;;; GNU Guix --- Functional package management for GNU ;;; Copyright © 2012 Ludovic Courtès <ludo@gnu.org> ;;; ;;; This file is part of GNU Guix. ;;; ;;; GNU Guix 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. ;;; ;;; GNU Guix 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 GNU Guix. If not, see <http://www.gnu.org/licenses/>. (define-module (guix base32) #:use-module (srfi srfi-1) #:use-module (srfi srfi-60) #:use-module (rnrs bytevectors) #:use-module (ice-9 vlist) #:export (bytevector-quintet-length bytevector->base32-string bytevector->nix-base32-string base32-string->bytevector nix-base32-string->bytevector)) ;;; Commentary: ;;; ;;; A generic, customizable to convert bytevectors to/from a base32 ;;; representation. ;;; ;;; Code: (define bytevector-quintet-ref (let* ((ref bytevector-u8-ref) (ref+ (lambda (bv offset) (let ((o (+ 1 offset))) (if (>= o (bytevector-length bv)) 0 (bytevector-u8-ref bv o))))) (ref0 (lambda (bv offset) (bit-field (ref bv offset) 3 8))) (ref1 (lambda (bv offset) (logior (ash (bit-field (ref bv offset) 0 3) 2) (bit-field (ref+ bv offset) 6 8)))) (ref2 (lambda (bv offset) (bit-field (ref bv offset) 1 6))) (ref3 (lambda (bv offset) (logior (ash (bit-field (ref bv offset) 0 1) 4) (bit-field (ref+ bv offset) 4 8)))) (ref4 (lambda (bv offset) (logior (ash (bit-field (ref bv offset) 0 4) 1) (bit-field (ref+ bv offset) 7 8)))) (ref5 (lambda (bv offset) (bit-field (ref bv offset) 2 7))) (ref6 (lambda (bv offset) (logior (ash (bit-field (ref bv offset) 0 2) 3) (bit-field (ref+ bv offset) 5 8)))) (ref7 (lambda (bv offset) (bit-field (ref bv offset) 0 5))) (refs (vector ref0 ref1 ref2 ref3 ref4 ref5 ref6 ref7))) (lambda (bv index) "Return the INDEXth quintet of BV." (let ((p (vector-ref refs (modulo index 8)))) (p bv (quotient (* index 5) 8)))))) (define bytevector-quintet-ref-right (let* ((ref bytevector-u8-ref) (ref+ (lambda (bv offset) (let ((o (+ 1 offset))) (if (>= o (bytevector-length bv)) 0 (bytevector-u8-ref bv o))))) (ref0 (lambda (bv offset) (bit-field (ref bv offset) 0 5))) (ref1 (lambda (bv offset) (logior (bit-field (ref bv offset) 5 8) (ash (bit-field (ref+ bv offset) 0 2) 3)))) (ref2 (lambda (bv offset) (bit-field (ref bv offset) 2 7))) (ref3 (lambda (bv offset) (logior (bit-field (ref bv offset) 7 8) (ash (bit-field (ref+ bv offset) 0 4) 1)))) (ref4 (lambda (bv offset) (logior (bit-field (ref bv offset) 4 8) (ash (bit-field (ref+ bv offset) 0 1) 4)))) (ref5 (lambda (bv offset) (bit-field (ref bv offset) 1 6))) (ref6 (lambda (bv offset) (logior (bit-field (ref bv offset) 6 8) (ash (bit-field (ref+ bv offset) 0 3) 2)))) (ref7 (lambda (bv offset) (bit-field (ref bv offset) 3 8))) (refs (vector ref0 ref1 ref2 ref3 ref4 ref5 ref6 ref7))) (lambda (bv index) "Return the INDEXth quintet of BV, assuming quintets start from the least-significant bits, contrary to what RFC 4648 describes." (let ((p (vector-ref refs (modulo index 8)))) (p bv (quotient (* index 5) 8)))))) (define (bytevector-quintet-length bv) "Return the number of quintets (including truncated ones) available in BV." (ceiling (/ (* (bytevector-length bv) 8) 5))) (define (bytevector-quintet-fold proc init bv) "Return the result of applying PROC to each quintet of BV and the result of the previous application or INIT." (define len (bytevector-quintet-length bv)) (let loop ((i 0) (r init)) (if (= i len) r (loop (1+ i) (proc (bytevector-quintet-ref bv i) r))))) (define (bytevector-quintet-fold-right proc init bv) "Return the result of applying PROC to each quintet of BV and the result of the previous application or INIT." (define len (bytevector-quintet-length bv)) (let loop ((i len) (r init)) (if (zero? i) r (let ((j (- i 1))) (loop j (proc (bytevector-quintet-ref-right bv j) r)))))) (define (make-bytevector->base32-string quintet-fold base32-chars) (lambda (bv) "Return a base32 encoding of BV using BASE32-CHARS as the alphabet." (let ((chars (quintet-fold (lambda (q r) (cons (vector-ref base32-chars q) r)) '() bv))) (list->string (reverse chars))))) (define %nix-base32-chars ;; See `libutil/hash.cc'. #(#\0 #\1 #\2 #\3 #\4 #\5 #\6 #\7 #\8 #\9 #\a #\b #\c #\d #\f #\g #\h #\i #\j #\k #\l #\m #\n #\p #\q #\r #\s #\v #\w #\x #\y #\z)) (define %rfc4648-base32-chars #(#\a #\b #\c #\d #\e #\f #\g #\h #\i #\j #\k #\l #\m #\n #\o #\p #\q #\r #\s #\t #\u #\v #\w #\x #\y #\z #\2 #\3 #\4 #\5 #\6 #\7)) (define bytevector->base32-string (make-bytevector->base32-string bytevector-quintet-fold %rfc4648-base32-chars)) (define bytevector->nix-base32-string (make-bytevector->base32-string bytevector-quintet-fold-right %nix-base32-chars)) (define bytevector-quintet-set! (let* ((setq! (lambda (bv offset start stop value) (let ((v (bytevector-u8-ref bv offset)) (w (arithmetic-shift value start)) (m (bitwise-xor (1- (expt 2 stop)) (1- (expt 2 start))))) (bytevector-u8-set! bv offset (bitwise-merge m w v))))) (set0! (lambda (bv offset value) (setq! bv offset 3 8 value))) (set1! (lambda (bv offset value) (setq! bv offset 0 3 (bit-field value 2 5)) (or (= (+ 1 offset) (bytevector-length bv)) (setq! bv (+ 1 offset) 6 8 (bit-field value 0 2))))) (set2! (lambda (bv offset value) (setq! bv offset 1 6 value))) (set3! (lambda (bv offset value) (setq! bv offset 0 1 (bit-field value 4 5)) (or (= (+ 1 offset) (bytevector-length bv)) (setq! bv (+ 1 offset) 4 8 (bit-field value 0 4))))) (set4! (lambda (bv offset value) (setq! bv offset 0 4 (bit-field value 1 5)) (or (= (+ 1 offset) (bytevector-length bv)) (setq! bv (+ 1 offset) 7 8 (bit-field value 0 1))))) (set5! (lambda (bv offset value) (setq! bv offset 2 7 value))) (set6! (lambda (bv offset value) (setq! bv offset 0 2 (bit-field value 3 5)) (or (= (+ 1 offset) (bytevector-length bv)) (setq! bv (+ 1 offset) 5 8 (bit-field value 0 3))))) (set7! (lambda (bv offset value) (setq! bv offset 0 5 value))) (sets (vector set0! set1! set2! set3! set4! set5! set6! set7!))) (lambda (bv index value) "Set the INDEXth quintet of BV to VALUE." (let ((p (vector-ref sets (modulo index 8)))) (p bv (quotient (* index 5) 8) (logand value #x1f)))))) (define bytevector-quintet-set-right! (let* ((setq! (lambda (bv offset start stop value) (let ((v (bytevector-u8-ref bv offset)) (w (arithmetic-shift value start)) (m (bitwise-xor (1- (expt 2 stop)) (1- (expt 2 start))))) (bytevector-u8-set! bv offset (bitwise-merge m w v))))) (set0! (lambda (bv offset value) (setq! bv offset 0 5 value))) (set1! (lambda (bv offset value) (setq! bv offset 5 8 (bit-field value 0 3)) (or (= (+ 1 offset) (bytevector-length bv)) (setq! bv (+ 1 offset) 0 2 (bit-field value 3 5))))) (set2! (lambda (bv offset value) (setq! bv offset 2 7 value))) (set3! (lambda (bv offset value) (setq! bv offset 7 8 (bit-field value 0 1)) (or (= (+ 1 offset) (bytevector-length bv)) (setq! bv (+ 1 offset) 0 4 (bit-field value 1 5))))) (set4! (lambda (bv offset value) (setq! bv offset 4 8 (bit-field value 0 4)) (or (= (+ 1 offset) (bytevector-length bv)) (setq! bv (+ 1 offset) 0 1 (bit-field value 4 5))))) (set5! (lambda (bv offset value) (setq! bv offset 1 6 value))) (set6! (lambda (bv offset value) (setq! bv offset 6 8 (bit-field value 0 2)) (or (= (+ 1 offset) (bytevector-length bv)) (setq! bv (+ 1 offset) 0 3 (bit-field value 2 5))))) (set7! (lambda (bv offset value) (setq! bv offset 3 8 value))) (sets (vector set0! set1! set2! set3! set4! set5! set6! set7!))) (lambda (bv index value) "Set the INDEXth quintet of BV to VALUE, assuming quintets start from the least-significant bits." (let ((p (vector-ref sets (modulo index 8)))) (p bv (quotient (* index 5) 8) (logand value #x1f)))))) (define (base32-string-unfold f s) "Given procedure F which, when applied to a character, returns the corresponding quintet, return the bytevector corresponding to string S." (define len (string-length s)) (let ((bv (make-bytevector (quotient (* len 5) 8)))) (string-fold (lambda (chr index) (bytevector-quintet-set! bv index (f chr)) (+ 1 index)) 0 s) bv)) (define (base32-string-unfold-right f s) "Given procedure F which, when applied to a character, returns the corresponding quintet, return the bytevector corresponding to string S, starting from the right of S." (define len (string-length s)) (let ((bv (make-bytevector (quotient (* len 5) 8)))) (string-fold-right (lambda (chr index) (bytevector-quintet-set-right! bv index (f chr)) (+ 1 index)) 0 s) bv)) (define (make-base32-string->bytevector base32-string-unfold base32-chars) (let ((char->value (let loop ((i 0) (v vlist-null)) (if (= i (vector-length base32-chars)) v (loop (+ 1 i) (vhash-consv (vector-ref base32-chars i) i v)))))) (lambda (s) "Return the binary representation of base32 string S as a bytevector." (base32-string-unfold (lambda (chr) (or (and=> (vhash-assv chr char->value) cdr) (error "invalid base32 character" chr))) s)))) (define base32-string->bytevector (make-base32-string->bytevector base32-string-unfold %rfc4648-base32-chars)) (define nix-base32-string->bytevector (make-base32-string->bytevector base32-string-unfold-right %nix-base32-chars)) ;;; base32.scm ends here