1 files changed, 62 insertions, 0 deletions
diff --git a/cli/tokio_write.rs b/cli/tokio_write.rs
new file mode 100644
index 000000000..31b4cda30
--- /dev/null
+++ b/cli/tokio_write.rs
@@ -0,0 +1,62 @@
+// Copyright 2018-2019 the Deno authors. All rights reserved. MIT license.
+use crate::resources::DenoAsyncWrite;
+use deno::ErrBox;
+use futures::{Future, Poll};
+use std::mem;
+
+/// A future used to write some data to a stream.
+///
+/// This is created by the [`write`] top-level method.
+///
+/// [`write`]: fn.write.html
+#[derive(Debug)]
+pub struct Write<A, T> {
+  state: State<A, T>,
+}
+
+#[derive(Debug)]
+enum State<A, T> {
+  Pending { a: A, buf: T },
+  Empty,
+}
+
+/// Creates a future that will write some of the buffer `buf` to
+/// the stream `a` provided.
+///
+/// Any error which happens during writing will cause both the stream and the
+/// buffer to get destroyed.
+pub fn write<A, T>(a: A, buf: T) -> Write<A, T>
+where
+  A: DenoAsyncWrite,
+  T: AsRef<[u8]>,
+{
+  Write {
+    state: State::Pending { a, buf },
+  }
+}
+
+/// This is almost the same implementation as in tokio, difference is
+/// that error type is `ErrBox` instead of `std::io::Error`.
+impl<A, T> Future for Write<A, T>
+where
+  A: DenoAsyncWrite,
+  T: AsRef<[u8]>,
+{
+  type Item = (A, T, usize);
+  type Error = ErrBox;
+
+  fn poll(&mut self) -> Poll<(A, T, usize), ErrBox> {
+    let nwritten = match self.state {
+      State::Pending {
+        ref mut a,
+        ref mut buf,
+      } => try_ready!(a.poll_write(buf.as_ref())),
+      State::Empty => panic!("poll a Read after it's done"),
+    };
+
+    match mem::replace(&mut self.state, State::Empty) {
+      State::Pending { a, buf } => Ok((a, buf, nwritten).into()),
+      State::Empty => panic!("invalid internal state"),
+    }
+  }
+}