From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756388AbZKCKI5 (ORCPT ); Tue, 3 Nov 2009 05:08:57 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756234AbZKCKI4 (ORCPT ); Tue, 3 Nov 2009 05:08:56 -0500 Received: from mxout-08.mxes.net ([216.86.168.183]:22379 "EHLO mxout-08.mxes.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756226AbZKCKIz (ORCPT ); Tue, 3 Nov 2009 05:08:55 -0500 From: Alan Jenkins To: greg@kroah.com Cc: linux-kbuild@vger.kernel.org, carmelo73@gmail.com, linux-kernel@vger.kernel.org, rusty@rustcorp.com.au, Tim Abbott , Alan Jenkins Subject: [PATCH 07/10] lib: Add generic binary search function to the kernel. Date: Tue, 3 Nov 2009 10:06:19 +0000 Message-Id: <1257242782-10496-8-git-send-email-alan-jenkins@tuffmail.co.uk> X-Mailer: git-send-email 1.6.3.2 In-Reply-To: <9b2b86520911020852q49c55695rb05d87090fa9ad33@mail.gmail.com> References: <9b2b86520911020852q49c55695rb05d87090fa9ad33@mail.gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Tim Abbott 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 Signed-off-by: Alan Jenkins --- 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); -- 1.6.3.2