sbin/rcorder/hash.c

   1 /*      $NetBSD: hash.c,v 1.5 2007/03/03 00:09:30 simonb Exp $  */
   2
   3 /*
   4  * Copyright (c) 1988, 1989, 1990 The Regents of the University of California.
   5  * All rights reserved.
   6  *
   7  * This code is derived from software contributed to Berkeley by
   8  * Adam de Boor.
   9  *
  10  * Redistribution and use in source and binary forms, with or without
  11  * modification, are permitted provided that the following conditions
  12  * are met:
  13  * 1. Redistributions of source code must retain the above copyright
  14  *    notice, this list of conditions and the following disclaimer.
  15  * 2. Redistributions in binary form must reproduce the above copyright
  16  *    notice, this list of conditions and the following disclaimer in the
  17  *    documentation and/or other materials provided with the distribution.
  18  * 3. Neither the name of the University nor the names of its contributors
  19  *    may be used to endorse or promote products derived from this software
  20  *    without specific prior written permission.
  21  *
  22  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  23  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  24  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  25  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  26  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  27  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  28  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  29  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  30  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  31  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  32  * SUCH DAMAGE.
  33  */
  34
  35 /*
  36  * Copyright (c) 1988, 1989 by Adam de Boor
  37  * Copyright (c) 1989 by Berkeley Softworks
  38  * All rights reserved.
  39  *
  40  * This code is derived from software contributed to Berkeley by
  41  * Adam de Boor.
  42  *
  43  * Redistribution and use in source and binary forms, with or without
  44  * modification, are permitted provided that the following conditions
  45  * are met:
  46  * 1. Redistributions of source code must retain the above copyright
  47  *    notice, this list of conditions and the following disclaimer.
  48  * 2. Redistributions in binary form must reproduce the above copyright
  49  *    notice, this list of conditions and the following disclaimer in the
  50  *    documentation and/or other materials provided with the distribution.
  51  * 3. All advertising materials mentioning features or use of this software
  52  *    must display the following acknowledgement:
  53  *      This product includes software developed by the University of
  54  *      California, Berkeley and its contributors.
  55  * 4. Neither the name of the University nor the names of its contributors
  56  *    may be used to endorse or promote products derived from this software
  57  *    without specific prior written permission.
  58  *
  59  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  60  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  61  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  62  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  63  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  64  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  65  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  66  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  67  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  68  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  69  * SUCH DAMAGE.
  70  */
  71
  72 #ifdef MAKE_BOOTSTRAP
  73 static char rcsid[] = "$NetBSD: hash.c,v 1.5 2007/03/03 00:09:30 simonb Exp $";
  74 #else
  75 #include <sys/cdefs.h>
  76 #ifndef lint
  77 #if 0
  78 static char sccsid[] = "@(#)hash.c      8.1 (Berkeley) 6/6/93";
  79 #else
  80 __RCSID("$NetBSD: hash.c,v 1.5 2007/03/03 00:09:30 simonb Exp $");
  81 #endif
  82 #endif /* not lint */
  83 #endif
  84
  85 #include <sys/types.h>
  86
  87 #include <stdlib.h>
  88 #include <string.h>
  89 #include <unistd.h>
  90 #include <err.h>
  91 #include <util.h>
  92
  93 /* hash.c --
  94  *
  95  *      This module contains routines to manipulate a hash table.
  96  *      See hash.h for a definition of the structure of the hash
  97  *      table.  Hash tables grow automatically as the amount of
  98  *      information increases.
  99  */
 100 #include "hash.h"
 101
 102 /*
 103  * Forward references to local procedures that are used before they're
 104  * defined:
 105  */
 106
 107 static void RebuildTable(Hash_Table *);
 108
 109 /*
 110  * The following defines the ratio of # entries to # buckets
 111  * at which we rebuild the table to make it larger.
 112  */
 113
 114 #define rebuildLimit 8
 115
 116 /*
 117  *---------------------------------------------------------
 118  *
 119  * Hash_InitTable --
 120  *
 121  *      This routine just sets up the hash table.
 122  *
 123  * Input:
 124  *      t               Structure to use to hold table.
 125  *      numBuckets      How many buckets to create for starters.  This number
 126  *                      is rounded up to a power of two.  If <= 0, a reasonable
 127  *                      default is chosen. The table will grow in size later
 128  *                      as needed.
 129  *
 130  * Results:
 131  *      None.
 132  *
 133  * Side Effects:
 134  *      Memory is allocated for the initial bucket area.
 135  *
 136  *---------------------------------------------------------
 137  */
 138
 139 void
 140 Hash_InitTable(Hash_Table *t, int numBuckets)
 141 {
 142         int i;
 143         struct Hash_Entry **hp;
 144
 145         /*
 146          * Round up the size to a power of two.
