duck-stream-ext.clj

(use 'clojure.contrib.duck-streams)
(in-ns 'clojure.contrib.duck-streams)
(import '(java.io File RandomAccessFile))
(import 'BufferedRandomAccessFile)

;; copied and adapted from c.c.ds

(defmulti #^{:arglist '([x])} random-access-reader class)
(defmethod random-access-reader File [#^File x]
  (BufferedRandomAccessFile. x "r"))
(defmethod random-access-reader String [#^String x]
  (random-access-reader (file-str x)))
(defmethod random-access-reader :default [x]
  (throw (Exception. (str "Cannot open " (pr-str x) " as a reader."))))

(defn next-line [raf]
  (.readLine2 raf))

(defn pos [raf]
  (.getFilePointer raf))

(defn seek [raf pos]
  (.seek raf pos))

(defn repeatedly-until-nil [f]
  (when-let [v (f)]
    (lazy-seq (cons v (repeatedly-until-nil f)))))

(defn lazy-rest [rar]
  (repeatedly-until-nil #(next-line rar)))

(defmacro save-excursion [ raf & body]
  `(let [pos# (pos raf)]
     ~@body
     (seek raf pos#)))