// vmm.c
// Author: Josh Holtrop
// Date: 09/30/03
// Rewritten from scratch: 12/23/03


void	vmm_init()
{
	dword *pageTables = (dword *)0xC0104000;	//this is the location of the page directory
	pageTables[0x3FF] = 0x104000|0x03;		//the last page directory entry points to the page directory itself
	if (videoMode)	//we are in a graphical mode
	{
		dword vidPages = video_mode.XResolution * video_mode.YResolution * (video_mode.BitsPerPixel >> 3);
		if (vidPages % 4096)
			vidPages = (vidPages >> 12) + 1;
		else
			vidPages = (vidPages >> 12);
		vmm_mapn(0xF0000000, video_mode.PhysBasePtr, vidPages);
	}
	dword firstHeapEntryBlock = (dword)mm_palloc();
	vmm_map1((dword)firstHeapEntry, firstHeapEntryBlock);
	HeapEntryBlock *heb = (HeapEntryBlock *)firstHeapEntry;
	vmm_heb_init(heb);
	heb->entry[0].base = (dword)firstHeapEntry;	//start of kernel's heap memory
	heb->entry[0].size = 4096;			//the first HeapEntryBlock is 1 page long
	heb->entry[0].attributes = VMM_HE_HEB;		//this is a HeapEntryBlock
	heb->entry[1].base = (dword)firstHeapEntry+4096;	//this is the start of the rest of the kernel's heap memory
	heb->entry[1].size = 0x10000000-4096;		//the rest of the kernel's heap memory: 256mb - 4kb
	heb->entry[1].attributes = VMM_HE_HOLE;		//this is a hold - an unmapped section of heap memory
}


void	vmm_heb_init(HeapEntryBlock *heb)
{
	int a;
	for (a = 0; a < 256; a++)
	{
		heb->entry[a].base = 0;
		heb->entry[a].size = 0;
		heb->entry[a].attributes = VMM_HE_UNUSED;
		heb->entry[a].link = (dword)&(heb->entry[a+1]);
	}
	heb->entry[255].link = 0;
}



void	vmm_map1(dword virt, dword physical)
{
	dword pde = virt >> 22;
	dword pte = (virt & 0x003FF000) >> 12;
	dword *pageTables = (dword *)0xC0104000;	//this is the location of the page directory
	if (!(pageTables[pde] & 0x01))		//the page directory entry does not exist, we must allocate a page for it
	{
		dword *newpagetable = mm_palloc();
		pageTables[pde] = ((dword)newpagetable) | 0x03;
		invlpg(virt);
		dword *newpteptr = (dword *)(0xFFC00000 | (pde << 12));	//points to first dword of newly allocated page table
		int a;
		for (a = 0; a < 1024; a++)
		{
			newpteptr[a] = 0;
		}
	}
	dword *pteptr = (dword *)(0xFFC00000 | (pde << 12) | (pte << 2));
	*pteptr = physical | 0x03;
	invlpg(virt);
}


void	vmm_mapn(dword virt, dword physical, dword n)
{
	for (; n > 0; n--)
	{
		vmm_map1(virt, physical);
		virt += 4096;
		physical += 4096;
	}
}


void	vmm_unmap1(dword virt)
{
	dword *pteptr = (dword *)(0xFFC00000 | ((virt & 0xFFC00000) >> 10) | ((virt & 0x003FF000) >> 10));
	*pteptr = 0;
 	invlpg(virt);
}


void	vmm_unmapn(dword virt, dword n)
{
	for (; n > 0; n--)
	{
		vmm_unmap1(virt);
		virt += 4096;
	}
}


void	*malloc(dword bytes)
{
	HeapEntry *he = firstHeapEntry;
	for (;;)
	{
		if ((he->size >= bytes) && (he->attributes = VMM_HE_FREE))
		{
			if (he->size == bytes)
			{
				he->attributes = VMM_HE_USED;
				return (void *)(he->base);
			}
			else
			{
				//get the next HeapEntry, save in it the free mem, save in this entry the used mem...
			}
		}
	}
	return 0;
}



int	free(void *ptr)
{




}