From patchwork Wed Sep 23 17:28:45 2009 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Tim Abbott X-Patchwork-Id: 49578 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 n8NHTl17018207 for ; Wed, 23 Sep 2009 17:29:47 GMT Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751767AbZIWR3n (ORCPT ); Wed, 23 Sep 2009 13:29:43 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751463AbZIWR3m (ORCPT ); Wed, 23 Sep 2009 13:29:42 -0400 Received: from BISCAYNE-ONE-STATION.MIT.EDU ([18.7.7.80]:44945 "EHLO biscayne-one-station.mit.edu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751296AbZIWR3l (ORCPT ); Wed, 23 Sep 2009 13:29:41 -0400 Received: from outgoing.mit.edu (OUTGOING-AUTH.MIT.EDU [18.7.22.103]) by biscayne-one-station.mit.edu (8.13.6/8.9.2) with ESMTP id n8NHTerC006749; Wed, 23 Sep 2009 13:29:41 -0400 (EDT) Received: from localhost (c-71-192-160-118.hsd1.nh.comcast.net [71.192.160.118]) (authenticated bits=0) (User authenticated as tabbott@ATHENA.MIT.EDU) by outgoing.mit.edu (8.13.6/8.12.4) with ESMTP id n8NHTe6O028198; Wed, 23 Sep 2009 13:29:40 -0400 (EDT) From: Tim Abbott To: Alan Jenkins Cc: Linux Kernel Mailing List , rusty@rustcorp.com.au, linux-kbuild@vger.kernel.org, linux-modules@vger.kernel.org, Tim Abbott Subject: [PATCH 1/2] lib: Add generic binary search function to the kernel. Date: Wed, 23 Sep 2009 13:28:45 -0400 Message-Id: <1253726926-5504-2-git-send-email-tabbott@ksplice.com> X-Mailer: git-send-email 1.6.3.3 In-Reply-To: <1253626718-18887-5-git-send-email-alan-jenkins@tuffmail.co.uk> References: <1253626718-18887-5-git-send-email-alan-jenkins@tuffmail.co.uk> X-Scanned-By: MIMEDefang 2.42 X-Spam-Flag: NO X-Spam-Score: 0.00 Sender: linux-kbuild-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kbuild@vger.kernel.org There a large number hand-coded binary searches in the kernel (run "git grep search | grep binary" to find many of them). Since in my experience, hand-coding binary searches can be error-prone, it seems worth cleaning this up by providing a generic binary search function. This generic binary search implementation comes from Ksplice. It has the same basic API as the C library bsearch() function. Ksplice uses it in half a dozen places with 4 different comparison functions, and I think our code is substantially cleaner because of this. Signed-off-by: Tim Abbott --- include/linux/bsearch.h | 9 ++++++++ lib/Makefile | 2 +- lib/bsearch.c | 53 +++++++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 63 insertions(+), 1 deletions(-) create mode 100644 include/linux/bsearch.h create mode 100644 lib/bsearch.c 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);