--- /dev/null
+;;; -*-Scheme-*-
+;;;
+;;; $Id: mime-codec.scm,v 14.1 2000/06/08 16:29:41 cph Exp $
+;;;
+;;; Copyright (c) 2000 Massachusetts Institute of Technology
+;;;
+;;; This program is free software; you can redistribute it and/or
+;;; modify it under the terms of the GNU General Public License as
+;;; published by the Free Software Foundation; either version 2 of the
+;;; License, or (at your option) any later version.
+;;;
+;;; This program is distributed in the hope that it will be useful,
+;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+;;; General Public License for more details.
+;;;
+;;; You should have received a copy of the GNU General Public License
+;;; along with this program; if not, write to the Free Software
+;;; Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+
+;;;; IMAIL mail reader: MIME support
+
+(declare (usual-integrations))
+\f
+;;;; Encode quoted-printable
+
+;;; Hair from two things: (1) delaying the decision to encode trailing
+;;; whitespace until we see what comes after it on the line; and (2)
+;;; an incremental line-breaking algorithm.
+
+(define-structure (qp-encoding-context
+ (conc-name qp-encoding-context/)
+ (constructor encode-quoted-printable:initialize
+ (port text?)))
+ (port #f read-only #t)
+ (text? #f read-only #t)
+ ;; Either #F, or an LWSP input that may or may not need to be
+ ;; encoded, depending on subsequent input.
+ (pending-lwsp #f)
+ ;; An exact integer between 0 and 75 inclusive, recording the number
+ ;; of characters that have been written on the current output line.
+ (column 0)
+ ;; Either #F, or an output string that may or may not fit on the
+ ;; current output line, depending on subsequent output.
+ (pending-output #f))
+
+(define (encode-quoted-printable:finalize context)
+ (encode-qp-pending-lwsp context #f 'INPUT-END)
+ (write-qp-pending-output context #t))
+
+(define (encode-quoted-printable:update context string start end)
+ (if (qp-encoding-context/text? context)
+ (let loop ((start start))
+ (let ((i (substring-find-next-char string start end #\newline)))
+ (if i
+ (begin
+ (encode-qp context string start i 'LINE-END)
+ (loop (fix:+ i 1)))
+ (encode-qp context string start end 'PARTIAL))))
+ (encode-qp context string start end 'PARTIAL)))
+
+(define (encode-qp context string start end type)
+ (encode-qp-pending-lwsp context (fix:< start end) type)
+ (let loop ((start start))
+ (cond ((fix:< start end)
+ (let ((char (string-ref string start))
+ (start (fix:+ start 1)))
+ (cond ((not (char-lwsp? char))
+ (if (char-qp-unencoded? char)
+ (write-qp-clear context char)
+ (write-qp-encoded context char))
+ (loop start))
+ ((and (eq? type 'PARTIAL)
+ (not (fix:< start end)))
+ (set-qp-encoding-context/pending-lwsp! context char))
+ (else
+ (if (fix:< start end)
+ (write-qp-clear context char)
+ (write-qp-encoded context char))
+ (loop start)))))
+ ((eq? type 'LINE-END)
+ (write-qp-hard-break context)))))
+
+(define (encode-qp-pending-lwsp context packet-not-empty? type)
+ (let ((pending (qp-encoding-context/pending-lwsp context)))
+ (if pending
+ (cond (packet-not-empty?
+ (set-qp-encoding-context/pending-lwsp! context #f)
+ (write-qp-clear context pending))
+ ((not (eq? type 'PARTIAL))
+ (set-qp-encoding-context/pending-lwsp! context #f)
+ (write-qp-encoded context pending))))))
+\f
+(define (write-qp-clear context char)
+ (write-qp-pending-output context #f)
+ (let ((port (qp-encoding-context/port context))
+ (column (qp-encoding-context/column context)))
+ (cond ((fix:< column 75)
+ (write-char char port)
+ (set-qp-encoding-context/column! context (fix:+ column 1)))
+ ((not (qp-encoding-context/text? context))
+ (write-qp-soft-break context)
+ (write-char char port)
+ (set-qp-encoding-context/column! context 1))
+ (else
+ (set-qp-encoding-context/pending-output! context (string char))))))
+
+(define (write-qp-encoded context char)
+ (write-qp-pending-output context #f)
+ (let ((port (qp-encoding-context/port context))
+ (column (qp-encoding-context/column context))
+ (d (char->integer char)))
+ (let ((c1 (hex-digit->char (fix:lsh d -4)))
+ (c2 (hex-digit->char (fix:and d #x0F))))
+ (if (fix:= column 73)
+ (set-qp-encoding-context/pending-output! context (string #\= c1 c2))
+ (begin
+ (if (fix:> column 73)
+ (write-qp-soft-break context))
+ (write-char #\= port)
+ (write-char c1 port)
+ (write-char c2 port)
+ (set-qp-encoding-context/column!
