lib/hash.cc

   1
   2 /*
   3  * $Id$
   4  *
   5  * DEBUG: section 00    Hash Tables
   6  * AUTHOR: Harvest Derived
   7  *
   8  * SQUID Web Proxy Cache          http://www.squid-cache.org/
   9  * ----------------------------------------------------------
  10  *
  11  *  Squid is the result of efforts by numerous individuals from
  12  *  the Internet community; see the CONTRIBUTORS file for full
  13  *  details.   Many organizations have provided support for Squid's
  14  *  development; see the SPONSORS file for full details.  Squid is
  15  *  Copyrighted (C) 2001 by the Regents of the University of
  16  *  California; see the COPYRIGHT file for full details.  Squid
  17  *  incorporates software developed and/or copyrighted by other
  18  *  sources; see the CREDITS file for full details.
  19  *
  20  *  This program is free software; you can redistribute it and/or modify
  21  *  it under the terms of the GNU General Public License as published by
  22  *  the Free Software Foundation; either version 2 of the License, or
  23  *  (at your option) any later version.
  24  *
  25  *  This program is distributed in the hope that it will be useful,
  26  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  27  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  28  *  GNU General Public License for more details.
  29  *
  30  *  You should have received a copy of the GNU General Public License
  31  *  along with this program; if not, write to the Free Software
  32  *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111, USA.
  33  *
  34  */
  35
  36 #include "squid.h"
  37 #include "hash.h"
  38 #include "profiler/Profiler.h"
  39
  40 #if HAVE_STDIO_H
  41 #include <stdio.h>
  42 #endif
  43 #if HAVE_STDLIB_H
  44 #include <stdlib.h>
  45 #endif
  46 #if HAVE_STRING_H
  47 #include <string.h>
  48 #endif
  49 #if HAVE_UNISTD_H
  50 #include <unistd.h>
  51 #endif
  52 #if HAVE_GNUMALLLOC_H
  53 #include <gnumalloc.h>
  54 #elif HAVE_MALLOC_H
  55 #include <malloc.h>
  56 #endif
  57 #if HAVE_ASSERT_H
  58 #include <assert.h>
  59 #endif
  60 #if HAVE_MATH_H
  61 #include <math.h>
  62 #endif
  63
  64 static void hash_next_bucket(hash_table * hid);
  65
  66 unsigned int
  67 hash_string(const void *data, unsigned int size)
  68 {
  69     const unsigned char *s = static_cast<const unsigned char *>(data);
  70     unsigned int n = 0;
  71     unsigned int j = 0;
  72     unsigned int i = 0;
  73     while (*s) {
  74         ++j;
  75         n ^= 271 * *s;
  76         ++s;
  77     }
  78     i = n ^ (j * 271);
  79     return i % size;
  80 }
  81
  82 /* the following function(s) were adapted from
  83  *    usr/src/lib/libc/db/hash_func.c, 4.4 BSD lite */
  84
  85 /* Hash function from Chris Torek. */
  86 unsigned int
  87 hash4(const void *data, unsigned int size)
  88 {
  89     const char *key = static_cast<const char *>(data);
  90     size_t loop;
  91     unsigned int h;
  92     size_t len;
  93
  94 #define HASH4a   h = (h << 5) - h + *key++;
  95 #define HASH4b   h = (h << 5) + h + *key++;
  96 #define HASH4 HASH4b
  97
  98     h = 0;
  99     len = strlen(key);
 100     loop = len >> 3;
 101     switch (len & (8 - 1)) {
 102     case 0:
 103         break;
 104     case 7:
 105         HASH4;
 106         /* FALLTHROUGH */
 107     case 6:
 108         HASH4;
 109         /* FALLTHROUGH */
 110     case 5:
 111         HASH4;
 112         /* FALLTHROUGH */
 113     case 4:
 114         HASH4;
 115         /* FALLTHROUGH */
 116     case 3:
 117         HASH4;
 118         /* FALLTHROUGH */
 119     case 2:
 120         HASH4;
 121         /* FALLTHROUGH */
 122     case 1:
 123         HASH4;
 124     }
 125     while (loop) {
 126         --loop;
 127         HASH4;
 128         HASH4;
 129         HASH4;
 130         HASH4;
 131         HASH4;
 132         HASH4;
 133         HASH4;
 134         HASH4;
 135     }
 136     return h % size;
 137 }
 138
 139 /**
 140  *  hash_create - creates a new hash table, uses the cmp_func
 141  *  to compare keys.  Returns the identification for the hash table;
 142  *  otherwise returns a negative number on error.
