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-;; -*- 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 (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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