Annotation of embedaddon/sqlite3/ext/fts1/ft_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: #include "ft_hash.h"
! 21:
! 22: void *malloc_and_zero(int n){
! 23: void *p = malloc(n);
! 24: if( p ){
! 25: memset(p, 0, n);
! 26: }
! 27: return p;
! 28: }
! 29:
! 30: /* Turn bulk memory into a hash table object by initializing the
! 31: ** fields of the Hash structure.
! 32: **
! 33: ** "pNew" is a pointer to the hash table that is to be initialized.
! 34: ** keyClass is one of the constants HASH_INT, HASH_POINTER,
! 35: ** HASH_BINARY, or HASH_STRING. The value of keyClass
! 36: ** determines what kind of key the hash table will use. "copyKey" is
! 37: ** true if the hash table should make its own private copy of keys and
! 38: ** false if it should just use the supplied pointer. CopyKey only makes
! 39: ** sense for HASH_STRING and HASH_BINARY and is ignored
! 40: ** for other key classes.
! 41: */
! 42: void HashInit(Hash *pNew, int keyClass, int copyKey){
! 43: assert( pNew!=0 );
! 44: assert( keyClass>=HASH_STRING && keyClass<=HASH_BINARY );
! 45: pNew->keyClass = keyClass;
! 46: #if 0
! 47: if( keyClass==HASH_POINTER || keyClass==HASH_INT ) copyKey = 0;
! 48: #endif
! 49: pNew->copyKey = copyKey;
! 50: pNew->first = 0;
! 51: pNew->count = 0;
! 52: pNew->htsize = 0;
! 53: pNew->ht = 0;
! 54: pNew->xMalloc = malloc_and_zero;
! 55: pNew->xFree = free;
! 56: }
! 57:
! 58: /* Remove all entries from a hash table. Reclaim all memory.
! 59: ** Call this routine to delete a hash table or to reset a hash table
! 60: ** to the empty state.
! 61: */
! 62: void HashClear(Hash *pH){
! 63: HashElem *elem; /* For looping over all elements of the table */
! 64:
! 65: assert( pH!=0 );
! 66: elem = pH->first;
! 67: pH->first = 0;
! 68: if( pH->ht ) pH->xFree(pH->ht);
! 69: pH->ht = 0;
! 70: pH->htsize = 0;
! 71: while( elem ){
! 72: HashElem *next_elem = elem->next;
! 73: if( pH->copyKey && elem->pKey ){
! 74: pH->xFree(elem->pKey);
! 75: }
! 76: pH->xFree(elem);
! 77: elem = next_elem;
! 78: }
! 79: pH->count = 0;
! 80: }
! 81:
! 82: #if 0 /* NOT USED */
! 83: /*
! 84: ** Hash and comparison functions when the mode is HASH_INT
! 85: */
! 86: static int intHash(const void *pKey, int nKey){
! 87: return nKey ^ (nKey<<8) ^ (nKey>>8);
! 88: }
! 89: static int intCompare(const void *pKey1, int n1, const void *pKey2, int n2){
! 90: return n2 - n1;
! 91: }
! 92: #endif
! 93:
! 94: #if 0 /* NOT USED */
! 95: /*
! 96: ** Hash and comparison functions when the mode is HASH_POINTER
! 97: */
! 98: static int ptrHash(const void *pKey, int nKey){
! 99: uptr x = Addr(pKey);
! 100: return x ^ (x<<8) ^ (x>>8);
! 101: }
! 102: static int ptrCompare(const void *pKey1, int n1, const void *pKey2, int n2){
! 103: if( pKey1==pKey2 ) return 0;
! 104: if( pKey1<pKey2 ) return -1;
! 105: return 1;
! 106: }
! 107: #endif
! 108:
! 109: /*
! 110: ** Hash and comparison functions when the mode is HASH_STRING
! 111: */
! 112: static int strHash(const void *pKey, int nKey){
! 113: const char *z = (const char *)pKey;
! 114: int h = 0;
! 115: if( nKey<=0 ) nKey = (int) strlen(z);
! 116: while( nKey > 0 ){
! 117: h = (h<<3) ^ h ^ *z++;
! 118: nKey--;
! 119: }
! 120: return h & 0x7fffffff;
! 121: }
! 122: static int strCompare(const void *pKey1, int n1, const void *pKey2, int n2){
! 123: if( n1!=n2 ) return 1;
! 124: return strncmp((const char*)pKey1,(const char*)pKey2,n1);
! 125: }
! 126:
! 127: /*
! 128: ** Hash and comparison functions when the mode is HASH_BINARY
! 129: */
! 130: static int binHash(const void *pKey, int nKey){
! 131: int h = 0;
! 132: const char *z = (const char *)pKey;
! 133: while( nKey-- > 0 ){
! 134: h = (h<<3) ^ h ^ *(z++);
! 135: }
! 136: return h & 0x7fffffff;
! 137: }
! 138: static int binCompare(const void *pKey1, int n1, const void *pKey2, int n2){
! 139: if( n1!=n2 ) return 1;
! 140: return memcmp(pKey1,pKey2,n1);
! 141: }
! 142:
! 143: /*
! 144: ** Return a pointer to the appropriate hash function given the key class.
