/usr/share/gauche-0.9/0.9.1/lib/rfc/base64.scm is in gauche 0.9.1-5.
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;;; base64.scm - base64 encoding/decoding routine
;;;
;;; Copyright (c) 2000-2010 Shiro Kawai <shiro@acm.org>
;;;
;;; Redistribution and use in source and binary forms, with or without
;;; modification, are permitted provided that the following conditions
;;; are met:
;;;
;;; 1. Redistributions of source code must retain the above copyright
;;; notice, this list of conditions and the following disclaimer.
;;;
;;; 2. Redistributions in binary form must reproduce the above copyright
;;; notice, this list of conditions and the following disclaimer in the
;;; documentation and/or other materials provided with the distribution.
;;;
;;; 3. Neither the name of the authors nor the names of its contributors
;;; may be used to endorse or promote products derived from this
;;; software without specific prior written permission.
;;;
;;; THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
;;; "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
;;; LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
;;; A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
;;; OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
;;; SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
;;; TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
;;; PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
;;; LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
;;; NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
;;; SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
;;;
;; Implements Base64 encoding/decoding routine
;; Ref: RFC2045 section 6.8 <http://www.rfc-editor.org/rfc/rfc2045.txt>
;; and RFC3548 <http://www.rfc-editor.org/rfc/rfc3548.txt>
;; TODO: using uvector for binary source/sink
(define-module rfc.base64
(export base64-encode base64-encode-string
base64-decode base64-decode-string))
(select-module rfc.base64)
(define *decode-table*
;; ! " # $ % & ' ( ) * + , - . /
#(#f #f #f #f #f #f #f #f #f #f #f 62 #f #f #f 63
;;0 1 2 3 4 5 6 7 8 9 : ; < = > ?
52 53 54 55 56 57 58 59 60 61 #f #f #f #f #f #f
;;@ A B C D E F G H I J K L M N O
#f 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
;;P Q R S T U V W X Y Z [ \ ] ^ _
15 16 17 18 19 20 21 22 23 24 25 #f #f #f #f #f
;;` a b c d e f g h i j k l m n o
#f 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40
;;p q r s t u v w x y z { | } ~
41 42 43 44 45 46 47 48 49 50 51 #f #f #f #f #f
))
(define *encode-table*
;;0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
#(#\A #\B #\C #\D #\E #\F #\G #\H #\I #\J #\K #\L #\M #\N #\O #\P
;;16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
#\Q #\R #\S #\T #\U #\V #\W #\X #\Y #\Z #\a #\b #\c #\d #\e #\f
;;32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47
#\g #\h #\i #\j #\k #\l #\m #\n #\o #\p #\q #\r #\s #\t #\u #\v
;;48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63
#\w #\x #\y #\z #\0 #\1 #\2 #\3 #\4 #\5 #\6 #\7 #\8 #\9 #\+ #\/
;;pad
#\=
))
(define (base64-decode)
(let-syntax ((lookup (syntax-rules ()
((_ c)
(let ((i (char->integer c)))
(and (< 32 i 128)
(vector-ref *decode-table* (- i 32)))))))
)
(define (d0 c)
(cond ((eof-object? c))
((eqv? c #\=))
((lookup c) => (lambda (v) (d1 (read-char) v)))
(else (d0 (read-char)))))
(define (d1 c hi)
(cond ((eof-object? c))
((eqv? c #\=))
((lookup c) => (lambda (lo)
(write-byte (+ (* hi 4) (quotient lo 16)))
(d2 (read-char) (modulo lo 16))))
(else (d1 (read-char) hi))))
(define (d2 c hi)
(cond ((eof-object? c))
((eqv? c #\=))
((lookup c) => (lambda (lo)
(write-byte (+ (* hi 16) (quotient lo 4)))
(d3 (read-char) (modulo lo 4))))
(else (d2 (read-char) hi))))
(define (d3 c hi)
(cond ((eof-object? c))
((eqv? c #\=))
((lookup c) => (lambda (lo)
(write-byte (+ (* hi 64) lo))
(d0 (read-char))))
(else (d3 (read-char) hi))))
(d0 (read-char))))
(define (base64-decode-string string)
(with-output-to-string
(lambda ()
(with-input-from-string string base64-decode))))
(define (base64-encode :key (line-width 76))
(define maxcol (and line-width (> line-width 0) (- line-width 1)))
(letrec-syntax ([emit*
(syntax-rules ()
[(_ col) col]
[(_ col idx idx2 ...)
(begin
(write-char (vector-ref *encode-table* idx))
(let1 col2 (cond [(eqv? col maxcol) (newline) 0]
[else (+ col 1)])
(emit* col2 idx2 ...)))])])
(define (e0 c col)
(cond [(eof-object? c)]
[else
(e1 (read-byte) (modulo c 4) (emit* col (quotient c 4)))]))
(define (e1 c hi col)
(cond [(eof-object? c)
(emit* col (* hi 16) 64 64)]
[else
(e2 (read-byte) (modulo c 16)
(emit* col (+ (* hi 16) (quotient c 16))))]))
(define (e2 c hi col)
(cond [(eof-object? c)
(emit* col (* hi 4) 64)]
[else
(e0 (read-byte)
(emit* col (+ (* hi 4) (quotient c 64)) (modulo c 64)))]))
(e0 (read-byte) 0)))
(define (base64-encode-string string . opts)
(with-string-io string (cut apply base64-encode opts)))
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