 143  */
 144 hash_table *
 145 hash_create(HASHCMP * cmp_func, int hash_sz, HASHHASH * hash_func)
 146 {
 147     hash_table *hid = (hash_table *)xcalloc(1, sizeof(hash_table));
 148     if (!hash_sz)
 149         hid->size = (unsigned int) DEFAULT_HASH_SIZE;
 150     else
 151         hid->size = (unsigned int) hash_sz;
 152     /* allocate and null the buckets */
 153     hid->buckets = (hash_link **)xcalloc(hid->size, sizeof(hash_link *));
 154     hid->cmp = cmp_func;
 155     hid->hash = hash_func;
 156     hid->next = NULL;
 157     hid->current_slot = 0;
 158     return hid;
 159 }
 160
 161 /**
 162  *  hash_join - joins a hash_link under its key lnk->key
 163  *  into the hash table 'hid'.
 164  *
 165  *  It does not copy any data into the hash table, only links pointers.
 166  */
 167 void
 168 hash_join(hash_table * hid, hash_link * lnk)
 169 {
 170     int i;
 171     i = hid->hash(lnk->key, hid->size);
 172     lnk->next = hid->buckets[i];
 173     hid->buckets[i] = lnk;
 174     ++hid->count;
 175 }
 176
 177 /**
 178  *  hash_lookup - locates the item under the key 'k' in the hash table
 179  *  'hid'.  Returns a pointer to the hash bucket on success; otherwise
 180  *  returns NULL.
 181  */
 182 hash_link *
 183 hash_lookup(hash_table * hid, const void *k)
 184 {
 185     int b;
 186     PROF_start(hash_lookup);
 187     assert(k != NULL);
 188     b = hid->hash(k, hid->size);
 189     for (hash_link *walker = hid->buckets[b]; walker != NULL; walker = walker->next) {
 190         if ((hid->cmp) (k, walker->key) == 0) {
 191             PROF_stop(hash_lookup);
 192             return (walker);
 193         }
 194         assert(walker != walker->next);
 195     }
 196     PROF_stop(hash_lookup);
 197     return NULL;
 198 }
 199
 200 static void
 201 hash_next_bucket(hash_table * hid)
 202 {
 203     while (hid->next == NULL && ++hid->current_slot < hid->size)
 204         hid->next = hid->buckets[hid->current_slot];
 205 }
 206
 207 /**
 208  *  hash_first - initializes the hash table for the hash_next()
 209  *  function.
 210  */
 211 void
 212 hash_first(hash_table * hid)
 213 {
 214     assert(NULL == hid->next);
 215     hid->current_slot = 0;
 216     hid->next = hid->buckets[hid->current_slot];
 217     if (NULL == hid->next)
 218         hash_next_bucket(hid);
 219 }
 220
 221 /**
 222  *  hash_next - returns the next item in the hash table 'hid'.
 223  *  Otherwise, returns NULL on error or end of list.
 224  *
 225  *  MUST call hash_first() before hash_next().
 226  */
 227 hash_link *
 228 hash_next(hash_table * hid)
 229 {
 230     hash_link *p = hid->next;
 231     if (NULL == p)
 232         return NULL;
 233     hid->next = p->next;
 234     if (NULL == hid->next)
 235         hash_next_bucket(hid);
 236     return p;
 237 }
 238
 239 /**
 240  *  hash_last - resets hash traversal state to NULL
 241  *
 242  */
 243 void
 244 hash_last(hash_table * hid)
 245 {
 246     assert(hid != NULL);
 247     hid->next = NULL;
 248     hid->current_slot = 0;
 249 }
 250
 251 /**
 252  *  hash_remove_link - deletes the given hash_link node from the
 253  *  hash table 'hid'.  Does not free the item, only removes it
 254  *  from the list.
 255  *
 256  *  An assertion is triggered if the hash_link is not found in the
 257  *  list.
 258  */
 259 void
 260 hash_remove_link(hash_table * hid, hash_link * hl)
 261 {
 262     assert(hl != NULL);
 263     int i = hid->hash(hl->key, hid->size);
 264     for (hash_link **P = &hid->buckets[i]; *P; P = &(*P)->next) {
 265         if (*P != hl)
 266             continue;
 267         *P = hl->next;
 268         if (hid->next == hl) {
 269             hid->next = hl->next;
 270             if (NULL == hid->next)
 271                 hash_next_bucket(hid);
 272         }
 273         --hid->count;
 274         return;
 275     }
 276     assert(0);
 277 }
 278
 279 /**
 280  *  hash_get_bucket - returns the head item of the bucket
 281  *  in the hash table 'hid'. Otherwise, returns NULL on error.