! 145: **
! 146: ** The C syntax in this function definition may be unfamilar to some
! 147: ** programmers, so we provide the following additional explanation:
! 148: **
! 149: ** The name of the function is "hashFunction". The function takes a
! 150: ** single parameter "keyClass". The return value of hashFunction()
! 151: ** is a pointer to another function. Specifically, the return value
! 152: ** of hashFunction() is a pointer to a function that takes two parameters
! 153: ** with types "const void*" and "int" and returns an "int".
! 154: */
! 155: static int (*hashFunction(int keyClass))(const void*,int){
! 156: #if 0 /* HASH_INT and HASH_POINTER are never used */
! 157: switch( keyClass ){
! 158: case HASH_INT: return &intHash;
! 159: case HASH_POINTER: return &ptrHash;
! 160: case HASH_STRING: return &strHash;
! 161: case HASH_BINARY: return &binHash;;
! 162: default: break;
! 163: }
! 164: return 0;
! 165: #else
! 166: if( keyClass==HASH_STRING ){
! 167: return &strHash;
! 168: }else{
! 169: assert( keyClass==HASH_BINARY );
! 170: return &binHash;
! 171: }
! 172: #endif
! 173: }
! 174:
! 175: /*
! 176: ** Return a pointer to the appropriate hash function given the key class.
! 177: **
! 178: ** For help in interpreted the obscure C code in the function definition,
! 179: ** see the header comment on the previous function.
! 180: */
! 181: static int (*compareFunction(int keyClass))(const void*,int,const void*,int){
! 182: #if 0 /* HASH_INT and HASH_POINTER are never used */
! 183: switch( keyClass ){
! 184: case HASH_INT: return &intCompare;
! 185: case HASH_POINTER: return &ptrCompare;
! 186: case HASH_STRING: return &strCompare;
! 187: case HASH_BINARY: return &binCompare;
! 188: default: break;
! 189: }
! 190: return 0;
! 191: #else
! 192: if( keyClass==HASH_STRING ){
! 193: return &strCompare;
! 194: }else{
! 195: assert( keyClass==HASH_BINARY );
! 196: return &binCompare;
! 197: }
! 198: #endif
! 199: }
! 200:
! 201: /* Link an element into the hash table
! 202: */
! 203: static void insertElement(
! 204: Hash *pH, /* The complete hash table */
! 205: struct _ht *pEntry, /* The entry into which pNew is inserted */
! 206: HashElem *pNew /* The element to be inserted */
! 207: ){
! 208: HashElem *pHead; /* First element already in pEntry */
! 209: pHead = pEntry->chain;
! 210: if( pHead ){
! 211: pNew->next = pHead;
! 212: pNew->prev = pHead->prev;
! 213: if( pHead->prev ){ pHead->prev->next = pNew; }
! 214: else { pH->first = pNew; }
! 215: pHead->prev = pNew;
! 216: }else{
! 217: pNew->next = pH->first;
! 218: if( pH->first ){ pH->first->prev = pNew; }
! 219: pNew->prev = 0;
! 220: pH->first = pNew;
! 221: }
! 222: pEntry->count++;
! 223: pEntry->chain = pNew;
! 224: }
! 225:
! 226:
! 227: /* Resize the hash table so that it cantains "new_size" buckets.
