secure delete file

core.clj

(require '[clojure.java.io :as io])

(defn secure-delete-file
  "fill file content with mask 0x55AA and then delete it.
  return nil."
  [^String fname]
  (let [length (.length (io/file fname))
        buf-len 4096
        w (quot length buf-len)
        r (rem length buf-len)
        buf (byte-array (take buf-len (cycle [0x55 0xAA])))]
    (with-open [out (io/output-stream (io/file fname))]
      (dotimes [n w]
        (.write out buf))
      (.write out (byte-array (take r (cycle [0x55 0xAA])))))
    (io/delete-file (io/file fname))
    nil))