sbin/rcorder/hash.c

   1 /*
   2  * Copyright (c) 1988, 1989, 1990 The Regents of the University of California.
   3  * Copyright (c) 1988, 1989 by Adam de Boor
   4  * Copyright (c) 1989 by Berkeley Softworks
   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. All advertising materials mentioning features or use of this software
  19  *    must display the following acknowledgement:
  20  *      This product includes software developed by the University of
  21  *      California, Berkeley and its contributors.
  22  * 4. Neither the name of the University nor the names of its contributors
  23  *    may be used to endorse or promote products derived from this software
  24  *    without specific prior written permission.
  25  *
  26  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  27  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  28  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  29  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  30  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  31  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  32  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  33  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  34  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  35  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  36  * SUCH DAMAGE.
  37  *
  38  * $NetBSD: hash.c,v 1.1.1.1 1999/11/19 04:30:56 mrg Exp $
  39  */
  40
  41 #include <sys/types.h>
  42
  43 #include <stdlib.h>
  44 #include <string.h>
  45 #include <unistd.h>
  46
  47 /* hash.c --
  48  *
  49  *      This module contains routines to manipulate a hash table.
  50  *      See hash.h for a definition of the structure of the hash
  51  *      table.  Hash tables grow automatically as the amount of
  52  *      information increases.
  53  */
  54 #include "sprite.h"
  55 #ifndef ORDER
  56 #include "make.h"
  57 #endif /* ORDER */
  58 #include "hash.h"
  59 #include "ealloc.h"
  60
  61 /*
  62  * Forward references to local procedures that are used before they're
  63  * defined:
  64  */
  65
  66 static void RebuildTable(Hash_Table *);
  67
  68 /*
  69  * The following defines the ratio of # entries to # buckets
  70  * at which we rebuild the table to make it larger.
  71  */
  72
  73 #define rebuildLimit 8
  74
  75 /*
  76  *---------------------------------------------------------
  77  *
  78  * Hash_InitTable --
  79  *
  80  *      This routine just sets up the hash table.
  81  *
  82  * Results:
  83  *      None.
  84  *
  85  * Side Effects:
  86  *      Memory is allocated for the initial bucket area.
  87  *
  88  *---------------------------------------------------------
  89  */
  90
  91 /*
  92  * Hash_Table *t;       Structure to use to hold table.
  93  * int numBuckets;                      How many buckets to create for starters.
  94  *                                                              This number is rounded up to a power of
  95  *                                                              two.   If <= 0, a reasonable default is
  96  *                                                              chosen. The table will grow in size later
  97  *                                                              as needed.
  98  */
  99 void
 100 Hash_InitTable(Hash_Table *t, int numBuckets)
 101 {
 102         int i;
 103         struct Hash_Entry **hp;
 104
 105         /*
 106          * Round up the size to a power of two.
 107          */
 108         if (numBuckets <= 0)
 109                 i = 16;
 110         else {
 111                 for (i = 2; i < numBuckets; i <<= 1)
 112                          continue;
 113         }
 114         t->numEntries = 0;
 115         t->size = i;
 116         t->mask = i - 1;
 117         t->bucketPtr = hp = (struct Hash_Entry **)emalloc(sizeof(*hp) * i);
 118         while (--i >= 0)
 119                 *hp++ = NULL;
 120 }
 121
 122 /*
 123  *---------------------------------------------------------
 124  *
 125  * Hash_DeleteTable --
 126  *
 127  *      This routine removes everything from a hash table
 128  *      and frees up the memory space it occupied (except for
 129  *      the space in the Hash_Table structure).
 130  *
 131  * Results:
 132  *      None.
 133  *
 134  * Side Effects:
 135  *      Lots of memory is freed up.
 136  *
 137  *---------------------------------------------------------
 138  */
 139
 140 void
 141 Hash_DeleteTable(Hash_Table *t)
 142 {
 143         struct Hash_Entry **hp, *h, *nexth = NULL;
 144         int i;
 145
 146         for (hp = t->bucketPtr, i = t->size; --i >= 0;) {
 147                 for (h = *hp++; h != NULL; h = nexth) {
 148                         nexth = h->next;
 149                         free((char *)h);
 150                 }
 151         }
 152         free((char *)t->bucketPtr);
 153
 154         /*
 155          * Set up the hash table to cause memory faults on any future access
 156          * attempts until re-initialization.
