--- /dev/null
+;; -*- mode: scheme; coding: utf-8 -*-
+;; Copyright © 2009, 2010, 2012, 2013 Göran Weinholt <goran@weinholt.se>
+
+;; Permission is hereby granted, free of charge, to any person obtaining a
+;; copy of this software and associated documentation files (the "Software"),
+;; to deal in the Software without restriction, including without limitation
+;; the rights to use, copy, modify, merge, publish, distribute, sublicense,
+;; and/or sell copies of the Software, and to permit persons to whom the
+;; Software is furnished to do so, subject to the following conditions:
+
+;; The above copyright notice and this permission notice shall be included in
+;; all copies or substantial portions of the Software.
+
+;; THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+;; IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+;; FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+;; THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+;; LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+;; FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+;; DEALINGS IN THE SOFTWARE.
+#!r6rs
+
+;; RFC 4648 Base-N Encodings
+
+(library (8sync contrib base64)
+ (export base64-encode
+ base64-decode
+ base64-alphabet
+ base64url-alphabet
+ get-delimited-base64
+ put-delimited-base64)
+ (import (rnrs)
+ (only (srfi :13 strings)
+ string-index
+ string-prefix? string-suffix?
+ string-concatenate string-trim-both))
+
+ (define base64-alphabet
+ "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/")
+
+ (define base64url-alphabet
+ "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_")
+
+ (define base64-encode
+ (case-lambda
+ ;; Simple interface. Returns a string containing the canonical
+ ;; base64 representation of the given bytevector.
+ ((bv)
+ (base64-encode bv 0 (bytevector-length bv) #f #f base64-alphabet #f))
+ ((bv start)
+ (base64-encode bv start (bytevector-length bv) #f #f base64-alphabet #f))
+ ((bv start end)
+ (base64-encode bv start end #f #f base64-alphabet #f))
+ ((bv start end line-length)
+ (base64-encode bv start end line-length #f base64-alphabet #f))
+ ((bv start end line-length no-padding)
+ (base64-encode bv start end line-length no-padding base64-alphabet #f))
+ ((bv start end line-length no-padding alphabet)
+ (base64-encode bv start end line-length no-padding alphabet #f))
+ ;; Base64 encodes the bytes [start,end[ in the given bytevector.
+ ;; Lines are limited to line-length characters (unless #f),
+ ;; which must be a multiple of four. To omit the padding
+ ;; characters (#\=) set no-padding to a true value. If port is
+ ;; #f, returns a string.
+ ((bv start end line-length no-padding alphabet port)
+ (assert (or (not line-length) (zero? (mod line-length 4))))
+ (let-values (((p extract) (if port
+ (values port (lambda () (values)))
+ (open-string-output-port))))
+ (letrec ((put (if line-length
+ (let ((chars 0))
+ (lambda (p c)
+ (when (fx=? chars line-length)
+ (set! chars 0)
+ (put-char p #\linefeed))
+ (set! chars (fx+ chars 1))
+ (put-char p c)))
+ put-char)))
+ (let lp ((i start))
+ (cond ((= i end))
+ ((<= (+ i 3) end)
+ (let ((x (bytevector-uint-ref bv i (endianness big) 3)))
+ (put p (string-ref alphabet (fxbit-field x 18 24)))
+ (put p (string-ref alphabet (fxbit-field x 12 18)))
+ (put p (string-ref alphabet (fxbit-field x 6 12)))
+ (put p (string-ref alphabet (fxbit-field x 0 6)))
+ (lp (+ i 3))))
+ ((<= (+ i 2) end)
+ (let ((x (fxarithmetic-shift-left (bytevector-u16-ref bv i (endianness big)) 8)))
+ (put p (string-ref alphabet (fxbit-field x 18 24)))
+ (put p (string-ref alphabet (fxbit-field x 12 18)))
+ (put p (string-ref alphabet (fxbit-field x 6 12)))
+ (unless no-padding
+ (put p #\=))))
+ (else
+ (let ((x (fxarithmetic-shift-left (bytevector-u8-ref bv i) 16)))
+ (put p (string-ref alphabet (fxbit-field x 18 24)))
+ (put p (string-ref alphabet (fxbit-field x 12 18)))
+ (unless no-padding
+ (put p #\=)
+ (put p #\=)))))))
+ (extract)))))
+
+ ;; Create a lookup table for the alphabet and remember the latest table.
