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
 26/*
 27 * This is a common helper function for find_next_bit and
 28 * find_next_zero_bit.  The difference is the "invert" argument, which
 29 * is XORed with each fetched word before searching it for one bits.
 30 */
 31static unsigned long _find_next_bit(const unsigned long *addr,
 32		unsigned long nbits, unsigned long start, unsigned long invert)
 33{
 34	unsigned long tmp;
 35
 36	if (!nbits || start >= nbits)
 37		return nbits;
 38
 39	tmp = addr[start / BITS_PER_LONG] ^ invert;
 40
 41	/* Handle 1st word. */
 42	tmp &= BITMAP_FIRST_WORD_MASK(start);
 43	start = round_down(start, BITS_PER_LONG);
 44
 45	while (!tmp) {
 46		start += BITS_PER_LONG;
 47		if (start >= nbits)
 48			return nbits;
 49
 50		tmp = addr[start / BITS_PER_LONG] ^ invert;
 51	}
 52
 53	return min(start + __ffs(tmp), nbits);
 54}
 55#endif
 56
 57#ifndef find_next_bit
 58/*
 59 * Find the next set bit in a memory region.
 60 */
 61unsigned long find_next_bit(const unsigned long *addr, unsigned long size,
 62			    unsigned long offset)
 63{
 64	return _find_next_bit(addr, size, offset, 0UL);
 65}
 66EXPORT_SYMBOL(find_next_bit);
 67#endif
 68
 69#ifndef find_next_zero_bit
 70unsigned long find_next_zero_bit(const unsigned long *addr, unsigned long size,
 71				 unsigned long offset)
 72{
 73	return _find_next_bit(addr, size, offset, ~0UL);
 74}
 75EXPORT_SYMBOL(find_next_zero_bit);
 76#endif
 77
 78#ifndef find_first_bit
 79/*
 80 * Find the first set bit in a memory region.
 81 */
 82unsigned long find_first_bit(const unsigned long *addr, unsigned long size)
 83{
 84	unsigned long idx;
 85
 86	for (idx = 0; idx * BITS_PER_LONG < size; idx++) {
 87		if (addr[idx])
 88			return min(idx * BITS_PER_LONG + __ffs(addr[idx]), size);
 89	}
 90
 91	return size;
 92}
 93EXPORT_SYMBOL(find_first_bit);
 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}
111EXPORT_SYMBOL(find_first_zero_bit);
112#endif
113
114#ifndef find_last_bit
115unsigned long find_last_bit(const unsigned long *addr, unsigned long size)
116{
117	if (size) {
118		unsigned long val = BITMAP_LAST_WORD_MASK(size);
119		unsigned long idx = (size-1) / BITS_PER_LONG;
120
121		do {
122			val &= addr[idx];
123			if (val)
124				return idx * BITS_PER_LONG + __fls(val);
125
126			val = ~0ul;
127		} while (idx--);
128	}
129	return size;
130}
131EXPORT_SYMBOL(find_last_bit);
132#endif
133
134#ifdef __BIG_ENDIAN
135
136/* include/linux/byteorder does not support "unsigned long" type */
137static inline unsigned long ext2_swab(const unsigned long y)
138{
139#if BITS_PER_LONG == 64
140	return (unsigned long) __swab64((u64) y);
141#elif BITS_PER_LONG == 32
142	return (unsigned long) __swab32((u32) y);
143#else
144#error BITS_PER_LONG not defined
145#endif
146}
147
148#if !defined(find_next_bit_le) || !defined(find_next_zero_bit_le)
149static unsigned long _find_next_bit_le(const unsigned long *addr,
150		unsigned long nbits, unsigned long start, unsigned long invert)
151{
152	unsigned long tmp;
153
154	if (!nbits || start >= nbits)
155		return nbits;
156
157	tmp = addr[start / BITS_PER_LONG] ^ invert;
158
159	/* Handle 1st word. */
160	tmp &= ext2_swab(BITMAP_FIRST_WORD_MASK(start));
161	start = round_down(start, BITS_PER_LONG);
162
163	while (!tmp) {
164		start += BITS_PER_LONG;
165		if (start >= nbits)
166			return nbits;
167
168		tmp = addr[start / BITS_PER_LONG] ^ invert;
169	}
170
171	return min(start + __ffs(ext2_swab(tmp)), nbits);
172}
173#endif
174
175#ifndef find_next_zero_bit_le
176unsigned long find_next_zero_bit_le(const void *addr, unsigned
177		long size, unsigned long offset)
178{
179	return _find_next_bit_le(addr, size, offset, ~0UL);
180}
181EXPORT_SYMBOL(find_next_zero_bit_le);
182#endif
183
184#ifndef find_next_bit_le
185unsigned long find_next_bit_le(const void *addr, unsigned
186		long size, unsigned long offset)
187{
188	return _find_next_bit_le(addr, size, offset, 0UL);
189}
190EXPORT_SYMBOL(find_next_bit_le);
191#endif
192
193#endif /* __BIG_ENDIAN */