1 files changed, 64 insertions, 0 deletions
diff --git a/cli/tokio_read.rs b/cli/tokio_read.rs
new file mode 100644
index 000000000..25c4df191
--- /dev/null
+++ b/cli/tokio_read.rs
@@ -0,0 +1,64 @@
+// Copyright (c) 2019 Tokio Contributors. All rights reserved. MIT license.
+// Copyright 2018-2019 the Deno authors. All rights reserved. MIT license.
+// Forked from: https://github.com/tokio-rs/tokio/blob/9b3f8564af4bb1aee07fab3c401eb412ca5eeac5/tokio-io/src/io/read.rs
+use crate::resources::DenoAsyncRead;
+use deno::ErrBox;
+use futures::{Future, Poll};
+use std::mem;
+
+/// This is almost the same implementation as in tokio, the only difference is
+/// that error type is `ErrBox` instead of `std::io::Error`.
+
+#[derive(Debug)]
+enum State<R, T> {
+  Pending { rd: R, buf: T },
+  Empty,
+}
+
+/// Tries to read some bytes directly into the given `buf` in asynchronous
+/// manner, returning a future type.
+///
+/// The returned future will resolve to both the I/O stream and the buffer
+/// as well as the number of bytes read once the read operation is completed.
+pub fn read<R, T>(rd: R, buf: T) -> Read<R, T>
+where
+  R: DenoAsyncRead,
+  T: AsMut<[u8]>,
+{
+  Read {
+    state: State::Pending { rd, buf },
+  }
+}
+
+/// A future which can be used to easily read available number of bytes to fill
+/// a buffer.
+///
+/// Created by the [`read`] function.
+#[derive(Debug)]
+pub struct Read<R, T> {
+  state: State<R, T>,
+}
+
+impl<R, T> Future for Read<R, T>
+where
+  R: DenoAsyncRead,
+  T: AsMut<[u8]>,
+{
+  type Item = (R, T, usize);
+  type Error = ErrBox;
+
+  fn poll(&mut self) -> Poll<(R, T, usize), ErrBox> {
+    let nread = match self.state {
+      State::Pending {
+        ref mut rd,
+        ref mut buf,
+      } => try_ready!(rd.poll_read(&mut buf.as_mut()[..])),
+      State::Empty => panic!("poll a Read after it's done"),
+    };
+
+    match mem::replace(&mut self.state, State::Empty) {
+      State::Pending { rd, buf } => Ok((rd, buf, nread).into()),
+      State::Empty => panic!("invalid internal state"),
+    }
+  }
+}