rust-fatfs/src/utils.rs
Rafał Harabień de9977e571 Don't panic in Drop.
The same behavior exists (without logging) in BufWriter from std crate.
It's not recommended to depend on flush during drop.
Instead user should flush explicitly and check for error.
2017-11-07 01:13:02 +01:00

139 lines
3.5 KiB
Rust

use std::io::prelude::*;
use std::io;
use std::cmp;
pub trait ReadSeek: Read + Seek {}
impl<T> ReadSeek for T where T: Read + Seek {}
pub trait ReadWriteSeek: Read + Write + Seek {}
impl<T> ReadWriteSeek for T where T: Read + Write + Seek {}
const BUF_SIZE: usize = 512;
pub struct BufStream<T: Read+Write+Seek> {
inner: T,
buf: [u8; BUF_SIZE],
len: usize,
pos: usize,
write: bool,
}
/// The BufStream struct adds buffering to underlying file or device.
///
/// It's basically composition of BufReader and BufWritter.
impl<T: Read+Write+Seek> BufStream<T> {
/// Creates new BufStream object for given stream.
pub fn new(inner: T) -> Self {
BufStream::<T> {
inner,
buf: [0; BUF_SIZE],
pos: 0,
len: 0,
write: false,
}
}
fn flush_buf(&mut self) -> io::Result<()> {
if self.write {
self.inner.write_all(&self.buf[..self.pos])?;
self.pos = 0;
}
Ok(())
}
fn make_reader(&mut self) -> io::Result<()> {
if self.write {
self.flush_buf()?;
self.write = false;
self.len = 0;
self.pos = 0;
}
Ok(())
}
fn make_writter(&mut self) -> io::Result<()> {
if !self.write {
self.inner.seek(io::SeekFrom::Current(-(self.len as i64 - self.pos as i64)))?;
self.write = true;
self.len = 0;
self.pos = 0;
}
Ok(())
}
}
impl<T: Read+Write+Seek> BufRead for BufStream<T> {
fn fill_buf(&mut self) -> io::Result<&[u8]> {
self.make_reader()?;
if self.pos >= self.len {
self.len = self.inner.read(&mut self.buf)?;
self.pos = 0;
}
Ok(&self.buf[self.pos..self.len])
}
fn consume(&mut self, amt: usize) {
self.pos = cmp::min(self.pos + amt, self.len);
}
}
impl<T: Read+Write+Seek> Read for BufStream<T> {
fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
// Make sure we are in read mode
self.make_reader()?;
// Check if this read is bigger than buffer size
if self.pos == self.len && buf.len() >= BUF_SIZE {
return self.inner.read(buf);
}
let nread = {
let mut rem = self.fill_buf()?;
rem.read(buf)?
};
self.consume(nread);
Ok(nread)
}
}
impl<T: Read+Write+Seek> Write for BufStream<T> {
fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
// Make sure we are in write mode
self.make_writter()?;
if self.pos + buf.len() > BUF_SIZE {
self.flush_buf()?;
if buf.len() >= BUF_SIZE {
return self.inner.write(buf);
}
}
let written = (&mut self.buf[self.pos..]).write(buf)?;
self.pos += written;
Ok(written)
}
fn flush(&mut self) -> io::Result<()> {
self.flush_buf()?;
self.inner.flush()
}
}
impl<T: Read+Write+Seek> Seek for BufStream<T> {
fn seek(&mut self, pos: io::SeekFrom) -> io::Result<u64> {
self.flush_buf()?;
let new_pos = match pos {
io::SeekFrom::Current(x) => io::SeekFrom::Current(x - (self.len as i64 - self.pos as i64)),
_ => pos,
};
self.pos = 0;
self.len = 0;
self.inner.seek(new_pos)
}
}
impl<T: Read+Write+Seek> Drop for BufStream<T> {
fn drop(&mut self) {
match self.flush() {
Err(err) => error!("flush failed {}", err),
_ => {},
}
}
}