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  * $DragonFly: src/sbin/rcorder/hash.c,v 1.5 2004/12/18 22:43:40 swildner Exp $
  40  */
  41
  42 #ifdef MAKE_BOOTSTRAP
  43 static char rcsid[] = "$NetBSD: hash.c,v 1.1.1.1 1999/11/19 04:30:56 mrg Exp $";
  44 #else
  45 #include <sys/cdefs.h>
  46 #ifndef lint
  47 #if 0
  48 static char sccsid[] = "@(#)hash.c      8.1 (Berkeley) 6/6/93";
  49 #else
  50 __RCSID("$NetBSD: hash.c,v 1.1.1.1 1999/11/19 04:30:56 mrg Exp $");
  51 #endif
  52 #endif /* not lint */
  53 #endif
  54
  55 #include <sys/types.h>
  56
  57 #include <stdlib.h>
  58 #include <string.h>
  59 #include <unistd.h>
  60
  61 /* hash.c --
  62  *
  63  *      This module contains routines to manipulate a hash table.
  64  *      See hash.h for a definition of the structure of the hash
  65  *      table.  Hash tables grow automatically as the amount of
  66  *      information increases.
  67  */
  68 #include "sprite.h"
  69 #ifndef ORDER
  70 #include "make.h"
  71 #endif /* ORDER */
  72 #include "hash.h"
  73 #include "ealloc.h"
  74
  75 /*
  76  * Forward references to local procedures that are used before they're
  77  * defined:
  78  */
  79
  80 static void RebuildTable(Hash_Table *);
  81
  82 /*
  83  * The following defines the ratio of # entries to # buckets
  84  * at which we rebuild the table to make it larger.
  85  */
  86
  87 #define rebuildLimit 8
  88
  89 /*
  90  *---------------------------------------------------------
  91  *
  92  * Hash_InitTable --
  93  *
  94  *      This routine just sets up the hash table.
  95  *
  96  * Results:
  97  *      None.
  98  *
  99  * Side Effects:
 100  *      Memory is allocated for the initial bucket area.
 101  *
 102  *---------------------------------------------------------
 103  */
 104
 105 /*
 106  * Hash_Table *t;       Structure to use to hold table.
 107  * int numBuckets;                      How many buckets to create for starters.
 108  *                                                              This number is rounded up to a power of
 109  *                                                              two.   If <= 0, a reasonable default is
 110  *                                                              chosen. The table will grow in size later
 111  *                                                              as needed.
 112  */
 113 void
 114 Hash_InitTable(Hash_Table *t, int numBuckets)
 115 {
 116         int i;
 117         struct Hash_Entry **hp;
 118
 119         /*
 120          * Round up the size to a power of two.
 121          */
 122         if (numBuckets <= 0)
 123                 i = 16;
 124         else {
 125                 for (i = 2; i < numBuckets; i <<= 1)
 126                          continue;
 127         }
 128         t->numEntries = 0;
 129         t->size = i;
 130         t->mask = i - 1;
 131         t->bucketPtr = hp = (struct Hash_Entry **)emalloc(sizeof(*hp) * i);
 132         while (--i >= 0)
 133                 *hp++ = NULL;
 134 }
 135
 136 /*
 137  *---------------------------------------------------------
 138  *
 139  * Hash_DeleteTable --
 140  *
 141  *      This routine removes everything from a hash table
 142  *      and frees up the memory space it occupied (except for
 143  *      the space in the Hash_Table structure).
 144  *
 145  * Results:
 146  *      None.
 147  *
 148  * Side Effects:
 149  *      Lots of memory is freed up.
 150  *
 151  *---------------------------------------------------------
 152  */
 153
 154 void
 155 Hash_DeleteTable(Hash_Table *t)
 156 {
 157         struct Hash_Entry **hp, *h, *nexth = NULL;
 158         int i;
 159
 160         for (hp = t->bucketPtr, i = t->size; --i >= 0;) {
 161                 for (h = *hp++; h != NULL; h = nexth) {
 162                         nexth = h->next;
 163                         free((char *)h);
 164                 }
 165         }
 166         free((char *)t->bucketPtr);
 167
 168         /*
 169          * Set up the hash table to cause memory faults on any future access
 170          * attempts until re-initialization.
