Clojure - generating binary data big/little endian

gensin.clj

(defn get-nth-byte [v n]
  (bit-and 0xff (bit-shift-right v (* 8 n))))

(defn pack-little-endian [v n]
  (let [l []]
    (for [i (range n)]
      (into (get-nth-byte v i) l))))

(defn pack-big-endian [v n]
  (let [l []]
    (for [i (range n)]
      (into (get-nth-byte v (- n 1 i)) l))))

;; core> (pack-vector pack-big-endian 2 [16384 16385])
;; [64 0 64 1]
(defn pack-vector [f n xs]
  (reduce (fn [l e]
            (reduce conj l (f e n)))
          []
          xs))

(defn gen-sin [n a t]
  (for [i (range n)]
    (int (+ t
            (* a
               (Math/sin
                (* i (/ (* 2 Math/PI) n))))))))

;; core> (save-sin "sin.dat" 2 128 32767 32768)
;; core> (save-sin "sin.dat" 2 128 32767 32768 :big-endian true)
;; core> (save-sin "sin.dat" 2 128 32767 32768 :big-endian false)
(defn save-sin
  "Writes a sin table to a file named [fname] with each value encoded as
  big-endian (default) or little-endian (based on a key parameter)
  in [sz] bytes. Sinus table is [n] values long with amplitude [a] and
  offset [t]"
  [fname sz n a t & {:keys [big-endian] :or {big-endian true}}]
  (let [packfn (if big-endian pack-big-endian pack-little-endian)]
    (with-open [w (clojure.java.io/output-stream fname)]
      (->>
        (gen-sin n a t)
        (pack-vector packfn sz)
        (byte-array)
        (.write w)))))