Annotation of embedaddon/sqlite3/ext/fts1/fts1_hash.c, revision 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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