 147          */
 148         if (numBuckets <= 0)
 149                 i = 16;
 150         else {
 151                 for (i = 2; i < numBuckets; i <<= 1)
 152                          continue;
 153         }
 154         t->numEntries = 0;
 155         t->size = i;
 156         t->mask = i - 1;
 157         t->bucketPtr = hp = (struct Hash_Entry **)emalloc(sizeof(*hp) * i);
 158         while (--i >= 0)
 159                 *hp++ = NULL;
 160 }
 161
 162 /*
 163  *---------------------------------------------------------
 164  *
 165  * Hash_DeleteTable --
 166  *
 167  *      This routine removes everything from a hash table
 168  *      and frees up the memory space it occupied (except for
 169  *      the space in the Hash_Table structure).
 170  *
 171  * Results:
 172  *      None.
 173  *
 174  * Side Effects:
 175  *      Lots of memory is freed up.
 176  *
 177  *---------------------------------------------------------
 178  */
 179
 180 void
 181 Hash_DeleteTable(Hash_Table *t)
 182 {
 183         struct Hash_Entry **hp, *h, *nexth;
 184         int i;
 185
 186         nexth = NULL;
 187         for (hp = t->bucketPtr, i = t->size; --i >= 0;) {
 188                 for (h = *hp++; h != NULL; h = nexth) {
 189                         nexth = h->next;
 190                         free(h);
 191                 }
 192         }
 193         free(t->bucketPtr);
 194
 195         /*
 196          * Set up the hash table to cause memory faults on any future access
 197          * attempts until re-initialization.
 198          */
 199         t->bucketPtr = NULL;
 200 }
 201
 202 /*
 203  *---------------------------------------------------------
 204  *
 205  * Hash_FindEntry --
 206  *
 207  *      Searches a hash table for an entry corresponding to key.
 208  *
 209  * Input:
 210  *      t       Hash table to search.
 211  *      key     A hash key.
 212  *
 213  * Results:
 214  *      The return value is a pointer to the entry for key,
 215  *      if key was present in the table.  If key was not
 216  *      present, NULL is returned.
 217  *
 218  * Side Effects:
 219  *      None.
 220  *
 221  *---------------------------------------------------------
 222  */
 223
 224 Hash_Entry *
 225 Hash_FindEntry(Hash_Table *t, char *key)
 226 {
 227         Hash_Entry *e;
 228         unsigned h;
 229         char *p;
 230
 231         for (h = 0, p = key; *p;)
 232                 h = (h << 5) - h + *p++;
 233         p = key;
 234         for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next)
 235                 if (e->namehash == h && strcmp(e->name, p) == 0)
 236                         return (e);
 237         return (NULL);
 238 }
 239
 240 /*
 241  *---------------------------------------------------------
 242  *
 243  * Hash_CreateEntry --
 244  *
 245  *      Searches a hash table for an entry corresponding to
 246  *      key.  If no entry is found, then one is created.
 247  *
 248  * Input:
 249  *      t       Hash table to search.
 250  *      key     A hash key.
 251  *      newPtr  Filled in with 1 if new entry created, 0 otherwise.
 252  *
 253  * Results:
 254  *      The return value is a pointer to the entry.  If *newPtr
 255  *      isn't NULL, then *newPtr is filled in with TRUE if a
 256  *      new entry was created, and FALSE if an entry already existed
 257  *      with the given key.
 258  *
 259  * Side Effects:
 260  *      Memory may be allocated, and the hash buckets may be modified.
 261  *---------------------------------------------------------
 262  */
 263
 264 Hash_Entry *
 265 Hash_CreateEntry(Hash_Table *t, char *key, int *newPtr)
 266 {
 267         Hash_Entry *e;
 268         unsigned h;
 269         char *p;
 270         int keylen;
 271         struct Hash_Entry **hp;
 272
 273         /*
 274          * Hash the key.  As a side effect, save the length (strlen) of the
 275          * key in case we need to create the entry.
 276          */
 277         for (h = 0, p = key; *p;)
 278                 h = (h << 5) - h + *p++;
 279         keylen = p - key;
 280         p = key;
 281         for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next) {
 282                 if (e->namehash == h && strcmp(e->name, p) == 0) {
 283                         if (newPtr != NULL)
 284                                 *newPtr = 0;
 285                         return (e);
 286                 }
 287         }
 288
 289         /*
 290          * The desired entry isn't there.  Before allocating a new entry,
 291          * expand the table if necessary (and this changes the resulting
 292          * bucket chain).
 293          */
 294         if (t->numEntries >= rebuildLimit * t->size)
 295                 RebuildTable(t);
 296         e = (Hash_Entry *) emalloc(sizeof(*e) + keylen);
 297         hp = &t->bucketPtr[h & t->mask];
 298         e->next = *hp;
 299         *hp = e;
 300         e->clientData = NULL;
 301         e->namehash = h;
 302         (void) strcpy(e->name, p);
 303         t->numEntries++;
 304
 305         if (newPtr != NULL)
 306                 *newPtr = 1;
 307         return (e);
 308 }
 309
 310 /*
 311  *---------------------------------------------------------
 312  *
 313  * Hash_DeleteEntry --
 314  *
 315  *      Delete the given hash table entry and free memory associated with
 316  *      it.
