1/* bit search implementation
 2 *
 3 * Copied from lib/find_bit.c to tools/lib/find_bit.c
 4 *
 5 * Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
 6 * Written by David Howells (dhowells@redhat.com)
 7 *
 8 * Copyright (C) 2008 IBM Corporation
 9 * 'find_last_bit' is written by Rusty Russell <rusty@rustcorp.com.au>
10 * (Inspired by David Howell's find_next_bit implementation)
11 *
12 * Rewritten by Yury Norov <yury.norov@gmail.com> to decrease
13 * size and improve performance, 2015.
14 *
15 * This program is free software; you can redistribute it and/or
16 * modify it under the terms of the GNU General Public License
17 * as published by the Free Software Foundation; either version
18 * 2 of the License, or (at your option) any later version.
19 */
20
21#include <linux/bitops.h>
22#include <linux/bitmap.h>
23#include <linux/kernel.h>
24
25#if !defined(find_next_bit)
26
27/*
28 * This is a common helper function for find_next_bit and
29 * find_next_zero_bit.  The difference is the "invert" argument, which
30 * is XORed with each fetched word before searching it for one bits.
31 */
32static unsigned long _find_next_bit(const unsigned long *addr,
33		unsigned long nbits, unsigned long start, unsigned long invert)
34{
35	unsigned long tmp;
36
37	if (!nbits || start >= nbits)
38		return nbits;
39
40	tmp = addr[start / BITS_PER_LONG] ^ invert;
41
42	/* Handle 1st word. */
43	tmp &= BITMAP_FIRST_WORD_MASK(start);
44	start = round_down(start, BITS_PER_LONG);
45
46	while (!tmp) {
47		start += BITS_PER_LONG;
48		if (start >= nbits)
49			return nbits;
50
51		tmp = addr[start / BITS_PER_LONG] ^ invert;
52	}
53
54	return min(start + __ffs(tmp), nbits);
55}
56#endif
57
58#ifndef find_next_bit
59/*
60 * Find the next set bit in a memory region.
61 */
62unsigned long find_next_bit(const unsigned long *addr, unsigned long size,
63			    unsigned long offset)
64{
65	return _find_next_bit(addr, size, offset, 0UL);
66}
67#endif
68
69#ifndef find_first_bit
70/*
71 * Find the first set bit in a memory region.
72 */
73unsigned long find_first_bit(const unsigned long *addr, unsigned long size)
74{
75	unsigned long idx;
76
77	for (idx = 0; idx * BITS_PER_LONG < size; idx++) {
78		if (addr[idx])
79			return min(idx * BITS_PER_LONG + __ffs(addr[idx]), size);
80	}
81
82	return size;
83}
84#endif