304 lines
13 KiB
Scheme
304 lines
13 KiB
Scheme
;;; GNU Guix --- Functional package management for GNU
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;;; Copyright © 2012, 2015 Ludovic Courtès <ludo@gnu.org>
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;;;
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;;; This file is part of GNU Guix.
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;;;
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;;; GNU Guix is free software; you can redistribute it and/or modify it
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;;; 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 (at
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;;; your option) any later version.
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;;;
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;;; GNU Guix is distributed in the hope that it will be useful, but
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;;; 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 GNU Guix. If not, see <http://www.gnu.org/licenses/>.
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(define-module (guix base32)
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#:use-module (srfi srfi-1)
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#:use-module (srfi srfi-34)
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#:use-module (srfi srfi-35)
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#:use-module (srfi srfi-60)
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#:use-module (rnrs bytevectors)
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#:use-module (ice-9 vlist)
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#:export (bytevector-quintet-length
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bytevector->base32-string
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bytevector->nix-base32-string
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base32-string->bytevector
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nix-base32-string->bytevector
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&invalid-base32-character
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invalid-base32-character?
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invalid-base32-character-value
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invalid-base32-character-string))
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;;; Commentary:
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;;;
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;;; A generic, customizable to convert bytevectors to/from a base32
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;;; representation.
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;;;
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;;; Code:
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(define bytevector-quintet-ref
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(let* ((ref bytevector-u8-ref)
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(ref+ (lambda (bv offset)
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(let ((o (+ 1 offset)))
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(if (>= o (bytevector-length bv))
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0
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(bytevector-u8-ref bv o)))))
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(ref0 (lambda (bv offset)
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(bit-field (ref bv offset) 3 8)))
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(ref1 (lambda (bv offset)
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(logior (ash (bit-field (ref bv offset) 0 3) 2)
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(bit-field (ref+ bv offset) 6 8))))
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(ref2 (lambda (bv offset)
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(bit-field (ref bv offset) 1 6)))
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(ref3 (lambda (bv offset)
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(logior (ash (bit-field (ref bv offset) 0 1) 4)
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(bit-field (ref+ bv offset) 4 8))))
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(ref4 (lambda (bv offset)
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(logior (ash (bit-field (ref bv offset) 0 4) 1)
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(bit-field (ref+ bv offset) 7 8))))
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(ref5 (lambda (bv offset)
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(bit-field (ref bv offset) 2 7)))
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(ref6 (lambda (bv offset)
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(logior (ash (bit-field (ref bv offset) 0 2) 3)
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(bit-field (ref+ bv offset) 5 8))))
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(ref7 (lambda (bv offset)
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(bit-field (ref bv offset) 0 5)))
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(refs (vector ref0 ref1 ref2 ref3 ref4 ref5 ref6 ref7)))
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(lambda (bv index)
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"Return the INDEXth quintet of BV."
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(let ((p (vector-ref refs (modulo index 8))))
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(p bv (quotient (* index 5) 8))))))
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(define bytevector-quintet-ref-right
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(let* ((ref bytevector-u8-ref)
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(ref+ (lambda (bv offset)
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(let ((o (+ 1 offset)))
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(if (>= o (bytevector-length bv))
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0
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(bytevector-u8-ref bv o)))))
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(ref0 (lambda (bv offset)
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(bit-field (ref bv offset) 0 5)))
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(ref1 (lambda (bv offset)
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(logior (bit-field (ref bv offset) 5 8)
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(ash (bit-field (ref+ bv offset) 0 2) 3))))
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(ref2 (lambda (bv offset)
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(bit-field (ref bv offset) 2 7)))
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(ref3 (lambda (bv offset)
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(logior (bit-field (ref bv offset) 7 8)
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(ash (bit-field (ref+ bv offset) 0 4) 1))))
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(ref4 (lambda (bv offset)
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(logior (bit-field (ref bv offset) 4 8)
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(ash (bit-field (ref+ bv offset) 0 1) 4))))
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(ref5 (lambda (bv offset)
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(bit-field (ref bv offset) 1 6)))
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(ref6 (lambda (bv offset)
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(logior (bit-field (ref bv offset) 6 8)
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(ash (bit-field (ref+ bv offset) 0 3) 2))))
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(ref7 (lambda (bv offset)
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(bit-field (ref bv offset) 3 8)))
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(refs (vector ref0 ref1 ref2 ref3 ref4 ref5 ref6 ref7)))
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(lambda (bv index)
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"Return the INDEXth quintet of BV, assuming quintets start from the
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least-significant bits, contrary to what RFC 4648 describes."
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(let ((p (vector-ref refs (modulo index 8))))
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(p bv (quotient (* index 5) 8))))))
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(define (bytevector-quintet-length bv)
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"Return the number of quintets (including truncated ones) available in BV."
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(ceiling (/ (* (bytevector-length bv) 8) 5)))
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(define (bytevector-quintet-fold proc init bv)
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"Return the result of applying PROC to each quintet of BV and the result of
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the previous application or INIT."
