1 /* find_next_bit.c: fallback find next bit implementation
3 * Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
4 * Written by David Howells (dhowells@redhat.com)
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public License
8 * as published by the Free Software Foundation; either version
9 * 2 of the License, or (at your option) any later version.
12 #include <linux/bitops.h>
13 #include <linux/module.h>
14 #include <asm/types.h>
15 #include <asm/byteorder.h>
17 #define BITOP_WORD(nr) ((nr) / BITS_PER_LONG)
20 * Find the next set bit in a memory region.
22 unsigned long __find_next_bit(const unsigned long *addr,
23 unsigned long size, unsigned long offset)
25 const unsigned long *p = addr + BITOP_WORD(offset);
26 unsigned long result = offset & ~(BITS_PER_LONG-1);
32 offset %= BITS_PER_LONG;
35 tmp &= (~0UL << offset);
36 if (size < BITS_PER_LONG)
40 size -= BITS_PER_LONG;
41 result += BITS_PER_LONG;
43 while (size & ~(BITS_PER_LONG-1)) {
46 result += BITS_PER_LONG;
47 size -= BITS_PER_LONG;
54 tmp &= (~0UL >> (BITS_PER_LONG - size));
55 if (tmp == 0UL) /* Are any bits set? */
56 return result + size; /* Nope. */
58 return result + __ffs(tmp);
60 EXPORT_SYMBOL(__find_next_bit);
63 * This implementation of find_{first,next}_zero_bit was stolen from
64 * Linus' asm-alpha/bitops.h.
66 unsigned long __find_next_zero_bit(const unsigned long *addr,
67 unsigned long size, unsigned long offset)
69 const unsigned long *p = addr + BITOP_WORD(offset);
70 unsigned long result = offset & ~(BITS_PER_LONG-1);
76 offset %= BITS_PER_LONG;
79 tmp |= ~0UL >> (BITS_PER_LONG - offset);
80 if (size < BITS_PER_LONG)
84 size -= BITS_PER_LONG;
85 result += BITS_PER_LONG;
87 while (size & ~(BITS_PER_LONG-1)) {
90 result += BITS_PER_LONG;
91 size -= BITS_PER_LONG;
99 if (tmp == ~0UL) /* Are any bits zero? */
100 return result + size; /* Nope. */
102 return result + ffz(tmp);
104 EXPORT_SYMBOL(__find_next_zero_bit);
108 /* include/linux/byteorder does not support "unsigned long" type */
109 static inline unsigned long ext2_swabp(const unsigned long * x)
111 #if BITS_PER_LONG == 64
112 return (unsigned long) __swab64p((u64 *) x);
113 #elif BITS_PER_LONG == 32
114 return (unsigned long) __swab32p((u32 *) x);
116 #error BITS_PER_LONG not defined
120 /* include/linux/byteorder doesn't support "unsigned long" type */
121 static inline unsigned long ext2_swab(const unsigned long y)
123 #if BITS_PER_LONG == 64
124 return (unsigned long) __swab64((u64) y);
125 #elif BITS_PER_LONG == 32
126 return (unsigned long) __swab32((u32) y);
128 #error BITS_PER_LONG not defined
132 unsigned long generic_find_next_zero_le_bit(const unsigned long *addr, unsigned
133 long size, unsigned long offset)
135 const unsigned long *p = addr + BITOP_WORD(offset);
136 unsigned long result = offset & ~(BITS_PER_LONG - 1);
142 offset &= (BITS_PER_LONG - 1UL);
144 tmp = ext2_swabp(p++);
145 tmp |= (~0UL >> (BITS_PER_LONG - offset));
146 if (size < BITS_PER_LONG)
150 size -= BITS_PER_LONG;
151 result += BITS_PER_LONG;
154 while (size & ~(BITS_PER_LONG - 1)) {
156 goto found_middle_swap;
157 result += BITS_PER_LONG;
158 size -= BITS_PER_LONG;
165 if (tmp == ~0UL) /* Are any bits zero? */
166 return result + size; /* Nope. Skip ffz */
168 return result + ffz(tmp);
171 return result + ffz(ext2_swab(tmp));
174 EXPORT_SYMBOL(generic_find_next_zero_le_bit);
176 unsigned long generic_find_next_le_bit(const unsigned long *addr, unsigned
177 long size, unsigned long offset)
179 const unsigned long *p = addr + BITOP_WORD(offset);
180 unsigned long result = offset & ~(BITS_PER_LONG - 1);
186 offset &= (BITS_PER_LONG - 1UL);
188 tmp = ext2_swabp(p++);
189 tmp &= (~0UL << offset);
190 if (size < BITS_PER_LONG)
194 size -= BITS_PER_LONG;
195 result += BITS_PER_LONG;
198 while (size & ~(BITS_PER_LONG - 1)) {
201 goto found_middle_swap;
202 result += BITS_PER_LONG;
203 size -= BITS_PER_LONG;
209 tmp &= (~0UL >> (BITS_PER_LONG - size));
210 if (tmp == 0UL) /* Are any bits set? */
211 return result + size; /* Nope. */
213 return result + __ffs(tmp);
216 return result + __ffs(ext2_swab(tmp));
218 EXPORT_SYMBOL(generic_find_next_le_bit);
219 #endif /* __BIG_ENDIAN */