1 files changed, 96 insertions, 0 deletions
diff --git a/third_party/rust/h2/src/frame/stream_id.rs b/third_party/rust/h2/src/frame/stream_id.rs
new file mode 100644
index 0000000000..10a14d3c82
--- /dev/null
+++ b/third_party/rust/h2/src/frame/stream_id.rs
@@ -0,0 +1,96 @@
+use std::u32;
+
+/// A stream identifier, as described in [Section 5.1.1] of RFC 7540.
+///
+/// Streams are identified with an unsigned 31-bit integer. Streams
+/// initiated by a client MUST use odd-numbered stream identifiers; those
+/// initiated by the server MUST use even-numbered stream identifiers.  A
+/// stream identifier of zero (0x0) is used for connection control
+/// messages; the stream identifier of zero cannot be used to establish a
+/// new stream.
+///
+/// [Section 5.1.1]: https://tools.ietf.org/html/rfc7540#section-5.1.1
+#[derive(Debug, Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Hash)]
+pub struct StreamId(u32);
+
+#[derive(Debug, Copy, Clone)]
+pub struct StreamIdOverflow;
+
+const STREAM_ID_MASK: u32 = 1 << 31;
+
+impl StreamId {
+    /// Stream ID 0.
+    pub const ZERO: StreamId = StreamId(0);
+
+    /// The maximum allowed stream ID.
+    pub const MAX: StreamId = StreamId(u32::MAX >> 1);
+
+    /// Parse the stream ID
+    #[inline]
+    pub fn parse(buf: &[u8]) -> (StreamId, bool) {
+        let mut ubuf = [0; 4];
+        ubuf.copy_from_slice(&buf[0..4]);
+        let unpacked = u32::from_be_bytes(ubuf);
+        let flag = unpacked & STREAM_ID_MASK == STREAM_ID_MASK;
+
+        // Now clear the most significant bit, as that is reserved and MUST be
+        // ignored when received.
+        (StreamId(unpacked & !STREAM_ID_MASK), flag)
+    }
+
+    /// Returns true if this stream ID corresponds to a stream that
+    /// was initiated by the client.
+    pub fn is_client_initiated(&self) -> bool {
+        let id = self.0;
+        id != 0 && id % 2 == 1
+    }
+
+    /// Returns true if this stream ID corresponds to a stream that
+    /// was initiated by the server.
+    pub fn is_server_initiated(&self) -> bool {
+        let id = self.0;
+        id != 0 && id % 2 == 0
+    }
+
+    /// Return a new `StreamId` for stream 0.
+    #[inline]
+    pub fn zero() -> StreamId {
+        StreamId::ZERO
+    }
+
+    /// Returns true if this stream ID is zero.
+    pub fn is_zero(&self) -> bool {
+        self.0 == 0
+    }
+
+    /// Returns the next stream ID initiated by the same peer as this stream
+    /// ID, or an error if incrementing this stream ID would overflow the
+    /// maximum.
+    pub fn next_id(&self) -> Result<StreamId, StreamIdOverflow> {
+        let next = self.0 + 2;
+        if next > StreamId::MAX.0 {
+            Err(StreamIdOverflow)
+        } else {
+            Ok(StreamId(next))
+        }
+    }
+}
+
+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
+    }
+}
+
+impl PartialEq<u32> for StreamId {
+    fn eq(&self, other: &u32) -> bool {
+        self.0 == *other
+    }
+}