+ (define get-decode-table
+ (let ((ascii-table #f)
+ (extra-table '()) ;in the unlikely case of unicode chars
+ (table-alphabet #f))
+ (lambda (alphabet)
+ (unless (eq? alphabet table-alphabet)
+ ;; Rebuild the table.
+ (do ((ascii (make-vector 128 #f))
+ (extra '())
+ (i 0 (+ i 1)))
+ ((= i (string-length alphabet))
+ (set! ascii-table ascii)
+ (set! extra-table extra))
+ (let ((c (char->integer (string-ref alphabet i))))
+ (if (fx<=? c 127)
+ (vector-set! ascii c i)
+ (set! extra (cons (cons c i) extra)))))
+ (set! table-alphabet alphabet))
+ (values ascii-table extra-table))))
+
+ ;; Decodes a correctly padded base64 string, optionally ignoring
+ ;; non-alphabet characters.
+ (define base64-decode
+ (case-lambda
+ ((str)
+ (base64-decode str base64-alphabet #f))
+ ((str alphabet)
+ (base64-decode str alphabet #f))
+ ((str alphabet port)
+ (base64-decode str alphabet port #t))
+ ((str alphabet port strict?)
+ (define (pad? c) (eqv? c (char->integer #\=)))
+ (let-values (((p extract) (if port
+ (values port (lambda () (values)))
+ (open-bytevector-output-port)))
+ ((ascii extra) (get-decode-table alphabet)))
+ (define-syntax lookup
+ (syntax-rules ()
+ ((_ c) (or (and (fx<=? c 127) (vector-ref ascii c))
+ (cond ((assv c extra) => cdr)
+ (else #f))))))
+ (let* ((len (if strict?
+ (string-length str)
+ (let lp ((i (fx- (string-length str) 1)))
+ ;; Skip trailing invalid chars.
+ (cond ((fxzero? i) 0)
+ ((let ((c (char->integer (string-ref str i))))
+ (or (lookup c) (pad? c)))
+ (fx+ i 1))
+ (else (lp (fx- i 1))))))))
+ (let lp ((i 0))
+ (cond
+ ((fx=? i len)
+ (extract))
+ ((fx<=? i (fx- len 4))
+ (let lp* ((c1 (char->integer (string-ref str i)))
+ (c2 (char->integer (string-ref str (fx+ i 1))))
+ (c3 (char->integer (string-ref str (fx+ i 2))))
+ (c4 (char->integer (string-ref str (fx+ i 3))))
+ (i i))
+ (let ((i1 (lookup c1)) (i2 (lookup c2))
+ (i3 (lookup c3)) (i4 (lookup c4)))
+ (cond
+ ((and i1 i2 i3 i4)
+ ;; All characters present and accounted for.
+ ;; The most common case.
+ (let ((x (fxior (fxarithmetic-shift-left i1 18)
+ (fxarithmetic-shift-left i2 12)
+ (fxarithmetic-shift-left i3 6)
+ i4)))
+ (put-u8 p (fxbit-field x 16 24))
+ (put-u8 p (fxbit-field x 8 16))
+ (put-u8 p (fxbit-field x 0 8))
+ (lp (fx+ i 4))))
+ ((and i1 i2 i3 (pad? c4) (= i (- len 4)))
+ ;; One padding character at the end of the input.
+ (let ((x (fxior (fxarithmetic-shift-left i1 18)
+ (fxarithmetic-shift-left i2 12)
+ (fxarithmetic-shift-left i3 6))))
+ (put-u8 p (fxbit-field x 16 24))
+ (put-u8 p (fxbit-field x 8 16))
+ (lp (fx+ i 4))))
+ ((and i1 i2 (pad? c3) (pad? c4) (= i (- len 4)))
+ ;; Two padding characters.
