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use crate::bindings::cli::{
stderr, stdin, stdout, terminal_input, terminal_output, terminal_stderr, terminal_stdin,
terminal_stdout,
};
use crate::bindings::io::streams;
use crate::pipe;
use crate::{
HostInputStream, HostOutputStream, StreamError, StreamResult, Subscribe, WasiImpl, WasiView,
};
use bytes::Bytes;
use std::io::IsTerminal;
use std::sync::Arc;
use tokio::sync::Mutex;
use wasmtime::component::Resource;
/// A trait used to represent the standard input to a guest program.
///
/// This is used to implement various WASI APIs via the method implementations
/// below.
///
/// Built-in implementations are provided for [`Stdin`],
/// [`pipe::MemoryInputPipe`], and [`pipe::ClosedInputStream`].
pub trait StdinStream: Send {
/// Creates a fresh stream which is reading stdin.
///
/// Note that the returned stream must share state with all other streams
/// previously created. Guests may create multiple handles to the same stdin
/// and they should all be synchronized in their progress through the
/// program's input.
///
/// Note that this means that if one handle becomes ready for reading they
/// all become ready for reading. Subsequently if one is read from it may
/// mean that all the others are no longer ready for reading. This is
/// basically a consequence of the way the WIT APIs are designed today.
fn stream(&self) -> Box<dyn HostInputStream>;
/// Returns whether this stream is backed by a TTY.
fn isatty(&self) -> bool;
}
impl StdinStream for pipe::MemoryInputPipe {
fn stream(&self) -> Box<dyn HostInputStream> {
Box::new(self.clone())
}
fn isatty(&self) -> bool {
false
}
}
impl StdinStream for pipe::ClosedInputStream {
fn stream(&self) -> Box<dyn HostInputStream> {
Box::new(*self)
}
fn isatty(&self) -> bool {
false
}
}
/// An impl of [`StdinStream`] built on top of [`crate::pipe::AsyncReadStream`].
//
// Note the usage of `tokio::sync::Mutex` here as opposed to a
// `std::sync::Mutex`. This is intentionally done to implement the `Subscribe`
// variant of this trait. Note that in doing so we're left with the quandry of
// how to implement methods of `HostInputStream` since those methods are not
// `async`. They're currently implemented with `try_lock`, which then raises the
// question of what to do on contention. Currently traps are returned.
//
// Why should it be ok to return a trap? In general concurrency/contention
// shouldn't return a trap since it should be able to happen normally. The
// current assumption, though, is that WASI stdin/stdout streams are special
// enough that the contention case should never come up in practice. Currently
// in WASI there is no actually concurrency, there's just the items in a single
// `Store` and that store owns all of its I/O in a single Tokio task. There's no
// means to actually spawn multiple Tokio tasks that use the same store. This
// means at the very least that there's zero parallelism. Due to the lack of
// multiple tasks that also means that there's no concurrency either.
//
// This `AsyncStdinStream` wrapper is only intended to be used by the WASI
// bindings themselves. It's possible for the host to take this and work with it
// on its own task, but that's niche enough it's not designed for.
