1/* bit search implementation
  2 *
  3 * Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
  4 * Written by David Howells (dhowells@redhat.com)
  5 *
  6 * Copyright (C) 2008 IBM Corporation
  7 * 'find_last_bit' is written by Rusty Russell <rusty@rustcorp.com.au>
  8 * (Inspired by David Howell's find_next_bit implementation)
  9 *
 10 * Rewritten by Yury Norov <yury.norov@gmail.com> to decrease
 11 * size and improve performance, 2015.
 12 *
 13 * This program is free software; you can redistribute it and/or
 14 * modify it under the terms of the GNU General Public License
 15 * as published by the Free Software Foundation; either version
 16 * 2 of the License, or (at your option) any later version.
 17 */
 18
 19#include <linux/bitops.h>
 20#include <linux/bitmap.h>
 21#include <linux/export.h>
 22#include <linux/kernel.h>
 23
 24#if !defined(find_next_bit) || !defined(find_next_zero_bit) || \
 25		!defined(find_next_and_bit)
 26
 27/*
 28 * This is a common helper function for find_next_bit, find_next_zero_bit, and
 29 * find_next_and_bit. The differences are:
 30 *  - The "invert" argument, which is XORed with each fetched word before
 31 *    searching it for one bits.
 32 *  - The optional "addr2", which is anded with "addr1" if present.
 33 */
 34static inline unsigned long _find_next_bit(const unsigned long *addr1,
 35		const unsigned long *addr2, unsigned long nbits,
 36		unsigned long start, unsigned long invert)
 37{
 38	unsigned long tmp;
 39
 40	if (unlikely(start >= nbits))
 41		return nbits;
 42
 43	tmp = addr1[start / BITS_PER_LONG];
 44	if (addr2)
 45		tmp &= addr2[start / BITS_PER_LONG];
 46	tmp ^= invert;
 47
 48	/* Handle 1st word. */
 49	tmp &= BITMAP_FIRST_WORD_MASK(start);
 50	start = round_down(start, BITS_PER_LONG);
 51
 52	while (!tmp) {
 53		start += BITS_PER_LONG;
 54		if (start >= nbits)
 55			return nbits;
 56
 57		tmp = addr1[start / BITS_PER_LONG];
 58		if (addr2)
 59			tmp &= addr2[start / BITS_PER_LONG];
 60		tmp ^= invert;
 61	}
 62
 63	return min(start + __ffs(tmp), nbits);
 64}
 65#endif
 66
 67#ifndef find_next_bit
 68/*
 69 * Find the next set bit in a memory region.
 70 */
 71unsigned long find_next_bit(const unsigned long *addr, unsigned long size,
 72			    unsigned long offset)
 73{
 74	return _find_next_bit(addr, NULL, size, offset, 0UL);
 75}
 76EXPORT_SYMBOL(find_next_bit);
 77#endif
 78
 79#ifndef find_next_zero_bit
 80unsigned long find_next_zero_bit(const unsigned long *addr, unsigned long size,
 81				 unsigned long offset)
 82{
 83	return _find_next_bit(addr, NULL, size, offset, ~0UL);
 84}
 85EXPORT_SYMBOL(find_next_zero_bit);
 86#endif
 87
 88#if !defined(find_next_and_bit)
 89unsigned long find_next_and_bit(const unsigned long *addr1,
 90		const unsigned long *addr2, unsigned long size,
 91		unsigned long offset)
 92{
 93	return _find_next_bit(addr1, addr2, size, offset, 0UL);
 94}
 95EXPORT_SYMBOL(find_next_and_bit);
 96#endif
 97
 98#ifndef find_first_bit
 99/*
100 * Find the first set bit in a memory region.
101 */
102unsigned long find_first_bit(const unsigned long *addr, unsigned long size)
103{
104	unsigned long idx;
105
106	for (idx = 0; idx * BITS_PER_LONG < size; idx++) {
107		if (addr[idx])
108			return min(idx * BITS_PER_LONG + __ffs(addr[idx]), size);
109	}
110
111	return size;
112}
113EXPORT_SYMBOL(find_first_bit);
114#endif
115
116#ifndef find_first_zero_bit
117/*
118 * Find the first cleared bit in a memory region.
119 */
120unsigned long find_first_zero_bit(const unsigned long *addr, unsigned long size)
121{
122	unsigned long idx;
123
124	for (idx = 0; idx * BITS_PER_LONG < size; idx++) {
125		if (addr[idx] != ~0UL)
126			return min(idx * BITS_PER_LONG + ffz(addr[idx]), size);
127	}
128
129	return size;
130}
131EXPORT_SYMBOL(find_first_zero_bit);
132#endif
133
134#ifndef find_last_bit
135unsigned long find_last_bit(const unsigned long *addr, unsigned long size)
136{
137	if (size) {
138		unsigned long val = BITMAP_LAST_WORD_MASK(size);
139		unsigned long idx = (size-1) / BITS_PER_LONG;
140
141		do {
142			val &= addr[idx];
143			if (val)
144				return idx * BITS_PER_LONG + __fls(val);
145
146			val = ~0ul;
147		} while (idx--);
148	}
149	return size;
150}
151EXPORT_SYMBOL(find_last_bit);
152#endif
153
154#ifdef __BIG_ENDIAN
155
156/* include/linux/byteorder does not support "unsigned long" type */
157static inline unsigned long ext2_swab(const unsigned long y)
158{
159#if BITS_PER_LONG == 64
160	return (unsigned long) __swab64((u64) y);
161#elif BITS_PER_LONG == 32
162	return (unsigned long) __swab32((u32) y);
163#else
164#error BITS_PER_LONG not defined
165#endif
166}
167
168#if !defined(find_next_bit_le) || !defined(find_next_zero_bit_le)
169static inline unsigned long _find_next_bit_le(const unsigned long *addr1,
170		const unsigned long *addr2, unsigned long nbits,
171		unsigned long start, unsigned long invert)
172{
173	unsigned long tmp;
174
175	if (unlikely(start >= nbits))
176		return nbits;
177
178	tmp = addr1[start / BITS_PER_LONG];
179	if (addr2)
180		tmp &= addr2[start / BITS_PER_LONG];
181	tmp ^= invert;
182
183	/* Handle 1st word. */
184	tmp &= ext2_swab(BITMAP_FIRST_WORD_MASK(start));
185	start = round_down(start, BITS_PER_LONG);
186
187	while (!tmp) {
188		start += BITS_PER_LONG;
189		if (start >= nbits)
190			return nbits;
191
192		tmp = addr1[start / BITS_PER_LONG];
193		if (addr2)
194			tmp &= addr2[start / BITS_PER_LONG];
195		tmp ^= invert;
196	}
197
198	return min(start + __ffs(ext2_swab(tmp)), nbits);
199}
200#endif
201
202#ifndef find_next_zero_bit_le
203unsigned long find_next_zero_bit_le(const void *addr, unsigned
204		long size, unsigned long offset)
205{
206	return _find_next_bit_le(addr, NULL, size, offset, ~0UL);
207}
208EXPORT_SYMBOL(find_next_zero_bit_le);
209#endif
210
211#ifndef find_next_bit_le
212unsigned long find_next_bit_le(const void *addr, unsigned
213		long size, unsigned long offset)
214{
215	return _find_next_bit_le(addr, NULL, size, offset, 0UL);
216}
217EXPORT_SYMBOL(find_next_bit_le);
218#endif
219
220#endif /* __BIG_ENDIAN */