stdlib/bsearch.c

   1 /* Copyright (C) 1991, 1992, 1997, 2000 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Library General Public License as
   6    published by the Free Software Foundation; either version 2 of the
   7    License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Library General Public License for more details.
  13
  14    You should have received a copy of the GNU Library General Public
  15    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  16    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  17    Boston, MA 02111-1307, USA.  */
  18
  19 #include <stdlib.h>
  20
  21
  22 /* Perform a binary search for KEY in BASE which has NMEMB elements
  23    of SIZE bytes each.  The comparisons are done by (*COMPAR)().  */
  24 void *
  25 bsearch (const void *key, const void *base, size_t nmemb, size_t size,
  26          int (*compar) (const void *, const void *))
  27 {
  28   size_t l, u, idx;
  29   const void *p;
  30   int comparison;
  31
  32   l = 0;
  33   u = nmemb;
  34   while (l < u)
  35     {
  36       idx = (l + u) / 2;
  37       p = (void *) (((const char *) base) + (idx * size));
  38       comparison = (*compar) (key, p);
  39       if (comparison < 0)
  40         u = idx;
  41       else if (comparison > 0)
  42         l = idx + 1;
  43       else
  44         return (void *) p;
  45     }
  46
  47   return NULL;
  48 }