Annotation of embedaddon/sqlite3/ext/fts1/fts1_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: /*
21: ** The code in this file is only compiled if:
22: **
23: ** * The FTS1 module is being built as an extension
24: ** (in which case SQLITE_CORE is not defined), or
25: **
26: ** * The FTS1 module is being built into the core of
27: ** SQLite (in which case SQLITE_ENABLE_FTS1 is defined).
28: */
29: #if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS1)
30:
31:
32: #include "fts1_hash.h"
33:
34: static void *malloc_and_zero(int n){
35: void *p = malloc(n);
36: if( p ){
37: memset(p, 0, n);
38: }
39: return p;
40: }
41:
42: /* Turn bulk memory into a hash table object by initializing the
43: ** fields of the Hash structure.
44: **
45: ** "pNew" is a pointer to the hash table that is to be initialized.
46: ** keyClass is one of the constants
47: ** FTS1_HASH_BINARY or FTS1_HASH_STRING. The value of keyClass
48: ** determines what kind of key the hash table will use. "copyKey" is
49: ** true if the hash table should make its own private copy of keys and
50: ** false if it should just use the supplied pointer.
51: */
52: void sqlite3Fts1HashInit(fts1Hash *pNew, int keyClass, int copyKey){
53: assert( pNew!=0 );
54: assert( keyClass>=FTS1_HASH_STRING && keyClass<=FTS1_HASH_BINARY );
55: pNew->keyClass = keyClass;
56: pNew->copyKey = copyKey;
57: pNew->first = 0;
58: pNew->count = 0;
59: pNew->htsize = 0;
60: pNew->ht = 0;
61: pNew->xMalloc = malloc_and_zero;
62: pNew->xFree = free;
63: }
64:
65: /* Remove all entries from a hash table. Reclaim all memory.
66: ** Call this routine to delete a hash table or to reset a hash table
67: ** to the empty state.
68: */
69: void sqlite3Fts1HashClear(fts1Hash *pH){
70: fts1HashElem *elem; /* For looping over all elements of the table */
71:
72: assert( pH!=0 );
73: elem = pH->first;
74: pH->first = 0;
75: if( pH->ht ) pH->xFree(pH->ht);
76: pH->ht = 0;
77: pH->htsize = 0;
78: while( elem ){
79: fts1HashElem *next_elem = elem->next;
80: if( pH->copyKey && elem->pKey ){
81: pH->xFree(elem->pKey);
82: }
83: pH->xFree(elem);
84: elem = next_elem;
85: }
86: pH->count = 0;
87: }
88:
89: /*
90: ** Hash and comparison functions when the mode is FTS1_HASH_STRING
91: */
92: static int strHash(const void *pKey, int nKey){
93: const char *z = (const char *)pKey;
94: int h = 0;
95: if( nKey<=0 ) nKey = (int) strlen(z);
96: while( nKey > 0 ){
97: h = (h<<3) ^ h ^ *z++;
98: nKey--;
99: }
100: return h & 0x7fffffff;
101: }
102: static int strCompare(const void *pKey1, int n1, const void *pKey2, int n2){
103: if( n1!=n2 ) return 1;
104: return strncmp((const char*)pKey1,(const char*)pKey2,n1);
105: }
106:
107: /*
108: ** Hash and comparison functions when the mode is FTS1_HASH_BINARY
109: */
110: static int binHash(const void *pKey, int nKey){
111: int h = 0;
112: const char *z = (const char *)pKey;
113: while( nKey-- > 0 ){
114: h = (h<<3) ^ h ^ *(z++);
115: }
116: return h & 0x7fffffff;
117: }
118: static int binCompare(const void *pKey1, int n1, const void *pKey2, int n2){
119: if( n1!=n2 ) return 1;
120: return memcmp(pKey1,pKey2,n1);
121: }
122:
123: /*
124: ** Return a pointer to the appropriate hash function given the key class.
125: **
126: ** The C syntax in this function definition may be unfamilar to some
127: ** programmers, so we provide the following additional explanation:
128: **
129: ** The name of the function is "hashFunction". The function takes a
130: ** single parameter "keyClass". The return value of hashFunction()
131: ** is a pointer to another function. Specifically, the return value
132: ** of hashFunction() is a pointer to a function that takes two parameters
133: ** with types "const void*" and "int" and returns an "int".
