bsearch.c

一个C源代码分析器

/* Copyright (C) 1991, 1992 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 Library General Public License as
published by the Free Software Foundation; either version 2 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
Library General Public License for more details.

You should have received a copy of the GNU Library General Public
License along with the GNU C Library; see the file COPYING.LIB.  If
not, write to the Free Software Foundation, Inc., 675 Mass Ave,
Cambridge, MA 02139, USA.  */

#include <ansidecl.h>
#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)().  */
PTR
DEFUN(bsearch, (key, base, nmemb, size, compar),
      register CONST PTR key AND register CONST PTR base AND
      size_t nmemb AND register size_t size AND
      register int EXFUN((*compar), (CONST PTR, CONST PTR)))
{
  register size_t l, u, idx;
  register CONST PTR p;
  register int comparison;

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

  return NULL;
}