Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755570Ab1DPN1H (ORCPT ); Sat, 16 Apr 2011 09:27:07 -0400 Received: from mail-ww0-f44.google.com ([74.125.82.44]:49434 "EHLO mail-ww0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752453Ab1DPN02 (ORCPT ); Sat, 16 Apr 2011 09:26:28 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=sender:from:to:cc:subject:date:message-id:x-mailer:in-reply-to :references:mime-version:content-type:content-transfer-encoding; b=aD/mLsXSrxgMwpt+6qwfyiecv17KBIN2/x7X0X0Lsp5ZcEq04h5ob2fIssKl96Oicq 4iIFpVC00LECxD8X/5pXyAgqNXXoIyOJJCtzfJv5P1OYsMWx7Iuk8LNmvzPEmF5DDhwJ MgJB1BFCu2esKhsuDyaLBkrqLFsSLYEMIAQxg= From: Alessio Igor Bogani To: Rusty Russell , Tim Abbott , Anders Kaseorg , Jason Wessel , Tim Bird Cc: LKML , Linux Embedded , Alessio Igor Bogani Subject: [PATCH 3/4] lib: Add generic binary search function to the kernel. Date: Sat, 16 Apr 2011 15:26:12 +0200 Message-Id: <1302960373-5309-4-git-send-email-abogani@kernel.org> X-Mailer: git-send-email 1.7.4.1 In-Reply-To: <1302960373-5309-1-git-send-email-abogani@kernel.org> References: <1302960373-5309-1-git-send-email-abogani@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4221 Lines: 122 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 Extra-bikeshedding-by: Alan Jenkins Extra-bikeshedding-by: André Goddard Rosa Extra-bikeshedding-by: Rusty Russell Signed-off-by: Rusty Russell Signed-off-by: Alessio Igor Bogani --- include/linux/bsearch.h | 9 ++++++++ lib/Makefile | 3 +- lib/bsearch.c | 53 +++++++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 64 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 ef0f285..4b49a24 100644 --- a/lib/Makefile +++ b/lib/Makefile @@ -21,7 +21,8 @@ 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 lcm.o list_sort.o uuid.o flex_array.o + string_helpers.o gcd.o lcm.o list_sort.o uuid.o flex_array.o \ + bsearch.o obj-y += kstrtox.o obj-$(CONFIG_TEST_KSTRTOX) += test-kstrtox.o diff --git a/lib/bsearch.c b/lib/bsearch.c new file mode 100644 index 0000000..5b54758 --- /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 first element to search + * @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)) +{ + size_t start = 0, end = num; + int result; + + while (start < end) { + size_t mid = start + (end - start) / 2; + + result = cmp(key, base + mid * size); + if (result < 0) + end = mid; + else if (result > 0) + start = mid + 1; + else + return (void *)base + mid * size; + } + + return NULL; +} +EXPORT_SYMBOL(bsearch); -- 1.7.4.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/