+ (let ((x (fxior (fxarithmetic-shift-left i1 18)
+ (fxarithmetic-shift-left i2 12))))
+ (put-u8 p (fxbit-field x 16 24))
+ (lp (fx+ i 4))))
+ ((not strict?)
+ ;; Non-alphabet characters.
+ (let lp ((i i) (c* '()) (n 4))
+ (cond ((fxzero? n)
+ ;; Found four valid characters.
+ (lp* (cadddr c*) (caddr c*) (cadr c*) (car c*)
+ (fx- i 4)))
+ ((fx=? i len)
+ (error 'base64-decode
+ "Invalid input in non-strict mode."
+ i c*))
+ (else
+ ;; Gather alphabetic (or valid
+ ;; padding) characters.
+ (let ((c (char->integer (string-ref str i))))
+ (cond ((or (lookup c)
+ (and (pad? c)
+ (fx<=? n 2)
+ (fx=? i (fx- len n))))
+ (lp (fx+ i 1) (cons c c*) (fx- n 1)))
+ (else
+ (lp (fx+ i 1) c* n))))))))
+ (else
+ (error 'base64-decode
+ "Invalid input in strict mode."
+ c1 c2 c3 c4))))))
+ (else
+ (error 'base64-decode
+ "The input is too short, it may be missing padding."
+ i)))))))))
+
+ (define (get-line-comp f port)
+ (if (port-eof? port)
+ (eof-object)
+ (f (get-line port))))
+
+ ;; Reads the common -----BEGIN/END type----- delimited format from
+ ;; the given port. Returns two values: a string with the type and a
+ ;; bytevector containing the base64 decoded data. The second value
+ ;; is the eof object if there is an eof before the BEGIN delimiter.
+ (define get-delimited-base64
+ (case-lambda
+ ((port)
+ (get-delimited-base64 port #t))
+ ((port strict)
+ (define (get-first-data-line port)
+ ;; Some MIME data has header fields in the same format as mail
+ ;; or http. These are ignored.
+ (let ((line (get-line-comp string-trim-both port)))
+ (cond ((eof-object? line) line)
+ ((string-index line #\:)
+ (let lp () ;read until empty line
+ (let ((line (get-line-comp string-trim-both port)))
+ (if (string=? line "")
+ (get-line-comp string-trim-both port)
+ (lp)))))
+ (else line))))
+ (let ((line (get-line-comp string-trim-both port)))
+ (cond ((eof-object? line)
+ (values "" (eof-object)))
+ ((string=? line "")
+ (get-delimited-base64 port))
+ ((and (string-prefix? "-----BEGIN " line)
+ (string-suffix? "-----" line))
+ (let* ((type (substring line 11 (- (string-length line) 5)))
+ (endline (string-append "-----END " type "-----")))
+ (let-values (((outp extract) (open-bytevector-output-port)))
+ (let lp ((line (get-first-data-line port)))
+ (cond ((eof-object? line)
+ (error 'get-delimited-base64
+ "unexpected end of file"))
+ ((string-prefix? "-" line)
+ (unless (string=? line endline)
+ (error 'get-delimited-base64
+ "bad end delimiter" type line))
+ (values type (extract)))
+ (else
+ (unless (and (= (string-length line) 5)
+ (string-prefix? "=" line)) ;Skip Radix-64 checksum
+ (base64-decode line base64-alphabet outp))
+ (lp (get-line-comp string-trim-both port))))))))
+ (else ;skip garbage (like in openssl x509 -in foo -text output).
+ (get-delimited-base64 port)))))))
+
+ (define put-delimited-base64
+ (case-lambda
+ ((port type bv line-length)
+ (display (string-append "-----BEGIN " type "-----\n") port)
+ (base64-encode bv 0 (bytevector-length bv)
+ line-length #f base64-alphabet port)
+ (display (string-append "\n-----END " type "-----\n") port))
+ ((port type bv)
+ (put-delimited-base64 port type bv 76)))))
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