Return to fts2_hash.c CVS log | Up to [ELWIX - Embedded LightWeight unIX -] / embedaddon / sqlite3 / ext / fts2 |
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) */