Root/lib/find_last_bit.c

1/* find_last_bit.c: fallback find next bit implementation
2 *
3 * Copyright (C) 2008 IBM Corporation
4 * Written by Rusty Russell <rusty@rustcorp.com.au>
5 * (Inspired by David Howell's find_next_bit implementation)
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
9 * as published by the Free Software Foundation; either version
10 * 2 of the License, or (at your option) any later version.
11 */
12
13#include <linux/bitops.h>
14#include <linux/module.h>
15#include <asm/types.h>
16#include <asm/byteorder.h>
17
18unsigned long find_last_bit(const unsigned long *addr, unsigned long size)
19{
20    unsigned long words;
21    unsigned long tmp;
22
23    /* Start at final word. */
24    words = size / BITS_PER_LONG;
25
26    /* Partial final word? */
27    if (size & (BITS_PER_LONG-1)) {
28        tmp = (addr[words] & (~0UL >> (BITS_PER_LONG
29                     - (size & (BITS_PER_LONG-1)))));
30        if (tmp)
31            goto found;
32    }
33
34    while (words) {
35        tmp = addr[--words];
36        if (tmp) {
37found:
38            return words * BITS_PER_LONG + __fls(tmp);
39        }
40    }
41
42    /* Not found */
43    return size;
44}
45EXPORT_SYMBOL(find_last_bit);
46

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