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) || !defined(find_next_zero_bit) || \
 26		!defined(find_next_and_bit)
 27
 28/*
 29 * This is a common helper function for find_next_bit, find_next_zero_bit, and
 30 * find_next_and_bit. The differences are:
 31 *  - The "invert" argument, which is XORed with each fetched word before
 32 *    searching it for one bits.
 33 *  - The optional "addr2", which is anded with "addr1" if present.
 34 */
 35static inline unsigned long _find_next_bit(const unsigned long *addr1,
 36		const unsigned long *addr2, unsigned long nbits,
 37		unsigned long start, unsigned long invert)
 38{
 39	unsigned long tmp;
 40
 41	if (unlikely(start >= nbits))
 42		return nbits;
 43
 44	tmp = addr1[start / BITS_PER_LONG];
 45	if (addr2)
 46		tmp &= addr2[start / BITS_PER_LONG];
 47	tmp ^= invert;
 48
 49	/* Handle 1st word. */
 50	tmp &= BITMAP_FIRST_WORD_MASK(start);
 51	start = round_down(start, BITS_PER_LONG);
 52
 53	while (!tmp) {
 54		start += BITS_PER_LONG;
 55		if (start >= nbits)
 56			return nbits;
 57
 58		tmp = addr1[start / BITS_PER_LONG];
 59		if (addr2)
 60			tmp &= addr2[start / BITS_PER_LONG];
 61		tmp ^= invert;
 62	}
 63
 64	return min(start + __ffs(tmp), nbits);
 65}
 66#endif
 67
 68#ifndef find_next_bit
 69/*
 70 * Find the next set bit in a memory region.
 71 */
 72unsigned long find_next_bit(const unsigned long *addr, unsigned long size,
 73			    unsigned long offset)
 74{
 75	return _find_next_bit(addr, NULL, size, offset, 0UL);
 76}
 77#endif
 78
 79#ifndef find_first_bit
 80/*
 81 * Find the first set bit in a memory region.
 82 */
 83unsigned long find_first_bit(const unsigned long *addr, unsigned long size)
 84{
 85	unsigned long idx;
 86
 87	for (idx = 0; idx * BITS_PER_LONG < size; idx++) {
 88		if (addr[idx])
 89			return min(idx * BITS_PER_LONG + __ffs(addr[idx]), size);
 90	}
 91
 92	return size;
 93}
 94#endif
 95
 96#ifndef find_first_zero_bit
 97/*
 98 * Find the first cleared bit in a memory region.
 99 */
100unsigned long find_first_zero_bit(const unsigned long *addr, unsigned long size)
101{
102	unsigned long idx;
103
104	for (idx = 0; idx * BITS_PER_LONG < size; idx++) {
105		if (addr[idx] != ~0UL)
106			return min(idx * BITS_PER_LONG + ffz(addr[idx]), size);
107	}
108
109	return size;
110}
111#endif
112
113#ifndef find_next_zero_bit
114unsigned long find_next_zero_bit(const unsigned long *addr, unsigned long size,
115				 unsigned long offset)
116{
117	return _find_next_bit(addr, NULL, size, offset, ~0UL);
118}
119#endif
120
121#ifndef find_next_and_bit
122unsigned long find_next_and_bit(const unsigned long *addr1,
123		const unsigned long *addr2, unsigned long size,
124		unsigned long offset)
125{
126	return _find_next_bit(addr1, addr2, size, offset, 0UL);
127}
128#endif