+ context
+ (fix:+ (qp-encoding-context/column context) 3)))))))
+
+(define (write-qp-hard-break context)
+ (write-qp-pending-output context #t)
+ (newline (qp-encoding-context/port context))
+ (set-qp-encoding-context/column! context 0))
+
+(define (write-qp-pending-output context newline?)
+ (let ((pending (qp-encoding-context/pending-output context)))
+ (if pending
+ (begin
+ (if (not newline?)
+ (write-qp-soft-break context))
+ (write-string pending (qp-encoding-context/port context))
+ (set-qp-encoding-context/pending-output! context #f)
+ (set-qp-encoding-context/column!
+ context
+ (fix:+ (qp-encoding-context/column context)
+ (string-length pending)))))))
+
+(define (write-qp-soft-break context)
+ (let ((port (qp-encoding-context/port context)))
+ (write-char #\= port)
+ (newline port))
+ (set-qp-encoding-context/column! context 0))
+\f
+;;;; Decode quoted-printable
+
+;;; This decoder is unbelievably hairy. The hair is due to the fact
+;;; that the input to the decoder is arbitrarily packetized, and the
+;;; encoder really wants to operate on units of input lines. The
+;;; strategy is that we process as much of the input packet as
+;;; possible, then save enough state to continue when the next packet
+;;; comes along.
+
+(define-structure (qp-decoding-context
+ (conc-name qp-decoding-context/)
+ (constructor decode-quoted-printable:initialize
+ (port text?)))
+ (port #f read-only #t)
+ (text? #f read-only #t)
+ ;; Pending input that can't be processed until more input is
+ ;; available. Can take on one of the following values:
+ ;; * #F means no pending input.
+ ;; * A string, consisting entirely of LWSP characters, is whitespace
+ ;; that appeared at the end of an input packet. We are waiting to
+ ;; see if it is followed by a newline, meaning it is to be
+ ;; discarded. Otherwise it is part of the output.
+ ;; * The character #\=, meaning that the equals-sign character has
+ ;; been seen and we need more characters to decide what to do with
+ ;; it.
+ ;; * A hexadecimal-digit character (0-9, A-F), meaning that an
+ ;; equals sign and that character have been seen, and we are
+ ;; waiting for the second hexadecimal digit to arrive.
+ (pending #f))
+
+(define (decode-quoted-printable:finalize context)
+ (decode-qp context "" 0 0 'INPUT-END))
+
+(define (decode-quoted-printable:update context string start end)
+ (let loop ((start start))
+ (let ((i (substring-find-next-char string start end #\newline)))
+ (if i
+ (begin
+ (decode-qp context
+ string start (skip-lwsp-backwards string start i)
+ 'LINE-END)
+ (loop (fix:+ i 1)))
+ (decode-qp context string start end 'PARTIAL)))))
+\f
+(define (decode-qp context string start end type)
+ (let ((port (qp-decoding-context/port context))
+ (end* (skip-lwsp-backwards string start end)))
+
+ (define (loop start)
+ (if (fix:< start end*)
+ (let ((char (string-ref string start))
+ (start (fix:+ start 1)))
+ (if (char=? char #\=)
+ (handle-equals start)
+ (begin
+ ;; RFC 2045 recommends dropping illegal encoded char.
+ (if (char-qp-unencoded? char)
+ (write-char char port))
+ (loop start))))
+ (finish)))
+
+ (define (handle-equals start)
+ (if (fix:< (fix:+ start 1) end*)
+ (loop (decode-qp-hex context
+ (string-ref string start)
+ (string-ref string (fix:+ start 1))
+ (fix:+ start 2)))
+ (begin
+ (if (fix:< start end*)
+ (let ((char (string-ref string start)))
+ (if (char-hex-digit? char)
+ (set-qp-decoding-context/pending! context char)
+ ;; Illegal: RFC 2045 recommends leaving as is.
