xref: /linux/lib/find_bit.c (revision 36ec807b627b4c0a0a382f0ae48eac7187d14b2b)
1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* bit search implementation
3  *
4  * Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
5  * Written by David Howells (dhowells@redhat.com)
6  *
7  * Copyright (C) 2008 IBM Corporation
8  * 'find_last_bit' is written by Rusty Russell <rusty@rustcorp.com.au>
9  * (Inspired by David Howell's find_next_bit implementation)
10  *
11  * Rewritten by Yury Norov <yury.norov@gmail.com> to decrease
12  * size and improve performance, 2015.
13  */
14 
15 #include <linux/bitops.h>
16 #include <linux/bitmap.h>
17 #include <linux/export.h>
18 #include <linux/math.h>
19 #include <linux/minmax.h>
20 #include <linux/swab.h>
21 
22 /*
23  * Common helper for find_bit() function family
24  * @FETCH: The expression that fetches and pre-processes each word of bitmap(s)
25  * @MUNGE: The expression that post-processes a word containing found bit (may be empty)
26  * @size: The bitmap size in bits
27  */
28 #define FIND_FIRST_BIT(FETCH, MUNGE, size)					\
29 ({										\
30 	unsigned long idx, val, sz = (size);					\
31 										\
32 	for (idx = 0; idx * BITS_PER_LONG < sz; idx++) {			\
33 		val = (FETCH);							\
34 		if (val) {							\
35 			sz = min(idx * BITS_PER_LONG + __ffs(MUNGE(val)), sz);	\
36 			break;							\
37 		}								\
38 	}									\
39 										\
40 	sz;									\
41 })
42 
43 /*
44  * Common helper for find_next_bit() function family
45  * @FETCH: The expression that fetches and pre-processes each word of bitmap(s)
46  * @MUNGE: The expression that post-processes a word containing found bit (may be empty)
47  * @size: The bitmap size in bits
48  * @start: The bitnumber to start searching at
49  */
50 #define FIND_NEXT_BIT(FETCH, MUNGE, size, start)				\
51 ({										\
52 	unsigned long mask, idx, tmp, sz = (size), __start = (start);		\
53 										\
54 	if (unlikely(__start >= sz))						\
55 		goto out;							\
56 										\
57 	mask = MUNGE(BITMAP_FIRST_WORD_MASK(__start));				\
58 	idx = __start / BITS_PER_LONG;						\
59 										\
60 	for (tmp = (FETCH) & mask; !tmp; tmp = (FETCH)) {			\
61 		if ((idx + 1) * BITS_PER_LONG >= sz)				\
62 			goto out;						\
63 		idx++;								\
64 	}									\
65 										\
66 	sz = min(idx * BITS_PER_LONG + __ffs(MUNGE(tmp)), sz);			\
67 out:										\
68 	sz;									\
69 })
70 
71 #define FIND_NTH_BIT(FETCH, size, num)						\
72 ({										\
73 	unsigned long sz = (size), nr = (num), idx, w, tmp;			\
74 										\
75 	for (idx = 0; (idx + 1) * BITS_PER_LONG <= sz; idx++) {			\
76 		if (idx * BITS_PER_LONG + nr >= sz)				\
77 			goto out;						\
78 										\
79 		tmp = (FETCH);							\
80 		w = hweight_long(tmp);						\
81 		if (w > nr)							\
82 			goto found;						\
83 										\
84 		nr -= w;							\
85 	}									\
86 										\
87 	if (sz % BITS_PER_LONG)							\
88 		tmp = (FETCH) & BITMAP_LAST_WORD_MASK(sz);			\
89 found:										\
90 	sz = idx * BITS_PER_LONG + fns(tmp, nr);				\
91 out:										\
92 	sz;									\
93 })
94 
95 #ifndef find_first_bit
96 /*
97  * Find the first set bit in a memory region.
98  */
99 unsigned long _find_first_bit(const unsigned long *addr, unsigned long size)
100 {
101 	return FIND_FIRST_BIT(addr[idx], /* nop */, size);
102 }
103 EXPORT_SYMBOL(_find_first_bit);
104 #endif
105 
106 #ifndef find_first_and_bit
107 /*
108  * Find the first set bit in two memory regions.
109  */
110 unsigned long _find_first_and_bit(const unsigned long *addr1,
111 				  const unsigned long *addr2,
112 				  unsigned long size)
113 {
114 	return FIND_FIRST_BIT(addr1[idx] & addr2[idx], /* nop */, size);
115 }
116 EXPORT_SYMBOL(_find_first_and_bit);
117 #endif
118 
119 /*
120  * Find the first set bit in three memory regions.
121  */
122 unsigned long _find_first_and_and_bit(const unsigned long *addr1,
123 				      const unsigned long *addr2,
124 				      const unsigned long *addr3,
125 				      unsigned long size)
126 {
127 	return FIND_FIRST_BIT(addr1[idx] & addr2[idx] & addr3[idx], /* nop */, size);
128 }
129 EXPORT_SYMBOL(_find_first_and_and_bit);
130 
131 #ifndef find_first_zero_bit
132 /*
133  * Find the first cleared bit in a memory region.
