diff --git a/src/stream_async/mod.rs b/src/stream_async/mod.rs
new file mode 100644
index 0000000..add6495
--- /dev/null
+++ b/src/stream_async/mod.rs
@@ -0,0 +1,146 @@
+use super::*;
+use key::*;
+
+use std::io;
+use tokio::io::AsyncWrite;
+use std::{
+    pin::Pin,
+    task::{Context, Poll},
+};
+
+use std::fmt;
+use openssl::{
+    symm::Crypter,
+    error::ErrorStack,
+};
+
+/// Size of the in-structure buffer
+#[cfg(feature="smallvec")]
+pub const BUFFER_SIZE: usize = 32;
+
+#[cfg(feature="smallvec")]
+type BufferVec = smallvec::SmallVec<[u8; BUFFER_SIZE]>;
+#[cfg(not(feature="smallvec"))]
+type BufferVec = Vec<u8>;
+
+pub type Error = ErrorStack;
+
+pub mod sink;
+pub use sink::Sink;
+
+#[cfg(test)]
+mod test
+{
+    use tokio::prelude::*;
+    #[tokio::test]
+    async fn sink_sync()
+    {
+	let mut output = Vec::new();
+	let input = "Hello world!";
+	let (key, iv) = crate::cha::keygen();
+	
+	let encrypted = {
+	    let mut sink = super::Sink::encrypt(&mut output, key, iv).expect("Sink::encrypt");
+	    sink.write_all(input.as_bytes()).await.expect("Sink::write_all");
+	    sink.flush().await.expect("Sink::flush");
+	    sink.shutdown().await.expect("Sink::shutdown");
+
+	    sink.into_inner().clone()
+	};
+
+	output.clear();
+	let decrypted = {
+	    let mut sink = super::Sink::decrypt(&mut output, key, iv).expect("Sink::decrypt");
+	    sink.write_all(&encrypted[..]).await.expect("Sink::write_all");
+	    
+	    sink.flush().await.expect("Sink::flush");
+	    sink.shutdown().await.expect("Sink::shutdown");
+
+	    sink.into_inner().clone()
+	};
+	assert_eq!(&decrypted[..], input.as_bytes());
+    }
+    #[tokio::test]
+    async fn sink_mem()
+    {
+	const BACKLOG: usize = 4;
+	let (mut client, mut server) = tokio::io::duplex(BACKLOG);
+	let (key, iv) = crate::cha::keygen();
+
+	let input = "Hello!";
+
+	let enctask = tokio::spawn(async move {
+	    let mut sink = super::Sink::encrypt(&mut client, key, iv).expect("Sink::encrypt");
+	    sink.write_all(input.as_bytes()).await.expect("Sink::write_all");
+	    sink.flush().await.expect("Sink::flush");
+	    sink.shutdown().await.expect("Sink::shutdown");
+
+	    drop(client);
+	});
+
+	let (mut declient, mut deserver) = tokio::io::duplex(BACKLOG * 2);
+	let dectask = tokio::spawn(async move {
+	    
+	    let mut sink = super::Sink::decrypt(&mut declient, key, iv).expect("Sink::encrypt");
+	    tokio::io::copy(&mut server, &mut sink).await.expect("Copy to sink failed");
+	    sink.flush().await.expect("Sink::flush");
+	    sink.shutdown().await.expect("Sink::shutdown");
+	});
+
+	let (de, en) = tokio::join![dectask, enctask];
+	
+	de.expect("Dec task panic");
+	en.expect("Enc task panic");
+	
+	let mut output = Vec::new();
+	tokio::io::copy(&mut deserver, &mut output).await.expect("Copy into vec");
+
+	println!("In: {}, Out: {}", String::from_utf8_lossy(&output[..]), input);
+	assert_eq!(&output[..], input.as_bytes());
+    }
+    #[tokio::test]
+    async fn sink_files()
+    {
+	let mut output = tokio::fs::File::from_std(tempfile::tempfile().unwrap());
+	
+	let input = "Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!";
+	let (key, iv) = crate::cha::keygen();
+	
+	{
+	    let mut sink = super::Sink::encrypt(&mut output, key, iv).expect("Sink::encrypt");
+	    sink.write_all(input.as_bytes()).await.expect("Sink::write_all");
+	    sink.flush().await.expect("Sink::flush");
+	    sink.shutdown().await.expect("Sink::shutdown");
+	}
+
+	let mut encrypted = output;
+	encrypted.seek(tokio::io::SeekFrom::Start(0)).await.unwrap();
+	
+	let mut output = tokio::fs::File::from_std(tempfile::tempfile().unwrap());
+	{
+	    let mut sink = super::Sink::decrypt(&mut output, key, iv).expect("Sink::decrypt");
+	    tokio::io::copy(&mut encrypted, &mut sink).await.expect("Copy to sinl");
+	    
+	    sink.flush().await.expect("Sink::flush");
+	    sink.shutdown().await.expect("Sink::shutdown");
+	}
+	let mut decrypted = output;
+
+	let (r1, r2) = tokio::join![encrypted.sync_data(),
+				    decrypted.sync_data()];
+	r1.expect("enc sync");
+	r2.expect("dec sync");
+
+	let decrypted = {
+	    decrypted.seek(tokio::io::SeekFrom::Start(0)).await.unwrap();
+
+	    let mut output = vec![0u8; input.len()];
+	    decrypted.read_exact(&mut output[..]).await.expect("Read decrypted");
+
+	    output
+	};
+	
+	assert_eq!(&decrypted[..], input.as_bytes());
+    }
+}
+
diff --git a/src/stream_async.rs b/src/stream_async/sink.rs
similarity index 54%
rename from src/stream_async.rs
rename to src/stream_async/sink.rs
index bca460f..b925782 100644
--- a/src/stream_async.rs
+++ b/src/stream_async/sink.rs
@@ -1,29 +1,5 @@
+//! Asyncronous `Write` wrapper.