+ (begin
+ (write-char #\= port)
+ (write-char char port))))
+ (set-qp-decoding-context/pending! context #\=))
+ (finish))))
+
+ (define (finish)
+ (let ((pending (qp-decoding-context/pending context)))
+ (set-qp-decoding-context/pending! context #f)
+ (cond ((eq? type 'PARTIAL)
+ (set-qp-decoding-context/pending!
+ context
+ (decode-qp-pending-string pending string end* end)))
+ ((not pending)
+ (if (and (eq? type 'LINE-END)
+ (qp-decoding-context/text? context))
+ ;; Hard line break.
+ (newline port)))
+ ((eqv? pending #\=)
+ (if (eq? type 'LINE-END)
+ ;; Soft line break.
+ unspecific
+ ;; Illegal: RFC 2045 recommends leaving as is.
+ (write-char #\= port)))
+ ((char? pending)
+ ;; Illegal: RFC 2045 recommends leaving as is.
+ (write-char #\= port)
+ (write-char pending port))
+ ((string? pending)
+ ;; Trailing whitespace: discard.
+ unspecific)
+ (else (error "Illegal PENDING value:" pending)))))
+
+ (let ((pending (qp-decoding-context/pending context)))
+ (if (and pending (fix:< start end*))
+ (begin
+ (set-qp-decoding-context/pending! context #f)
+ (cond ((eqv? pending #\=)
+ (handle-equals start))
+ ((char? pending)
+ (loop (decode-qp-hex context
+ pending
+ (string-ref string start)
+ (fix:+ start 1))))
+ ((string? pending)
+ (write-string pending port)
+ (loop start))
+ (else (error "Illegal PENDING value:" pending))))
+ (loop start)))))
+\f
+(define (decode-qp-pending-string pending string start end)
+ (if (fix:< start end)
+ (if pending
+ (let ((s
+ (make-string
+ (fix:+ (string-length pending) (fix:- end start)))))
+ (substring-move! string start end
+ s (string-move! pending s 0))
+ s)
+ (substring string start end))
+ pending))
+
+(define-integrable (char-qp-unencoded? char)
+ (char-set-member? char-set:qp-unencoded char))
+
+(define char-set:qp-unencoded
+ (char-set-union (char-set-difference (ascii-range->char-set #x21 #x7F)
+ (char-set #\=))
+ (char-set #\space #\tab)))
+
+(define (char-lwsp? char)
+ (or (char=? #\space char)
+ (char=? #\tab char)))
+
+(define (skip-lwsp-backwards string start end)
+ (let loop ((end end))
+ (if (and (fix:< start end)
+ (char-lwsp? (string-ref string (fix:- end 1))))
+ (loop (fix:- end 1))
+ end)))
+
+(define (decode-qp-hex context c1 c2 start)
+ (let ((port (qp-decoding-context/port context)))
+ (let ((char
+ (let ((d1 (char->hex-digit c1))
+ (d2 (char->hex-digit c2)))
+ (and (fix:< d1 #x10)
+ (fix:< d2 #x10)
+ (integer->char (fix:or (fix:lsh d1 4) d2))))))
+ (if char
+ (begin
+ (write-char char port)
+ start)
+ ;; This case is illegal. RFC 2045 recommends
+ ;; leaving it unconverted.
+ (begin
+ (write-char #\= port)
+ (write-char c1 port)
+ (fix:- start 1))))))
+
+(define-integrable (char-hex-digit? char)
+ (fix:< (char->hex-digit char) #x10))
+
+(define-integrable (char->hex-digit char)
+ (vector-8b-ref hex-char-table (char->integer char)))
+
+(define-integrable (hex-digit->char digit)
+ (string-ref hex-digit-table digit))
+
+(define hex-char-table)
+(define hex-digit-table)
+(let ((char-table (make-string 256 (integer->char #xff)))
+ (digit-table (make-string 16)))
+ (define (do-range low high value)
+ (do-char low value)
+ (if (fix:< low high)
+ (do-range (fix:+ low 1) high (fix:+ value 1))))
+ (define (do-char code value)
+ (vector-8b-set! char-table code value)
+ (vector-8b-set! digit-table value code))
+ (do-range (char->integer #\0) (char->integer #\9) 0)
+ (do-range (char->integer #\A) (char->integer #\F) 10)
+ (do-range (char->integer #\a) (char->integer #\f) 10)
+ (set! hex-char-table char-table)
+ (set! hex-digit-table digit-table)
+ unspecific)
+\f
+;;;; Encode BASE64
+
+(define-structure (base64-encoding-context
+ (conc-name base64-encoding-context/)
+ (constructor encode-base64:initialize (port text?)))
