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 34static 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*/ 52void 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*/ 69void 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*/ 92static 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} 102static 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*/ 110static 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} 118static 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*/ 135static 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*/ 150static 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*/ 161static 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*/ 189static 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*/ 212static 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*/ 240static 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*/ 278void *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*/ 307void *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) */ 370