//
// Overall that means that the guest is either calling `Subscribe` or it's
// calling `HostInputStream` methods. This means that there should never be
// contention between the two at this time. This may all change in the future
// with WASI 0.3, but perhaps we'll have a better story for stdio at that time
// (see the doc block on the `HostOutputStream` impl below)
pub struct AsyncStdinStream(Arc<Mutex<crate::pipe::AsyncReadStream>>);
impl AsyncStdinStream {
pub fn new(s: crate::pipe::AsyncReadStream) -> Self {
Self(Arc::new(Mutex::new(s)))
}
}
impl StdinStream for AsyncStdinStream {
fn stream(&self) -> Box<dyn HostInputStream> {
Box::new(Self(self.0.clone()))
}
fn isatty(&self) -> bool {
false
}
}
#[async_trait::async_trait]
impl HostInputStream for AsyncStdinStream {
fn read(&mut self, size: usize) -> Result<bytes::Bytes, StreamError> {
match self.0.try_lock() {
Ok(mut stream) => stream.read(size),
Err(_) => Err(StreamError::trap("concurrent reads are not supported")),
}
}
fn skip(&mut self, size: usize) -> Result<usize, StreamError> {
match self.0.try_lock() {
Ok(mut stream) => stream.skip(size),
Err(_) => Err(StreamError::trap("concurrent skips are not supported")),
}
}
async fn cancel(&mut self) {
// Cancel the inner stream if we're the last reference to it:
if let Some(mutex) = Arc::get_mut(&mut self.0) {
match mutex.try_lock() {
Ok(mut stream) => stream.cancel().await,
Err(_) => {}
}
}
}
}
#[async_trait::async_trait]
impl Subscribe for AsyncStdinStream {
async fn ready(&mut self) {
self.0.lock().await.ready().await
}
}
mod worker_thread_stdin;
pub use self::worker_thread_stdin::{stdin, Stdin};
/// Similar to [`StdinStream`], except for output.
pub trait StdoutStream: Send {
/// Returns a fresh new stream which can write to this output stream.
///
/// Note that all output streams should output to the same logical source.
/// This means that it's possible for each independent stream to acquire a
/// separate "permit" to write and then act on that permit. Note that
/// additionally at this time once a permit is "acquired" there's no way to
/// release it, for example you can wait for readiness and then never
/// actually write in WASI. This means that acquisition of a permit for one
/// stream cannot discount the size of a permit another stream could
/// obtain.
///
/// Implementations must be able to handle this
fn stream(&self) -> Box<dyn HostOutputStream>;
/// Returns whether this stream is backed by a TTY.
fn isatty(&self) -> bool;
}
impl StdoutStream for pipe::MemoryOutputPipe {
fn stream(&self) -> Box<dyn HostOutputStream> {
Box::new(self.clone())
}
fn isatty(&self) -> bool {
false
}
}
impl StdoutStream for pipe::SinkOutputStream {
fn stream(&self) -> Box<dyn HostOutputStream> {
Box::new(*self)
}
fn isatty(&self) -> bool {
false
}
}
impl StdoutStream for pipe::ClosedOutputStream {
fn stream(&self) -> Box<dyn HostOutputStream> {
Box::new(*self)
}
fn isatty(&self) -> bool {
false
}
}
/// This implementation will yield output streams that block on writes, and
/// output directly to a file. If truly async output is required, [`AsyncStdoutStream`]
/// should be used instead.
pub struct OutputFile {
file: Arc<std::fs::File>,
}
impl OutputFile {
pub fn new(file: std::fs::File) -> Self {
Self {
file: Arc::new(file),
}
}
}
impl StdoutStream for OutputFile {
fn stream(&self) -> Box<dyn HostOutputStream> {
Box::new(OutputFileStream {
file: Arc::clone(&self.file),
})
}
fn isatty(&self) -> bool {
false
}
}
struct OutputFileStream {
file: Arc<std::fs::File>,
}
#[async_trait::async_trait]
impl Subscribe for OutputFileStream {
async fn ready(&mut self) {}
}
impl HostOutputStream for OutputFileStream {
fn write(&mut self, bytes: Bytes) -> StreamResult<()> {
use std::io::Write;
self.file
.write_all(&bytes)
.map_err(|e| StreamError::LastOperationFailed(anyhow::anyhow!(e)))
}
fn flush(&mut self) -> StreamResult<()> {
use std::io::Write;
self.file
.flush()
.map_err(|e| StreamError::LastOperationFailed(anyhow::anyhow!(e)))
}
fn check_write(&mut self) -> StreamResult<usize> {
Ok(1024 * 1024)
}
}
/// This implementation will yield output streams that block on writes, as they
/// inherit the implementation directly from the rust std library. A different
/// implementation of [`StdoutStream`] will be necessary if truly async output
/// streams are required.
pub struct Stdout;
/// Returns a stream that represents the host's standard out.
