#ifndef _KMALLOC_H
#define _KMALLOC_H

#include "types.h"

// This function allocates size bytes of contiguous memory.
// Returns a pointer to allocated memory or NULL.
void* kmalloc(size_t size);

// This function allocates size bytes of contiguous, zeroed-out memory.
// Returns a pointer to allocated memory or NULL.
void* kzalloc(size_t size);

// This function allocates memory for count elements each of size bytes,
// zeroed-out memory. Returns a pointer to allocated memory or NULL.
void* kcalloc(size_t count, size_t size);

// 9 bytes in 8 bytes
#define TAG_SHIFT 56
#define TAG_MASK ((uintptr_t)0xFF << TAG_SHIFT)
#define SIGN_BIT ((uintptr_t)1 << 55)

typedef struct {
	uintptr_t bits;
} tagged_ptr;

static inline tagged_ptr tp_make(void* p, uint8_t tag) {
	uintptr_t addr = (uintptr_t)p & ~TAG_MASK;
	return (tagged_ptr){addr | ((uintptr_t)tag << TAG_SHIFT)};
}

static inline uint8_t tp_tag(tagged_ptr t) {
	return (uint8_t)(t.bits >> TAG_SHIFT);
}

static inline void* tp_ptr(tagged_ptr t) {
	/* Bits 48..55 were untouched and still equal the canonical sign.
	   Copy bit 55 into bits 56..63. */
	uintptr_t addr =
	    (t.bits & SIGN_BIT) ? (t.bits | TAG_MASK) : (t.bits & ~TAG_MASK);
	return (void*)addr;
}

// powers of 2
#define KMALLOC_MAX_SIZE 17
#define LOWEST_POWER 3

struct freelist {
	struct freelist* nextnode;
};

struct partialy_freelist {
	struct freelist* freelist_nextnode;
	struct partialy_freelist* partialy_freelist_nextnode;
};

// this is used when object is too small to hold the big one in this case we use
// first object as pointer storage and dont allocate it
struct partialy_freelist_short {
	struct partialy_freelist_short* partialy_freelist_nextnode;
};

union freelists_list {
	struct freelist* freelists[KMALLOC_MAX_SIZE];
	struct {
		struct freelist* kmalloc_8;
		struct freelist* kmalloc_16;
		struct freelist* kmalloc_32;
		struct freelist* kmalloc_64;
		struct freelist* kmalloc_128;
		struct freelist* kmalloc_256;
		struct freelist* kmalloc_512;
		struct freelist* kmalloc_1024;
		struct freelist* kmalloc_2048;
		struct freelist* kmalloc_4096;
		struct freelist* kmalloc_8192;
		struct freelist* kmalloc_16384;
		struct freelist* kmalloc_32768;
		struct freelist* kmalloc_65536;
		struct freelist* kmalloc_131072;
	};
};

union partialy_freelists_list {
	struct partialy_freelist* partialy_freelists[KMALLOC_MAX_SIZE];
	struct {
		struct partialy_freelist* kmalloc_8;
		struct partialy_freelist* kmalloc_16;
		struct partialy_freelist* kmalloc_32;
		struct partialy_freelist* kmalloc_64;
		struct partialy_freelist* kmalloc_128;
		struct partialy_freelist* kmalloc_256;
		struct partialy_freelist* kmalloc_512;
		struct partialy_freelist* kmalloc_1024;
		struct partialy_freelist* kmalloc_2048;
		struct partialy_freelist* kmalloc_4096;
		struct partialy_freelist* kmalloc_8192;
		struct partialy_freelist* kmalloc_16384;
		struct partialy_freelist* kmalloc_32768;
		struct partialy_freelist* kmalloc_65536;
		struct partialy_freelist* kmalloc_131072;
	};
};

#endif