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use crate::block_device::{BlockDevice, BLOCK_SIZE};
use std::sync::Arc;
pub struct Bitmap {
pub starting_block: usize,
pub length: usize,
pub device: Arc<dyn BlockDevice>,
pub data: Vec<u8>,
pub dirty_blocks: Vec<usize>,
}
impl Bitmap {
pub fn new(starting_block: usize, length: usize, device: Arc<dyn BlockDevice>) -> Self {
Self {
starting_block,
length,
device,
data: vec![0u8; length * BLOCK_SIZE],
dirty_blocks: Vec::new(),
}
}
pub fn allocate(&mut self) -> usize {
for (i, byte) in self.data.iter_mut().enumerate() {
let leading_ones = byte.leading_ones();
if leading_ones != 8 {
*byte |= (1 << (7 - leading_ones)) as u8;
self.dirty_blocks.push(i / BLOCK_SIZE);
return i * 8 + leading_ones as usize;
}
}
panic!("No more space for allocation!")
}
pub fn query(&self, index: usize) -> bool {
self.data[index / 8] & ((1 << (7 - index % 8)) as u8) != 0
}
fn write_back(&mut self) {
for block_index_offset in self.dirty_blocks.iter() {
let buffer_front_index = BLOCK_SIZE * block_index_offset;
let buffer_back_index = BLOCK_SIZE * (block_index_offset + 1);
self.device.write(
self.starting_block + block_index_offset,
&self.data[buffer_front_index..buffer_back_index],
);
}
self.dirty_blocks = Vec::new();
}
}
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