ext/fts1/ft_hash.c

   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 }