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Revision base0 == NULL is allowed when nmemb == 0, in fact the nsdispatch code calls bsearch this way. |

/* $NetBSD: bsearch.c,v 1.15 2012/03/04 20:01:45 christos Exp $ */ /* * Copyright (c) 1990, 1993 * The Regents of the University of California. All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. Neither the name of the University nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. */ #include <sys/cdefs.h> #if defined(LIBC_SCCS) && !defined(lint) #if 0 static char sccsid[] = "@(#)bsearch.c 8.1 (Berkeley) 6/4/93"; #else __RCSID("$NetBSD: bsearch.c,v 1.15 2012/03/04 20:01:45 christos Exp $"); #endif #endif /* LIBC_SCCS and not lint */ #include <assert.h> #include <errno.h> #include <stdlib.h> /* * Perform a binary search. * * The code below is a bit sneaky. After a comparison fails, we * divide the work in half by moving either left or right. If lim * is odd, moving left simply involves halving lim: e.g., when lim * is 5 we look at item 2, so we change lim to 2 so that we will * look at items 0 & 1. If lim is even, the same applies. If lim * is odd, moving right again involes halving lim, this time moving * the base up one item past p: e.g., when lim is 5 we change base * to item 3 and make lim 2 so that we will look at items 3 and 4. * If lim is even, however, we have to shrink it by one before * halving: e.g., when lim is 4, we still looked at item 2, so we * have to make lim 3, then halve, obtaining 1, so that we will only * look at item 3. */ void * bsearch(const void *key, const void *base0, size_t nmemb, size_t size, int (*compar)(const void *, const void *)) { const char *base = base0; size_t lim; int cmp; const void *p; _DIAGASSERT(key != NULL); _DIAGASSERT(base0 != NULL || nmemb == 0); _DIAGASSERT(compar != NULL); for (lim = nmemb; lim != 0; lim >>= 1) { p = base + (lim >> 1) * size; cmp = (*compar)(key, p); if (cmp == 0) return __UNCONST(p); if (cmp > 0) { /* key > p: move right */ base = (const char *)p + size; lim--; } /* else move left */ } return (NULL); }