Add huffman encoding

src/hpack/encoder.rs

@@ -1 +1,24 @@
-pub struct Encoder;
+use http::header::{HeaderMap, HeaderName, HeaderValue};
+use bytes::BytesMut;
+
+pub struct Encoder {
+    table: HeaderMap<()>,
+
+    // The remote sent a max size update, we must shrink the table on next call
+    // to encode.
+    max_size_update: Option<usize>,
+
+    // Current max table size
+    max_size: usize,
+}
+
+pub enum EncoderError {
+}
+
+impl Encoder {
+    pub fn encode<'a, I>(&mut self, headers: I, dst: &mut BytesMut) -> Result<(), EncoderError>
+        where I: IntoIterator<Item=(&'a HeaderName, &'a HeaderValue)>,
+    {
+        unimplemented!();
+    }
+}