use super::page_table::{PAGE_SIZE, PageTable};
use crate::board;

// Boot bump allocator for kernel-only memory; must never reach the user pool.
static mut NEXT_FREE: usize = 0;

pub fn init_allocator(start: usize) {
    unsafe {
        NEXT_FREE = start;
    }
}

pub fn alloc_zeroed_page() -> usize {
    unsafe {
        let addr = NEXT_FREE;
        if addr + PAGE_SIZE > super::phys_to_virt(board::USER_POOL_BASE) {
            crate::halt(&crate::hw::uart::Uart::new(), "boot allocator exhausted");
        }
        NEXT_FREE += PAGE_SIZE;
        core::ptr::write_bytes(addr as *mut u8, 0, PAGE_SIZE);
        addr
    }
}

pub fn alloc_page_table() -> &'static mut PageTable {
    unsafe { &mut *(alloc_zeroed_page() as *mut PageTable) }
}