1// SPDX-License-Identifier: GPL-2.0-or-later
  2/* bit search implementation
  3 *
  4 * Copied from lib/find_bit.c to tools/lib/find_bit.c
  5 *
  6 * Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
  7 * Written by David Howells (dhowells@redhat.com)
  8 *
  9 * Copyright (C) 2008 IBM Corporation
 10 * 'find_last_bit' is written by Rusty Russell <rusty@rustcorp.com.au>
 11 * (Inspired by David Howell's find_next_bit implementation)
 12 *
 13 * Rewritten by Yury Norov <yury.norov@gmail.com> to decrease
 14 * size and improve performance, 2015.
 15 */
 16
 17#include <linux/bitops.h>
 18#include <linux/bitmap.h>
 19#include <linux/kernel.h>
 20
 21#if !defined(find_next_bit) || !defined(find_next_zero_bit) || \
 22		!defined(find_next_and_bit)
 23
 24/*
 25 * This is a common helper function for find_next_bit, find_next_zero_bit, and
 26 * find_next_and_bit. The differences are:
 27 *  - The "invert" argument, which is XORed with each fetched word before
 28 *    searching it for one bits.
 29 *  - The optional "addr2", which is anded with "addr1" if present.
 30 */
 31static inline unsigned long _find_next_bit(const unsigned long *addr1,
 32		const unsigned long *addr2, unsigned long nbits,
 33		unsigned long start, unsigned long invert)
 34{
 35	unsigned long tmp;
 36
 37	if (unlikely(start >= nbits))
 38		return nbits;
 39
 40	tmp = addr1[start / BITS_PER_LONG];
 41	if (addr2)
 42		tmp &= addr2[start / BITS_PER_LONG];
 43	tmp ^= invert;
 44
 45	/* Handle 1st word. */
 46	tmp &= BITMAP_FIRST_WORD_MASK(start);
 47	start = round_down(start, BITS_PER_LONG);
 48
 49	while (!tmp) {
 50		start += BITS_PER_LONG;
 51		if (start >= nbits)
 52			return nbits;
 53
 54		tmp = addr1[start / BITS_PER_LONG];
 55		if (addr2)
 56			tmp &= addr2[start / BITS_PER_LONG];
 57		tmp ^= invert;
 58	}
 59
 60	return min(start + __ffs(tmp), nbits);
 61}
 62#endif
 63
 64#ifndef find_next_bit
 65/*
 66 * Find the next set bit in a memory region.
 67 */
 68unsigned long find_next_bit(const unsigned long *addr, unsigned long size,
 69			    unsigned long offset)
 70{
 71	return _find_next_bit(addr, NULL, size, offset, 0UL);
 72}
 73#endif
 74
 75#ifndef find_first_bit
 76/*
 77 * Find the first set bit in a memory region.
 78 */
 79unsigned long find_first_bit(const unsigned long *addr, unsigned long size)
 80{
 81	unsigned long idx;
 82
 83	for (idx = 0; idx * BITS_PER_LONG < size; idx++) {
 84		if (addr[idx])
 85			return min(idx * BITS_PER_LONG + __ffs(addr[idx]), size);
 86	}
 87
 88	return size;
 89}
 90#endif
 91
 92#ifndef find_first_zero_bit
 93/*
 94 * Find the first cleared bit in a memory region.
 95 */
 96unsigned long find_first_zero_bit(const unsigned long *addr, unsigned long size)
 97{
 98	unsigned long idx;
 99
100	for (idx = 0; idx * BITS_PER_LONG < size; idx++) {
101		if (addr[idx] != ~0UL)
102			return min(idx * BITS_PER_LONG + ffz(addr[idx]), size);
103	}
104
105	return size;
106}
107#endif
108
109#ifndef find_next_zero_bit
110unsigned long find_next_zero_bit(const unsigned long *addr, unsigned long size,
111				 unsigned long offset)
112{
113	return _find_next_bit(addr, NULL, size, offset, ~0UL);
114}
115#endif
116
117#ifndef find_next_and_bit
118unsigned long find_next_and_bit(const unsigned long *addr1,
119		const unsigned long *addr2, unsigned long size,
120		unsigned long offset)
121{
122	return _find_next_bit(addr1, addr2, size, offset, 0UL);
123}
124#endif