134  */
135 unsigned long _find_first_zero_bit(const unsigned long *addr, unsigned long size)
136 {
137 	return FIND_FIRST_BIT(~addr[idx], /* nop */, size);
138 }
139 EXPORT_SYMBOL(_find_first_zero_bit);
140 #endif
141 
142 #ifndef find_next_bit
143 unsigned long _find_next_bit(const unsigned long *addr, unsigned long nbits, unsigned long start)
144 {
145 	return FIND_NEXT_BIT(addr[idx], /* nop */, nbits, start);
146 }
147 EXPORT_SYMBOL(_find_next_bit);
148 #endif
149 
150 unsigned long __find_nth_bit(const unsigned long *addr, unsigned long size, unsigned long n)
151 {
152 	return FIND_NTH_BIT(addr[idx], size, n);
153 }
154 EXPORT_SYMBOL(__find_nth_bit);
155 
156 unsigned long __find_nth_and_bit(const unsigned long *addr1, const unsigned long *addr2,
157 				 unsigned long size, unsigned long n)
158 {
159 	return FIND_NTH_BIT(addr1[idx] & addr2[idx], size, n);
160 }
161 EXPORT_SYMBOL(__find_nth_and_bit);
162 
163 unsigned long __find_nth_andnot_bit(const unsigned long *addr1, const unsigned long *addr2,
164 				 unsigned long size, unsigned long n)
165 {
166 	return FIND_NTH_BIT(addr1[idx] & ~addr2[idx], size, n);
167 }
168 EXPORT_SYMBOL(__find_nth_andnot_bit);
169 
170 unsigned long __find_nth_and_andnot_bit(const unsigned long *addr1,
171 					const unsigned long *addr2,
172 					const unsigned long *addr3,
173 					unsigned long size, unsigned long n)
174 {
175 	return FIND_NTH_BIT(addr1[idx] & addr2[idx] & ~addr3[idx], size, n);
176 }
177 EXPORT_SYMBOL(__find_nth_and_andnot_bit);
178 
179 #ifndef find_next_and_bit
180 unsigned long _find_next_and_bit(const unsigned long *addr1, const unsigned long *addr2,
181 					unsigned long nbits, unsigned long start)
182 {
183 	return FIND_NEXT_BIT(addr1[idx] & addr2[idx], /* nop */, nbits, start);
184 }
185 EXPORT_SYMBOL(_find_next_and_bit);
186 #endif
187 
188 #ifndef find_next_andnot_bit
189 unsigned long _find_next_andnot_bit(const unsigned long *addr1, const unsigned long *addr2,
190 					unsigned long nbits, unsigned long start)
191 {
192 	return FIND_NEXT_BIT(addr1[idx] & ~addr2[idx], /* nop */, nbits, start);
193 }
194 EXPORT_SYMBOL(_find_next_andnot_bit);
195 #endif
196 
197 #ifndef find_next_or_bit
198 unsigned long _find_next_or_bit(const unsigned long *addr1, const unsigned long *addr2,
199 					unsigned long nbits, unsigned long start)
200 {
201 	return FIND_NEXT_BIT(addr1[idx] | addr2[idx], /* nop */, nbits, start);
202 }
203 EXPORT_SYMBOL(_find_next_or_bit);
204 #endif
205 
206 #ifndef find_next_zero_bit
207 unsigned long _find_next_zero_bit(const unsigned long *addr, unsigned long nbits,
208 					 unsigned long start)
209 {
210 	return FIND_NEXT_BIT(~addr[idx], /* nop */, nbits, start);
211 }
212 EXPORT_SYMBOL(_find_next_zero_bit);
213 #endif
214 
215 #ifndef find_last_bit
216 unsigned long _find_last_bit(const unsigned long *addr, unsigned long size)
217 {
218 	if (size) {
219 		unsigned long val = BITMAP_LAST_WORD_MASK(size);
220 		unsigned long idx = (size-1) / BITS_PER_LONG;
221 
222 		do {
223 			val &= addr[idx];
224 			if (val)
225 				return idx * BITS_PER_LONG + __fls(val);
226 
227 			val = ~0ul;
228 		} while (idx--);
229 	}
230 	return size;
231 }
232 EXPORT_SYMBOL(_find_last_bit);
233 #endif
234 
235 unsigned long find_next_clump8(unsigned long *clump, const unsigned long *addr,
236 			       unsigned long size, unsigned long offset)
237 {
238 	offset = find_next_bit(addr, size, offset);
239 	if (offset == size)
240 		return size;
241 
242 	offset = round_down(offset, 8);
243 	*clump = bitmap_get_value8(addr, offset);
244 
245 	return offset;
246 }
247 EXPORT_SYMBOL(find_next_clump8);
248 
249 #ifdef __BIG_ENDIAN
250 
251 #ifndef find_first_zero_bit_le
252 /*
253  * Find the first cleared bit in an LE memory region.
254  */
255 unsigned long _find_first_zero_bit_le(const unsigned long *addr, unsigned long size)
256 {
257 	return FIND_FIRST_BIT(~addr[idx], swab, size);
258 }
259 EXPORT_SYMBOL(_find_first_zero_bit_le);
260 
261 #endif
262 
263 #ifndef find_next_zero_bit_le
264 unsigned long _find_next_zero_bit_le(const unsigned long *addr,
265 					unsigned long size, unsigned long offset)
266 {
267 	return FIND_NEXT_BIT(~addr[idx], swab, size, offset);
268 }
269 EXPORT_SYMBOL(_find_next_zero_bit_le);
270 #endif
271 
272 #ifndef find_next_bit_le
273 unsigned long _find_next_bit_le(const unsigned long *addr,
274 				unsigned long size, unsigned long offset)
275 {
276 	return FIND_NEXT_BIT(addr[idx], swab, size, offset);
277 }
278 EXPORT_SYMBOL(_find_next_bit_le);
279 
280 #endif
281 
282 #endif /* __BIG_ENDIAN */
283