169 lines
4.0 KiB
C
169 lines
4.0 KiB
C
/* find_next_bit.c: fallback find next bit implementation
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*
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* Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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*
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* Rewritten by Yury Norov <yury.norov@gmail.com> to decrease
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* size and improve performance, 2015.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*/
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#include <linux/bitops.h>
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#include <linux/export.h>
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#include <linux/kernel.h>
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#if !defined(find_next_bit) || !defined(find_next_zero_bit)
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/*
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* This is a common helper function for find_next_bit and
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* find_next_zero_bit. The difference is the "invert" argument, which
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* is XORed with each fetched word before searching it for one bits.
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*/
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static unsigned long _find_next_bit(const unsigned long *addr,
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unsigned long nbits, unsigned long start, unsigned long invert)
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{
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unsigned long tmp;
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if (!nbits || start >= nbits)
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return nbits;
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tmp = addr[start / BITS_PER_LONG] ^ invert;
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/* Handle 1st word. */
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tmp &= BITMAP_FIRST_WORD_MASK(start);
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start = round_down(start, BITS_PER_LONG);
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while (!tmp) {
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start += BITS_PER_LONG;
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if (start >= nbits)
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return nbits;
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tmp = addr[start / BITS_PER_LONG] ^ invert;
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}
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return min(start + __ffs(tmp), nbits);
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}
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#endif
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#ifndef find_next_bit
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/*
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* Find the next set bit in a memory region.
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*/
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unsigned long find_next_bit(const unsigned long *addr, unsigned long size,
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unsigned long offset)
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{
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return _find_next_bit(addr, size, offset, 0UL);
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}
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EXPORT_SYMBOL(find_next_bit);
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#endif
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#ifndef find_next_zero_bit
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unsigned long find_next_zero_bit(const unsigned long *addr, unsigned long size,
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unsigned long offset)
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{
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return _find_next_bit(addr, size, offset, ~0UL);
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}
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EXPORT_SYMBOL(find_next_zero_bit);
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#endif
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#ifndef find_first_bit
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/*
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* Find the first set bit in a memory region.
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*/
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unsigned long find_first_bit(const unsigned long *addr, unsigned long size)
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{
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unsigned long idx;
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for (idx = 0; idx * BITS_PER_LONG < size; idx++) {
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if (addr[idx])
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return min(idx * BITS_PER_LONG + __ffs(addr[idx]), size);
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}
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return size;
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}
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EXPORT_SYMBOL(find_first_bit);
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#endif
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#ifndef find_first_zero_bit
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/*
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* Find the first cleared bit in a memory region.
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*/
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unsigned long find_first_zero_bit(const unsigned long *addr, unsigned long size)
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{
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unsigned long idx;
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for (idx = 0; idx * BITS_PER_LONG < size; idx++) {
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if (addr[idx] != ~0UL)
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return min(idx * BITS_PER_LONG + ffz(addr[idx]), size);
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}
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return size;
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}
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EXPORT_SYMBOL(find_first_zero_bit);
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#endif
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#ifdef __BIG_ENDIAN
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/* include/linux/byteorder does not support "unsigned long" type */
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static inline unsigned long ext2_swab(const unsigned long y)
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{
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#if BITS_PER_LONG == 64
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return (unsigned long) __swab64((u64) y);
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#elif BITS_PER_LONG == 32
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return (unsigned long) __swab32((u32) y);
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#else
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#error BITS_PER_LONG not defined
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#endif
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}
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#if !defined(find_next_bit_le) || !defined(find_next_zero_bit_le)
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static unsigned long _find_next_bit_le(const unsigned long *addr,
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unsigned long nbits, unsigned long start, unsigned long invert)
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{
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unsigned long tmp;
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if (!nbits || start >= nbits)
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return nbits;
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tmp = addr[start / BITS_PER_LONG] ^ invert;
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/* Handle 1st word. */
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tmp &= ext2_swab(BITMAP_FIRST_WORD_MASK(start));
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start = round_down(start, BITS_PER_LONG);
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while (!tmp) {
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start += BITS_PER_LONG;
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if (start >= nbits)
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return nbits;
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tmp = addr[start / BITS_PER_LONG] ^ invert;
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}
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return min(start + __ffs(ext2_swab(tmp)), nbits);
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}
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#endif
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#ifndef find_next_zero_bit_le
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unsigned long find_next_zero_bit_le(const void *addr, unsigned
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long size, unsigned long offset)
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{
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return _find_next_bit_le(addr, size, offset, ~0UL);
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}
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EXPORT_SYMBOL(find_next_zero_bit_le);
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#endif
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#ifndef find_next_bit_le
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unsigned long find_next_bit_le(const void *addr, unsigned
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long size, unsigned long offset)
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{
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return _find_next_bit_le(addr, size, offset, 0UL);
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}
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EXPORT_SYMBOL(find_next_bit_le);
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#endif
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#endif /* __BIG_ENDIAN */
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