///
/// Suitable for passing to
/// [`WasiCtxBuilder::stdout`](crate::WasiCtxBuilder::stdout).
pub fn stdout() -> Stdout {
Stdout
}
impl StdoutStream for Stdout {
fn stream(&self) -> Box<dyn HostOutputStream> {
Box::new(OutputStream::Stdout)
}
fn isatty(&self) -> bool {
std::io::stdout().is_terminal()
}
}
/// This implementation will yield output streams that block on writes, as they
/// inherit the implementation directly from the rust std library. A different
/// implementation of [`StdoutStream`] will be necessary if truly async output
/// streams are required.
pub struct Stderr;
/// Returns a stream that represents the host's standard err.
///
/// Suitable for passing to
/// [`WasiCtxBuilder::stderr`](crate::WasiCtxBuilder::stderr).
pub fn stderr() -> Stderr {
Stderr
}
impl StdoutStream for Stderr {
fn stream(&self) -> Box<dyn HostOutputStream> {
Box::new(OutputStream::Stderr)
}
fn isatty(&self) -> bool {
std::io::stderr().is_terminal()
}
}
enum OutputStream {
Stdout,
Stderr,
}
impl HostOutputStream for OutputStream {
fn write(&mut self, bytes: Bytes) -> StreamResult<()> {
use std::io::Write;
match self {
OutputStream::Stdout => std::io::stdout().write_all(&bytes),
OutputStream::Stderr => std::io::stderr().write_all(&bytes),
}
.map_err(|e| StreamError::LastOperationFailed(anyhow::anyhow!(e)))
}
fn flush(&mut self) -> StreamResult<()> {
use std::io::Write;
match self {
OutputStream::Stdout => std::io::stdout().flush(),
OutputStream::Stderr => std::io::stderr().flush(),
}
.map_err(|e| StreamError::LastOperationFailed(anyhow::anyhow!(e)))
}
fn check_write(&mut self) -> StreamResult<usize> {
Ok(1024 * 1024)
}
}
#[async_trait::async_trait]
impl Subscribe for OutputStream {
async fn ready(&mut self) {}
}
/// A wrapper of [`crate::pipe::AsyncWriteStream`] that implements
/// [`StdoutStream`]. Note that the [`HostOutputStream`] impl for this is not
/// correct when used for interleaved async IO.
//
// Note that the use of `tokio::sync::Mutex` here is intentional, in addition to
// the `try_lock()` calls below in the implementation of `HostOutputStream`. For
// more information see the documentation on `AsyncStdinStream`.
pub struct AsyncStdoutStream(Arc<Mutex<crate::pipe::AsyncWriteStream>>);
impl AsyncStdoutStream {
pub fn new(s: crate::pipe::AsyncWriteStream) -> Self {
Self(Arc::new(Mutex::new(s)))
}
}
impl StdoutStream for AsyncStdoutStream {
fn stream(&self) -> Box<dyn HostOutputStream> {
Box::new(Self(self.0.clone()))
}
fn isatty(&self) -> bool {
false
}
}
// This implementation is known to be bogus. All check-writes and writes are
// directed at the same underlying stream. The check-write/write protocol does
// require the size returned by a check-write to be accepted by write, even if
// other side-effects happen between those calls, and this implementation
// permits another view (created by StdoutStream::stream()) of the same
// underlying stream to accept a write which will invalidate a prior
// check-write of another view.
// Ultimately, the Std{in,out}Stream::stream() methods exist because many
// different places in a linked component (which may itself contain many
// modules) may need to access stdio without any coordination to keep those
// accesses all using pointing to the same resource. So, we allow many
// resources to be created. We have the reasonable expectation that programs
// won't attempt to interleave async IO from these disparate uses of stdio.
// If that expectation doesn't turn out to be true, and you find yourself at
// this comment to correct it: sorry about that.