 157          */
 158         t->bucketPtr = NULL;
 159 }
 160
 161 /*
 162  *---------------------------------------------------------
 163  *
 164  * Hash_FindEntry --
 165  *
 166  *      Searches a hash table for an entry corresponding to key.
 167  *
 168  * Results:
 169  *      The return value is a pointer to the entry for key,
 170  *      if key was present in the table.  If key was not
 171  *      present, NULL is returned.
 172  *
 173  * Side Effects:
 174  *      None.
 175  *
 176  *---------------------------------------------------------
 177  */
 178
 179 Hash_Entry *
 180 Hash_FindEntry(Hash_Table *t, char *key)
 181 {
 182         Hash_Entry *e;
 183         unsigned h;
 184         char *p;
 185
 186         for (h = 0, p = key; *p;)
 187                 h = (h << 5) - h + *p++;
 188         p = key;
 189         for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next)
 190                 if (e->namehash == h && strcmp(e->name, p) == 0)
 191                         return (e);
 192         return (NULL);
 193 }
 194
 195 /*
 196  *---------------------------------------------------------
 197  *
 198  * Hash_CreateEntry --
 199  *
 200  *      Searches a hash table for an entry corresponding to
 201  *      key.  If no entry is found, then one is created.
 202  *
 203  * Results:
 204  *      The return value is a pointer to the entry.  If *newPtr
 205  *      isn't NULL, then *newPtr is filled in with TRUE if a
 206  *      new entry was created, and FALSE if an entry already existed
 207  *      with the given key.
 208  *
 209  * Side Effects:
 210  *      Memory may be allocated, and the hash buckets may be modified.
 211  *---------------------------------------------------------
 212  */
 213
 214 Hash_Entry *
 215 Hash_CreateEntry(Hash_Table *t, char *key, Boolean *newPtr)
 216 {
 217         Hash_Entry *e;
 218         unsigned h;
 219         char *p;
 220         int keylen;
 221         struct Hash_Entry **hp;
 222
 223         /*
 224          * Hash the key.  As a side effect, save the length (strlen) of the
 225          * key in case we need to create the entry.
 226          */
 227         for (h = 0, p = key; *p;)
 228                 h = (h << 5) - h + *p++;
 229         keylen = p - key;
 230         p = key;
 231         for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next) {
 232                 if (e->namehash == h && strcmp(e->name, p) == 0) {
 233                         if (newPtr != NULL)
 234                                 *newPtr = FALSE;
 235                         return (e);
 236                 }
 237         }
 238
 239         /*
 240          * The desired entry isn't there.  Before allocating a new entry,
 241          * expand the table if necessary (and this changes the resulting
 242          * bucket chain).
 243          */
 244         if (t->numEntries >= rebuildLimit * t->size)
 245                 RebuildTable(t);
 246         e = (Hash_Entry *) emalloc(sizeof(*e) + keylen);
 247         hp = &t->bucketPtr[h & t->mask];
 248         e->next = *hp;
 249         *hp = e;
 250         e->clientData = NULL;
 251         e->namehash = h;
 252         strcpy(e->name, p);
 253         t->numEntries++;
 254
 255         if (newPtr != NULL)
 256                 *newPtr = TRUE;
 257         return (e);
 258 }
 259
 260 /*
 261  *---------------------------------------------------------
 262  *
 263  * Hash_DeleteEntry --
 264  *
 265  *      Delete the given hash table entry and free memory associated with
 266  *      it.
 267  *
 268  * Results:
 269  *      None.
 270  *
 271  * Side Effects:
 272  *      Hash chain that entry lives in is modified and memory is freed.
