encoder: add AsyncWrite implementation

Cargo.toml

@@ -16,6 +16,8 @@ travis-ci = { repository = "gyscos/zstd-rs" }
 [dependencies]
 libc = "0.2"
 zstd-sys = { path="zstd-sys", version = "1.1.5-a", default-features = false }
+tokio-io = { version = "0.1", optional = true }
+futures = { version = "0.1", optional = true }
 
 [dev-dependencies]
 clap = "2.6.0"
@@ -24,3 +26,4 @@ clap = "2.6.0"
 default = ["legacy"]
 legacy = ["zstd-sys/legacy"]
 bindgen = ["zstd-sys/bindgen"]
+tokio = ["tokio-io", "futures"]

src/lib.rs

@@ -31,6 +31,13 @@ pub mod stream;
 pub mod block;
 pub mod dict;
 
+#[cfg(feature = "tokio")]
+#[macro_use]
+extern crate tokio_io;
+#[cfg(feature = "tokio")]
+extern crate futures;
+
+
 use std::ffi::CStr;
 
 use std::io;

src/stream/encoder.rs

@@ -4,6 +4,11 @@ use parse_code;
 use std::io::{self, Write};
 use zstd_sys;
 
+#[cfg(feature = "tokio")]
+use futures::Poll;
+#[cfg(feature = "tokio")]
+use tokio_io::AsyncWrite;
+
 struct EncoderContext {
     s: *mut zstd_sys::ZSTD_CStream,
 }
@@ -328,6 +333,14 @@ impl<W: Write> Write for Encoder<W> {
     }
 }
 
+#[cfg(feature = "tokio")]
+impl <W: AsyncWrite> AsyncWrite for Encoder<W> {
+    fn shutdown(&mut self) -> Poll<(), io::Error> {
+        try_nb!(self.do_finish());
+        self.writer.shutdown()
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::Encoder;