Messages in this thread Patch in this message | | | Date | Thu, 26 Jan 2006 12:33:20 +0900 | Subject | [PATCH 5/12] generic find_{next,first}{,_zero}_bit() | From | (Akinobu Mita) |
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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);
HAVE_ARCH_FIND_BITOPS is defined when the architecture has its own version of these functions.
This code largely copied from: arch/powerpc/lib/bitops.c
Index: 2.6-git/include/asm-generic/bitops.h =================================================================== --- 2.6-git.orig/include/asm-generic/bitops.h 2006-01-25 19:14:10.000000000 +0900 +++ 2.6-git/include/asm-generic/bitops.h 2006-01-25 19:14:10.000000000 +0900 @@ -286,6 +286,101 @@ #endif /* HAVE_ARCH_FLS64_BITOPS */ +#ifndef HAVE_ARCH_FIND_BITOPS + +/** + * 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 + */ +static inline unsigned long find_next_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; + + if (offset >= size) + return size; + size -= result; + offset %= BITS_PER_LONG; + if (offset) { + 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; + +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); +} + +/* + * This implementation of find_{first,next}_zero_bit was stolen from + * Linus' asm-alpha/bitops.h. + */ +static inline 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; + + 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; + +found_first: + tmp |= ~0UL << size; + if (tmp == ~0UL) /* Are any bits zero? */ + return result + size; /* Nope. */ +found_middle: + return result + ffz(tmp); +} + +#define find_first_zero_bit(addr, size) find_next_zero_bit((addr), (size), 0) +#define find_first_bit(addr, size) find_next_bit((addr), (size), 0) + +#endif /* HAVE_ARCH_FIND_BITOPS */ + #ifdef __KERNEL__ /* - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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