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1 ;;; base64.clj: Experimental Base-64 encoding and (later) decoding
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2
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3 ;; by Stuart Sierra, http://stuartsierra.com/
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4 ;; August 19, 2009
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5
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6 ;; Copyright (c) Stuart Sierra, 2009. All rights reserved. The use
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7 ;; and distribution terms for this software are covered by the Eclipse
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8 ;; Public License 1.0 (http://opensource.org/licenses/eclipse-1.0.php)
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9 ;; which can be found in the file epl-v10.html at the root of this
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10 ;; distribution. By using this software in any fashion, you are
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11 ;; agreeing to be bound by the terms of this license. You must not
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12 ;; remove this notice, or any other, from this software.
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13
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14
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15 (ns ^{:doc "Base-64 encoding and (maybe later) decoding.
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16
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17 This is mainly here as an example. It is much slower than the
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18 Apache Commons Codec implementation or sun.misc.BASE64Encoder."
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19 :author "Stuart Sierra"}
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20 clojure.contrib.base64
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21 (:import (java.io InputStream Writer ByteArrayInputStream
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22 StringWriter)))
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23
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24 (def *base64-alphabet*
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25 "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=")
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26
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27 (defn encode
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28 "Encodes bytes of input, writing Base 64 text on output. alphabet
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29 is a 65-character String containing the 64 characters to use in the
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30 encoding; the 65th character is the pad character. line-length is
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31 the maximum number of characters per line, nil for no line breaks."
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32 [^InputStream input ^Writer output ^String alphabet line-length]
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33 (let [buffer (make-array Byte/TYPE 3)]
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34 (loop [line 0]
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35 (let [len (.read input buffer)]
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36 (when (pos? len)
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37 ;; Pre-boxing the bytes as Integers is more efficient for
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38 ;; Clojure's bit operations.
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39 (let [b0 (Integer/valueOf (int (aget buffer 0)))
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40 b1 (Integer/valueOf (int (aget buffer 1)))
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41 b2 (Integer/valueOf (int (aget buffer 2)))]
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42 (cond (= len 3)
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43 (let [s0 (bit-and 0x3F (bit-shift-right b0 2))
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44 s1 (bit-and 0x3F
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45 (bit-or (bit-shift-left b0 4)
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46 (bit-shift-right b1 4)))
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47 s2 (bit-and 0x3F
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48 (bit-or (bit-shift-left b1 2)
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49 (bit-shift-right b2 6)))
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50 s3 (bit-and 0x3F b2)]
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51 (.append output (.charAt alphabet s0))
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52 (.append output (.charAt alphabet s1))
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53 (.append output (.charAt alphabet s2))
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54 (.append output (.charAt alphabet s3)))
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55
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56 (= len 2)
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57 (let [s0 (bit-and 0x3F (bit-shift-right b0 2))
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58 s1 (bit-and 0x3F
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59 (bit-or (bit-shift-left b0 4)
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60 (bit-shift-right b1 4)))
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61 s2 (bit-and 0x3F (bit-shift-left b1 2))]
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62 (.append output (.charAt alphabet s0))
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63 (.append output (.charAt alphabet s1))
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64 (.append output (.charAt alphabet s2))
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65 (.append output (.charAt alphabet 64)))
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66
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67 (= len 1)
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68 (let [s0 (bit-and 0x3F (bit-shift-right b0 2))
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69 s1 (bit-and 0x3F (bit-shift-left b0 4))]
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70 (.append output (.charAt alphabet s0))
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71 (.append output (.charAt alphabet s1))
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72 (.append output (.charAt alphabet 64))
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73 (.append output (.charAt alphabet 64)))))
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74 (if (and line-length (> (+ line 4) line-length))
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75 (do (.append output \newline)
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76 (recur 0))
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77 (recur (+ line 4))))))))
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78
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79 (defn encode-str
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80 "Encodes String in base 64; returns a String. If not specified,
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81 encoding is UTF-8 and line-length is nil."
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82 ([s] (encode-str s "UTF-8" nil))
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83 ([^String s ^String encoding line-length]
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84 (let [output (StringWriter.)]
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85 (encode (ByteArrayInputStream. (.getBytes s encoding))
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86 output *base64-alphabet* line-length)
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87 (.toString output))))
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88
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89
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90 ;;; tests
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91
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92 ;; (deftest t-encode-str
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93 ;; (is (= (encode-str "") ""))
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94 ;; (is (= (encode-str "f") "Zg=="))
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95 ;; (is (= (encode-str "fo") "Zm8="))
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96 ;; (is (= (encode-str "foo") "Zm9v"))
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97 ;; (is (= (encode-str "foob") "Zm9vYg=="))
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98 ;; (is (= (encode-str "fooba") "Zm9vYmE="))
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99 ;; (is (= (encode-str "foobar") "Zm9vYmFy")))
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