+ (port #f read-only #t)
+ (text? #f read-only #t)
+ (buffer (make-string 48) read-only #t)
+ (index 0))
+
+(define (encode-base64:finalize context)
+ (write-base64-line context))
+
+(define (encode-base64:update context string start end)
+ (if (base64-encoding-context/text? context)
+ (let loop ((start start))
+ (let ((index (substring-find-next-char string start end #\newline)))
+ (if index
+ (begin
+ (encode-base64 context string start index)
+ (encode-base64 context "\r\n" 0 2)
+ (loop (fix:+ index 1)))
+ (encode-base64 context string start end))))
+ (encode-base64 context string start end)))
+
+(define (encode-base64 context string start end)
+ (let ((buffer (base64-encoding-context/buffer context)))
+ (let loop ((start start))
+ (if (fix:< start end)
+ (let ((i (base64-encoding-context/index context)))
+ (let ((start* (fix:min end (fix:+ start (fix:- 48 i)))))
+ (let ((i (substring-move! string start start* buffer i)))
+ (set-base64-encoding-context/index! context i)
+ (if (fix:= i 48)
+ (write-base64-line context)))
+ (loop start*)))))))
+
+(define (write-base64-line context)
+ (let ((buffer (base64-encoding-context/buffer context))
+ (end (base64-encoding-context/index context))
+ (port (base64-encoding-context/port context)))
+ (if (fix:> end 0)
+ (begin
+ (let ((write-digit
+ (lambda (d)
+ (write-char (string-ref base64-digit-table (fix:and #x3F d))
+ port))))
+ (let loop ((start 0))
+ (let ((n (fix:- end start)))
+ (cond ((fix:>= n 3)
+ (let ((d1 (vector-8b-ref buffer start))
+ (d2 (vector-8b-ref buffer (fix:+ start 1)))
+ (d3 (vector-8b-ref buffer (fix:+ start 2))))
+ (write-digit (fix:lsh d1 -2))
+ (write-digit (fix:or (fix:lsh d1 4) (fix:lsh d2 -4)))
+ (write-digit (fix:or (fix:lsh d2 2) (fix:lsh d3 -6)))
+ (write-digit d3))
+ (loop (fix:+ start 3)))
+ ((fix:= n 2)
+ (let ((d1 (vector-8b-ref buffer start))
+ (d2 (vector-8b-ref buffer (fix:+ start 1))))
+ (write-digit (fix:lsh d1 -2))
+ (write-digit (fix:or (fix:lsh d1 4) (fix:lsh d2 -4)))
+ (write-digit (fix:lsh d2 2)))
+ (write-char #\= port))
+ ((fix:= n 1)
+ (let ((d1 (vector-8b-ref buffer start)))
+ (write-digit (fix:lsh d1 -2))
+ (write-digit (fix:lsh d1 4)))
+ (write-char #\= port)
+ (write-char #\= port))))))
+ (newline port)
+ (set-base64-encoding-context/index! context 0)))))
+\f
+;;;; Decode BASE64
+
+(define-structure (base64-decoding-context
+ (conc-name base64-decoding-context/)
+ (constructor decode-base64:initialize (port text?)))
+ (port #f read-only #t)
+ (text? #f read-only #t)
+ (input-buffer (make-string 4) read-only #t)
+ (input-index 0)
+ (output-buffer (make-string 3) read-only #t)
+ (pending-return? #f))
+
+(define (decode-base64:finalize context)
+ (if (fix:> (base64-decoding-context/input-index context) 0)
+ (error "BASE64 input length is not a multiple of 4."))
