#pypp 0
#include "kernel.hh"

static FreePage *zero_pages, *junk_pages

extern unsigned _end
unsigned init_memory (unsigned mem):
	zero_pages = NULL
	// Fill junk pages with all memory not currently used.
	junk_pages = (FreePage *)(((unsigned)&_end + ~PAGE_MASK) & PAGE_MASK)
	FreePage *p, *next
	unsigned count = 1
	for p = junk_pages, next = p; (unsigned)next - 0x80000000 < mem; p = next, next = (FreePage *)((unsigned)p + PAGE_SIZE):
		p->next = next
		++count
	p->next = NULL
	return count

unsigned raw_zalloc ():
	FreePage *ret = zero_pages
	if !ret:
		ret = junk_pages
		junk_pages = ret->next
		for unsigned i = 0; i < (PAGE_SIZE >> 2); ++i:
			((unsigned *)ret)[i] = 0
	else:
		zero_pages = ret->next
		ret->next = NULL
	return (unsigned)ret

void raw_pfree (unsigned page):
	if !page:
		return
	FreePage *p = (FreePage *)page
	p->next = junk_pages
	junk_pages = p

unsigned Memory::palloc ():
	if !use ():
		return NULL
	FreePage *ret = junk_pages
	if !ret:
		ret = zero_pages
		zero_pages = ret->next
	else:
		junk_pages = ret->next
	return (unsigned)ret
	
unsigned Memory::zalloc ():
	if !use ():
		return NULL
	return raw_zalloc ()

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

void Memory::zfree (unsigned page):
	unuse ()
	FreePage *p = (FreePage *)page
	p->next = zero_pages
	zero_pages = p