#[async_trait::async_trait]
impl HostOutputStream for AsyncStdoutStream {
fn check_write(&mut self) -> Result<usize, StreamError> {
match self.0.try_lock() {
Ok(mut stream) => stream.check_write(),
Err(_) => Err(StreamError::trap("concurrent writes are not supported")),
}
}
fn write(&mut self, bytes: Bytes) -> Result<(), StreamError> {
match self.0.try_lock() {
Ok(mut stream) => stream.write(bytes),
Err(_) => Err(StreamError::trap("concurrent writes not supported yet")),
}
}
fn flush(&mut self) -> Result<(), StreamError> {
match self.0.try_lock() {
Ok(mut stream) => stream.flush(),
Err(_) => Err(StreamError::trap("concurrent flushes not supported yet")),
}
}
async fn cancel(&mut self) {
// Cancel the inner stream if we're the last reference to it:
if let Some(mutex) = Arc::get_mut(&mut self.0) {
match mutex.try_lock() {
Ok(mut stream) => stream.cancel().await,
Err(_) => {}
}
}
}
}
#[async_trait::async_trait]
impl Subscribe for AsyncStdoutStream {
async fn ready(&mut self) {
self.0.lock().await.ready().await
}
}
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum IsATTY {
Yes,
No,
}
impl<T> stdin::Host for WasiImpl<T>
where
T: WasiView,
{
fn get_stdin(&mut self) -> Result<Resource<streams::InputStream>, anyhow::Error> {
let stream = self.ctx().stdin.stream();
Ok(self.table().push(stream)?)
}
}
impl<T> stdout::Host for WasiImpl<T>
where
T: WasiView,
{
fn get_stdout(&mut self) -> Result<Resource<streams::OutputStream>, anyhow::Error> {
let stream = self.ctx().stdout.stream();
Ok(self.table().push(stream)?)
}
}
impl<T> stderr::Host for WasiImpl<T>
where
T: WasiView,
{
fn get_stderr(&mut self) -> Result<Resource<streams::OutputStream>, anyhow::Error> {
let stream = self.ctx().stderr.stream();
Ok(self.table().push(stream)?)
}
}
pub struct TerminalInput;
pub struct TerminalOutput;
impl<T> terminal_input::Host for WasiImpl<T> where T: WasiView {}
impl<T> terminal_input::HostTerminalInput for WasiImpl<T>
where
T: WasiView,
{
fn drop(&mut self, r: Resource<TerminalInput>) -> anyhow::Result<()> {
self.table().delete(r)?;
Ok(())
}
}
impl<T> terminal_output::Host for WasiImpl<T> where T: WasiView {}
impl<T> terminal_output::HostTerminalOutput for WasiImpl<T>
where
T: WasiView,
{
fn drop(&mut self, r: Resource<TerminalOutput>) -> anyhow::Result<()> {
self.table().delete(r)?;
Ok(())
}
}
impl<T> terminal_stdin::Host for WasiImpl<T>
where
T: WasiView,
{
fn get_terminal_stdin(&mut self) -> anyhow::Result<Option<Resource<TerminalInput>>> {
if self.ctx().stdin.isatty() {
let fd = self.table().push(TerminalInput)?;
Ok(Some(fd))
} else {
Ok(None)
}
}
}
impl<T> terminal_stdout::Host for WasiImpl<T>
where
T: WasiView,
{
fn get_terminal_stdout(&mut self) -> anyhow::Result<Option<Resource<TerminalOutput>>> {
if self.ctx().stdout.isatty() {
let fd = self.table().push(TerminalOutput)?;
Ok(Some(fd))
} else {
Ok(None)
}
}
}
impl<T> terminal_stderr::Host for WasiImpl<T>
where
T: WasiView,
{
fn get_terminal_stderr(&mut self) -> anyhow::Result<Option<Resource<TerminalOutput>>> {
if self.ctx().stderr.isatty() {
let fd = self.table().push(TerminalOutput)?;
Ok(Some(fd))
} else {
Ok(None)
}
}
}
#[cfg(test)]
mod test {
use crate::stdio::StdoutStream;
use crate::write_stream::AsyncWriteStream;
use crate::{AsyncStdoutStream, HostOutputStream};
use anyhow::Result;
use bytes::Bytes;
use tokio::io::AsyncReadExt;
#[test]
fn memory_stdin_stream() {
// A StdinStream has the property that there are multiple
// HostInputStreams created, using the stream() method which are each
// views on the same shared state underneath. Consuming input on one
// stream results in consuming that input on all streams.