+ (if (base64-decoding-context/pending-return? context)
+ (write-char #\return (base64-decoding-context/port context))))
+
+(define (decode-base64:update context string start end)
+ (let ((buffer (base64-decoding-context/input-buffer context)))
+ (let loop
+ ((start start)
+ (index (base64-decoding-context/input-index context)))
+ (if (fix:< start end)
+ (let ((char (string-ref string start))
+ (start (fix:+ start 1)))
+ (if (or (char=? char #\=)
+ (fix:< (vector-8b-ref base64-char-table
+ (char->integer char))
+ #x40))
+ (begin
+ (string-set! buffer index char)
+ (if (fix:< index 3)
+ (loop start (fix:+ index 1))
+ (begin
+ (decode-base64-quantum context)
+ (loop start 0))))
+ (loop start index)))
+ (set-base64-decoding-context/input-index! context index)))))
+\f
+(define (decode-base64-quantum context)
+ (let ((input (base64-decoding-context/input-buffer context))
+ (output (base64-decoding-context/output-buffer context))
+ (port (base64-decoding-context/port context)))
+ (let ((n (decode-base64-quantum-1 input output)))
+ (if (base64-decoding-context/text? context)
+ (let loop
+ ((index 0)
+ (pending? (base64-decoding-context/pending-return? context)))
+ (if (fix:< index n)
+ (let ((char (string-ref output index)))
+ (if pending?
+ (if (char=? char #\linefeed)
+ (begin
+ (newline port)
+ (loop (fix:+ index 1) #f))
+ (begin
+ (write-char #\return port)
+ (loop index #f)))
+ (if (char=? char #\return)
+ (loop (fix:+ index 1) #t)
+ (begin
+ (write-char char port)
+ (loop (fix:+ index 1) #f)))))
+ (set-base64-decoding-context/pending-return?! context
+ pending?)))
+ (write-substring output 0 n port)))))
+
+(define (decode-base64-quantum-1 input output)
+ (let ((d1 (decode-base64-char input 0))
+ (d2 (decode-base64-char input 1)))
+ (cond ((not (char=? (string-ref input 3) #\=))
+ (let ((n
+ (fix:+ (fix:+ (fix:lsh d1 18)
+ (fix:lsh d2 12))
+ (fix:+ (fix:lsh (decode-base64-char input 2) 6)
+ (decode-base64-char input 3)))))
+ (vector-8b-set! output 0 (fix:lsh n -16))
+ (vector-8b-set! output 1 (fix:and #xFF (fix:lsh n -8)))
+ (vector-8b-set! output 2 (fix:and #xFF n))
+ 3))
+ ((not (char=? (string-ref input 2) #\=))
+ (let ((n
+ (fix:+ (fix:+ (fix:lsh d1 10) (fix:lsh d2 4))
+ (fix:lsh (decode-base64-char input 2) -2))))
+ (vector-8b-set! output 0 (fix:lsh n -8))
+ (vector-8b-set! output 1 (fix:and #xFF n)))
+ 2)
+ (else
+ (vector-8b-set! output 0 (fix:+ (fix:lsh d1 2) (fix:lsh d2 -4)))
+ 1))))
+
+(define (decode-base64-char input index)
+ (let ((digit (vector-8b-ref base64-char-table (vector-8b-ref input index))))
+ (if (fix:> digit #x40)
+ (error "Misplaced #\= in BASE64 input."))
+ digit))
+
+(define base64-char-table)
+(define base64-digit-table)
+(let ((char-table (make-string 256 (integer->char #xff)))
+ (digit-table (make-string 64)))
+ (define (do-range low high value)
+ (do-char low value)
+ (if (fix:< low high)
+ (do-range (fix:+ low 1) high (fix:+ value 1))))
+ (define (do-char code value)
+ (vector-8b-set! char-table code value)
+ (vector-8b-set! digit-table value code))
+ (do-range (char->integer #\A) (char->integer #\Z) 0)
+ (do-range (char->integer #\a) (char->integer #\z) 26)
+ (do-range (char->integer #\0) (char->integer #\9) 52)
+ (do-char (char->integer #\+) 62)
+ (do-char (char->integer #\/) 63)
+ (set! base64-char-table char-table)
+ (set! base64-digit-table digit-table)
+ unspecific)
\ No newline at end of file
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