 282  */
 283 hash_link *
 284 hash_get_bucket(hash_table * hid, unsigned int bucket)
 285 {
 286     if (bucket >= hid->size)
 287         return NULL;
 288     return (hid->buckets[bucket]);
 289 }
 290
 291 void
 292 hashFreeItems(hash_table * hid, HASHFREE * free_func)
 293 {
 294     hash_link *l;
 295     int i = 0;
 296     hash_link **list = (hash_link **)xcalloc(hid->count, sizeof(hash_link *));
 297     hash_first(hid);
 298     while ((l = hash_next(hid)) && i < hid->count) {
 299         *(list + i) = l;
 300         ++i;
 301     }
 302     for (int j = 0; j < i; ++j)
 303         free_func(*(list + j));
 304     xfree(list);
 305 }
 306
 307 void
 308 hashFreeMemory(hash_table * hid)
 309 {
 310     if (hid == NULL)
 311         return;
 312     if (hid->buckets)
 313         xfree(hid->buckets);
 314     xfree(hid);
 315 }
 316
 317 static int hash_primes[] = {
 318     103,
 319     229,
 320     467,
 321     977,
 322     1979,
 323     4019,
 324     6037,
 325     7951,
 326     12149,
 327     16231,
 328     33493,
 329     65357
 330 };
 331
 332 int
 333 hashPrime(int n)
 334 {
 335     int I = sizeof(hash_primes) / sizeof(int);
 336     int best_prime = hash_primes[0];
 337     double min = fabs(log((double) n) - log((double) hash_primes[0]));
 338     double d;
 339     for (int i = 0; i < I; ++i) {
 340         d = fabs(log((double) n) - log((double) hash_primes[i]));
 341         if (d > min)
 342             continue;
 343         min = d;
 344         best_prime = hash_primes[i];
 345     }
 346     return best_prime;
 347 }
 348
 349 /**
 350  * return the key of a hash_link as a const string
 351  */
 352 const char *
 353 hashKeyStr(hash_link * hl)
 354 {
 355     return (const char *) hl->key;
 356 }
 357
 358 #if USE_HASH_DRIVER
 359 /**
 360  *  hash-driver - Run with a big file as stdin to insert each line into the
 361  *  hash table, then prints the whole hash table, then deletes a random item,
 362  *  and prints the table again...
 363  */
 364 int
 365 main(void)
 366 {
 367     hash_table *hid;
 368     LOCAL_ARRAY(char, buf, BUFSIZ);
 369     LOCAL_ARRAY(char, todelete, BUFSIZ);
 370     hash_link *walker = NULL;
 371
 372     todelete[0] = '\0';
 373     printf("init\n");
 374
 375     printf("creating hash table\n");
 376     if ((hid = hash_create((HASHCMP *) strcmp, 229, hash4)) < 0) {
 377         printf("hash_create error.\n");
 378         exit(1);
 379     }
 380     printf("done creating hash table: %d\n", hid);
 381
 382     while (fgets(buf, BUFSIZ, stdin)) {
 383         buf[strlen(buf) - 1] = '\0';
 384         printf("Inserting '%s' for item %p to hash table: %d\n",
 385                buf, buf, hid);
 386         hash_insert(hid, xstrdup(buf), (void *) 0x12345678);
 387         if (random() % 17 == 0)
 388             strcpy(todelete, buf);
 389     }
 390
 391     printf("walking hash table...\n");
 392     for (int i = 0, walker = hash_first(hid); walker; walker = hash_next(hid)) {
 393         printf("item %5d: key: '%s' item: %p\n", i++, walker->key,
 394                walker->item);
 395     }
 396     printf("done walking hash table...\n");
 397
 398     if (todelete[0]) {
 399         printf("deleting %s from %d\n", todelete, hid);
 400         if (hash_delete(hid, todelete))
 401             printf("hash_delete error\n");
 402     }
 403     printf("walking hash table...\n");
 404     for (int i = 0, walker = hash_first(hid); walker; walker = hash_next(hid)) {
 405         printf("item %5d: key: '%s' item: %p\n", i++, walker->key,
 406                walker->item);
 407     }
 408     printf("done walking hash table...\n");
 409
 410     printf("driver finished.\n");
 411     exit(0);
 412 }
 413 #endif