From patchwork Sat Nov 7 21:03:58 2009 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alan Jenkins X-Patchwork-Id: 58382 Received: from vger.kernel.org (vger.kernel.org [209.132.176.167]) by demeter.kernel.org (8.14.2/8.14.2) with ESMTP id nA7L6Ftb019420 for ; Sat, 7 Nov 2009 21:06:17 GMT Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753024AbZKGVFd (ORCPT ); Sat, 7 Nov 2009 16:05:33 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752958AbZKGVFc (ORCPT ); Sat, 7 Nov 2009 16:05:32 -0500 Received: from mxout-08.mxes.net ([216.86.168.183]:39943 "EHLO mxout-08.mxes.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752938AbZKGVEU (ORCPT ); Sat, 7 Nov 2009 16:04:20 -0500 Received: from localhost.localdomain (unknown [86.53.68.233]) by smtp.mxes.net (Postfix) with ESMTPA id C68BB509DF; Sat, 7 Nov 2009 16:04:24 -0500 (EST) From: Alan Jenkins To: rusty@rustcorp.com.au Cc: linux-kernel@vger.kernel.org, linux-kbuild@vger.kernel.org, Tim Abbott , Alan Jenkins Subject: [PATCH 07/10] lib: Add generic binary search function to the kernel. Date: Sat, 7 Nov 2009 21:03:58 +0000 Message-Id: <1257627841-15817-7-git-send-email-alan-jenkins@tuffmail.co.uk> X-Mailer: git-send-email 1.6.3.3 In-Reply-To: <4AF5DF9F.5020208@tuffmail.co.uk> References: <4AF5DF9F.5020208@tuffmail.co.uk> Sender: linux-kbuild-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kbuild@vger.kernel.org diff --git a/include/linux/bsearch.h b/include/linux/bsearch.h new file mode 100644 index 0000000..90b1aa8 --- /dev/null +++ b/include/linux/bsearch.h @@ -0,0 +1,9 @@ +#ifndef _LINUX_BSEARCH_H +#define _LINUX_BSEARCH_H + +#include + +void *bsearch(const void *key, const void *base, size_t num, size_t size, + int (*cmp)(const void *key, const void *elt)); + +#endif /* _LINUX_BSEARCH_H */ diff --git a/lib/Makefile b/lib/Makefile index 2e78277..fb60af1 100644 --- a/lib/Makefile +++ b/lib/Makefile @@ -21,7 +21,7 @@ lib-y += kobject.o kref.o klist.o obj-y += bcd.o div64.o sort.o parser.o halfmd4.o debug_locks.o random32.o \ bust_spinlocks.o hexdump.o kasprintf.o bitmap.o scatterlist.o \ - string_helpers.o gcd.o + string_helpers.o gcd.o bsearch.o ifeq ($(CONFIG_DEBUG_KOBJECT),y) CFLAGS_kobject.o += -DDEBUG diff --git a/lib/bsearch.c b/lib/bsearch.c new file mode 100644 index 0000000..4297c98 --- /dev/null +++ b/lib/bsearch.c @@ -0,0 +1,53 @@ +/* + * A generic implementation of binary search for the Linux kernel + * + * Copyright (C) 2008-2009 Ksplice, Inc. + * Author: Tim Abbott + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License as + * published by the Free Software Foundation; version 2. + */ + +#include +#include + +/* + * bsearch - binary search an array of elements + * @key: pointer to item being searched for + * @base: pointer to data to sort + * @num: number of elements + * @size: size of each element + * @cmp: pointer to comparison function + * + * This function does a binary search on the given array. The + * contents of the array should already be in ascending sorted order + * under the provided comparison function. + * + * Note that the key need not have the same type as the elements in + * the array, e.g. key could be a string and the comparison function + * could compare the string with the struct's name field. However, if + * the key and elements in the array are of the same type, you can use + * the same comparison function for both sort() and bsearch(). + */ +void *bsearch(const void *key, const void *base, size_t num, size_t size, + int (*cmp)(const void *key, const void *elt)) +{ + int start = 0, end = num - 1, mid, result; + if (num == 0) + return NULL; + + while (start <= end) { + mid = (start + end) / 2; + result = cmp(key, base + mid * size); + if (result < 0) + end = mid - 1; + else if (result > 0) + start = mid + 1; + else + return (void *)base + mid * size; + } + + return NULL; +} +EXPORT_SYMBOL(bsearch);