 171          */
 172         t->bucketPtr = NULL;
 173 }
 174
 175 /*
 176  *---------------------------------------------------------
 177  *
 178  * Hash_FindEntry --
 179  *
 180  *      Searches a hash table for an entry corresponding to key.
 181  *
 182  * Results:
 183  *      The return value is a pointer to the entry for key,
 184  *      if key was present in the table.  If key was not
 185  *      present, NULL is returned.
 186  *
 187  * Side Effects:
 188  *      None.
 189  *
 190  *---------------------------------------------------------
 191  */
 192
 193 Hash_Entry *
 194 Hash_FindEntry(Hash_Table *t, char *key)
 195 {
 196         Hash_Entry *e;
 197         unsigned h;
 198         char *p;
 199
 200         for (h = 0, p = key; *p;)
 201                 h = (h << 5) - h + *p++;
 202         p = key;
 203         for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next)
 204                 if (e->namehash == h && strcmp(e->name, p) == 0)
 205                         return (e);
 206         return (NULL);
 207 }
 208
 209 /*
 210  *---------------------------------------------------------
 211  *
 212  * Hash_CreateEntry --
 213  *
 214  *      Searches a hash table for an entry corresponding to
 215  *      key.  If no entry is found, then one is created.
 216  *
 217  * Results:
 218  *      The return value is a pointer to the entry.  If *newPtr
 219  *      isn't NULL, then *newPtr is filled in with TRUE if a
 220  *      new entry was created, and FALSE if an entry already existed
 221  *      with the given key.
 222  *
 223  * Side Effects:
 224  *      Memory may be allocated, and the hash buckets may be modified.
 225  *---------------------------------------------------------
 226  */
 227
 228 Hash_Entry *
 229 Hash_CreateEntry(Hash_Table *t, char *key, Boolean *newPtr)
 230 {
 231         Hash_Entry *e;
 232         unsigned h;
 233         char *p;
 234         int keylen;
 235         struct Hash_Entry **hp;
 236
 237         /*
 238          * Hash the key.  As a side effect, save the length (strlen) of the
 239          * key in case we need to create the entry.
 240          */
 241         for (h = 0, p = key; *p;)
 242                 h = (h << 5) - h + *p++;
 243         keylen = p - key;
 244         p = key;
 245         for (e = t->bucketPtr[h & t->mask]; e != NULL; e = e->next) {
 246                 if (e->namehash == h && strcmp(e->name, p) == 0) {
 247                         if (newPtr != NULL)
 248                                 *newPtr = FALSE;
 249                         return (e);
 250                 }
 251         }
 252
 253         /*
 254          * The desired entry isn't there.  Before allocating a new entry,
 255          * expand the table if necessary (and this changes the resulting
 256          * bucket chain).
 257          */
 258         if (t->numEntries >= rebuildLimit * t->size)
 259                 RebuildTable(t);
 260         e = (Hash_Entry *) emalloc(sizeof(*e) + keylen);
 261         hp = &t->bucketPtr[h & t->mask];
 262         e->next = *hp;
 263         *hp = e;
 264         e->clientData = NULL;
 265         e->namehash = h;
 266         strcpy(e->name, p);
 267         t->numEntries++;
 268
 269         if (newPtr != NULL)
 270                 *newPtr = TRUE;
 271         return (e);
 272 }
 273
 274 /*
 275  *---------------------------------------------------------
 276  *
 277  * Hash_DeleteEntry --
 278  *
 279  *      Delete the given hash table entry and free memory associated with
 280  *      it.
 281  *
 282  * Results:
 283  *      None.
 284  *
 285  * Side Effects:
 286  *      Hash chain that entry lives in is modified and memory is freed.