134: */
135: static int (*hashFunction(int keyClass))(const void*,int){
136: if( keyClass==FTS1_HASH_STRING ){
137: return &strHash;
138: }else{
139: assert( keyClass==FTS1_HASH_BINARY );
140: return &binHash;
141: }
142: }
143:
144: /*
145: ** Return a pointer to the appropriate hash function given the key class.
146: **
147: ** For help in interpreted the obscure C code in the function definition,
148: ** see the header comment on the previous function.
149: */
150: static int (*compareFunction(int keyClass))(const void*,int,const void*,int){
151: if( keyClass==FTS1_HASH_STRING ){
152: return &strCompare;
153: }else{
154: assert( keyClass==FTS1_HASH_BINARY );
155: return &binCompare;
156: }
157: }
158:
159: /* Link an element into the hash table
160: */
161: static void insertElement(
162: fts1Hash *pH, /* The complete hash table */
163: struct _fts1ht *pEntry, /* The entry into which pNew is inserted */
164: fts1HashElem *pNew /* The element to be inserted */
165: ){
166: fts1HashElem *pHead; /* First element already in pEntry */
167: pHead = pEntry->chain;
168: if( pHead ){
169: pNew->next = pHead;
170: pNew->prev = pHead->prev;
171: if( pHead->prev ){ pHead->prev->next = pNew; }
172: else { pH->first = pNew; }
173: pHead->prev = pNew;
174: }else{
175: pNew->next = pH->first;
176: if( pH->first ){ pH->first->prev = pNew; }
177: pNew->prev = 0;
178: pH->first = pNew;
179: }
180: pEntry->count++;
181: pEntry->chain = pNew;
182: }
183:
184:
185: /* Resize the hash table so that it cantains "new_size" buckets.
186: ** "new_size" must be a power of 2. The hash table might fail
187: ** to resize if sqliteMalloc() fails.
188: */
189: static void rehash(fts1Hash *pH, int new_size){
190: struct _fts1ht *new_ht; /* The new hash table */
191: fts1HashElem *elem, *next_elem; /* For looping over existing elements */
192: int (*xHash)(const void*,int); /* The hash function */
193:
194: assert( (new_size & (new_size-1))==0 );
195: new_ht = (struct _fts1ht *)pH->xMalloc( new_size*sizeof(struct _fts1ht) );
196: if( new_ht==0 ) return;
197: if( pH->ht ) pH->xFree(pH->ht);
198: pH->ht = new_ht;
199: pH->htsize = new_size;
200: xHash = hashFunction(pH->keyClass);
201: for(elem=pH->first, pH->first=0; elem; elem = next_elem){
202: int h = (*xHash)(elem->pKey, elem->nKey) & (new_size-1);
203: next_elem = elem->next;
204: insertElement(pH, &new_ht[h], elem);
205: }
206: }
207:
208: /* This function (for internal use only) locates an element in an
209: ** hash table that matches the given key. The hash for this key has
210: ** already been computed and is passed as the 4th parameter.
211: */
212: static fts1HashElem *findElementGivenHash(
213: const fts1Hash *pH, /* The pH to be searched */
214: const void *pKey, /* The key we are searching for */
215: int nKey,
216: int h /* The hash for this key. */
217: ){
218: fts1HashElem *elem; /* Used to loop thru the element list */
219: int count; /* Number of elements left to test */
220: int (*xCompare)(const void*,int,const void*,int); /* comparison function */
221:
222: if( pH->ht ){
223: struct _fts1ht *pEntry = &pH->ht[h];
224: elem = pEntry->chain;
225: count = pEntry->count;
226: xCompare = compareFunction(pH->keyClass);
227: while( count-- && elem ){
228: if( (*xCompare)(elem->pKey,elem->nKey,pKey,nKey)==0 ){
229: return elem;
230: }
231: elem = elem->next;
232: }
233: }
234: return 0;
235: }
236:
237: /* Remove a single entry from the hash table given a pointer to that
238: ** element and a hash on the element's key.
