gnu/libexec/uucp/libuucp/bsrch.c

/* Copyright (C) 1991 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.

This file was modified slightly by Ian Lance Taylor, May 1992, for
Taylor UUCP.  */

#include "uucp.h"

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

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

  return NULL;
}