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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,
}
impl<T: Read+Write+Seek> BufStream<T> {
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> {
self.make_reader()?;
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> {
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),
_ => {},
}
}
}