pub const PAGE_SHIFT: usize = 12;
pub const PAGE_SIZE: usize = 1 << PAGE_SHIFT;

pub const PTE_SHIFT: u32 = 12;
pub const PMD_SHIFT: u32 = 21;
pub const PUD_SHIFT: u32 = 30;
pub const PGD_SHIFT: u32 = 39;

pub const PTE_SIZE: usize = 1 << PTE_SHIFT;
pub const PMD_SIZE: usize = 1 << PMD_SHIFT;
pub const PUD_SIZE: usize = 1 << PUD_SHIFT;
pub const PGD_SIZE: usize = 1 << PGD_SHIFT;

pub const PTE_MASK: usize = 1 << PTE_SHIFT - 1;
pub const PMD_MASK: usize = 1 << PMD_SHIFT - 1;
pub const PUD_MASK: usize = 1 << PUD_SHIFT - 1;
pub const PGD_MASK: usize = 1 << PGD_SHIFT - 1;

pub const ENTRIES_PER_TABLE: usize = PAGE_SIZE / 64;

pub const PFType = struct{
    pub const PROT: usize = 0;
    pub const WRITE: usize = 1<<1;
    pub const USER: usize = 1<<2;
    pub const RSVD: usize = 1<<3;
    pub const INSTR: usize = 1<<4;
    pub const PK: usize = 1<<5;
    pub const SHSTK: usize = 1<<6;
};

pub const PGDEntry = packed struct {
    present: u1,
    write: u1,
    supervisor: u1,
    write_through: u1,
    cache_disable: u1,
    accessed: u1,
    _padding_1: u6,
    addr: u40,
    pub fn getIndex(self: usize) usize {
        return (self >> PGD_SHIFT) & 0x1FF;
    }
};