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Diffstat (limited to '')
| -rw-r--r-- | lib/find_bit.c | 208 |
1 files changed, 208 insertions, 0 deletions
diff --git a/lib/find_bit.c b/lib/find_bit.c new file mode 100644 index 000000000..8a5492173 --- /dev/null +++ b/lib/find_bit.c @@ -0,0 +1,208 @@ +/* bit search implementation + * + * Copyright (C) 2004 Red Hat, Inc. All Rights Reserved. + * Written by David Howells (dhowells@redhat.com) + * + * Copyright (C) 2008 IBM Corporation + * 'find_last_bit' is written by Rusty Russell <rusty@rustcorp.com.au> + * (Inspired by David Howell's find_next_bit implementation) + * + * Rewritten by Yury Norov <yury.norov@gmail.com> to decrease + * size and improve performance, 2015. + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License + * as published by the Free Software Foundation; either version + * 2 of the License, or (at your option) any later version. + */ + +#include <linux/bitops.h> +#include <linux/bitmap.h> +#include <linux/export.h> +#include <linux/kernel.h> + +#if !defined(find_next_bit) || !defined(find_next_zero_bit) || \ + !defined(find_next_and_bit) + +/* + * This is a common helper function for find_next_bit, find_next_zero_bit, and + * find_next_and_bit. The differences are: + * - The "invert" argument, which is XORed with each fetched word before + * searching it for one bits. + * - The optional "addr2", which is anded with "addr1" if present. + */ +static inline unsigned long _find_next_bit(const unsigned long *addr1, + const unsigned long *addr2, unsigned long nbits, + unsigned long start, unsigned long invert) +{ + unsigned long tmp; + + if (unlikely(start >= nbits)) + return nbits; + + tmp = addr1[start / BITS_PER_LONG]; + if (addr2) + tmp &= addr2[start / BITS_PER_LONG]; + tmp ^= invert; + + /* Handle 1st word. */ + tmp &= BITMAP_FIRST_WORD_MASK(start); + start = round_down(start, BITS_PER_LONG); + + while (!tmp) { + start += BITS_PER_LONG; + if (start >= nbits) + return nbits; + + tmp = addr1[start / BITS_PER_LONG]; + if (addr2) + tmp &= addr2[start / BITS_PER_LONG]; + tmp ^= invert; + } + + return min(start + __ffs(tmp), nbits); +} +#endif + +#ifndef find_next_bit +/* + * Find the next set bit in a memory region. + */ +unsigned long find_next_bit(const unsigned long *addr, unsigned long size, + unsigned long offset) +{ + return _find_next_bit(addr, NULL, size, offset, 0UL); +} +EXPORT_SYMBOL(find_next_bit); +#endif + +#ifndef find_next_zero_bit +unsigned long find_next_zero_bit(const unsigned long *addr, unsigned long size, + unsigned long offset) +{ + return _find_next_bit(addr, NULL, size, offset, ~0UL); +} +EXPORT_SYMBOL(find_next_zero_bit); +#endif + +#if !defined(find_next_and_bit) +unsigned long find_next_and_bit(const unsigned long *addr1, + const unsigned long *addr2, unsigned long size, + unsigned long offset) +{ + return _find_next_bit(addr1, addr2, size, offset, 0UL); +} +EXPORT_SYMBOL(find_next_and_bit); +#endif + +#ifndef find_first_bit +/* + * Find the first set bit in a memory region. + */ +unsigned long find_first_bit(const unsigned long *addr, unsigned long size) +{ + unsigned long idx; + + for (idx = 0; idx * BITS_PER_LONG < size; idx++) { + if (addr[idx]) + return min(idx * BITS_PER_LONG + __ffs(addr[idx]), size); + } + + return size; +} +EXPORT_SYMBOL(find_first_bit); +#endif + +#ifndef find_first_zero_bit +/* + * Find the first cleared bit in a memory region. + */ +unsigned long find_first_zero_bit(const unsigned long *addr, unsigned long size) +{ + unsigned long idx; + + for (idx = 0; idx * BITS_PER_LONG < size; idx++) { + if (addr[idx] != ~0UL) + return min(idx * BITS_PER_LONG + ffz(addr[idx]), size); + } + + return size; +} +EXPORT_SYMBOL(find_first_zero_bit); +#endif + +#ifndef find_last_bit +unsigned long find_last_bit(const unsigned long *addr, unsigned long size) +{ + if (size) { + unsigned long val = BITMAP_LAST_WORD_MASK(size); + unsigned long idx = (size-1) / BITS_PER_LONG; + + do { + val &= addr[idx]; + if (val) + return idx * BITS_PER_LONG + __fls(val); + + val = ~0ul; + } while (idx--); + } + return size; +} +EXPORT_SYMBOL(find_last_bit); +#endif + +#ifdef __BIG_ENDIAN + +#if !defined(find_next_bit_le) || !defined(find_next_zero_bit_le) +static inline unsigned long _find_next_bit_le(const unsigned long *addr1, + const unsigned long *addr2, unsigned long nbits, + unsigned long start, unsigned long invert) +{ + unsigned long tmp; + + if (unlikely(start >= nbits)) + return nbits; + + tmp = addr1[start / BITS_PER_LONG]; + if (addr2) + tmp &= addr2[start / BITS_PER_LONG]; + tmp ^= invert; + + /* Handle 1st word. */ + tmp &= swab(BITMAP_FIRST_WORD_MASK(start)); + start = round_down(start, BITS_PER_LONG); + + while (!tmp) { + start += BITS_PER_LONG; + if (start >= nbits) + return nbits; + + tmp = addr1[start / BITS_PER_LONG]; + if (addr2) + tmp &= addr2[start / BITS_PER_LONG]; + tmp ^= invert; + } + + return min(start + __ffs(swab(tmp)), nbits); +} +#endif + +#ifndef find_next_zero_bit_le +unsigned long find_next_zero_bit_le(const void *addr, unsigned + long size, unsigned long offset) +{ + return _find_next_bit_le(addr, NULL, size, offset, ~0UL); +} +EXPORT_SYMBOL(find_next_zero_bit_le); +#endif + +#ifndef find_next_bit_le +unsigned long find_next_bit_le(const void *addr, unsigned + long size, unsigned long offset) +{ + return _find_next_bit_le(addr, NULL, size, offset, 0UL); +} +EXPORT_SYMBOL(find_next_bit_le); +#endif + +#endif /* __BIG_ENDIAN */ |