| 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 | */ |
| 31 | static 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 | */ |
| 61 | unsigned 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 | } |
| 66 | EXPORT_SYMBOL(find_next_bit); |
| 67 | #endif |
| 68 | |
| 69 | #ifndef find_next_zero_bit |
| 70 | unsigned 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 | } |
| 75 | EXPORT_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 | */ |
| 82 | unsigned 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 | } |
| 93 | EXPORT_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 | */ |
| 100 | unsigned 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 | } |
| 111 | EXPORT_SYMBOL(find_first_zero_bit); |
| 112 | #endif |
| 113 | |
| 114 | #ifndef find_last_bit |
| 115 | unsigned 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 | } |
| 131 | EXPORT_SYMBOL(find_last_bit); |
| 132 | #endif |
| 133 | |
| 134 | #ifdef __BIG_ENDIAN |
| 135 | |
| 136 | /* include/linux/byteorder does not support "unsigned long" type */ |
| 137 | static 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) |
| 149 | static 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 |
| 176 | unsigned 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 | } |
| 181 | EXPORT_SYMBOL(find_next_zero_bit_le); |
| 182 | #endif |
| 183 | |
| 184 | #ifndef find_next_bit_le |
| 185 | unsigned 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 | } |
| 190 | EXPORT_SYMBOL(find_next_bit_le); |
| 191 | #endif |
| 192 | |
| 193 | #endif /* __BIG_ENDIAN */ |