0; elem; elem = next_elem){
207: int h = (*xHash)(elem->pKey, elem->nKey) & (new_size-1);
208: next_elem = elem->next;
209: insertElement(pH, &new_ht[h], elem);
210: }
211: }
212:
213: /* This function (for internal use only) locates an element in an
214: ** hash table that matches the given key. The hash for this key has
215: ** already been computed and is passed as the 4th parameter.
216: */
217: static fts2HashElem *findElementGivenHash(
218: const fts2Hash *pH, /* The pH to be searched */
219: const void *pKey, /* The key we are searching for */
220: int nKey,
221: int h /* The hash for this key. */
222: ){
223: fts2HashElem *elem; /* Used to loop thru the element list */
224: int count; /* Number of elements left to test */
225: int (*xCompare)(const void*,int,const void*,int); /* comparison function */
226:
227: if( pH->ht ){
228: struct _fts2ht *pEntry = &pH->ht[h];
229: elem = pEntry->chain;
230: count = pEntry->count;
231: xCompare = compareFunction(pH->keyClass);
232: while( count-- && elem ){
233: if( (*xCompare)(elem->pKey,elem->nKey,pKey,nKey)==0 ){
234: return elem;
235: }
236: elem = elem->next;
237: }
238: }
239: return 0;
240: }
241:
242: /* Remove a single entry from the hash table given a pointer to that
243: ** element and a hash on the element's key.
244: */
245: static void removeElementGivenHash(
246: fts2Hash *pH, /* The pH containing "elem" */
247: fts2HashElem* elem, /* The element to be removed from the pH */
248: int h /* Hash value for the element */
249: ){
250: struct _fts2ht *pEntry;
251: if( elem->prev ){
252: elem->prev->next = elem->next;
253: }else{
254: pH->first = elem->next;
255: }
256: if( elem->next ){
257: elem->next->prev = elem->prev;
258: }
259: pEntry = &pH->ht[h];
260: if( pEntry->chain==elem ){
261: pEntry->chain = elem->next;
262: }
263: pEntry->count--;
264: if( pEntry->count<=0 ){
265: pEntry->chain = 0;
266: }
267: if( pH->copyKey && elem->pKey ){
268: fts2HashFree(elem->pKey);
269: }
270: fts2HashFree( elem );
271: pH->count--;
272: if( pH->count<=0 ){
273: assert( pH->first==0 );
274: assert( pH->count==0 );
275: fts2HashClear(pH);
276: }
277: }
278:
279: /* Attempt to locate an element of the hash table pH with a key
280: ** that matches pKey,nKey. Return the data for this element if it is
281: ** found, or NULL if there is no match.
282: */
283: void *sqlite3Fts2HashFind(const fts2Hash *pH, const void *pKey, int nKey){
284: int h; /* A hash on key */
285: fts2HashElem *elem; /* The element that matches key */
286: int (*xHash)(const void*,int); /* The hash function */
287:
288: if( pH==0 || pH->ht==0 ) return 0;
289: xHash = hashFunction(pH->keyClass);
290: assert( xHash!=0 );
291: h = (*xHash)(pKey,nKey);
292: assert( (pH->htsize & (pH->htsize-1))==0 );
293: elem = findElementGivenHash(pH,pKey,nKey, h & (pH->htsize-1));
294: return elem ? elem->data : 0;
295: }
296:
297: /* Insert an element into the hash table pH. The key is pKey,nKey
298: ** and the data is "data".
299: **
300: ** If no element exists with a matching key, then a new
301: ** element is created. A copy of the key is made if the copyKey
302: ** flag is set. NULL is returned.
303: **
304: ** If another element already exists with the same key, then the
305: ** new data replaces the old data and the old data is returned.
306: ** The key is not copied in this instance. If a malloc fails, then
307: ** the new data is returned and the hash table is unchanged.
308: **
309: ** If the "data" parameter to this function is NULL, then the
310: ** element corresponding to "key" is removed from the hash table.
311: */
312: void *sqlite3Fts2HashInsert(
313: fts2Hash *pH, /* The hash table to insert into */
314: const void *pKey, /* The key */
315: int nKey, /* Number of bytes in the key */
316: void *data /* The data */
317: ){
318: int hraw; /* Raw hash value of the key */
319: int h; /* the hash of the key modulo hash table size */
320: fts2HashElem *elem; /* Used to loop thru the element list */
321: fts2HashElem *new_elem; /* New element added to the pH */
322: int (*xHash)(const void*,int); /* The hash function */
323:
324: assert( pH!=0 );
325: xHash = hashFunction(pH->keyClass);
326: assert( xHash!=0 );
327: hraw = (*xHash)(pKey, nKey);
328: assert( (pH->htsize & (pH->htsize-1))==0 );
329: h = hraw & (pH->htsize-1);
330: elem = findElementGivenHash(pH,pKey,nKey,h);
331: if( elem ){
332: void *old_data = elem->data;
333: if( data==0 ){
334: removeElementGivenHash(pH,elem,h);
335: }else{
336: elem->data = data;
337: }
338: return old_data;
339: }
340: if( data==0 ) return 0;
341: new_elem = (fts2HashElem*)fts2HashMalloc( sizeof(fts2HashElem) );
342: if( new_elem==0 ) return data;
343: if( pH->copyKey && pKey!=0 ){
344: new_elem->pKey = fts2HashMalloc( nKey );
345: if( new_elem->pKey==0 ){
346: fts2HashFree(new_elem);
347: return data;
348: }
349: memcpy((void*)new_elem->pKey, pKey, nKey);
350: }else{
351: new_elem->pKey = (void*)pKey;
352: }
353: new_elem->nKey = nKey;
354: pH->count++;
355: if( pH->htsize==0 ){
356: rehash(pH,8);
357: if( pH->htsize==0 ){
358: pH->count = 0;
359: fts2HashFree(new_elem);
360: return data;
361: }
362: }
363: if( pH->count > pH->htsize ){
364: rehash(pH,pH->htsize*2);
365: }
366: assert( pH->htsize>0 );
367: assert( (pH->htsize & (pH->htsize-1))==0 );
368: h = hraw & (pH->htsize-1);
369: insertElement(pH, &pH->ht[h], new_elem);
370: new_elem->data = data;
371: return 0;
372: }
373:
374: #endif /* !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS2) */
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