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/export.h>
15#include <asm/types.h>
16#include <asm/byteorder.h>
17
18#ifndef find_last_bit
19
20unsigned long find_last_bit(const unsigned long *addr, unsigned long size)
21{
22    unsigned long words;
23    unsigned long tmp;
24
25    /* Start at final word. */
26    words = size / BITS_PER_LONG;
27
28    /* Partial final word? */
29    if (size & (BITS_PER_LONG-1)) {
30        tmp = (addr[words] & (~0UL >> (BITS_PER_LONG
31                     - (size & (BITS_PER_LONG-1)))));
32        if (tmp)
33            goto found;
34    }
35
36    while (words) {
37        tmp = addr[--words];
38        if (tmp) {
39found:
40            return words * BITS_PER_LONG + __fls(tmp);
41        }
42    }
43
44    /* Not found */
45    return size;
46}
47EXPORT_SYMBOL(find_last_bit);
48
49#endif
50

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