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| -rw-r--r-- | base64.scm | 230 |
1 files changed, 230 insertions, 0 deletions
diff --git a/base64.scm b/base64.scm new file mode 100644 index 0000000..2568ae0 --- /dev/null +++ b/base64.scm @@ -0,0 +1,230 @@ +;; -*- mode: scheme; coding: utf-8 -*- +;; +;; This module was renamed from (weinholt text base64 (1 0 20100612)) to +;; (guix base64) by Nikita Karetnikov <nikita@karetnikov.org> on +;; February 12, 2014. +;; +;; Some optimizations made by Ludovic Courtès <ludo@gnu.org>, 2015. +;; +;; Copyright © 2009, 2010 Göran Weinholt <goran@weinholt.se> +;; +;; 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 3 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, see <http://www.gnu.org/licenses/>. +#!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) + (only (guile) ash logior)) + + + (define-syntax define-alias + (syntax-rules () + ((_ new old) + (define-syntax new (identifier-syntax old))))) + + ;; Force the use of Guile's own primitives to avoid the overhead of its 'fx' + ;; procedures. + (define-alias fxbit-field bitwise-bit-field) + (define-alias fxarithmetic-shift ash) + (define-alias fxarithmetic-shift-left ash) + (define-alias fxand logand) + (define-alias fxior logior) + (define-alias fxxor logxor) + + (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))))) + + ;; Decodes a base64 string. The string must contain only pure + ;; unpadded base64 data. + (define base64-decode + (case-lambda + ((str) + (base64-decode str base64-alphabet #f)) + ((str alphabet) + (base64-decode str alphabet #f)) + ((str alphabet port) + (unless (zero? (mod (string-length str) 4)) + (error 'base64-decode + "input string must be a multiple of four characters")) + (let-values (((p extract) (if port + (values port (lambda () (values))) + (open-bytevector-output-port)))) + (do ((i 0 (+ i 4))) + ((= i (string-length str)) + (extract)) + (let ((c1 (string-ref str i)) + (c2 (string-ref str (+ i 1))) + (c3 (string-ref str (+ i 2))) + (c4 (string-ref str (+ i 3)))) + ;; TODO: be more clever than string-index + (let ((i1 (string-index alphabet c1)) + (i2 (string-index alphabet c2)) + (i3 (string-index alphabet c3)) + (i4 (string-index alphabet c4))) + (cond ((and i1 i2 i3 i4) + (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)))) + ((and i1 i2 i3 (char=? c4 #\=) + (= i (- (string-length str) 4))) + (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)))) + ((and i1 i2 (char=? c3 #\=) (char=? c4 #\=) + (= i (- (string-length str) 4))) + (let ((x (fxior (fxarithmetic-shift-left i1 18) + (fxarithmetic-shift-left i2 12)))) + (put-u8 p (fxbit-field x 16 24)))) + (else + (error 'base64-decode "invalid input" + (list c1 c2 c3 c4))))))))))) + + (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 port) + (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))))) |