usr.bin/m4/lib/ohash_lookup_interval.c

   1 /* $OpenBSD: ohash_lookup_interval.c,v 1.3 2006/01/16 15:52:25 espie Exp $ */
   2 /* ex:ts=8 sw=4:
   3  */
   4
   5 /* Copyright (c) 1999, 2004 Marc Espie <espie@openbsd.org>
   6  *
   7  * Permission to use, copy, modify, and distribute this software for any
   8  * purpose with or without fee is hereby granted, provided that the above
   9  * copyright notice and this permission notice appear in all copies.
  10  *
  11  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
  12  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  13  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
  14  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  15  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  16  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  17  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  18  */
  19
  20 #include "ohash_int.h"
  21
  22 unsigned int
  23 ohash_lookup_interval(struct ohash *h, const char *start, const char *end,
  24     uint32_t hv)
  25 {
  26         unsigned int    i, incr;
  27         unsigned int    empty;
  28
  29 #ifdef STATS_HASH
  30         STAT_HASH_LOOKUP++;
  31 #endif
  32         empty = NONE;
  33         i = hv % h->size;
  34         incr = ((hv % (h->size-2)) & ~1) + 1;
  35         while (h->t[i].p != NULL) {
  36 #ifdef STATS_HASH
  37                 STAT_HASH_LENGTH++;
  38 #endif
  39                 if (h->t[i].p == DELETED) {
  40                         if (empty == NONE)
  41                                 empty = i;
  42                 } else if (h->t[i].hv == hv &&
  43                     strncmp(h->t[i].p+h->info.key_offset, start,
  44                         end - start) == 0 &&
  45                     (h->t[i].p+h->info.key_offset)[end-start] == '\0') {
  46                         if (empty != NONE) {
  47                                 h->t[empty].hv = hv;
  48                                 h->t[empty].p = h->t[i].p;
  49                                 h->t[i].p = DELETED;
  50                                 return empty;
  51                         } else {
  52 #ifdef STATS_HASH
  53                                 STAT_HASH_POSITIVE++;
  54 #endif
  55                                 return i;
  56                         }
  57                 }
  58                 i += incr;
  59                 if (i >= h->size)
  60                         i -= h->size;
  61         }
  62
  63         /* Found an empty position.  */
  64         if (empty != NONE)
  65                 i = empty;
  66         h->t[i].hv = hv;
  67         return i;
  68 }