(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))))))))
Used in 0 other vars
Source
clojure/contrib/base64.clj:27
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