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;;; base64.clj: Experimental Base-64 encoding and (later) decoding
;; by Stuart Sierra, http://stuartsierra.com/
;; August 19, 2009
;; Copyright (c) Stuart Sierra, 2009. All rights reserved. The use
;; and distribution terms for this software are covered by the Eclipse
;; Public License 1.0 (http://opensource.org/licenses/eclipse-1.0.php)
;; which can be found in the file epl-v10.html at the root of this
;; distribution. By using this software in any fashion, you are
;; agreeing to be bound by the terms of this license. You must not
;; remove this notice, or any other, from this software.
(ns #^{:doc "Base-64 encoding and (maybe later) decoding.
This is mainly here as an example. It is much slower than the
Apache Commons Codec implementation or sun.misc.BASE64Encoder."
:author "Stuart Sierra"}
clojure.contrib.base64
(:import (java.io InputStream Writer ByteArrayInputStream
StringWriter)))
(def *base64-alphabet*
"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=")
(defn encode
"Encodes bytes of input, writing Base 64 text on output. alphabet
is a 65-character String containing the 64 characters to use in the
encoding; the 65th character is the pad character. line-length is
the maximum number of characters per line, nil for no line breaks."
[#^InputStream input #^Writer output #^String alphabet line-length]
(let [buffer (make-array Byte/TYPE 3)]
(loop [line 0]
(let [len (.read input buffer)]
(when (pos? len)
;; Pre-boxing the bytes as Integers is more efficient for
;; Clojure's bit operations.
(let [b0 (Integer/valueOf (int (aget buffer 0)))
b1 (Integer/valueOf (int (aget buffer 1)))
b2 (Integer/valueOf (int (aget buffer 2)))]
(cond (= len 3)
(let [s0 (bit-and 0x3F (bit-shift-right b0 2))
s1 (bit-and 0x3F
(bit-or (bit-shift-left b0 4)
(bit-shift-right b1 4)))
s2 (bit-and 0x3F
(bit-or (bit-shift-left b1 2)
(bit-shift-right b2 6)))
s3 (bit-and 0x3F b2)]
(.append output (.charAt alphabet s0))
(.append output (.charAt alphabet s1))
(.append output (.charAt alphabet s2))
(.append output (.charAt alphabet s3)))
(= len 2)
(let [s0 (bit-and 0x3F (bit-shift-right b0 2))
s1 (bit-and 0x3F
(bit-or (bit-shift-left b0 4)
(bit-shift-right b1 4)))
s2 (bit-and 0x3F (bit-shift-left b1 2))]
(.append output (.charAt alphabet s0))
(.append output (.charAt alphabet s1))
(.append output (.charAt alphabet s2))
(.append output (.charAt alphabet 64)))
(= len 1)
(let [s0 (bit-and 0x3F (bit-shift-right b0 2))
s1 (bit-and 0x3F (bit-shift-left b0 4))]
(.append output (.charAt alphabet s0))
(.append output (.charAt alphabet s1))
(.append output (.charAt alphabet 64))
(.append output (.charAt alphabet 64)))))
(if (and line-length (> (+ line 4) line-length))
(do (.append output \newline)
(recur 0))
(recur (+ line 4))))))))
(defn encode-str
"Encodes String in base 64; returns a String. If not specified,
encoding is UTF-8 and line-length is nil."
([s] (encode-str s "UTF-8" nil))
([#^String s #^String encoding line-length]
(let [output (StringWriter.)]
(encode (ByteArrayInputStream. (.getBytes s encoding))
output *base64-alphabet* line-length)
(.toString output))))
;;; tests
;; (deftest t-encode-str
;; (is (= (encode-str "") ""))
;; (is (= (encode-str "f") "Zg=="))
;; (is (= (encode-str "fo") "Zm8="))
;; (is (= (encode-str "foo") "Zm9v"))
;; (is (= (encode-str "foob") "Zm9vYg=="))
;; (is (= (encode-str "fooba") "Zm9vYmE="))
;; (is (= (encode-str "foobar") "Zm9vYmFy")))
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