1 /* 2 * A generic implementation of binary search for the Linux kernel 3 * 4 * Copyright (C) 2008-2009 Ksplice, Inc. 5 * Author: Tim Abbott <tabbott@ksplice.com> 6 * 7 * This program is free software; you can redistribute it and/or 8 * modify it under the terms of the GNU General Public License as 9 * published by the Free Software Foundation; version 2. 10 */ 11 12 #include <linux/export.h> 13 #include <linux/bsearch.h> 14 15 /* 16 * bsearch - binary search an array of elements 17 * @key: pointer to item being searched for 18 * @base: pointer to first element to search 19 * @num: number of elements 20 * @size: size of each element 21 * @cmp: pointer to comparison function 22 * 23 * This function does a binary search on the given array. The 24 * contents of the array should already be in ascending sorted order 25 * under the provided comparison function. 26 * 27 * Note that the key need not have the same type as the elements in 28 * the array, e.g. key could be a string and the comparison function 29 * could compare the string with the struct's name field. However, if 30 * the key and elements in the array are of the same type, you can use 31 * the same comparison function for both sort() and bsearch(). 32 */ bsearch(const void * key,const void * base,size_t num,size_t size,int (* cmp)(const void * key,const void * elt))33 void *bsearch(const void *key, const void *base, size_t num, size_t size, 34 int (*cmp)(const void *key, const void *elt)) 35 { 36 size_t start = 0, end = num; 37 int result; 38 39 while (start < end) { 40 size_t mid = start + (end - start) / 2; 41 42 result = cmp(key, base + mid * size); 43 if (result < 0) 44 end = mid; 45 else if (result > 0) 46 start = mid + 1; 47 else 48 return (void *)base + mid * size; 49 } 50 51 return NULL; 52 } 53 EXPORT_SYMBOL(bsearch); 54