rust-fatfs/src/file.rs

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use std::cmp;
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use std::io::prelude::*;
use std::io::{SeekFrom, ErrorKind};
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use std::io;
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use fs::FileSystemRef;
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#[derive(Clone)]
pub struct File<'a, 'b: 'a> {
first_cluster: Option<u32>,
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size: Option<u32>,
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offset: u32,
current_cluster: Option<u32>,
fs: FileSystemRef<'a, 'b>,
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}
impl <'a, 'b> File<'a, 'b> {
pub(crate) fn new(first_cluster: Option<u32>, size: Option<u32>, fs: FileSystemRef<'a, 'b>) -> Self {
File {
first_cluster, size, fs,
current_cluster: first_cluster,
offset: 0,
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}
}
}
impl <'a, 'b> Read for File<'a, 'b> {
fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
let mut buf_offset: usize = 0;
let cluster_size = self.fs.get_cluster_size();
loop {
let current_cluster = match self.current_cluster {
Some(n) => n,
None => break,
};
let offset_in_cluster = self.offset % cluster_size;
let bytes_left_in_cluster = (cluster_size - offset_in_cluster) as usize;
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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;
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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 offset_in_fs = self.fs.offset_from_cluster(current_cluster) + (offset_in_cluster as u64);
let read_bytes = {
let mut rdr = self.fs.rdr.borrow_mut();
rdr.seek(SeekFrom::Start(offset_in_fs))?;
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 {
let r = self.fs.cluster_iter(current_cluster).skip(1).next();
self.current_cluster = match r {
Some(Err(err)) => return Err(err),
Some(Ok(n)) => Some(n),
None => None,
};
}
}
Ok(buf_offset)
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}
}
impl <'a, 'b> Seek for File<'a, 'b> {
fn seek(&mut self, pos: SeekFrom) -> io::Result<u64> {
let new_offset = match pos {
SeekFrom::Current(x) => self.offset as i64 + x,
SeekFrom::Start(x) => x as i64,
SeekFrom::End(x) => self.size.expect("cannot seek from end if size is unknown") as i64 + x,
};
if new_offset < 0 {
return Err(io::Error::new(ErrorKind::InvalidInput, "invalid seek"));
}
let cluster_size = self.fs.get_cluster_size();
let cluster_count = (new_offset / cluster_size as i64) as usize;
let new_cluster = if cluster_count > 0 {
match self.first_cluster {
Some(n) => {
match self.fs.cluster_iter(n).skip(cluster_count).next() {
Some(Err(err)) => return Err(err),
Some(Ok(n)) => Some(n),
None => None,
}
},
None => None,
}
} else {
self.first_cluster
};
self.offset = new_offset as u32;
self.current_cluster = new_cluster;
Ok(self.offset as u64)
}
}