//
// The simplest way to measure this is to check if the MemoryInputPipe
// impl of StdinStream follows this property.
let pipe = super::pipe::MemoryInputPipe::new(
"the quick brown fox jumped over the three lazy dogs",
);
use super::StdinStream;
let mut view1 = pipe.stream();
let mut view2 = pipe.stream();
let read1 = view1.read(10).expect("read first 10 bytes");
assert_eq!(read1, "the quick ".as_bytes(), "first 10 bytes");
let read2 = view2.read(10).expect("read second 10 bytes");
assert_eq!(read2, "brown fox ".as_bytes(), "second 10 bytes");
let read3 = view1.read(10).expect("read third 10 bytes");
assert_eq!(read3, "jumped ove".as_bytes(), "third 10 bytes");
let read4 = view2.read(10).expect("read fourth 10 bytes");
assert_eq!(read4, "r the thre".as_bytes(), "fourth 10 bytes");
}
#[tokio::test]
async fn async_stdin_stream() {
// A StdinStream has the property that there are multiple
// HostInputStreams created, using the stream() method which are each
// views on the same shared state underneath. Consuming input on one
// stream results in consuming that input on all streams.
//
// AsyncStdinStream is a slightly more complex impl of StdinStream
// than the MemoryInputPipe above. We can create an AsyncReadStream
// from a file on the disk, and an AsyncStdinStream from that common
// stream, then check that the same property holds as above.
let dir = tempfile::tempdir().unwrap();
let mut path = std::path::PathBuf::from(dir.path());
path.push("file");
std::fs::write(&path, "the quick brown fox jumped over the three lazy dogs").unwrap();
let file = tokio::fs::File::open(&path)
.await
.expect("open created file");
let stdin_stream = super::AsyncStdinStream::new(crate::pipe::AsyncReadStream::new(file));
use super::StdinStream;
let mut view1 = stdin_stream.stream();
let mut view2 = stdin_stream.stream();
view1.ready().await;
let read1 = view1.read(10).expect("read first 10 bytes");
assert_eq!(read1, "the quick ".as_bytes(), "first 10 bytes");
let read2 = view2.read(10).expect("read second 10 bytes");
assert_eq!(read2, "brown fox ".as_bytes(), "second 10 bytes");
let read3 = view1.read(10).expect("read third 10 bytes");
assert_eq!(read3, "jumped ove".as_bytes(), "third 10 bytes");
let read4 = view2.read(10).expect("read fourth 10 bytes");
assert_eq!(read4, "r the thre".as_bytes(), "fourth 10 bytes");
}
#[tokio::test]
async fn async_stdout_stream_unblocks() {
let (mut read, write) = tokio::io::duplex(32);
let stdout = AsyncStdoutStream::new(AsyncWriteStream::new(32, write));
let task = tokio::task::spawn(async move {
let mut stream = stdout.stream();
blocking_write_and_flush(&mut *stream, "x".into())
.await
.unwrap();
});
let mut buf = [0; 100];
let n = read.read(&mut buf).await.unwrap();
assert_eq!(&buf[..n], b"x");
task.await.unwrap();
}
async fn blocking_write_and_flush(
s: &mut dyn HostOutputStream,
mut bytes: Bytes,
) -> Result<()> {
while !bytes.is_empty() {
let permit = s.write_ready().await?;
let len = bytes.len().min(permit);
let chunk = bytes.split_to(len);
s.write(chunk)?;
}
s.flush()?;
s.write_ready().await?;
Ok(())
}
}