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use crate::defs::{self, Mem};
use core::ffi::c_void;
use core::{ptr, slice};
// this is POC code, it will be ugly
extern "C" {
pub fn ___KERNEL_END__();
}
type BitU8 = u8;
/// Bitmap for physical frames
pub struct FMap {
pub bm: &'static mut [BitU8],
// skip over the kernel image and the bitmap itself.
pub skip_byte: usize,
}
pub enum PMAError {
DoubleFree,
}
impl FMap {
pub fn new() -> Self {
let map_start = ___KERNEL_END__ as usize;
let fmap = Self {
bm: unsafe { slice::from_raw_parts_mut(map_start as *mut u8, Mem::PHY_BM_SIZE) },
// looks ugly, perhaps FIXME
// We'll waste several frames for the sake of easy alignment
skip_byte: 1 + ((map_start >> Mem::PAGE_SHIFT) / 8),
};
fmap
}
/// return : index to the bitmap u8 , bit mask to retrive the bit.
fn locate_bit(addr: usize) -> Option<(usize, u8)> {
if addr >= Mem::PHY_TOP {
return None;
}
let pn = addr >> Mem::PAGE_SHIFT;
let idx = pn / 8;
let mask: u8 = 1 << (pn % 8);
Some((idx, mask))
}
pub fn alloc_frame(&mut self) -> usize {
for i in self.skip_byte..self.bm.len() {
if self.bm[i] == 0xff {
continue;
}
todo!()
}
0
}
pub fn dealloc_frame(&mut self) -> Result<(), PMAError> {
Ok(())
}
pub fn init(&mut self) {
for i in 0..self.skip_byte {
self.bm[i] = 0xff;
}
for i in self.skip_byte..self.bm.len() {
self.bm[i] = 0;
}
}
}
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