b2ad9d9b08
* guix/base64.scm (define-alias): New macro. (fxbit-field, fxarithmetic-shift, fxarithmetic-shift-left, fxand, fxior, fxxor): New aliases.
231 lines
10 KiB
Scheme
231 lines
10 KiB
Scheme
;; -*- mode: scheme; coding: utf-8 -*-
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;;
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;; This module was renamed from (weinholt text base64 (1 0 20100612)) to
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;; (guix base64) by Nikita Karetnikov <nikita@karetnikov.org> on
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;; February 12, 2014.
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;;
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;; Some optimizations made by Ludovic Courtès <ludo@gnu.org>, 2015.
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;;
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;; Copyright © 2009, 2010 Göran Weinholt <goran@weinholt.se>
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;;
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;; This program is free software: you can redistribute it and/or modify
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;; it under the terms of the GNU General Public License as published by
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;; the Free Software Foundation, either version 3 of the License, or
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;; (at your option) any later version.
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;;
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;; This program is distributed in the hope that it will be useful,
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;; but WITHOUT ANY WARRANTY; without even the implied warranty of
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;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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;; GNU General Public License for more details.
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;;
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;; You should have received a copy of the GNU General Public License
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;; along with this program. If not, see <http://www.gnu.org/licenses/>.
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#!r6rs
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;; RFC 4648 Base-N Encodings
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(library (guix base64)
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(export base64-encode
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base64-decode
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base64-alphabet
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base64url-alphabet
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get-delimited-base64
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put-delimited-base64)
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(import (rnrs)
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(only (srfi :13 strings)
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string-index
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string-prefix? string-suffix?
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string-concatenate string-trim-both)
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(only (guile) ash logior))
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(define-syntax define-alias
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(syntax-rules ()
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((_ new old)
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(define-syntax new (identifier-syntax old)))))
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;; Force the use of Guile's own primitives to avoid the overhead of its 'fx'
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;; procedures.
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(define-alias fxbit-field bitwise-bit-field)
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(define-alias fxarithmetic-shift ash)
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(define-alias fxarithmetic-shift-left ash)
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(define-alias fxand logand)
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(define-alias fxior logior)
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(define-alias fxxor logxor)
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(define base64-alphabet
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"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/")
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(define base64url-alphabet
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"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_")
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(define base64-encode
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(case-lambda
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;; Simple interface. Returns a string containing the canonical
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;; base64 representation of the given bytevector.
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((bv)
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(base64-encode bv 0 (bytevector-length bv) #f #f base64-alphabet #f))
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((bv start)
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(base64-encode bv start (bytevector-length bv) #f #f base64-alphabet #f))
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((bv start end)
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(base64-encode bv start end #f #f base64-alphabet #f))
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((bv start end line-length)
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(base64-encode bv start end line-length #f base64-alphabet #f))
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((bv start end line-length no-padding)
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(base64-encode bv start end line-length no-padding base64-alphabet #f))
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((bv start end line-length no-padding alphabet)
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(base64-encode bv start end line-length no-padding alphabet #f))
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;; Base64 encodes the bytes [start,end[ in the given bytevector.
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;; Lines are limited to line-length characters (unless #f),
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;; which must be a multiple of four. To omit the padding
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;; characters (#\=) set no-padding to a true value. If port is
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;; #f, returns a string.
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((bv start end line-length no-padding alphabet port)
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(assert (or (not line-length) (zero? (mod line-length 4))))
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(let-values (((p extract) (if port
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(values port (lambda () (values)))
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(open-string-output-port))))
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(letrec ((put (if line-length
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(let ((chars 0))
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(lambda (p c)
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(when (fx=? chars line-length)
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(set! chars 0)
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(put-char p #\linefeed))
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(set! chars (fx+ chars 1))
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(put-char p c)))
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put-char)))
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(let lp ((i start))
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(cond ((= i end))
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((<= (+ i 3) end)
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(let ((x (bytevector-uint-ref bv i (endianness big) 3)))
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(put p (string-ref alphabet (fxbit-field x 18 24)))
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(put p (string-ref alphabet (fxbit-field x 12 18)))
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(put p (string-ref alphabet (fxbit-field x 6 12)))
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(put p (string-ref alphabet (fxbit-field x 0 6)))
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(lp (+ i 3))))
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((<= (+ i 2) end)
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(let ((x (fxarithmetic-shift-left (bytevector-u16-ref bv i (endianness big)) 8)))
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(put p (string-ref alphabet (fxbit-field x 18 24)))
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(put p (string-ref alphabet (fxbit-field x 12 18)))
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(put p (string-ref alphabet (fxbit-field x 6 12)))
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(unless no-padding
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(put p #\=))))
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(else
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(let ((x (fxarithmetic-shift-left (bytevector-u8-ref bv i) 16)))
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(put p (string-ref alphabet (fxbit-field x 18 24)))
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(put p (string-ref alphabet (fxbit-field x 12 18)))
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(unless no-padding
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(put p #\=)
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(put p #\=)))))))
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(extract)))))
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;; Decodes a base64 string. The string must contain only pure
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;; unpadded base64 data.