 317  *
 318  * Results:
 319  *      None.
 320  *
 321  * Side Effects:
 322  *      Hash chain that entry lives in is modified and memory is freed.
 323  *
 324  *---------------------------------------------------------
 325  */
 326
 327 void
 328 Hash_DeleteEntry(Hash_Table *t, Hash_Entry *e)
 329 {
 330         Hash_Entry **hp, *p;
 331
 332         if (e == NULL)
 333                 return;
 334         for (hp = &t->bucketPtr[e->namehash & t->mask];
 335              (p = *hp) != NULL; hp = &p->next) {
 336                 if (p == e) {
 337                         *hp = p->next;
 338                         free(p);
 339                         t->numEntries--;
 340                         return;
 341                 }
 342         }
 343         (void)write(2, "bad call to Hash_DeleteEntry\n", 29);
 344         abort();
 345 }
 346
 347 /*
 348  *---------------------------------------------------------
 349  *
 350  * Hash_EnumFirst --
 351  *      This procedure sets things up for a complete search
 352  *      of all entries recorded in the hash table.
 353  *
 354  * Input:
 355  *      t               Table to be searched.
 356  *      searchPtr       Area in which to keep state about search.
 357  *
 358  * Results:
 359  *      The return value is the address of the first entry in
 360  *      the hash table, or NULL if the table is empty.
 361  *
 362  * Side Effects:
 363  *      The information in searchPtr is initialized so that successive
 364  *      calls to Hash_Next will return successive HashEntry's
 365  *      from the table.
 366  *
 367  *---------------------------------------------------------
 368  */
 369
 370 Hash_Entry *
 371 Hash_EnumFirst(Hash_Table *t, Hash_Search *searchPtr)
 372 {
 373
 374         searchPtr->tablePtr = t;
 375         searchPtr->nextIndex = 0;
 376         searchPtr->hashEntryPtr = NULL;
 377         return Hash_EnumNext(searchPtr);
 378 }
 379
 380 /*
 381  *---------------------------------------------------------
 382  *
 383  * Hash_EnumNext --
 384  *    This procedure returns successive entries in the hash table.
 385  *
 386  * Results:
 387  *    The return value is a pointer to the next HashEntry
 388  *    in the table, or NULL when the end of the table is
 389  *    reached.
 390  *
 391  * Side Effects:
 392  *    The information in searchPtr is modified to advance to the
 393  *    next entry.
 394  *
 395  *---------------------------------------------------------
 396  */
 397
 398 Hash_Entry *
 399 Hash_EnumNext(Hash_Search *searchPtr)
 400 {
 401         Hash_Entry *e;
 402         Hash_Table *t = searchPtr->tablePtr;
 403
 404         /*
 405          * The hashEntryPtr field points to the most recently returned
 406          * entry, or is nil if we are starting up.  If not nil, we have
 407          * to start at the next one in the chain.
 408          */
 409         e = searchPtr->hashEntryPtr;
 410         if (e != NULL)
 411                 e = e->next;
 412         /*
 413          * If the chain ran out, or if we are starting up, we need to
 414          * find the next nonempty chain.
 415          */
 416         while (e == NULL) {
 417                 if (searchPtr->nextIndex >= t->size)
 418                         return (NULL);
 419                 e = t->bucketPtr[searchPtr->nextIndex++];
 420         }
 421         searchPtr->hashEntryPtr = e;
 422         return (e);
 423 }
 424
 425 /*
 426  *---------------------------------------------------------
 427  *
 428  * RebuildTable --
 429  *      This local routine makes a new hash table that
 430  *      is larger than the old one.
 431  *
 432  * Results:
 433  *      None.
 434  *
 435  * Side Effects:
 436  *      The entire hash table is moved, so any bucket numbers
 437  *      from the old table are invalid.
 438  *
 439  *---------------------------------------------------------
 440  */
 441
 442 static void
 443 RebuildTable(Hash_Table *t)
 444 {
 445         Hash_Entry *e, *next, **hp, **xp;
 446         int i, mask;
 447         Hash_Entry **oldhp;
 448         int oldsize;
 449
 450         next = NULL;
 451         oldhp = t->bucketPtr;
 452         oldsize = i = t->size;
 453         i <<= 1;
 454         t->size = i;
 455         t->mask = mask = i - 1;
 456         t->bucketPtr = hp = (struct Hash_Entry **) emalloc(sizeof(*hp) * i);
 457         while (--i >= 0)
 458                 *hp++ = NULL;
 459         for (hp = oldhp, i = oldsize; --i >= 0;) {
 460                 for (e = *hp++; e != NULL; e = next) {
 461                         next = e->next;
 462                         xp = &t->bucketPtr[e->namehash & mask];
 463                         e->next = *xp;
 464                         *xp = e;
 465                 }
 466         }
 467         free(oldhp);
 468 }