LXR linux/lib/find_last

   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