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(define base64-decode
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(case-lambda
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((str)
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(base64-decode str base64-alphabet #f))
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((str alphabet)
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(base64-decode str alphabet #f))
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((str alphabet port)
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(unless (zero? (mod (string-length str) 4))
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(error 'base64-decode
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"input string must be a multiple of four characters"))
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(let-values (((p extract) (if port
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(values port (lambda () (values)))
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(open-bytevector-output-port))))
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(do ((i 0 (+ i 4)))
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((= i (string-length str))
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(extract))
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(let ((c1 (string-ref str i))
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(c2 (string-ref str (+ i 1)))
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(c3 (string-ref str (+ i 2)))
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(c4 (string-ref str (+ i 3))))
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;; TODO: be more clever than string-index
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(let ((i1 (string-index alphabet c1))
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(i2 (string-index alphabet c2))
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(i3 (string-index alphabet c3))
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(i4 (string-index alphabet c4)))
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(cond ((and i1 i2 i3 i4)
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(let ((x (fxior (fxarithmetic-shift-left i1 18)
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(fxarithmetic-shift-left i2 12)
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(fxarithmetic-shift-left i3 6)
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i4)))
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(put-u8 p (fxbit-field x 16 24))
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(put-u8 p (fxbit-field x 8 16))
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(put-u8 p (fxbit-field x 0 8))))
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((and i1 i2 i3 (char=? c4 #\=)
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(= i (- (string-length str) 4)))
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(let ((x (fxior (fxarithmetic-shift-left i1 18)
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(fxarithmetic-shift-left i2 12)
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(fxarithmetic-shift-left i3 6))))
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(put-u8 p (fxbit-field x 16 24))
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(put-u8 p (fxbit-field x 8 16))))
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((and i1 i2 (char=? c3 #\=) (char=? c4 #\=)
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(= i (- (string-length str) 4)))
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(let ((x (fxior (fxarithmetic-shift-left i1 18)
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(fxarithmetic-shift-left i2 12))))
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(put-u8 p (fxbit-field x 16 24))))
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(else
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(error 'base64-decode "invalid input"
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(list c1 c2 c3 c4)))))))))))
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(define (get-line-comp f port)
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(if (port-eof? port)
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(eof-object)
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(f (get-line port))))
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;; Reads the common -----BEGIN/END type----- delimited format from
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;; the given port. Returns two values: a string with the type and a
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;; bytevector containing the base64 decoded data. The second value
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;; is the eof object if there is an eof before the BEGIN delimiter.
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(define (get-delimited-base64 port)
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(define (get-first-data-line port)
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;; Some MIME data has header fields in the same format as mail
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;; or http. These are ignored.
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(let ((line (get-line-comp string-trim-both port)))
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(cond ((eof-object? line) line)
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((string-index line #\:)
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(let lp () ;read until empty line
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(let ((line (get-line-comp string-trim-both port)))
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(if (string=? line "")
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(get-line-comp string-trim-both port)
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(lp)))))
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(else line))))
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(let ((line (get-line-comp string-trim-both port)))
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(cond ((eof-object? line)
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(values "" (eof-object)))
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((string=? line "")
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(get-delimited-base64 port))
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((and (string-prefix? "-----BEGIN " line)
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(string-suffix? "-----" line))
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(let* ((type (substring line 11 (- (string-length line) 5)))
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(endline (string-append "-----END " type "-----")))
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(let-values (((outp extract) (open-bytevector-output-port)))
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(let lp ((line (get-first-data-line port)))
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(cond ((eof-object? line)
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(error 'get-delimited-base64
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"unexpected end of file"))
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((string-prefix? "-" line)
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(unless (string=? line endline)
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(error 'get-delimited-base64
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"bad end delimiter" type line))
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(values type (extract)))
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(else
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(unless (and (= (string-length line) 5)
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(string-prefix? "=" line)) ;Skip Radix-64 checksum
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(base64-decode line base64-alphabet outp))
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(lp (get-line-comp string-trim-both port))))))))
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(else ;skip garbage (like in openssl x509 -in foo -text output).
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(get-delimited-base64 port)))))
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(define put-delimited-base64
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(case-lambda
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((port type bv line-length)
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(display (string-append "-----BEGIN " type "-----\n") port)
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(base64-encode bv 0 (bytevector-length bv)
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line-length #f base64-alphabet port)
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(display (string-append "\n-----END " type "-----\n") port))
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((port type bv)
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(put-delimited-base64 port type bv 76)))))
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