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bsearch.c
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1991-07-08
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/* 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. */
#ifdef STDC_HEADERS
#include <stdlib.h>
#else
#define NULL 0
#include <sys/types.h>
#endif
/* Perform a binary search for KEY in BASE which has NMEMB elements
of SIZE bytes each. The comparisons are done by (*COMPAR)(). */
char *
bsearch (key, base, nmemb, size, compar)
register char *key;
register char *base;
size_t nmemb;
register size_t size;
register int (*compar) ();
{
register size_t l, u, idx;
register char *p;
register int comparison;
l = 0;
u = nmemb - 1;
while (l <= u)
{
idx = (l + u) / 2;
p = (char *) (((char *) base) + (idx * size));
comparison = (*compar) (key, p);
/* Don't make U negative because it will wrap around. */
if (comparison < 0)
{
if (idx == 0)
break;
u = idx - 1;
}
else if (comparison > 0)
l = idx + 1;
else
return (char *) p;
}
return NULL;
}