New send flow control (#25)

Restructure send flow control such that sending data is always accepted by `Stream`. Data frames will be buffered until there is available window to send them. Producers can monitor the available window capacity to decide if data should be produced.

tests/flow_control.rs

@@ -1,3 +1,53 @@
+pub mod support;
+use support::*;
+
+// In this case, the stream & connection both have capacity, but capacity is not
+// explicitly requested.
+#[test]
+fn send_data_without_requesting_capacity() {
+    let _ = ::env_logger::init();
+
+    let payload = [0; 1024];
+
+    let mock = mock_io::Builder::new()
+        .handshake()
+        .write(&[
+            // POST /
+            0, 0, 16, 1, 4, 0, 0, 0, 1, 131, 135, 65, 139, 157, 41,
+            172, 75, 143, 168, 233, 25, 151, 33, 233, 132,
+        ])
+        .write(&[
+            // DATA
+            0, 4, 0, 0, 1, 0, 0, 0, 1,
+        ])
+        .write(&payload[..])
+        .write(frames::SETTINGS_ACK)
+        // Read response
+        .read(&[0, 0, 1, 1, 5, 0, 0, 0, 1, 0x89])
+        .build();
+
+    let mut h2 = Client::handshake(mock)
+        .wait().unwrap();
+
+    let request = Request::builder()
+        .method(method::POST)
+        .uri("https://http2.akamai.com/")
+        .body(()).unwrap();
+
+    let mut stream = h2.request(request, false).unwrap();
+
+    // The capacity should be immediately allocated
+    assert_eq!(stream.capacity(), 0);
+
+    // Send the data
+    stream.send_data(payload[..].into(), true).unwrap();
+
+    // Get the response
+    let resp = h2.run(poll_fn(|| stream.poll_response())).unwrap();
+    assert_eq!(resp.status(), status::NO_CONTENT);
+
+    h2.wait().unwrap();
+}
 
 #[test]
 #[ignore]

tests/prioritization.rs

@@ -34,6 +34,12 @@ fn single_stream_send_large_body() {
 
     let mut stream = h2.request(request, false).unwrap();
 
+    // Reserve capacity to send the payload
+    stream.reserve_capacity(payload.len()).unwrap();
+
+    // The capacity should be immediately allocated
+    assert_eq!(stream.capacity(), payload.len());
+
     // Send the data
     stream.send_data(payload[..].into(), true).unwrap();
 
@@ -82,6 +88,11 @@ fn single_stream_send_extra_large_body_multi_frames_one_buffer() {
 
     let mut stream = h2.request(request, false).unwrap();
 
+    stream.reserve_capacity(payload.len()).unwrap();
+
+    // The capacity should be immediately allocated
+    assert_eq!(stream.capacity(), payload.len());
+
     // Send the data
     stream.send_data(payload.into(), true).unwrap();
 
@@ -142,6 +153,11 @@ fn single_stream_send_extra_large_body_multi_frames_multi_buffer() {
 
     let mut stream = h2.request(request, false).unwrap();
 
+    stream.reserve_capacity(payload.len()).unwrap();
+
+    // The capacity should be immediately allocated
+    assert_eq!(stream.capacity(), payload.len());
+
     // Send the data
     stream.send_data(payload.into(), true).unwrap();
 

tests/stream_states.rs

@@ -74,6 +74,11 @@ fn send_recv_data() {
     info!("sending request");
     let mut stream = h2.request(request, false).unwrap();
 
+    // Reserve send capacity
+    stream.reserve_capacity(5).unwrap();
+
+    assert_eq!(stream.capacity(), 5);
+
     // Send the data
     stream.send_data("hello", true).unwrap();