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pipe.rs
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pipe.rs
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use crate::syscalls::types::*;
use crate::syscalls::{read_bytes, write_bytes};
use bytes::{Buf, Bytes};
use wasmer_vfs::VirtualFile;
use std::convert::TryInto;
use std::io::{Read, Write, Seek};
use std::ops::DerefMut;
use std::sync::mpsc::{self, TryRecvError};
use std::sync::Mutex;
use std::time::Duration;
use wasmer::WasmSlice;
use wasmer::{MemorySize, MemoryView};
#[derive(Debug)]
pub struct WasiPipe {
/// Sends bytes down the pipe
tx: Mutex<mpsc::Sender<Vec<u8>>>,
/// Receives bytes from the pipe
rx: Mutex<mpsc::Receiver<Vec<u8>>>,
/// Buffers the last read message from the pipe while its being consumed
read_buffer: Mutex<Option<Bytes>>,
}
impl WasiPipe {
pub fn new() -> (WasiPipe, WasiPipe) {
let (tx1, rx1) = mpsc::channel();
let (tx2, rx2) = mpsc::channel();
let pipe1 = WasiPipe {
tx: Mutex::new(tx1),
rx: Mutex::new(rx2),
read_buffer: Mutex::new(None),
};
let pipe2 = WasiPipe {
tx: Mutex::new(tx2),
rx: Mutex::new(rx1),
read_buffer: Mutex::new(None),
};
(pipe1, pipe2)
}
pub fn recv<M: MemorySize>(
&mut self,
memory: &MemoryView,
iov: WasmSlice<__wasi_iovec_t<M>>,
timeout: Duration,
) -> Result<usize, __wasi_errno_t> {
let mut elapsed = Duration::ZERO;
let mut tick_wait = 0u64;
loop {
{
let mut read_buffer = self.read_buffer.lock().unwrap();
if let Some(buf) = read_buffer.as_mut() {
let buf_len = buf.len();
if buf_len > 0 {
let reader = buf.as_ref();
let read = read_bytes(reader, memory, iov).map(|a| a as usize)?;
buf.advance(read);
return Ok(read);
}
}
}
let rx = self.rx.lock().unwrap();
let data = match rx.try_recv() {
Ok(a) => a,
Err(TryRecvError::Empty) => {
if elapsed > timeout {
return Err(__WASI_ETIMEDOUT);
}
// Linearly increasing wait time
tick_wait += 1;
let wait_time = u64::min(tick_wait / 10, 20);
let wait_time = std::time::Duration::from_millis(wait_time);
std::thread::park_timeout(wait_time);
elapsed += wait_time;
continue;
}
Err(TryRecvError::Disconnected) => {
return Ok(0);
}
};
drop(rx);
let mut read_buffer = self.read_buffer.lock().unwrap();
read_buffer.replace(Bytes::from(data));
}
}
pub fn send<M: MemorySize>(
&mut self,
memory: &MemoryView,
iov: WasmSlice<__wasi_ciovec_t<M>>,
) -> Result<usize, __wasi_errno_t> {
let buf_len: M::Offset = iov
.iter()
.filter_map(|a| a.read().ok())
.map(|a| a.buf_len)
.sum();
let buf_len: usize = buf_len.try_into().map_err(|_| __WASI_EINVAL)?;
let mut buf = Vec::with_capacity(buf_len);
write_bytes(&mut buf, memory, iov)?;
let tx = self.tx.lock().unwrap();
tx.send(buf).map_err(|_| __WASI_EIO)?;
Ok(buf_len)
}
pub fn close(&mut self) {
let (mut null_tx, _) = mpsc::channel();
let (_, mut null_rx) = mpsc::channel();
{
let mut guard = self.rx.lock().unwrap();
std::mem::swap(guard.deref_mut(), &mut null_rx);
}
{
let mut guard = self.tx.lock().unwrap();
std::mem::swap(guard.deref_mut(), &mut null_tx);
}
{
let mut read_buffer = self.read_buffer.lock().unwrap();
read_buffer.take();
}
}
}
impl Read for WasiPipe {
fn read(&mut self, buf: &mut [u8]) -> std::io::Result<usize> {
loop {
{
let mut read_buffer = self.read_buffer.lock().unwrap();
if let Some(inner_buf) = read_buffer.as_mut() {
let buf_len = inner_buf.len();
