LXR linux/lib/bsearch.c

   1// SPDX-License-Identifier: GPL-2.0-only
   2/*
   3 * A generic implementation of binary search for the Linux kernel
   4 *
   5 * Copyright (C) 2008-2009 Ksplice, Inc.
   6 * Author: Tim Abbott <tabbott@ksplice.com>
   7 */
   8
   9#include <linux/export.h>
  10#include <linux/bsearch.h>
  11#include <linux/kprobes.h>
  12
  13/*
  14 * bsearch - binary search an array of elements
  15 * @key: pointer to item being searched for
  16 * @base: pointer to first element to search
  17 * @num: number of elements
  18 * @size: size of each element
  19 * @cmp: pointer to comparison function
  20 *
  21 * This function does a binary search on the given array.  The
  22 * contents of the array should already be in ascending sorted order
  23 * under the provided comparison function.
  24 *
  25 * Note that the key need not have the same type as the elements in
  26 * the array, e.g. key could be a string and the comparison function
  27 * could compare the string with the struct's name field.  However, if
  28 * the key and elements in the array are of the same type, you can use
  29 * the same comparison function for both sort() and bsearch().
  30 */
  31void *bsearch(const void *key, const void *base, size_t num, size_t size,
  32              int (*cmp)(const void *key, const void *elt))
  33{
  34        const char *pivot;
  35        int result;
  36
  37        while (num > 0) {
  38                pivot = base + (num >> 1) * size;
  39                result = cmp(key, pivot);
  40
  41                if (result == 0)
  42                        return (void *)pivot;
  43
  44                if (result > 0) {
  45                        base = pivot + size;
  46                        num--;
  47                }
  48                num >>= 1;
  49        }
  50
  51        return NULL;
  52}
  53EXPORT_SYMBOL(bsearch);
  54NOKPROBE_SYMBOL(bsearch);
  55