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