text: /* find_next_bit.c: fallback find next bit implementation
   *
   * Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
   * Written by David Howells (dhowells@redhat.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; either version
   * 2 of the License, or (at your option) any later version.
   */
  
  #include <linux/types.h>
  #include <linux/bitops.h>
  
  #define BITOP_WORD(nr)		((nr) / BITS_PER_LONG)
  
  /*
   * Find the next set bit in a memory region.
   */
  unsigned long find_next_bit(const unsigned long *addr, unsigned long size,
  			    unsigned long offset)
  {
  	const unsigned long *p = addr + BITOP_WORD(offset);
  	unsigned long result = offset & ~(BITS_PER_LONG-1);
  	unsigned long tmp;
  
  	if (offset >= size)
  		return size;
  	size -= result;
  	offset %= BITS_PER_LONG;
  	if (offset) {
  		tmp = *(p++);
  		tmp &= (~0UL << offset);
  		if (size < BITS_PER_LONG)
  			goto found_first;
  		if (tmp)
  			goto found_middle;
  		size -= BITS_PER_LONG;
  		result += BITS_PER_LONG;
  	}
  	while (size & ~(BITS_PER_LONG-1)) {
  		if ((tmp = *(p++)))
  			goto found_middle;
  		result += BITS_PER_LONG;
  		size -= BITS_PER_LONG;
  	}
  	if (!size)
  		return result;
  	tmp = *p;
  
  found_first:
  	tmp &= (~0UL >> (BITS_PER_LONG - size));
  	if (tmp == 0UL)		/* Are any bits set? */
  		return result + size;	/* Nope. */
  found_middle:
  	return result + __ffs(tmp);
  }
  