From c7f612cdf091def01454e7e132c7d7a3f419fbc4 Mon Sep 17 00:00:00 2001 From: Akinobu Mita Date: Sun, 26 Mar 2006 01:39:11 -0800 Subject: [PATCH] bitops: generic find_{next,first}{,_zero}_bit() This patch introduces the C-language equivalents of the functions below: unsigned logn find_next_bit(const unsigned long *addr, unsigned long size, unsigned long offset); unsigned long find_next_zero_bit(const unsigned long *addr, unsigned long size, unsigned long offset); unsigned long find_first_zero_bit(const unsigned long *addr, unsigned long size); unsigned long find_first_bit(const unsigned long *addr, unsigned long size); In include/asm-generic/bitops/find.h This code largely copied from: arch/powerpc/lib/bitops.c Signed-off-by: Akinobu Mita Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- lib/find_next_bit.c | 112 +++++++++++++++++++++++++++++++++++++--------------- 1 file changed, 81 insertions(+), 31 deletions(-) (limited to 'lib/find_next_bit.c') diff --git a/lib/find_next_bit.c b/lib/find_next_bit.c index c05b4b19cf6c..9c90853b4472 100644 --- a/lib/find_next_bit.c +++ b/lib/find_next_bit.c @@ -11,48 +11,98 @@ #include #include +#include -int find_next_bit(const unsigned long *addr, int size, int offset) +#define BITOP_WORD(nr) ((nr) / BITS_PER_LONG) + +/** + * find_next_bit - find the next set bit in a memory region + * @addr: The address to base the search on + * @offset: The bitnumber to start searching at + * @size: The maximum size to search + */ +unsigned long find_next_bit(const unsigned long *addr, unsigned long size, + unsigned long offset) { - const unsigned long *base; - const int NBITS = sizeof(*addr) * 8; + const unsigned long *p = addr + BITOP_WORD(offset); + unsigned long result = offset & ~(BITS_PER_LONG-1); unsigned long tmp; - base = addr; + if (offset >= size) + return size; + size -= result; + offset %= BITS_PER_LONG; if (offset) { - int suboffset; - - addr += offset / NBITS; - - suboffset = offset % NBITS; - if (suboffset) { - tmp = *addr; - tmp >>= suboffset; - if (tmp) - goto finish; - } - - addr++; + tmp = *(p++); + tmp &= (~0UL << offset); + if (size < BITS_PER_LONG) + goto found_first; + if (tmp) + goto found_middle; + size -= BITS_PER_LONG; + result += BITS_PER_LONG; + } + while (size & ~(BITS_PER_LONG-1)) { + if ((tmp = *(p++))) + goto found_middle; + result += BITS_PER_LONG; + size -= BITS_PER_LONG; } + if (!size) + return result; + tmp = *p; - while ((tmp = *addr) == 0) - addr++; +found_first: + tmp &= (~0UL >> (BITS_PER_LONG - size)); + if (tmp == 0UL) /* Are any bits set? */ + return result + size; /* Nope. */ +found_middle: + return result + __ffs(tmp); +} - offset = (addr - base) * NBITS; +EXPORT_SYMBOL(find_next_bit); - finish: - /* count the remaining bits without using __ffs() since that takes a 32-bit arg */ - while (!(tmp & 0xff)) { - offset += 8; - tmp >>= 8; - } +/* + * This implementation of find_{first,next}_zero_bit was stolen from + * Linus' asm-alpha/bitops.h. + */ +unsigned long find_next_zero_bit(const unsigned long *addr, unsigned long size, + unsigned long offset) +{ + const unsigned long *p = addr + BITOP_WORD(offset); + unsigned long result = offset & ~(BITS_PER_LONG-1); + unsigned long tmp; - while (!(tmp & 1)) { - offset++; - tmp >>= 1; + if (offset >= size) + return size; + size -= result; + offset %= BITS_PER_LONG; + if (offset) { + tmp = *(p++); + tmp |= ~0UL >> (BITS_PER_LONG - offset); + if (size < BITS_PER_LONG) + goto found_first; + if (~tmp) + goto found_middle; + size -= BITS_PER_LONG; + result += BITS_PER_LONG; + } + while (size & ~(BITS_PER_LONG-1)) { + if (~(tmp = *(p++))) + goto found_middle; + result += BITS_PER_LONG; + size -= BITS_PER_LONG; } + if (!size) + return result; + tmp = *p; - return offset; +found_first: + tmp |= ~0UL << size; + if (tmp == ~0UL) /* Are any bits zero? */ + return result + size; /* Nope. */ +found_middle: + return result + ffz(tmp); } -EXPORT_SYMBOL(find_next_bit); +EXPORT_SYMBOL(find_next_zero_bit); -- cgit v1.2.3