if buf_len > 0 {
let mut reader = inner_buf.as_ref();
let read = reader.read(buf).map(|_| buf_len as usize)?;
inner_buf.advance(read);
return Ok(read);
}
}
}
let rx = self.rx.lock().unwrap();
if let Ok(data) = rx.recv() {
drop(rx);
let mut read_buffer = self.read_buffer.lock().unwrap();
read_buffer.replace(Bytes::from(data));
} else {
return Ok(0);
}
}
}
}
impl Write for WasiPipe {
fn write(&mut self, buf: &[u8]) -> std::io::Result<usize> {
let tx = self.tx.lock().unwrap();
tx.send(buf.to_vec())
.map_err(|_| Into::<std::io::Error>::into(std::io::ErrorKind::BrokenPipe))?;
Ok(buf.len())
}
fn flush(&mut self) -> std::io::Result<()> {
Ok(())
}
}
impl Seek for WasiPipe {
fn seek(&mut self, _pos: std::io::SeekFrom) -> std::io::Result<u64> {
Ok(0)
}
}
impl VirtualFile
for WasiPipe
{
/// the last time the file was accessed in nanoseconds as a UNIX timestamp
fn last_accessed(&self) -> u64 {
0
}
/// the last time the file was modified in nanoseconds as a UNIX timestamp
fn last_modified(&self) -> u64 {
0
}
/// the time at which the file was created in nanoseconds as a UNIX timestamp
fn created_time(&self) -> u64 {
0
}
/// the size of the file in bytes
fn size(&self) -> u64 {
0
}
/// Change the size of the file, if the `new_size` is greater than the current size
/// the extra bytes will be allocated and zeroed
fn set_len(&mut self, _new_size: u64) -> wasmer_vfs::Result<()> {
Ok(())
}
/// Request deletion of the file
fn unlink(&mut self) -> wasmer_vfs::Result<()> {
Ok(())
}
/// Store file contents and metadata to disk
/// Default implementation returns `Ok(())`. You should implement this method if you care
/// about flushing your cache to permanent storage
fn sync_to_disk(&self) -> wasmer_vfs::Result<()> {
Ok(())
}
/// Returns the number of bytes available. This function must not block
fn bytes_available(&self) -> wasmer_vfs::Result<usize> {
Ok(self.bytes_available_read()?.unwrap_or(0usize)
+ self.bytes_available_write()?.unwrap_or(0usize))
}
/// Returns the number of bytes available. This function must not block
/// Defaults to `None` which means the number of bytes is unknown
fn bytes_available_read(&self) -> wasmer_vfs::Result<Option<usize>> {
loop {
{
let read_buffer = self.read_buffer.lock().unwrap();
if let Some(inner_buf) = read_buffer.as_ref() {
let buf_len = inner_buf.len();
if buf_len > 0 {
return Ok(Some(buf_len));
}
}
}
let rx = self.rx.lock().unwrap();
if let Ok(data) = rx.try_recv() {
drop(rx);
let mut read_buffer = self.read_buffer.lock().unwrap();
read_buffer.replace(Bytes::from(data));
} else {
return Ok(Some(0));
}
}
}
/// Returns the number of bytes available. This function must not block
/// Defaults to `None` which means the number of bytes is unknown
fn bytes_available_write(&self) -> wasmer_vfs::Result<Option<usize>> {
Ok(None)
}
/// Indicates if the file is opened or closed. This function must not block
/// Defaults to a status of being constantly open
fn is_open(&self) -> bool {
true
}
/// Returns a special file descriptor when opening this file rather than
/// generating a new one
fn get_special_fd(&self) -> Option<u32> {
None
}
/// Used for polling. Default returns `None` because this method cannot be implemented for most types
/// Returns the underlying host fd
fn get_fd(&self) -> Option<wasmer_vfs::FileDescriptor> {
None
}
}