/// read the value in the given tls slot
pub unsafe fn read_tls(index: u32) -> usize {
    let mut tls_slot: usize;
    core::arch::asm!(
    "mov {x}, gs:[1480h + {y:r} * 8]",
    x = out(reg) tls_slot,
    y = in(reg) index
    );
    tls_slot
}

/// write a value into the given tls slot
pub unsafe fn write_tls(index: u32, value: usize) {
    core::arch::asm!(
    "mov gs:[1480h + {y:r} * 8], {x}",
    x = in(reg) value,
    y = in(reg) index
    );
}

#[inline(always)]
unsafe fn read_tls_bitmap() -> u64 {
    let mut _tls: u64 = 0;
    core::arch::asm!(
    "mov {x}, gs:[60h]",    // TEB->PEB
    "mov {x}, [{x} + 80h]", // PEB->TlsBitmap
    x = out(reg) _tls,
    );
    _tls
}

#[inline(always)]
unsafe fn write_tls_bitmap(value: u64) {
    let peb: u64 = 0;
    core::arch::asm!(
    "mov {x}, gs:[60h]",    // TEB->PEB
    "mov [{x} + 80h], {y}", // PEB->TlsBitmap
    x = in(reg) peb,
    y = in(reg) value,
    );
}

/// acquires a tls slot
pub unsafe fn acquire_tls() -> Option<u32> {
    let bitmap = read_tls_bitmap();
    (0..64)
        .filter(|i| bitmap & ( 1 << i ) == 0)
        .inspect(|i|{
            write_tls_bitmap(bitmap | ( 1 << i))
        }).next()
}

/// free's the given tls slot
pub unsafe fn release_tls(slot: u32) {
    write_tls_bitmap(read_tls_bitmap() & !(1 << slot ))
}