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Diffstat (limited to 'lib/find_bit.c')
| -rw-r--r-- | lib/find_bit.c | 252 |
1 files changed, 252 insertions, 0 deletions
diff --git a/lib/find_bit.c b/lib/find_bit.c new file mode 100644 index 000000000..18bc0a7ac --- /dev/null +++ b/lib/find_bit.c @@ -0,0 +1,252 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* 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. + */ + +#include <linux/bitops.h> +#include <linux/bitmap.h> +#include <linux/export.h> +#include <linux/math.h> +#include <linux/minmax.h> +#include <linux/swab.h> + +/* + * Common helper for find_bit() function family + * @FETCH: The expression that fetches and pre-processes each word of bitmap(s) + * @MUNGE: The expression that post-processes a word containing found bit (may be empty) + * @size: The bitmap size in bits + */ +#define FIND_FIRST_BIT(FETCH, MUNGE, size) \ +({ \ + unsigned long idx, val, sz = (size); \ + \ + for (idx = 0; idx * BITS_PER_LONG < sz; idx++) { \ + val = (FETCH); \ + if (val) { \ + sz = min(idx * BITS_PER_LONG + __ffs(MUNGE(val)), sz); \ + break; \ + } \ + } \ + \ + sz; \ +}) + +/* + * Common helper for find_next_bit() function family + * @FETCH: The expression that fetches and pre-processes each word of bitmap(s) + * @MUNGE: The expression that post-processes a word containing found bit (may be empty) + * @size: The bitmap size in bits + * @start: The bitnumber to start searching at + */ +#define FIND_NEXT_BIT(FETCH, MUNGE, size, start) \ +({ \ + unsigned long mask, idx, tmp, sz = (size), __start = (start); \ + \ + if (unlikely(__start >= sz)) \ + goto out; \ + \ + mask = MUNGE(BITMAP_FIRST_WORD_MASK(__start)); \ + idx = __start / BITS_PER_LONG; \ + \ + for (tmp = (FETCH) & mask; !tmp; tmp = (FETCH)) { \ + if ((idx + 1) * BITS_PER_LONG >= sz) \ + goto out; \ + idx++; \ + } \ + \ + sz = min(idx * BITS_PER_LONG + __ffs(MUNGE(tmp)), sz); \ +out: \ + sz; \ +}) + +#define FIND_NTH_BIT(FETCH, size, num) \ +({ \ + unsigned long sz = (size), nr = (num), idx, w, tmp; \ + \ + for (idx = 0; (idx + 1) * BITS_PER_LONG <= sz; idx++) { \ + if (idx * BITS_PER_LONG + nr >= sz) \ + goto out; \ + \ + tmp = (FETCH); \ + w = hweight_long(tmp); \ + if (w > nr) \ + goto found; \ + \ + nr -= w; \ + } \ + \ + if (sz % BITS_PER_LONG) \ + tmp = (FETCH) & BITMAP_LAST_WORD_MASK(sz); \ +found: \ + sz = min(idx * BITS_PER_LONG + fns(tmp, nr), sz); \ +out: \ + sz; \ +}) + +#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) +{ + return FIND_FIRST_BIT(addr[idx], /* nop */, size); +} +EXPORT_SYMBOL(_find_first_bit); +#endif + +#ifndef find_first_and_bit +/* + * Find the first set bit in two memory regions. + */ +unsigned long _find_first_and_bit(const unsigned long *addr1, + const unsigned long *addr2, + unsigned long size) +{ + return FIND_FIRST_BIT(addr1[idx] & addr2[idx], /* nop */, size); +} +EXPORT_SYMBOL(_find_first_and_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) +{ + return FIND_FIRST_BIT(~addr[idx], /* nop */, size); +} +EXPORT_SYMBOL(_find_first_zero_bit); +#endif + +#ifndef find_next_bit +unsigned long _find_next_bit(const unsigned long *addr, unsigned long nbits, unsigned long start) +{ + return FIND_NEXT_BIT(addr[idx], /* nop */, nbits, start); +} +EXPORT_SYMBOL(_find_next_bit); +#endif + +unsigned long __find_nth_bit(const unsigned long *addr, unsigned long size, unsigned long n) +{ + return FIND_NTH_BIT(addr[idx], size, n); +} +EXPORT_SYMBOL(__find_nth_bit); + +unsigned long __find_nth_and_bit(const unsigned long *addr1, const unsigned long *addr2, + unsigned long size, unsigned long n) +{ + return FIND_NTH_BIT(addr1[idx] & addr2[idx], size, n); +} +EXPORT_SYMBOL(__find_nth_and_bit); + +unsigned long __find_nth_andnot_bit(const unsigned long *addr1, const unsigned long *addr2, + unsigned long size, unsigned long n) +{ + return FIND_NTH_BIT(addr1[idx] & ~addr2[idx], size, n); +} +EXPORT_SYMBOL(__find_nth_andnot_bit); + +#ifndef find_next_and_bit +unsigned long _find_next_and_bit(const unsigned long *addr1, const unsigned long *addr2, + unsigned long nbits, unsigned long start) +{ + return FIND_NEXT_BIT(addr1[idx] & addr2[idx], /* nop */, nbits, start); +} +EXPORT_SYMBOL(_find_next_and_bit); +#endif + +#ifndef find_next_andnot_bit +unsigned long _find_next_andnot_bit(const unsigned long *addr1, const unsigned long *addr2, + unsigned long nbits, unsigned long start) +{ + return FIND_NEXT_BIT(addr1[idx] & ~addr2[idx], /* nop */, nbits, start); +} +EXPORT_SYMBOL(_find_next_andnot_bit); +#endif + +#ifndef find_next_zero_bit +unsigned long _find_next_zero_bit(const unsigned long *addr, unsigned long nbits, + unsigned long start) +{ + return FIND_NEXT_BIT(~addr[idx], /* nop */, nbits, start); +} +EXPORT_SYMBOL(_find_next_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 + +unsigned long find_next_clump8(unsigned long *clump, const unsigned long *addr, + unsigned long size, unsigned long offset) +{ + offset = find_next_bit(addr, size, offset); + if (offset == size) + return size; + + offset = round_down(offset, 8); + *clump = bitmap_get_value8(addr, offset); + + return offset; +} +EXPORT_SYMBOL(find_next_clump8); + +#ifdef __BIG_ENDIAN + +#ifndef find_first_zero_bit_le +/* + * Find the first cleared bit in an LE memory region. + */ +unsigned long _find_first_zero_bit_le(const unsigned long *addr, unsigned long size) +{ + return FIND_FIRST_BIT(~addr[idx], swab, size); +} +EXPORT_SYMBOL(_find_first_zero_bit_le); + +#endif + +#ifndef find_next_zero_bit_le +unsigned long _find_next_zero_bit_le(const unsigned long *addr, + unsigned long size, unsigned long offset) +{ + return FIND_NEXT_BIT(~addr[idx], swab, size, offset); +} +EXPORT_SYMBOL(_find_next_zero_bit_le); +#endif + +#ifndef find_next_bit_le +unsigned long _find_next_bit_le(const unsigned long *addr, + unsigned long size, unsigned long offset) +{ + return FIND_NEXT_BIT(addr[idx], swab, size, offset); +} +EXPORT_SYMBOL(_find_next_bit_le); + +#endif + +#endif /* __BIG_ENDIAN */ |