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 FTS3 module is being built as an extension
21: ** (in which case SQLITE_CORE is not defined), or
22: **
23: ** * The FTS3 module is being built into the core of
24: ** SQLite (in which case SQLITE_ENABLE_FTS3 is defined).
25: */
26: #include "fts3Int.h"
27: #if !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3)
28:
29: #include <assert.h>
30: #include <stdlib.h>
31: #include <string.h>
32:
33: #include "fts3_hash.h"
34:
35: /*
36: ** Malloc and Free functions
37: */
38: static void *fts3HashMalloc(int n){
39: void *p = sqlite3_malloc(n);
40: if( p ){
41: memset(p, 0, n);
42: }
43: return p;
44: }
45: static void fts3HashFree(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: ** FTS3_HASH_BINARY or FTS3_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 sqlite3Fts3HashInit(Fts3Hash *pNew, char keyClass, char copyKey){
60: assert( pNew!=0 );
61: assert( keyClass>=FTS3_HASH_STRING && keyClass<=FTS3_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 sqlite3Fts3HashClear(Fts3Hash *pH){
75: Fts3HashElem *elem; /* For looping over all elements of the table */
76:
77: assert( pH!=0 );
78: elem = pH->first;
79: pH->first = 0;
80: fts3HashFree(pH->ht);
81: pH->ht = 0;
82: pH->htsize = 0;
83: while( elem ){
84: Fts3HashElem *next_elem = elem->next;
85: if( pH->copyKey && elem->pKey ){
86: fts3HashFree(elem->pKey);
87: }
88: fts3HashFree(elem);
89: elem = next_elem;
90: }
91: pH->count = 0;
92: }
93:
94: /*
95: ** Hash and comparison functions when the mode is FTS3_HASH_STRING
96: */
97: static int fts3StrHash(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 fts3StrCompare(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 FTS3_HASH_BINARY
114: */
115: static int fts3BinHash(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 fts3BinCompare(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 "ftsHashFunction". The function takes a
135: ** single parameter "keyClass". The return value of ftsHashFunction()
136: ** is a pointer to another function. Specifically, the return value
137: ** of ftsHashFunction() 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 (*ftsHashFunction(int keyClass))(const void*,int){
141: if( keyClass==FTS3_HASH_STRING ){
142: return &fts3StrHash;
143: }else{
144: assert( keyClass==FTS3_HASH_BINARY );
145: return &fts3BinHash;
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 (*ftsCompareFunction(int keyClass))(const void*,int,const void*,int){
156: if( keyClass==FTS3_HASH_STRING ){
157: return &fts3StrCompare;
158: }else{
159: assert( keyClass==FTS3_HASH_BINARY );
160: return &fts3BinCompare;
161: }
162: }
163:
164: /* Link an element into the hash table
165: */
166: static void fts3HashInsertElement(
167: Fts3Hash *pH, /* The complete hash table */
168: struct _fts3ht *pEntry, /* The entry into which pNew is inserted */
169: Fts3HashElem *pNew /* The element to be inserted */
170: ){
171: Fts3HashElem *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: ** Return non-zero if a memory allocation error occurs.
195: */
196: static int fts3Rehash(Fts3Hash *pH, int new_size){
197: struct _fts3ht *new_ht; /* The new hash table */
198: Fts3HashElem *elem, *next_elem; /* For looping over existing elements */
199: int (*xHash)(const void*,int); /* The hash function */
200:
201: assert( (new_size & (new_size-1))==0 );
202: new_ht = (struct _fts3ht *)fts3HashMalloc( new_size*sizeof(struct _fts3ht) );
203: if( new_ht==0 ) return 1;
204: fts3HashFree(pH->ht);
205: pH->ht = new_ht;
206: pH->htsize = new_size;
207: xHash = ftsHashFunction(pH->keyClass);
208: for(elem=pH->first, pH->first=0; elem; elem = next_elem){
209: int h = (*xHash)(elem->pKey, elem->nKey) & (new_size-1);
210: next_elem = elem->next;
211: fts3HashInsertElement(pH, &new_ht[h], elem);
212: }
213: return 0;
214: }
215:
216: /* This function (for internal use only) locates an element in an
217: ** hash table that matches the given key. The hash for this key has
218: ** already been computed and is passed as the 4th parameter.
219: */
220: static Fts3HashElem *fts3FindElementByHash(
221: const Fts3Hash *pH, /* The pH to be searched */
222: const void *pKey, /* The key we are searching for */
223: int nKey,
224: int h /* The hash for this key. */
225: ){
226: Fts3HashElem *elem; /* Used to loop thru the element list */
227: int count; /* Number of elements left to test */
228: int (*xCompare)(const void*,int,const void*,int); /* comparison function */
229:
230: if( pH->ht ){
231: struct _fts3ht *pEntry = &pH->ht[h];
232: elem = pEntry->chain;
233: count = pEntry->count;
234: xCompare = ftsCompareFunction(pH->keyClass);
235: while( count-- && elem ){
236: if( (*xCompare)(elem->pKey,elem->nKey,pKey,nKey)==0 ){
237: return elem;
238: }
239: elem = elem->next;
240: }
241: }
242: return 0;
243: }
244:
245: /* Remove a single entry from the hash table given a pointer to that
246: ** element and a hash on the element's key.
