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
 85
 86#ifndef find_first_zero_bit
 87/*
 88 * Find the first cleared bit in a memory region.
 89 */
 90unsigned long find_first_zero_bit(const unsigned long *addr, unsigned long size)
 91{
 92	unsigned long idx;
 93
 94	for (idx = 0; idx * BITS_PER_LONG < size; idx++) {
 95		if (addr[idx] != ~0UL)
 96			return min(idx * BITS_PER_LONG + ffz(addr[idx]), size);
 97	}
 98
 99	return size;
100}
101#endif
102
103#ifndef find_next_zero_bit
104unsigned long find_next_zero_bit(const unsigned long *addr, unsigned long size,
105				 unsigned long offset)
106{
107	return _find_next_bit(addr, size, offset, ~0UL);
108}
109#endif