 287  *
 288  *---------------------------------------------------------
 289  */
 290
 291 void
 292 Hash_DeleteEntry(Hash_Table *t, Hash_Entry *e)
 293 {
 294         Hash_Entry **hp, *p;
 295
 296         if (e == NULL)
 297                 return;
 298         for (hp = &t->bucketPtr[e->namehash & t->mask];
 299              (p = *hp) != NULL; hp = &p->next) {
 300                 if (p == e) {
 301                         *hp = p->next;
 302                         free((char *)p);
 303                         t->numEntries--;
 304                         return;
 305                 }
 306         }
 307         write(2, "bad call to Hash_DeleteEntry\n", 29);
 308         abort();
 309 }
 310
 311 /*
 312  *---------------------------------------------------------
 313  *
 314  * Hash_EnumFirst --
 315  *      This procedure sets things up for a complete search
 316  *      of all entries recorded in the hash table.
 317  *
 318  * Results:
 319  *      The return value is the address of the first entry in
 320  *      the hash table, or NULL if the table is empty.
 321  *
 322  * Side Effects:
 323  *      The information in searchPtr is initialized so that successive
 324  *      calls to Hash_Next will return successive HashEntry's
 325  *      from the table.
 326  *
 327  *---------------------------------------------------------
 328  */
 329
 330 Hash_Entry *
 331 Hash_EnumFirst(Hash_Table *t, Hash_Search *searchPtr)
 332 {
 333         searchPtr->tablePtr = t;
 334         searchPtr->nextIndex = 0;
 335         searchPtr->hashEntryPtr = NULL;
 336         return Hash_EnumNext(searchPtr);
 337 }
 338
 339 /*
 340  *---------------------------------------------------------
 341  *
 342  * Hash_EnumNext --
 343  *    This procedure returns successive entries in the hash table.
 344  *
 345  * Results:
 346  *    The return value is a pointer to the next HashEntry
 347  *    in the table, or NULL when the end of the table is
 348  *    reached.
 349  *
 350  * Side Effects:
 351  *    The information in searchPtr is modified to advance to the
 352  *    next entry.
 353  *
 354  *---------------------------------------------------------
 355  */
 356
 357 Hash_Entry *
 358 Hash_EnumNext(Hash_Search *searchPtr)
 359 {
 360         Hash_Entry *e;
 361         Hash_Table *t = searchPtr->tablePtr;
 362
 363         /*
 364          * The hashEntryPtr field points to the most recently returned
 365          * entry, or is nil if we are starting up.  If not nil, we have
 366          * to start at the next one in the chain.
 367          */
 368         e = searchPtr->hashEntryPtr;
 369         if (e != NULL)
 370                 e = e->next;
 371         /*
 372          * If the chain ran out, or if we are starting up, we need to
 373          * find the next nonempty chain.
 374          */
 375         while (e == NULL) {
 376                 if (searchPtr->nextIndex >= t->size)
 377                         return (NULL);
 378                 e = t->bucketPtr[searchPtr->nextIndex++];
 379         }
 380         searchPtr->hashEntryPtr = e;
 381         return (e);
 382 }
 383
 384 /*
 385  *---------------------------------------------------------
 386  *
 387  * RebuildTable --
 388  *      This local routine makes a new hash table that
 389  *      is larger than the old one.
 390  *
 391  * Results:
 392  *      None.
 393  *
 394  * Side Effects:
 395  *      The entire hash table is moved, so any bucket numbers
 396  *      from the old table are invalid.
 397  *
 398  *---------------------------------------------------------
 399  */
 400
 401 static void
 402 RebuildTable(Hash_Table *t)
 403 {
 404         Hash_Entry *e, *next = NULL, **hp, **xp;
 405         int i, mask;
 406         Hash_Entry **oldhp;
 407         int oldsize;
 408
 409         oldhp = t->bucketPtr;
 410         oldsize = i = t->size;
 411         i <<= 1;
 412         t->size = i;
 413         t->mask = mask = i - 1;
 414         t->bucketPtr = hp = (struct Hash_Entry **) emalloc(sizeof(*hp) * i);
 415         while (--i >= 0)
 416                 *hp++ = NULL;
 417         for (hp = oldhp, i = oldsize; --i >= 0;) {
 418                 for (e = *hp++; e != NULL; e = next) {
 419                         next = e->next;
 420                         xp = &t->bucketPtr[e->namehash & mask];
 421                         e->next = *xp;
 422                         *xp = e;
 423                 }
 424         }
 425         free((char *)oldhp);
 426 }