websocket-decode-encode.clj

(defn get-chunk [conn buf]
  "returns map of bytes and size of buffer for data recieved in stream (buffered input stream);
   buf would be something like: (make-array Byte/TYPE 4096)"
    (let [bufsize (.read conn buf)] ;;blocking
      {:size bufsize :data buf}))


(defn- ws-decode [frame]
  "decodes websocket frame"
  (let [data (:data frame)
        dlen (bit-and (second data) 127)
        mstart (if (== dlen 127) 10 (if (== dlen 126) 4 2))
        mask (drop mstart (take (+ mstart 4) data))
        msg (make-array Byte/TYPE (- (:size frame) (+ mstart 4)))]
    (loop [i (+ mstart 4), j 0]
      (aset-byte msg j (byte (bit-xor (nth data i) (nth mask (mod j 4)))))
      (if (< i (dec(:size frame))) (recur (inc i) (inc j))))
    msg))


(defn- ws-encode [data]
  "takes in bytes, return websocket frame (no chunking available); todo:chunk"
  (let [len (count data)
        blen (if (> len 65535) 10 (if (> len 125) 4 2))
        buf (make-array Byte/TYPE (+ len blen))
        _ (aset-byte buf 0 -127) ;;(bit-or (unchecked-byte 0x80) (unchecked-byte 0x1)
        _ (if (= 2 blen) 
            (aset-byte buf 1 len) ;;mask 0, len
            (do
              (dorun(map #(aset-byte buf %1 (unchecked-byte (bit-and (bit-shift-right len (*(- %2 2) 8)) 255))) (range 2 blen) (into ()(range 2 blen))))
              (aset-byte buf 1 (if (> blen 4) 127 126))))
        _ (System/arraycopy data 0 buf blen len)]
    buf))