! 228: ** "new_size" must be a power of 2. The hash table might fail
! 229: ** to resize if sqliteMalloc() fails.
! 230: */
! 231: static void rehash(Hash *pH, int new_size){
! 232: struct _ht *new_ht; /* The new hash table */
! 233: HashElem *elem, *next_elem; /* For looping over existing elements */
! 234: int (*xHash)(const void*,int); /* The hash function */
! 235:
! 236: assert( (new_size & (new_size-1))==0 );
! 237: new_ht = (struct _ht *)pH->xMalloc( new_size*sizeof(struct _ht) );
! 238: if( new_ht==0 ) return;
! 239: if( pH->ht ) pH->xFree(pH->ht);
! 240: pH->ht = new_ht;
! 241: pH->htsize = new_size;
! 242: xHash = hashFunction(pH->keyClass);
! 243: for(elem=pH->first, pH->first=0; elem; elem = next_elem){
! 244: int h = (*xHash)(elem->pKey, elem->nKey) & (new_size-1);
! 245: next_elem = elem->next;
! 246: insertElement(pH, &new_ht[h], elem);
! 247: }
! 248: }
! 249:
! 250: /* This function (for internal use only) locates an element in an
! 251: ** hash table that matches the given key. The hash for this key has
! 252: ** already been computed and is passed as the 4th parameter.
! 253: */
! 254: static HashElem *findElementGivenHash(
! 255: const Hash *pH, /* The pH to be searched */
! 256: const void *pKey, /* The key we are searching for */
! 257: int nKey,
! 258: int h /* The hash for this key. */
! 259: ){
! 260: HashElem *elem; /* Used to loop thru the element list */
! 261: int count; /* Number of elements left to test */
! 262: int (*xCompare)(const void*,int,const void*,int); /* comparison function */
! 263:
! 264: if( pH->ht ){
! 265: struct _ht *pEntry = &pH->ht[h];
! 266: elem = pEntry->chain;
! 267: count = pEntry->count;
! 268: xCompare = compareFunction(pH->keyClass);
! 269: while( count-- && elem ){
! 270: if( (*xCompare)(elem->pKey,elem->nKey,pKey,nKey)==0 ){
! 271: return elem;
! 272: }
! 273: elem = elem->next;
! 274: }
! 275: }
! 276: return 0;
! 277: }
! 278:
! 279: /* Remove a single entry from the hash table given a pointer to that
! 280: ** element and a hash on the element's key.
! 281: */
! 282: static void removeElementGivenHash(
! 283: Hash *pH, /* The pH containing "elem" */
! 284: HashElem* elem, /* The element to be removed from the pH */
! 285: int h /* Hash value for the element */
! 286: ){
! 287: struct _ht *pEntry;
! 288: if( elem->prev ){
! 289: elem->prev->next = elem->next;
! 290: }else{
! 291: pH->first = elem->next;
! 292: }
! 293: if( elem->next ){
! 294: elem->next->prev = elem->prev;
! 295: }
! 296: pEntry = &pH->ht[h];
! 297: if( pEntry->chain==elem ){
! 298: pEntry->chain = elem->next;
! 299: }
! 300: pEntry->count--;
! 301: if( pEntry->count<=0 ){
! 302: pEntry->chain = 0;
! 303: }
! 304: if( pH->copyKey && elem->pKey ){
! 305: pH->xFree(elem->pKey);
! 306: }
! 307: pH->xFree( elem );
! 308: pH->count--;
! 309: if( pH->count<=0 ){
! 310: assert( pH->first==0 );
! 311: assert( pH->count==0 );
! 312: HashClear(pH);
! 313: }
! 314: }
! 315:
! 316: /* Attempt to locate an element of the hash table pH with a key
! 317: ** that matches pKey,nKey. Return the data for this element if it is
! 318: ** found, or NULL if there is no match.
