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// Copyright 2020 The Chromium OS Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
use std::fs::File;
use std::io::{self, BufRead, BufReader, Cursor, Read, Write};
use std::mem::size_of;
use std::os::unix::fs::FileExt;
use std::os::unix::io::AsRawFd;
use crate::filesystem::{FileSystem, ZeroCopyReader, ZeroCopyWriter};
use crate::server::{Mapper, Reader, Server, Writer};
use crate::sys;
use crate::{Error, Result};
struct DevFuseReader<'a> {
// File representing /dev/fuse for reading, with sufficient buffer to accommodate a FUSE read
// transaction.
reader: &'a mut BufReader<File>,
}
impl<'a> DevFuseReader<'a> {
pub fn new(reader: &'a mut BufReader<File>) -> Self {
DevFuseReader { reader }
}
}
impl Read for DevFuseReader<'_> {
fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
self.reader.read(buf)
}
}
impl Reader for DevFuseReader<'_> {}
impl ZeroCopyReader for DevFuseReader<'_> {
fn read_to(&mut self, f: &mut File, count: usize, off: u64) -> io::Result<usize> {
let buf = self.reader.fill_buf()?;
let end = std::cmp::min(count, buf.len());
let written = f.write_at(&buf[..end], off)?;
self.reader.consume(written);
Ok(written)
}
}
struct DevFuseWriter<'a> {
// File representing /dev/fuse for writing.
dev_fuse: &'a mut File,
// An internal buffer to allow generating data and header out of order, such that they can be
// flushed at once. This is wrapped by a cursor for tracking the current written position.
write_buf: &'a mut Cursor<Vec<u8>>,
}
impl<'a> DevFuseWriter<'a> {
pub fn new(dev_fuse: &'a mut File, write_buf: &'a mut Cursor<Vec<u8>>) -> Self {
debug_assert_eq!(write_buf.position(), 0);
DevFuseWriter {
dev_fuse,
write_buf,
}
}
}
impl Write for DevFuseWriter<'_> {
fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
self.write_buf.write(buf)
}
fn flush(&mut self) -> io::Result<()> {
self.dev_fuse.write_all(&self.write_buf.get_ref()[..])?;
self.write_buf.set_position(0);
self.write_buf.get_mut().clear();
Ok(())
}
}
impl Writer for DevFuseWriter<'_> {
type ClosureWriter = Self;
fn write_at<F>(&mut self, offset: usize, f: F) -> io::Result<usize>
where
F: Fn(&mut Self) -> io::Result<usize>,
{
// Restore the cursor for idempotent.
let original = self.write_buf.position();
self.write_buf.set_position(offset as u64);
let r = f(self);
self.write_buf.set_position(original);
r
}
fn has_sufficient_buffer(&self, size: u32) -> bool {
(self.write_buf.position() as usize + size as usize) < self.write_buf.get_ref().capacity()
}
}
impl ZeroCopyWriter for DevFuseWriter<'_> {
fn write_from(&mut self, f: &mut File, count: usize, off: u64) -> io::Result<usize> {
let pos = self.write_buf.position() as usize;
let end = pos + count;
let buf = self.write_buf.get_mut();
let old_end = buf.len();
buf.resize(end, 0);
let read = f.read_at(&mut buf[pos..end], off)?;
let new_end = pos + read;
debug_assert!(new_end >= old_end);
buf.truncate(new_end);
self.write_buf.set_position(new_end as u64);
Ok(read)
}
}
struct DevFuseMapper;
impl DevFuseMapper {
fn new() -> Self {
Self {}
}
}
impl Mapper for DevFuseMapper {
fn map(
&self,
_mem_offset: u64,
_size: usize,
_fd: &dyn AsRawFd,
_file_offset: u64,
_prot: u32,
) -> io::Result<()> {
Err(io::Error::from_raw_os_error(libc::EOPNOTSUPP))
}
fn unmap(&self, _offset: u64, _size: u64) -> io::Result<()> {
Err(io::Error::from_raw_os_error(libc::EOPNOTSUPP))
}
}
/// Start the FUSE message handling loop. Returns when an error happens.
pub fn start_message_loop<F: FileSystem + Sync>(
dev_fuse: File,
max_write: u32,
max_read: u32,
fs: F,
) -> Result<()> {
let server = Server::new(fs);
let mut buf_reader = BufReader::with_capacity(
max_write as usize + size_of::<sys::InHeader>() + size_of::<sys::WriteIn>(),
dev_fuse.try_clone().map_err(Error::EndpointSetup)?,
);
let mut write_buf = Cursor::new(Vec::with_capacity(max_read as usize));
let mut wfile = dev_fuse.try_clone().map_err(Error::EndpointSetup)?;
loop {
let dev_fuse_reader = DevFuseReader::new(&mut buf_reader);
let dev_fuse_writer = DevFuseWriter::new(&mut wfile, &mut write_buf);
let dev_fuse_mapper = DevFuseMapper::new();
if let Err(e) = server.handle_message(dev_fuse_reader, dev_fuse_writer, &dev_fuse_mapper) {
return Err(e);
}
}
}
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