include/linux/bitmap.h

// SPDX-License-Identifier: GPL-2.0+
#ifndef __LINUX_BITMAP_H
#define __LINUX_BITMAP_H

#include <asm/types.h>
#include <linux/types.h>
#include <linux/bitops.h>
#include <string.h>

extern unsigned long bitmap_find_next_zero_area_off(unsigned long *map,
                                                    unsigned long size,
                                                    unsigned long start,
                                                    unsigned int nr,
                                                    unsigned long align_mask,
                                                    unsigned long align_offset);

extern void __bitmap_set(unsigned long *map, unsigned int start, int len);
extern void __bitmap_clear(unsigned long *map, unsigned int start, int len);
/**
 * bitmap_find_next_zero_area - find a contiguous aligned zero area
 * @map: The address to base the search on
 * @size: The bitmap size in bits
 * @start: The bitnumber to start searching at
 * @nr: The number of zeroed bits we're looking for
 * @align_mask: Alignment mask for zero area
 *
 * The @align_mask should be one less than a power of 2; the effect is that
 * the bit offset of all zero areas this function finds is multiples of that
 * power of 2. A @align_mask of 0 means no alignment is required.
 */
static inline unsigned long
bitmap_find_next_zero_area(unsigned long *map,
                           unsigned long size,
                           unsigned long start,
                           unsigned int nr,
                           unsigned long align_mask)
{
        return bitmap_find_next_zero_area_off(map, size, start, nr,
                                              align_mask, 0);
}

#define BITMAP_FIRST_WORD_MASK(start) (~0UL << ((start) & (BITS_PER_LONG - 1)))
#define BITMAP_LAST_WORD_MASK(nbits) (~0UL >> (-(nbits) & (BITS_PER_LONG - 1)))

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

static inline void bitmap_zero(unsigned long *dst, int nbits)
{
	if (small_const_nbits(nbits)) {
		*dst = 0UL;
	} else {
		int len = BITS_TO_LONGS(nbits) * sizeof(unsigned long);

		memset(dst, 0, len);
	}
}

#ifdef __LITTLE_ENDIAN
#define BITMAP_MEM_ALIGNMENT 8
#else
#define BITMAP_MEM_ALIGNMENT (8 * sizeof(unsigned long))
#endif
#define BITMAP_MEM_MASK (BITMAP_MEM_ALIGNMENT - 1)

static __always_inline void bitmap_set(unsigned long *map, unsigned int start,
                unsigned int nbits)
{
        if (__builtin_constant_p(nbits) && nbits == 1)
                __set_bit(start, map);
        else if (__builtin_constant_p(start & BITMAP_MEM_MASK) &&
                 IS_ALIGNED(start, BITMAP_MEM_ALIGNMENT) &&
                 __builtin_constant_p(nbits & BITMAP_MEM_MASK) &&
                 IS_ALIGNED(nbits, BITMAP_MEM_ALIGNMENT))
                memset((char *)map + start / 8, 0xff, nbits / 8);
        else
		__bitmap_set(map, start, nbits);
}

static __always_inline void bitmap_clear(unsigned long *map, unsigned int start,
                unsigned int nbits)
{
        if (__builtin_constant_p(nbits) && nbits == 1)
                __clear_bit(start, map);
        else if (__builtin_constant_p(start & BITMAP_MEM_MASK) &&
                 IS_ALIGNED(start, BITMAP_MEM_ALIGNMENT) &&
                 __builtin_constant_p(nbits & BITMAP_MEM_MASK) &&
                 IS_ALIGNED(nbits, BITMAP_MEM_ALIGNMENT))
                memset((char *)map + start / 8, 0, nbits / 8);
        else
		__bitmap_clear(map, start, nbits);
}

#endif /* __LINUX_BITMAP_H */