1 files changed, 82 insertions, 0 deletions
diff --git a/src/io/copy.rs b/src/io/copy.rs
new file mode 100644
index 00000000..042e819b
--- /dev/null
+++ b/src/io/copy.rs
@@ -0,0 +1,82 @@
+use std::io::{self, Read, Write};
+
+use futures::{Future, Poll};
+
+/// A future which will copy all data from a reader into a writer.
+///
+/// Created by the `copy` function, this future will resolve to the number of
+/// bytes copied or an error if one happens.
+pub struct Copy<R, W> {
+    reader: R,
+    read_done: bool,
+    writer: W,
+    pos: usize,
+    cap: usize,
+    amt: u64,
+    buf: Box<[u8]>,
+}
+
+/// Creates a future which represents copying all the bytes from one object to
+/// another.
+///
+/// The returned future will copy all the bytes read from `reader` into the
+/// `writer` specified. This future will only complete once the `reader` has hit
+/// EOF and all bytes have been written to and flushed from the `writer`
+/// provided.
+///
+/// On success the number of bytes is returned and the `reader` and `writer` are
+/// consumed. On error the error is returned and the I/O objects are consumed as
+/// well.
+pub fn copy<R, W>(reader: R, writer: W) -> Copy<R, W>
+    where R: Read,
+          W: Write,
+{
+    Copy {
+        reader: reader,
+        read_done: false,
+        writer: writer,
+        amt: 0,
+        pos: 0,
+        cap: 0,
+        buf: Box::new([0; 2048]),
+    }
+}
+
+impl<R, W> Future for Copy<R, W>
+    where R: Read,
+          W: Write,
+{
+    type Item = u64;
+    type Error = io::Error;
+
+    fn poll(&mut self) -> Poll<u64, io::Error> {
+        loop {
+            // If our buffer is empty, then we need to read some data to
+            // continue.
+            if self.pos == self.cap && !self.read_done {
+                let n = try_nb!(self.reader.read(&mut self.buf));
+                if n == 0 {
+                    self.read_done = true;
+                } else {
+                    self.pos = 0;
+                    self.cap = n;
+                }
+            }
+
+            // If our buffer has some data, let's write it out!
+            while self.pos < self.cap {
+                let i = try_nb!(self.writer.write(&self.buf[self.pos..self.cap]));
+                self.pos += i;
+                self.amt += i as u64;
+            }
+
+            // If we've written al the data and we've seen EOF, flush out the
+            // data and finish the transfer.
+            // done with the entire transfer.
+            if self.pos == self.cap && self.read_done {
+                try_nb!(self.writer.flush());
+                return Poll::Ok(self.amt)
+            }
+        }
+    }
+}