rust-fatfs/src/file.rs

57 lines
1.9 KiB
Rust
Raw Normal View History

2017-09-23 06:22:31 +08:00
use std::cmp;
2017-09-23 04:27:39 +08:00
use std::io::prelude::*;
2017-09-23 06:22:31 +08:00
use std::io::SeekFrom;
2017-09-23 04:27:39 +08:00
use std::io;
2017-09-23 05:20:06 +08:00
use fs::FatSharedStateRef;
2017-09-23 04:27:39 +08:00
#[allow(dead_code)]
pub struct FatFile {
first_cluster: u32,
2017-09-24 03:53:32 +08:00
size: Option<u32>,
2017-09-23 04:27:39 +08:00
offset: u32,
current_cluster: Option<u32>,
state: FatSharedStateRef,
2017-09-23 04:27:39 +08:00
}
impl FatFile {
2017-09-24 03:53:32 +08:00
pub(crate) fn new(first_cluster: u32, size: Option<u32>, state: FatSharedStateRef) -> FatFile {
2017-09-23 04:27:39 +08:00
FatFile {
first_cluster, size, state,
current_cluster: Some(first_cluster),
offset: 0,
2017-09-23 04:27:39 +08:00
}
}
}
impl Read for FatFile {
fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
let mut buf_offset: usize = 0;
let cluster_size = self.state.borrow().get_cluster_size();
let mut state = self.state.borrow_mut();
loop {
let offset_in_cluster = self.offset % cluster_size;
let bytes_left_in_cluster = (cluster_size - offset_in_cluster) as usize;
2017-09-24 03:53:32 +08:00
let bytes_left_in_file = self.size.map(|size| (size - self.offset) as usize).unwrap_or(bytes_left_in_cluster);
let bytes_left_in_buf = buf.len() - buf_offset;
2017-09-24 03:53:32 +08:00
let read_size = cmp::min(cmp::min(bytes_left_in_buf, bytes_left_in_cluster), bytes_left_in_file);
if read_size == 0 {
break;
}
let current_cluster = self.current_cluster.unwrap();
let offset_in_fs = state.offset_from_cluster(current_cluster) + (offset_in_cluster as u64);
state.rdr.seek(SeekFrom::Start(offset_in_fs))?;
let read_bytes = state.rdr.read(&mut buf[buf_offset..buf_offset+read_size])?;
if read_bytes == 0 {
break;
}
self.offset += read_bytes as u32;
buf_offset += read_bytes;
if self.offset % cluster_size == 0 {
self.current_cluster = state.table.get_next_cluster(current_cluster);
}
}
Ok(buf_offset)
2017-09-23 04:27:39 +08:00
}
}