FreeBSD/Linux Kernel Cross Reference
sys/lib/bsearch.c

     /*
      * A generic implementation of binary search for the Linux kernel
      *
      * Copyright (C) 2008-2009 Ksplice, Inc.
      * Author: Tim Abbott <tabbott@ksplice.com>
      *
      * 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 <linux/export.h>
    #include <linux/bsearch.h>
    
    /*
     * 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);

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