Start state transition verification + refactors

src/frame/stream_id.rs

@@ -0,0 +1,55 @@
+use byteorder::{BigEndian, ByteOrder};
+use std::u32;
+
+#[derive(Debug, Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Hash)]
+pub struct StreamId(u32);
+
+const STREAM_ID_MASK: u32 = 1 << 31;
+
+impl StreamId {
+    /// Parse the stream ID
+    #[inline]
+    pub fn parse(buf: &[u8]) -> StreamId {
+        let unpacked = BigEndian::read_u32(buf);
+        // Now clear the most significant bit, as that is reserved and MUST be
+        // ignored when received.
+        StreamId(unpacked & !STREAM_ID_MASK)
+    }
+
+    pub fn is_client_initiated(&self) -> bool {
+        let id = self.0;
+        id != 0 && id % 2 == 1
+    }
+
+    pub fn is_server_initiated(&self) -> bool {
+        let id = self.0;
+        id != 0 && id % 2 == 0
+    }
+
+    #[inline]
+    pub fn zero() -> StreamId {
+        StreamId(0)
+    }
+
+    #[inline]
+    pub fn max() -> StreamId {
+        StreamId(u32::MAX >> 1)
+    }
+
+    pub fn is_zero(&self) -> bool {
+        self.0 == 0
+    }
+}
+
+impl From<u32> for StreamId {
+    fn from(src: u32) -> Self {
+        assert_eq!(src & STREAM_ID_MASK, 0, "invalid stream ID -- MSB is set");
+        StreamId(src)
+    }
+}
+
+impl From<StreamId> for u32 {
+    fn from(src: StreamId) -> Self {
+        src.0
+    }
+}