247: */
248: static void fts3RemoveElementByHash(
249: Fts3Hash *pH, /* The pH containing "elem" */
250: Fts3HashElem* elem, /* The element to be removed from the pH */
251: int h /* Hash value for the element */
252: ){
253: struct _fts3ht *pEntry;
254: if( elem->prev ){
255: elem->prev->next = elem->next;
256: }else{
257: pH->first = elem->next;
258: }
259: if( elem->next ){
260: elem->next->prev = elem->prev;
261: }
262: pEntry = &pH->ht[h];
263: if( pEntry->chain==elem ){
264: pEntry->chain = elem->next;
265: }
266: pEntry->count--;
267: if( pEntry->count<=0 ){
268: pEntry->chain = 0;
269: }
270: if( pH->copyKey && elem->pKey ){
271: fts3HashFree(elem->pKey);
272: }
273: fts3HashFree( elem );
274: pH->count--;
275: if( pH->count<=0 ){
276: assert( pH->first==0 );
277: assert( pH->count==0 );
278: fts3HashClear(pH);
279: }
280: }
281:
282: Fts3HashElem *sqlite3Fts3HashFindElem(
283: const Fts3Hash *pH,
284: const void *pKey,
285: int nKey
286: ){
287: int h; /* A hash on key */
288: int (*xHash)(const void*,int); /* The hash function */
289:
290: if( pH==0 || pH->ht==0 ) return 0;
291: xHash = ftsHashFunction(pH->keyClass);
292: assert( xHash!=0 );
293: h = (*xHash)(pKey,nKey);
294: assert( (pH->htsize & (pH->htsize-1))==0 );
295: return fts3FindElementByHash(pH,pKey,nKey, h & (pH->htsize-1));
296: }
297:
298: /*
299: ** Attempt to locate an element of the hash table pH with a key
300: ** that matches pKey,nKey. Return the data for this element if it is
301: ** found, or NULL if there is no match.
302: */
303: void *sqlite3Fts3HashFind(const Fts3Hash *pH, const void *pKey, int nKey){
304: Fts3HashElem *pElem; /* The element that matches key (if any) */
305:
306: pElem = sqlite3Fts3HashFindElem(pH, pKey, nKey);
307: return pElem ? pElem->data : 0;
308: }
309:
310: /* Insert an element into the hash table pH. The key is pKey,nKey
311: ** and the data is "data".
312: **
313: ** If no element exists with a matching key, then a new
314: ** element is created. A copy of the key is made if the copyKey
315: ** flag is set. NULL is returned.
316: **
317: ** If another element already exists with the same key, then the
318: ** new data replaces the old data and the old data is returned.
319: ** The key is not copied in this instance. If a malloc fails, then
320: ** the new data is returned and the hash table is unchanged.
321: **
322: ** If the "data" parameter to this function is NULL, then the
323: ** element corresponding to "key" is removed from the hash table.
324: */
325: void *sqlite3Fts3HashInsert(
326: Fts3Hash *pH, /* The hash table to insert into */
327: const void *pKey, /* The key */
328: int nKey, /* Number of bytes in the key */
329: void *data /* The data */
330: ){
331: int hraw; /* Raw hash value of the key */
332: int h; /* the hash of the key modulo hash table size */
333: Fts3HashElem *elem; /* Used to loop thru the element list */
334: Fts3HashElem *new_elem; /* New element added to the pH */
335: int (*xHash)(const void*,int); /* The hash function */
336:
337: assert( pH!=0 );
338: xHash = ftsHashFunction(pH->keyClass);
339: assert( xHash!=0 );
340: hraw = (*xHash)(pKey, nKey);
341: assert( (pH->htsize & (pH->htsize-1))==0 );
342: h = hraw & (pH->htsize-1);
343: elem = fts3FindElementByHash(pH,pKey,nKey,h);
344: if( elem ){
345: void *old_data = elem->data;
346: if( data==0 ){
347: fts3RemoveElementByHash(pH,elem,h);
348: }else{
349: elem->data = data;
350: }
351: return old_data;
352: }
353: if( data==0 ) return 0;
354: if( (pH->htsize==0 && fts3Rehash(pH,8))
355: || (pH->count>=pH->htsize && fts3Rehash(pH, pH->htsize*2))
356: ){
357: pH->count = 0;
358: return data;
359: }
360: assert( pH->htsize>0 );
361: new_elem = (Fts3HashElem*)fts3HashMalloc( sizeof(Fts3HashElem) );
362: if( new_elem==0 ) return data;
363: if( pH->copyKey && pKey!=0 ){
364: new_elem->pKey = fts3HashMalloc( nKey );
365: if( new_elem->pKey==0 ){
366: fts3HashFree(new_elem);
367: return data;
368: }
369: memcpy((void*)new_elem->pKey, pKey, nKey);
370: }else{
371: new_elem->pKey = (void*)pKey;
372: }
373: new_elem->nKey = nKey;
374: pH->count++;
375: assert( pH->htsize>0 );
376: assert( (pH->htsize & (pH->htsize-1))==0 );
377: h = hraw & (pH->htsize-1);
378: fts3HashInsertElement(pH, &pH->ht[h], new_elem);
379: new_elem->data = data;
380: return 0;
381: }
382:
383: #endif /* !defined(SQLITE_CORE) || defined(SQLITE_ENABLE_FTS3) */
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