find_bit.c

来自「Linux Kernel 2.6.9 for OMAP1710」· C语言 代码 · 共 127 行

#include <asm/bitops.h>

/**
 * 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 *p = addr + (offset >> 6);
	unsigned long result = offset & ~63UL;
	unsigned long tmp;

	if (offset >= size)
		return size;
	size -= result;
	offset &= 63UL;
	if (offset) {
		tmp = *(p++);
		tmp &= (~0UL << offset);
		if (size < 64)
			goto found_first;
		if (tmp)
			goto found_middle;
		size -= 64;
		result += 64;
	}
	while (size & ~63UL) {
		if ((tmp = *(p++)))
			goto found_middle;
		result += 64;
		size -= 64;
	}
	if (!size)
		return result;
	tmp = *p;

found_first:
	tmp &= (~0UL >> (64 - size));
	if (tmp == 0UL)        /* Are any bits set? */
		return result + size; /* Nope. */
found_middle:
	return result + __ffs(tmp);
}

/* find_next_zero_bit() finds the first zero bit in a bit string of length
 * 'size' bits, starting the search at bit 'offset'. This is largely based
 * on Linus's ALPHA routines, which are pretty portable BTW.
 */

unsigned long find_next_zero_bit(unsigned long *addr, unsigned long size, unsigned long offset)
{
	unsigned long *p = addr + (offset >> 6);
	unsigned long result = offset & ~63UL;
	unsigned long tmp;

	if (offset >= size)
		return size;
	size -= result;
	offset &= 63UL;
	if (offset) {
		tmp = *(p++);
		tmp |= ~0UL >> (64-offset);
		if (size < 64)
			goto found_first;
		if (~tmp)
			goto found_middle;
		size -= 64;
		result += 64;
	}
	while (size & ~63UL) {
		if (~(tmp = *(p++)))
			goto found_middle;
		result += 64;
		size -= 64;
	}
	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);
}

unsigned long find_next_zero_le_bit(unsigned long *addr, unsigned long size, unsigned long offset)
{
	unsigned long *p = addr + (offset >> 6);
	unsigned long result = offset & ~63UL;
	unsigned long tmp;

	if (offset >= size)
		return size;
	size -= result;
	offset &= 63UL;
	if(offset) {
		tmp = __swab64p(p++);
		tmp |= (~0UL >> (64-offset));
		if(size < 64)
			goto found_first;
		if(~tmp)
			goto found_middle;
		size -= 64;
		result += 64;
	}
	while(size & ~63) {
		if(~(tmp = __swab64p(p++)))
			goto found_middle;
		result += 64;
		size -= 64;
	}
	if(!size)
		return result;
	tmp = __swab64p(p);
found_first:
	tmp |= (~0UL << size);
	if (tmp == ~0UL)        /* Are any bits zero? */
		return result + size; /* Nope. */
found_middle:
	return result + ffz(tmp);
}