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) */ 375