239: */
240: static void removeElementGivenHash(
241: fts1Hash *pH, /* The pH containing "elem" */
242: fts1HashElem* elem, /* The element to be removed from the pH */
243: int h /* Hash value for the element */
244: ){
245: struct _fts1ht *pEntry;
246: if( elem->prev ){
247: elem->prev->next = elem->next;
248: }else{
249: pH->first = elem->next;
250: }
251: if( elem->next ){
252: elem->next->prev = elem->prev;
253: }
254: pEntry = &pH->ht[h];
255: if( pEntry->chain==elem ){
256: pEntry->chain = elem->next;
257: }
258: pEntry->count--;
259: if( pEntry->count<=0 ){
260: pEntry->chain = 0;
261: }
262: if( pH->copyKey && elem->pKey ){
263: pH->xFree(elem->pKey);
264: }
265: pH->xFree( elem );
266: pH->count--;
267: if( pH->count<=0 ){
268: assert( pH->first==0 );
269: assert( pH->count==0 );
270: fts1HashClear(pH);
271: }
272: }
273:
274: /* Attempt to locate an element of the hash table pH with a key
275: ** that matches pKey,nKey. Return the data for this element if it is
276: ** found, or NULL if there is no match.
277: */
278: void *sqlite3Fts1HashFind(const fts1Hash *pH, const void *pKey, int nKey){
279: int h; /* A hash on key */
280: fts1HashElem *elem; /* The element that matches key */
281: int (*xHash)(const void*,int); /* The hash function */
282:
283: if( pH==0 || pH->ht==0 ) return 0;
284: xHash = hashFunction(pH->keyClass);
285: assert( xHash!=0 );
286: h = (*xHash)(pKey,nKey);
287: assert( (pH->htsize & (pH->htsize-1))==0 );
288: elem = findElementGivenHash(pH,pKey,nKey, h & (pH->htsize-1));
289: return elem ? elem->data : 0;
290: }
291:
292: /* Insert an element into the hash table pH. The key is pKey,nKey
293: ** and the data is "data".
294: **
295: ** If no element exists with a matching key, then a new
296: ** element is created. A copy of the key is made if the copyKey
297: ** flag is set. NULL is returned.
298: **
299: ** If another element already exists with the same key, then the
300: ** new data replaces the old data and the old data is returned.
301: ** The key is not copied in this instance. If a malloc fails, then
302: ** the new data is returned and the hash table is unchanged.
303: **
304: ** If the "data" parameter to this function is NULL, then the
305: ** element corresponding to "key" is removed from the hash table.
306: */
307: void *sqlite3Fts1HashInsert(
308: fts1Hash *pH, /* The hash table to insert into */
309: const void *pKey, /* The key */
310: int nKey, /* Number of bytes in the key */
311: void *data /* The data */
312: ){
313: int hraw; /* Raw hash value of the key */
314: int h; /* the hash of the key modulo hash table size */
315: fts1HashElem *elem; /* Used to loop thru the element list */
316: fts1HashElem *new_elem; /* New element added to the pH */
317: int (*xHash)(const void*,int); /* The hash function */
318:
319: assert( pH!=0 );
320: xHash = hashFunction(pH->keyClass);
321: assert( xHash!=0 );
322: hraw = (*xHash)(pKey, nKey);
323: assert( (pH->htsize & (pH->htsize-1))==0 );
324: h = hraw & (pH->htsize-1);
325: elem = findElementGivenHash(pH,pKey,nKey,h);
326: if( elem ){
327: void *old_data = elem->data;
328: if( data==0 ){
329: removeElementGivenHash(pH,elem,h);
330: }else{
331: elem->data = data;
332: }
333: return old_data;
334: }
335: if( data==0 ) return 0;
336: new_elem = (fts1HashElem*)pH->xMalloc( sizeof(fts1HashElem) );
337: if( new_elem==0 ) return data;
338: if( pH->copyKey && pKey!=0 ){
339: new_elem->pKey = pH->xMalloc( nKey );
340: if( new_elem->pKey==0 ){
341: pH->xFree(new_elem);
342: return data;
343: }
344: memcpy((void*)new_elem->pKey, pKey, nKey);
345: }else{
346: new_elem->pKey = (void*)pKey;
347: }
348: new_elem->nKey = nKey;
349: pH->count++;
350: if( pH->htsize==0 ){
351: rehash(pH,8);
352: if( pH->htsize==0 ){
353: pH->count = 0;
354: pH->xFree(new_elem);
355: return data;
356: }
357: }
358: if( pH->count > pH->htsize ){
359: rehash(pH,pH->htsize*2);
360: }
361: assert( pH->htsize>0 );
362: assert( (pH->htsize & (pH->htsize-1))==0 );
363: h = hraw & (pH->htsize-1);
364: insertElement(pH, &pH->ht[h], new_elem);
365: new_elem->data = data;
366: return 0;
367: }
368:
369: #endif /* !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS1) */
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