1 files changed, 96 insertions, 0 deletions
diff --git a/tokio-util/tests/framed.rs b/tokio-util/tests/framed.rs
new file mode 100644
index 00000000..7aa40d88
--- /dev/null
+++ b/tokio-util/tests/framed.rs
@@ -0,0 +1,96 @@
+#![warn(rust_2018_idioms)]
+
+use tokio::prelude::*;
+use tokio_test::assert_ok;
+use tokio_util::codec::{Decoder, Encoder, Framed, FramedParts};
+
+use bytes::{Buf, BufMut, BytesMut, IntoBuf};
+use std::io::{self, Read};
+use std::pin::Pin;
+use std::task::{Context, Poll};
+
+const INITIAL_CAPACITY: usize = 8 * 1024;
+
+/// Encode and decode u32 values.
+struct U32Codec;
+
+impl Decoder for U32Codec {
+    type Item = u32;
+    type Error = io::Error;
+
+    fn decode(&mut self, buf: &mut BytesMut) -> io::Result<Option<u32>> {
+        if buf.len() < 4 {
+            return Ok(None);
+        }
+
+        let n = buf.split_to(4).into_buf().get_u32_be();
+        Ok(Some(n))
+    }
+}
+
+impl Encoder for U32Codec {
+    type Item = u32;
+    type Error = io::Error;
+
+    fn encode(&mut self, item: u32, dst: &mut BytesMut) -> io::Result<()> {
+        // Reserve space
+        dst.reserve(4);
+        dst.put_u32_be(item);
+        Ok(())
+    }
+}
+
+/// This value should never be used
+struct DontReadIntoThis;
+
+impl Read for DontReadIntoThis {
+    fn read(&mut self, _: &mut [u8]) -> io::Result<usize> {
+        Err(io::Error::new(
+            io::ErrorKind::Other,
+            "Read into something you weren't supposed to.",
+        ))
+    }
+}
+
+impl AsyncRead for DontReadIntoThis {
+    fn poll_read(
+        self: Pin<&mut Self>,
+        _cx: &mut Context<'_>,
+        _buf: &mut [u8],
+    ) -> Poll<io::Result<usize>> {
+        unreachable!()
+    }
+}
+
+#[tokio::test]
+async fn can_read_from_existing_buf() {
+    let mut parts = FramedParts::new(DontReadIntoThis, U32Codec);
+    parts.read_buf = vec![0, 0, 0, 42].into();
+
+    let mut framed = Framed::from_parts(parts);
+    let num = assert_ok!(framed.next().await.unwrap());
+
+    assert_eq!(num, 42);
+}
+
+#[test]
+fn external_buf_grows_to_init() {
+    let mut parts = FramedParts::new(DontReadIntoThis, U32Codec);
+    parts.read_buf = vec![0, 0, 0, 42].into();
+
+    let framed = Framed::from_parts(parts);
+    let FramedParts { read_buf, .. } = framed.into_parts();
+
+    assert_eq!(read_buf.capacity(), INITIAL_CAPACITY);
+}
+
+#[test]
+fn external_buf_does_not_shrink() {
+    let mut parts = FramedParts::new(DontReadIntoThis, U32Codec);
+    parts.read_buf = vec![0; INITIAL_CAPACITY * 2].into();
+
+    let framed = Framed::from_parts(parts);
+    let FramedParts { read_buf, .. } = framed.into_parts();
+
+    assert_eq!(read_buf.capacity(), INITIAL_CAPACITY * 2);
+}