Stub out priority

src/frame/priority.rs

@@ -0,0 +1,83 @@
+use frame::*;
+
+#[derive(Debug)]
+pub struct Priority {
+    stream_id: StreamId,
+    dependency: StreamDependency,
+}
+
+#[derive(Debug)]
+pub struct StreamDependency {
+    /// The ID of the stream dependency target
+    dependency_id: StreamId,
+
+    /// The weight for the stream. The value exposed (and set) here is always in
+    /// the range [0, 255], instead of [1, 256] (as defined in section 5.3.2.)
+    /// so that the value fits into a `u8`.
+    weight: u8,
+
+    /// True if the stream dependency is exclusive.
+    is_exclusive: bool,
+}
+
+impl Priority {
+    pub fn load(head: Head, payload: &[u8]) -> Result<Self, Error> {
+        let dependency = StreamDependency::load(payload)?;
+
+        if dependency.dependency_id() == head.stream_id() {
+            return Err(Error::InvalidDependencyId);
+        }
+
+        Ok(Priority {
+            stream_id: head.stream_id(),
+            dependency: dependency,
+        })
+    }
+}
+
+impl<B> From<Priority> for Frame<B> {
+    fn from(src: Priority) -> Self {
+        Frame::Priority(src)
+    }
+}
+
+// ===== impl StreamDependency =====
+
+impl StreamDependency {
+    pub fn new(dependency_id: StreamId, weight: u8, is_exclusive: bool) -> Self {
+        StreamDependency {
+            dependency_id,
+            weight,
+            is_exclusive,
+        }
+    }
+
+    pub fn load(src: &[u8]) -> Result<Self, Error> {
+        if src.len() != 5 {
+            return Err(Error::InvalidPayloadLength);
+        }
+
+        // Parse the stream ID and exclusive flag
+        let (dependency_id, is_exclusive) = StreamId::parse(&src[..4]);
+
+        // Read the weight
+        let weight = src[4];
+
+        Ok(StreamDependency::new(
+                dependency_id,
+                weight,
+                is_exclusive))
+    }
+
+    pub fn dependency_id(&self) -> StreamId {
+        self.dependency_id
+    }
+
+    pub fn weight(&self) -> u8 {
+        self.weight
+    }
+
+    pub fn is_exclusive(&self) -> bool {
+        self.is_exclusive
+    }
+}