 use super::*;
-use key::*;
-
-use std::io;
-use tokio::io::AsyncWrite;
-use std::{
-    pin::Pin,
-    task::{Context, Poll},
-};
-
-use std::fmt;
-use openssl::{
-    symm::Crypter,
-    error::ErrorStack,
-};
-
-/// Size of the in-structure buffer
-#[cfg(feature="smallvec")]
-pub const BUFFER_SIZE: usize = 32;
-
-#[cfg(feature="smallvec")]
-type BufferVec = smallvec::SmallVec<[u8; BUFFER_SIZE]>;
-#[cfg(not(feature="smallvec"))]
-type BufferVec = Vec<u8>;
-
-pub type Error = ErrorStack;
 
 /// Async ChaCha Sink
 ///
@@ -214,120 +190,3 @@ impl<W: AsyncWrite> AsyncWrite for Sink<W>
 	poll
     }
 }
-
-#[cfg(test)]
-mod test
-{
-    use tokio::prelude::*;
-    #[tokio::test]
-    async fn sink_sync()
-    {
-	let mut output = Vec::new();
-	let input = "Hello world!";
-	let (key, iv) = crate::cha::keygen();
-	
-	let encrypted = {
-	    let mut sink = super::Sink::encrypt(&mut output, key, iv).expect("Sink::encrypt");
-	    sink.write_all(input.as_bytes()).await.expect("Sink::write_all");
-	    sink.flush().await.expect("Sink::flush");
-	    sink.shutdown().await.expect("Sink::shutdown");
-
-	    sink.into_inner().clone()
-	};
-
-	output.clear();
-	let decrypted = {
-	    let mut sink = super::Sink::decrypt(&mut output, key, iv).expect("Sink::decrypt");
-	    sink.write_all(&encrypted[..]).await.expect("Sink::write_all");
-	    
-	    sink.flush().await.expect("Sink::flush");
-	    sink.shutdown().await.expect("Sink::shutdown");
-
-	    sink.into_inner().clone()
-	};
-	assert_eq!(&decrypted[..], input.as_bytes());
-    }
-    #[tokio::test]
-    async fn sink_mem()
-    {
-	const BACKLOG: usize = 4;
-	let (mut client, mut server) = tokio::io::duplex(BACKLOG);
-	let (key, iv) = crate::cha::keygen();
-
-	let input = "Hello!";
-
-	let enctask = tokio::spawn(async move {
-	    let mut sink = super::Sink::encrypt(&mut client, key, iv).expect("Sink::encrypt");
-	    sink.write_all(input.as_bytes()).await.expect("Sink::write_all");
-	    sink.flush().await.expect("Sink::flush");
-	    sink.shutdown().await.expect("Sink::shutdown");
-
-	    drop(client);
-	});
-
-	let (mut declient, mut deserver) = tokio::io::duplex(BACKLOG * 2);
-	let dectask = tokio::spawn(async move {
-	    
-	    let mut sink = super::Sink::decrypt(&mut declient, key, iv).expect("Sink::encrypt");
-	    tokio::io::copy(&mut server, &mut sink).await.expect("Copy to sink failed");
-	    sink.flush().await.expect("Sink::flush");
-	    sink.shutdown().await.expect("Sink::shutdown");
-	});
-
-	let (de, en) = tokio::join![dectask, enctask];
-	
-	de.expect("Dec task panic");
-	en.expect("Enc task panic");
-	
-	let mut output = Vec::new();
-	tokio::io::copy(&mut deserver, &mut output).await.expect("Copy into vec");
-
-	println!("In: {}, Out: {}", String::from_utf8_lossy(&output[..]), input);
-	assert_eq!(&output[..], input.as_bytes());
-    }
-    #[tokio::test]
-    async fn sink_files()
-    {
-	let mut output = tokio::fs::File::from_std(tempfile::tempfile().unwrap());
-	
-	let input = "Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!Hello world!";
-	let (key, iv) = crate::cha::keygen();
-	
-	{
-	    let mut sink = super::Sink::encrypt(&mut output, key, iv).expect("Sink::encrypt");
-	    sink.write_all(input.as_bytes()).await.expect("Sink::write_all");
-	    sink.flush().await.expect("Sink::flush");
-	    sink.shutdown().await.expect("Sink::shutdown");
-	}
-
-	let mut encrypted = output;
-	encrypted.seek(tokio::io::SeekFrom::Start(0)).await.unwrap();
-	
-	let mut output = tokio::fs::File::from_std(tempfile::tempfile().unwrap());
-	{
-	    let mut sink = super::Sink::decrypt(&mut output, key, iv).expect("Sink::decrypt");
-	    tokio::io::copy(&mut encrypted, &mut sink).await.expect("Copy to sinl");
-	    
-	    sink.flush().await.expect("Sink::flush");
-	    sink.shutdown().await.expect("Sink::shutdown");
-	}
-	let mut decrypted = output;
-
-	let (r1, r2) = tokio::join![encrypted.sync_data(),
-				    decrypted.sync_data()];
-	r1.expect("enc sync");
-	r2.expect("dec sync");
-
-	let decrypted = {
-	    decrypted.seek(tokio::io::SeekFrom::Start(0)).await.unwrap();
-
-	    let mut output = vec![0u8; input.len()];
-	    decrypted.read_exact(&mut output[..]).await.expect("Read decrypted");
-
-	    output
-	};
-	
-	assert_eq!(&decrypted[..], input.as_bytes());
-    }
-}
-