glibc/stdlib/bsearch.c

/* Copyright (C) 1991,92,97,2000,02 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, write to the Free
   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
   02111-1307 USA.  */

#include <stdlib.h>


/* Perform a binary search for KEY in BASE which has NMEMB elements
   of SIZE bytes each.  The comparisons are done by (*COMPAR)().  */
void *
bsearch (const void *key, const void *base, size_t nmemb, size_t size,
	 int (*compar) (const void *, const void *))
{
  size_t l, u, idx;
  const void *p;
  int comparison;

  l = 0;
  u = nmemb;
  while (l < u)
    {
      idx = (l + u) / 2;
      p = (void *) (((const char *) base) + (idx * size));
      comparison = (*compar) (key, p);
      if (comparison < 0)
	u = idx;
      else if (comparison > 0)
	l = idx + 1;
      else
	return (void *) p;
    }

  return NULL;
}
libc_hidden_def (bsearch)