! 319: */
! 320: void *HashFind(const Hash *pH, const void *pKey, int nKey){
! 321: int h; /* A hash on key */
! 322: HashElem *elem; /* The element that matches key */
! 323: int (*xHash)(const void*,int); /* The hash function */
! 324:
! 325: if( pH==0 || pH->ht==0 ) return 0;
! 326: xHash = hashFunction(pH->keyClass);
! 327: assert( xHash!=0 );
! 328: h = (*xHash)(pKey,nKey);
! 329: assert( (pH->htsize & (pH->htsize-1))==0 );
! 330: elem = findElementGivenHash(pH,pKey,nKey, h & (pH->htsize-1));
! 331: return elem ? elem->data : 0;
! 332: }
! 333:
! 334: /* Insert an element into the hash table pH. The key is pKey,nKey
! 335: ** and the data is "data".
! 336: **
! 337: ** If no element exists with a matching key, then a new
! 338: ** element is created. A copy of the key is made if the copyKey
! 339: ** flag is set. NULL is returned.
! 340: **
! 341: ** If another element already exists with the same key, then the
! 342: ** new data replaces the old data and the old data is returned.
! 343: ** The key is not copied in this instance. If a malloc fails, then
! 344: ** the new data is returned and the hash table is unchanged.
! 345: **
! 346: ** If the "data" parameter to this function is NULL, then the
! 347: ** element corresponding to "key" is removed from the hash table.
! 348: */
! 349: void *HashInsert(Hash *pH, const void *pKey, int nKey, void *data){
! 350: int hraw; /* Raw hash value of the key */
! 351: int h; /* the hash of the key modulo hash table size */
! 352: HashElem *elem; /* Used to loop thru the element list */
! 353: HashElem *new_elem; /* New element added to the pH */
! 354: int (*xHash)(const void*,int); /* The hash function */
! 355:
! 356: assert( pH!=0 );
! 357: xHash = hashFunction(pH->keyClass);
! 358: assert( xHash!=0 );
! 359: hraw = (*xHash)(pKey, nKey);
! 360: assert( (pH->htsize & (pH->htsize-1))==0 );
! 361: h = hraw & (pH->htsize-1);
! 362: elem = findElementGivenHash(pH,pKey,nKey,h);
! 363: if( elem ){
! 364: void *old_data = elem->data;
! 365: if( data==0 ){
! 366: removeElementGivenHash(pH,elem,h);
! 367: }else{
! 368: elem->data = data;
! 369: }
! 370: return old_data;
! 371: }
! 372: if( data==0 ) return 0;
! 373: new_elem = (HashElem*)pH->xMalloc( sizeof(HashElem) );
! 374: if( new_elem==0 ) return data;
! 375: if( pH->copyKey && pKey!=0 ){
! 376: new_elem->pKey = pH->xMalloc( nKey );
! 377: if( new_elem->pKey==0 ){
! 378: pH->xFree(new_elem);
! 379: return data;
! 380: }
! 381: memcpy((void*)new_elem->pKey, pKey, nKey);
! 382: }else{
! 383: new_elem->pKey = (void*)pKey;
! 384: }
! 385: new_elem->nKey = nKey;
! 386: pH->count++;
! 387: if( pH->htsize==0 ){
! 388: rehash(pH,8);
! 389: if( pH->htsize==0 ){
! 390: pH->count = 0;
! 391: pH->xFree(new_elem);
! 392: return data;
! 393: }
! 394: }
! 395: if( pH->count > pH->htsize ){
! 396: rehash(pH,pH->htsize*2);
! 397: }
! 398: assert( pH->htsize>0 );
! 399: assert( (pH->htsize & (pH->htsize-1))==0 );
! 400: h = hraw & (pH->htsize-1);
! 401: insertElement(pH, &pH->ht[h], new_elem);
! 402: new_elem->data = data;
! 403: return 0;
! 404: }
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