#ifndef JEMALLOC_INTERNAL_FB_H
#define JEMALLOC_INTERNAL_FB_H

/*
 * The flat bitmap module.  This has a larger API relative to the bitmap module
 * (supporting things like backwards searches, and searching for both set and
 * unset bits), at the cost of slower operations for very large bitmaps.
 *
 * Initialized flat bitmaps start at all-zeros (all bits unset).
 */

typedef unsigned long fb_group_t;
#define FB_GROUP_BITS (ZU(1) << (LG_SIZEOF_LONG + 3))
#define FB_NGROUPS(nbits) ((nbits) / FB_GROUP_BITS \
    + ((nbits) % FB_GROUP_BITS == 0 ? 0 : 1))

static inline void
fb_init(fb_group_t *fb, size_t nbits) {
	size_t ngroups = FB_NGROUPS(nbits);
	memset(fb, 0, ngroups * sizeof(fb_group_t));
}

static inline bool
fb_empty(fb_group_t *fb, size_t nbits) {
	size_t ngroups = FB_NGROUPS(nbits);
	for (size_t i = 0; i < ngroups; i++) {
		if (fb[i] != 0) {
			return false;
		}
	}
	return true;
}

static inline bool
fb_full(fb_group_t *fb, size_t nbits) {
	size_t ngroups = FB_NGROUPS(nbits);
	size_t trailing_bits = nbits % FB_GROUP_BITS;
	size_t limit = (trailing_bits == 0 ? ngroups : ngroups - 1);
	for (size_t i = 0; i < limit; i++) {
		if (fb[i] != ~(fb_group_t)0) {
			return false;
		}
	}
	if (trailing_bits == 0) {
		return true;
	}
	return fb[ngroups - 1] == ((fb_group_t)1 << trailing_bits) - 1;
}

static inline bool
fb_get(fb_group_t *fb, size_t nbits, size_t bit) {
	assert(bit < nbits);
	size_t group_ind = bit / FB_GROUP_BITS;
	size_t bit_ind = bit % FB_GROUP_BITS;
	return (bool)(fb[group_ind] & ((fb_group_t)1 << bit_ind));
}

static inline void
fb_set(fb_group_t *fb, size_t nbits, size_t bit) {
	assert(bit < nbits);
	size_t group_ind = bit / FB_GROUP_BITS;
	size_t bit_ind = bit % FB_GROUP_BITS;
	fb[group_ind] |= ((fb_group_t)1 << bit_ind);
}

static inline void
fb_unset(fb_group_t *fb, size_t nbits, size_t bit) {
	assert(bit < nbits);
	size_t group_ind = bit / FB_GROUP_BITS;
	size_t bit_ind = bit % FB_GROUP_BITS;
	fb[group_ind] &= ~((fb_group_t)1 << bit_ind);
}

JEMALLOC_ALWAYS_INLINE void
fb_assign_group_impl(fb_group_t *fb, size_t start, size_t cnt, bool val) {
	assert(cnt > 0);
	assert(start + cnt - 1 < FB_GROUP_BITS);
	fb_group_t bits = ((~(fb_group_t)0) >> (FB_GROUP_BITS - cnt)) << start;
	if (val) {
		*fb |= bits;
	} else {
		*fb &= ~bits;
	}
}

JEMALLOC_ALWAYS_INLINE void
fb_assign_impl(fb_group_t *fb, size_t nbits, size_t start, size_t cnt,
    bool val) {
	assert(start + cnt - 1 < nbits);
	size_t group_ind = start / FB_GROUP_BITS;
	size_t start_bit_ind = start % FB_GROUP_BITS;
	/*
	 * The first group is special; it's the only one we don't start writing
	 * to from bit 0.
	 */
	size_t first_group_cnt =
	    (start_bit_ind + cnt > FB_GROUP_BITS
		? FB_GROUP_BITS - start_bit_ind
		: cnt);
	/*
	 * We can basically split affected words into:
	 *   - The first group, where we touch only the high bits
	 *   - The last group, where we touch only the low bits
	 *   - The middle, where we set all the bits to the same thing.
	 * We treat each case individually.  The last two could be merged, but
	 * this can lead to bad codegen for those middle words.
	 */
	/* First group */
	fb_assign_group_impl(&fb[group_ind], start_bit_ind, first_group_cnt,
	    val);
	cnt -= first_group_cnt;
	group_ind++;
	/* Middle groups */
	while (cnt > FB_GROUP_BITS) {
		fb_assign_group_impl(&fb[group_ind], 0, FB_GROUP_BITS, val);
		cnt -= FB_GROUP_BITS;
		group_ind++;
	}
	/* Last group */
	if (cnt != 0) {
		fb_assign_group_impl(&fb[group_ind], 0, cnt, val);
	}
}

