bitmap.c

#include "asm/bitsperlong.h"

#define BIT_WORD(nr)		((nr) / BITS_PER_LONG)

#define BITMAP_FIRST_WORD_MASK(start) (~0ul << ((start) % BITS_PER_LONG))

#define BITMAP_LAST_WORD_MASK(nbits)					\
(									\
	((nbits) % BITS_PER_LONG) ?					\
		(1ul << ((nbits) % BITS_PER_LONG)) - 1 : ~0ul		\
)

#define small_const_nbits(nbits)					\
	(__builtin_constant_p(nbits) && (nbits) <= BITS_PER_LONG)

void bitmap_set(unsigned long *map, int start, int nr)
{
	unsigned long *p = map + BIT_WORD(start);
	const int size = start + nr;
	int bits_to_set = BITS_PER_LONG - (start % BITS_PER_LONG);
	unsigned long mask_to_set = BITMAP_FIRST_WORD_MASK(start);

	while (nr - bits_to_set >= 0) {
		*p |= mask_to_set;
		nr -= bits_to_set;
		bits_to_set = BITS_PER_LONG;
		mask_to_set = ~0UL;
		p++;
	}
	if (nr) {
		mask_to_set &= BITMAP_LAST_WORD_MASK(size);
		*p |= mask_to_set;
	}
}

void bitmap_clear(unsigned long *map, int start, int nr)
{
	unsigned long *p = map + BIT_WORD(start);
	const int size = start + nr;
	int bits_to_clear = BITS_PER_LONG - (start % BITS_PER_LONG);
	unsigned long mask_to_clear = BITMAP_FIRST_WORD_MASK(start);

	while (nr - bits_to_clear >= 0) {
		*p &= ~mask_to_clear;
		nr -= bits_to_clear;
		bits_to_clear = BITS_PER_LONG;
		mask_to_clear = ~0UL;
		p++;
	}
	if (nr) {
		mask_to_clear &= BITMAP_LAST_WORD_MASK(size);
		*p &= ~mask_to_clear;
	}
}