1a94dc35bc
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 <tabbott@ksplice.com> Extra-bikeshedding-by: Alan Jenkins <alan-jenkins@tuffmail.co.uk> Extra-bikeshedding-by: André Goddard Rosa <andre.goddard@gmail.com> Extra-bikeshedding-by: Rusty Russell <rusty@rustcorp.com.au> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Signed-off-by: Alessio Igor Bogani <abogani@kernel.org> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
53 lines
1.6 KiB
C
53 lines
1.6 KiB
C
/*
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* A generic implementation of binary search for the Linux kernel
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*
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* Copyright (C) 2008-2009 Ksplice, Inc.
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* Author: Tim Abbott <tabbott@ksplice.com>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation; version 2.
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*/
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#include <linux/module.h>
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#include <linux/bsearch.h>
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/*
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* bsearch - binary search an array of elements
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* @key: pointer to item being searched for
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* @base: pointer to first element to search
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* @num: number of elements
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* @size: size of each element
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* @cmp: pointer to comparison function
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*
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* This function does a binary search on the given array. The
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* contents of the array should already be in ascending sorted order
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* under the provided comparison function.
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*
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* Note that the key need not have the same type as the elements in
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* the array, e.g. key could be a string and the comparison function
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* could compare the string with the struct's name field. However, if
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* the key and elements in the array are of the same type, you can use
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* the same comparison function for both sort() and bsearch().
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*/
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void *bsearch(const void *key, const void *base, size_t num, size_t size,
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int (*cmp)(const void *key, const void *elt))
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{
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size_t start = 0, end = num;
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int result;
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while (start < end) {
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size_t mid = start + (end - start) / 2;
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result = cmp(key, base + mid * size);
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if (result < 0)
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end = mid;
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else if (result > 0)
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start = mid + 1;
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else
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return (void *)base + mid * size;
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}
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return NULL;
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}
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EXPORT_SYMBOL(bsearch);
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