/* Sets the cnt bits starting at position start.  Must not have a 0 count. */
static inline void
fb_set_range(fb_group_t *fb, size_t nbits, size_t start, size_t cnt) {
	fb_assign_impl(fb, nbits, start, cnt, true);
}

/* Unsets the cnt bits starting at position start.  Must not have a 0 count. */
static inline void
fb_unset_range(fb_group_t *fb, size_t nbits, size_t start, size_t cnt) {
	fb_assign_impl(fb, nbits, start, cnt, false);
}

/*
 * An implementation detail; find the first bit at position >= min_bit with the
 * value val.
 *
 * Returns the number of bits in the bitmap if no such bit exists.
 */
JEMALLOC_ALWAYS_INLINE ssize_t
fb_find_impl(fb_group_t *fb, size_t nbits, size_t start, bool val,
    bool forward) {
	assert(start < nbits);
	size_t ngroups = FB_NGROUPS(nbits);
	ssize_t group_ind = start / FB_GROUP_BITS;
	size_t bit_ind = start % FB_GROUP_BITS;

	fb_group_t maybe_invert = (val ? 0 : (fb_group_t)-1);

	fb_group_t group = fb[group_ind];
	group ^= maybe_invert;
	if (forward) {
		/* Only keep ones in bits bit_ind and above. */
		group &= ~((1LU << bit_ind) - 1);
	} else {
		/*
		 * Only keep ones in bits bit_ind and below.  You might more
		 * naturally express this as (1 << (bit_ind + 1)) - 1, but
		 * that shifts by an invalid amount if bit_ind is one less than
		 * FB_GROUP_BITS.
		 */
		group &= ((2LU << bit_ind) - 1);
	}
	ssize_t group_ind_bound = forward ? (ssize_t)ngroups : -1;
	while (group == 0) {
		group_ind += forward ? 1 : -1;
		if (group_ind == group_ind_bound) {
			return forward ? (ssize_t)nbits : (ssize_t)-1;
		}
		group = fb[group_ind];
		group ^= maybe_invert;
	}
	assert(group != 0);
	size_t bit = forward ? ffs_lu(group) : fls_lu(group);
	size_t pos = group_ind * FB_GROUP_BITS + bit;
	/*
	 * The high bits of a partially filled last group are zeros, so if we're
	 * looking for zeros we don't want to report an invalid result.
	 */
	if (forward && !val && pos > nbits) {
		return nbits;
	}
	return pos;
}

/*
 * Find the first set bit in the bitmap with an index >= min_bit.  Returns the
 * number of bits in the bitmap if no such bit exists.
 */
static inline size_t
fb_ffu(fb_group_t *fb, size_t nbits, size_t min_bit) {
	return (size_t)fb_find_impl(fb, nbits, min_bit, /* val */ false,
	    /* forward */ true);
}

/* The same, but looks for an unset bit. */
static inline size_t
fb_ffs(fb_group_t *fb, size_t nbits, size_t min_bit) {
	return (size_t)fb_find_impl(fb, nbits, min_bit, /* val */ true,
	    /* forward */ true);
}

/*
 * Find the last set bit in the bitmap with an index <= max_bit.  Returns -1 if
 * no such bit exists.
 */
static inline ssize_t
fb_flu(fb_group_t *fb, size_t nbits, size_t max_bit) {
	return fb_find_impl(fb, nbits, max_bit, /* val */ false,
	    /* forward */ false);
}

static inline ssize_t
fb_fls(fb_group_t *fb, size_t nbits, size_t max_bit) {
	return fb_find_impl(fb, nbits, max_bit, /* val */ true,
	    /* forward */ false);
}

#endif /* JEMALLOC_INTERNAL_FB_H */