#pypp 0
#include "kernel.hh"

extern unsigned _end

static void clear_page (unsigned page, unsigned num = 1):
	for unsigned i = 0; i < (num << (PAGE_BITS - 2)); ++i:
		((unsigned *)page)[i] = 0

#if 0

static unsigned free_begin
static unsigned free_end

unsigned init_memory (unsigned mem):
	free_begin = ((unsigned)&_end + ~PAGE_MASK) & PAGE_MASK
	free_end = (0x80000000 + mem) & PAGE_MASK
	return (free_end - free_begin) >> PAGE_BITS

unsigned phys_alloc (unsigned num):
	if free_begin + num * PAGE_SIZE > free_end:
		dbg_log ("memory allocation failed\n")
		return 0
	unsigned ret = free_begin
	free_begin += num * PAGE_SIZE
	clear_page (ret, num)
	return ret

void phys_free (unsigned page, unsigned num):
	// Not supported.

#else

struct FreePages:
	FreePages *prev, *next
	unsigned num

static FreePages *first_free

unsigned init_memory (unsigned mem):
	first_free = (FreePages *)(((unsigned)&_end + ~PAGE_MASK) & PAGE_MASK)
	first_free->prev = NULL
	first_free->next = NULL
	first_free->num = ((mem & PAGE_MASK) - ((unsigned)first_free - 0x80000000)) >> PAGE_BITS
	return first_free->num

unsigned phys_alloc (unsigned num):
	FreePages *choice = NULL
	for FreePages *p = first_free; p; p = p->next:
		if p->num < num:
			continue
		if choice && choice->num < p->num:
			continue
		choice = p
	if !choice:
		// TODO: reorganizing may work to allow allocation.
		dbg_log ("range memory allocation failed")
		return 0
	if choice->num == num:
		if choice->prev:
			choice->prev->next = choice->next
		else:
			first_free = choice->next
		if choice->next:
			choice->next->prev = choice->prev
		clear_page ((unsigned)choice, num)
		return (unsigned)choice
	choice->num -= num
	unsigned ret = (unsigned)choice + (choice->num << PAGE_BITS)
	clear_page (ret, num)
	return ret

void phys_free (unsigned page, unsigned num):
	return
	unsigned size = num << PAGE_BITS
	if !first_free || (unsigned)first_free > page:
		// This is the first free block.
		FreePages *n = (FreePages *)page
		n->prev = NULL
		if (unsigned)first_free == page + size:
			// It fits exactly before the previous first free block.
			n->next = first_free->next
			n->num = num + first_free->num
		else:
			// It is a new block.
			n->next = first_free
			n->num = num
		first_free = n
		if n->next:
			n->next->prev = n
		return
	FreePages *p
	for p = first_free; p->next && (unsigned)p->next < page; p = p->next:
		// Do nothing.
	// The new block should be inserted directly after p.
	if (unsigned)p->next == page + size:
		// It can be merged with the block after it: do that.
		FreePages *n = (FreePages *)page
		n->prev = p
		n->next = p->next->next
		if n->next:
			n->next->prev = n
		n->num = num + p->next->num
		p->next = n
		if (unsigned)p + (p->num << PAGE_BITS) == (unsigned)n:
			// It can also be merged with the page before it: do that as well.
			p->num += n->num
			p->next = n->next
			if p->next:
				p->next->prev = p
		return
	// The new block cannot be merged with the block after it.
	if (unsigned)p + (p->num << PAGE_BITS) == page:
		// But it can be merged with the one before it: do that.
		p->num += num
		return
	// The new block cannot be merged at all.
	FreePages *n = (FreePages *)page
	n->next = p->next
	n->prev = p
	if n->next:
		n->next->prev = n
	p->next = n
	n->num = num
#endif

unsigned raw_zalloc ():
	return phys_alloc (1)

void raw_pfree (unsigned page):
	return phys_free (page, 1)

unsigned Memory::zalloc ():
	if !use ():
		dbg_log ("limit reached: allocation not allowed")
		return NULL
	return raw_zalloc ()

void Memory::pfree (unsigned page):
	unuse ()
	return raw_pfree (page)

unsigned Memory::palloc ():
	return zalloc ()

void Memory::zfree (unsigned page):
	pfree (page)