 273  *
 274  *---------------------------------------------------------
 275  */
 276
 277 void
 278 Hash_DeleteEntry(Hash_Table *t, Hash_Entry *e)
 279 {
 280         Hash_Entry **hp, *p;
 281
 282         if (e == NULL)
 283                 return;
 284         for (hp = &t->bucketPtr[e->namehash & t->mask];
 285              (p = *hp) != NULL; hp = &p->next) {
 286                 if (p == e) {
 287                         *hp = p->next;
 288                         free((char *)p);
 289                         t->numEntries--;
 290                         return;
 291                 }
 292         }
 293         write(2, "bad call to Hash_DeleteEntry\n", 29);
 294         abort();
 295 }
 296
 297 /*
 298  *---------------------------------------------------------
 299  *
 300  * Hash_EnumFirst --
 301  *      This procedure sets things up for a complete search
 302  *      of all entries recorded in the hash table.
 303  *
 304  * Results:
 305  *      The return value is the address of the first entry in
 306  *      the hash table, or NULL if the table is empty.
 307  *
 308  * Side Effects:
 309  *      The information in searchPtr is initialized so that successive
 310  *      calls to Hash_Next will return successive HashEntry's
 311  *      from the table.
 312  *
 313  *---------------------------------------------------------
 314  */
 315
 316 Hash_Entry *
 317 Hash_EnumFirst(Hash_Table *t, Hash_Search *searchPtr)
 318 {
 319         searchPtr->tablePtr = t;
 320         searchPtr->nextIndex = 0;
 321         searchPtr->hashEntryPtr = NULL;
 322         return Hash_EnumNext(searchPtr);
 323 }
 324
 325 /*
 326  *---------------------------------------------------------
 327  *
 328  * Hash_EnumNext --
 329  *    This procedure returns successive entries in the hash table.
 330  *
 331  * Results:
 332  *    The return value is a pointer to the next HashEntry
 333  *    in the table, or NULL when the end of the table is
 334  *    reached.
 335  *
 336  * Side Effects:
 337  *    The information in searchPtr is modified to advance to the
 338  *    next entry.
 339  *
 340  *---------------------------------------------------------
 341  */
 342
 343 Hash_Entry *
 344 Hash_EnumNext(Hash_Search *searchPtr)
 345 {
 346         Hash_Entry *e;
 347         Hash_Table *t = searchPtr->tablePtr;
 348
 349         /*
 350          * The hashEntryPtr field points to the most recently returned
 351          * entry, or is nil if we are starting up.  If not nil, we have
 352          * to start at the next one in the chain.
 353          */
 354         e = searchPtr->hashEntryPtr;
 355         if (e != NULL)
 356                 e = e->next;
 357         /*
 358          * If the chain ran out, or if we are starting up, we need to
 359          * find the next nonempty chain.
 360          */
 361         while (e == NULL) {
 362                 if (searchPtr->nextIndex >= t->size)
 363                         return (NULL);
 364                 e = t->bucketPtr[searchPtr->nextIndex++];
 365         }
 366         searchPtr->hashEntryPtr = e;
 367         return (e);
 368 }
 369
 370 /*
 371  *---------------------------------------------------------
 372  *
 373  * RebuildTable --
 374  *      This local routine makes a new hash table that
 375  *      is larger than the old one.
 376  *
 377  * Results:
 378  *      None.
 379  *
 380  * Side Effects:
 381  *      The entire hash table is moved, so any bucket numbers
 382  *      from the old table are invalid.
 383  *
 384  *---------------------------------------------------------
 385  */
 386
 387 static void
 388 RebuildTable(Hash_Table *t)
 389 {
 390         Hash_Entry *e, *next = NULL, **hp, **xp;
 391         int i, mask;
 392         Hash_Entry **oldhp;
 393         int oldsize;
 394
 395         oldhp = t->bucketPtr;
 396         oldsize = i = t->size;
 397         i <<= 1;
 398         t->size = i;
 399         t->mask = mask = i - 1;
 400         t->bucketPtr = hp = (struct Hash_Entry **) emalloc(sizeof(*hp) * i);
 401         while (--i >= 0)
 402                 *hp++ = NULL;
 403         for (hp = oldhp, i = oldsize; --i >= 0;) {
 404                 for (e = *hp++; e != NULL; e = next) {
 405                         next = e->next;
 406                         xp = &t->bucketPtr[e->namehash & mask];
 407                         e->next = *xp;
 408                         *xp = e;
 409                 }
 410         }
 411         free((char *)oldhp);
 412 }