#ifndef _FLEX_ARRAY_H
#define _FLEX_ARRAY_H

typedef unsigned char u8;
typedef unsigned short u16;
typedef unsigned int u32;
typedef unsigned int uint32_t;
typedef unsigned long long u64;
typedef unsigned long long uint64_t;
typedef int gfp_t;
#define PAGE_SIZE 4096
#define FLEX_ARRAY_PART_SIZE PAGE_SIZE
#define FLEX_ARRAY_BASE_SIZE PAGE_SIZE

struct reciprocal_value {
	u32 m;
	u8 sh1, sh2;
};

static inline u32 reciprocal_divide(u32 a, struct reciprocal_value R)
{
	u32 t = (u32)(((u64)a * R.m) >> 32);
	return (t + ((a - t) >> R.sh1)) >> R.sh2;
}


#define min(x, y) ({				\
	typeof(x) _min1 = (x);			\
	typeof(y) _min2 = (y);			\
	(void) (&_min1 == &_min2);		\
	_min1 < _min2 ? _min1 : _min2; })

#define max(x, y) ({				\
	typeof(x) _max1 = (x);			\
	typeof(y) _max2 = (y);			\
	(void) (&_max1 == &_max2);		\
	_max1 > _max2 ? _max1 : _max2; })

#define FLEX_ARRAY_FREE	0x6c	/* for use-after-free poisoning */
#define offsetof(TYPE, MEMBER)	((size_t)&((TYPE *)0)->MEMBER)
struct flex_array_part;

struct flex_array {
	union {
		struct {
			int element_size;
			int total_nr_elements;
			int elems_per_part;
			struct reciprocal_value reciprocal_elems;
			struct flex_array_part *parts[];
		};
		/*
		 * This little trick makes sure that
		 * sizeof(flex_array) == PAGE_SIZE
		 */
		char padding[FLEX_ARRAY_BASE_SIZE];
	};
};

#define FLEX_ARRAY_BASE_BYTES_LEFT					\
	(FLEX_ARRAY_BASE_SIZE - offsetof(struct flex_array, parts))

#define FLEX_ARRAY_NR_BASE_PTRS						\
	(FLEX_ARRAY_BASE_BYTES_LEFT / sizeof(struct flex_array_part *))

#define FLEX_ARRAY_ELEMENTS_PER_PART(size)				\
	(FLEX_ARRAY_PART_SIZE / size)

#define DEFINE_FLEX_ARRAY(__arrayname, __element_size, __total)		\
	struct flex_array __arrayname = { { {				\
		.element_size = (__element_size),			\
		.total_nr_elements = (__total),				\
	} } };								\
	static inline void __arrayname##_invalid_parameter(void)	\
	{								\
		BUILD_BUG_ON((__total) > FLEX_ARRAY_NR_BASE_PTRS *	\
			FLEX_ARRAY_ELEMENTS_PER_PART(__element_size));	\
	}

struct flex_array *flex_array_alloc(int element_size, unsigned int total, gfp_t flags);
int flex_array_prealloc(struct flex_array *fa, unsigned int start, unsigned int nr_elements, gfp_t flags);
void flex_array_free(struct flex_array *fa);
void flex_array_free_parts(struct flex_array *fa);
int flex_array_put(struct flex_array *fa, unsigned int element_nr, void *src,
		gfp_t flags);
int flex_array_clear(struct flex_array *fa, unsigned int element_nr);
void *flex_array_get(struct flex_array *fa, unsigned int element_nr);
int flex_array_shrink(struct flex_array *fa);

#define flex_array_put_ptr(fa, nr, src, gfp) \
	flex_array_put(fa, nr, (void *)&(src), gfp)

void *flex_array_get_ptr(struct flex_array *fa, unsigned int element_nr);

#endif /* _FLEX_ARRAY_H */