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(define len
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(bytevector-quintet-length bv))
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(let loop ((i 0)
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(r init))
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(if (= i len)
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r
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(loop (1+ i) (proc (bytevector-quintet-ref bv i) r)))))
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(define (bytevector-quintet-fold-right proc init bv)
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"Return the result of applying PROC to each quintet of BV and the result of
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the previous application or INIT."
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(define len
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(bytevector-quintet-length bv))
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(let loop ((i len)
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(r init))
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(if (zero? i)
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r
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(let ((j (- i 1)))
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(loop j (proc (bytevector-quintet-ref-right bv j) r))))))
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(define (make-bytevector->base32-string quintet-fold base32-chars)
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(lambda (bv)
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"Return a base32 encoding of BV using BASE32-CHARS as the alphabet."
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(let ((chars (quintet-fold (lambda (q r)
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(cons (vector-ref base32-chars q)
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r))
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'()
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bv)))
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(list->string (reverse chars)))))
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(define %nix-base32-chars
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;; See `libutil/hash.cc'.
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#(#\0 #\1 #\2 #\3 #\4 #\5 #\6 #\7 #\8 #\9
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#\a #\b #\c #\d #\f #\g #\h #\i #\j #\k #\l #\m #\n
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#\p #\q #\r #\s #\v #\w #\x #\y #\z))
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(define %rfc4648-base32-chars
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#(#\a #\b #\c #\d #\e #\f #\g #\h #\i #\j #\k #\l #\m
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#\n #\o #\p #\q #\r #\s #\t #\u #\v #\w #\x #\y #\z
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#\2 #\3 #\4 #\5 #\6 #\7))
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(define bytevector->base32-string
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(make-bytevector->base32-string bytevector-quintet-fold
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%rfc4648-base32-chars))
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(define bytevector->nix-base32-string
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(make-bytevector->base32-string bytevector-quintet-fold-right
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%nix-base32-chars))
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(define bytevector-quintet-set!
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(let* ((setq! (lambda (bv offset start stop value)
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(let ((v (bytevector-u8-ref bv offset))
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(w (arithmetic-shift value start))
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(m (bitwise-xor (1- (expt 2 stop))
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(1- (expt 2 start)))))
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(bytevector-u8-set! bv offset
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(bitwise-merge m w v)))))
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(set0! (lambda (bv offset value)
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(setq! bv offset 3 8 value)))
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(set1! (lambda (bv offset value)
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(setq! bv offset 0 3 (bit-field value 2 5))
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(or (= (+ 1 offset) (bytevector-length bv))
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(setq! bv (+ 1 offset) 6 8 (bit-field value 0 2)))))
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(set2! (lambda (bv offset value)
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(setq! bv offset 1 6 value)))
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(set3! (lambda (bv offset value)
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(setq! bv offset 0 1 (bit-field value 4 5))
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(or (= (+ 1 offset) (bytevector-length bv))
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(setq! bv (+ 1 offset) 4 8 (bit-field value 0 4)))))
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(set4! (lambda (bv offset value)
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(setq! bv offset 0 4 (bit-field value 1 5))
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(or (= (+ 1 offset) (bytevector-length bv))
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(setq! bv (+ 1 offset) 7 8 (bit-field value 0 1)))))
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(set5! (lambda (bv offset value)
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(setq! bv offset 2 7 value)))
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(set6! (lambda (bv offset value)
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(setq! bv offset 0 2 (bit-field value 3 5))
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(or (= (+ 1 offset) (bytevector-length bv))
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(setq! bv (+ 1 offset) 5 8 (bit-field value 0 3)))))
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(set7! (lambda (bv offset value)
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(setq! bv offset 0 5 value)))
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(sets (vector set0! set1! set2! set3! set4! set5! set6! set7!)))
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(lambda (bv index value)
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"Set the INDEXth quintet of BV to VALUE."
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(let ((p (vector-ref sets (modulo index 8))))
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(p bv (quotient (* index 5) 8) (logand value #x1f))))))
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(define bytevector-quintet-set-right!
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(let* ((setq! (lambda (bv offset start stop value)
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(let ((v (bytevector-u8-ref bv offset))
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(w (arithmetic-shift value start))
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(m (bitwise-xor (1- (expt 2 stop))
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(1- (expt 2 start)))))
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(bytevector-u8-set! bv offset
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(bitwise-merge m w v)))))
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(set0! (lambda (bv offset value)
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(setq! bv offset 0 5 value)))
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(set1! (lambda (bv offset value)
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(setq! bv offset 5 8 (bit-field value 0 3))
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(or (= (+ 1 offset) (bytevector-length bv))
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(setq! bv (+ 1 offset) 0 2 (bit-field value 3 5)))))
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(set2! (lambda (bv offset value)
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(setq! bv offset 2 7 value)))
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(set3! (lambda (bv offset value)
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(setq! bv offset 7 8 (bit-field value 0 1))
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(or (= (+ 1 offset) (bytevector-length bv))
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(setq! bv (+ 1 offset) 0 4 (bit-field value 1 5)))))
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(set4! (lambda (bv offset value)
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(setq! bv offset 4 8 (bit-field value 0 4))
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(or (= (+ 1 offset) (bytevector-length bv))
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(setq! bv (+ 1 offset) 0 1 (bit-field value 4 5)))))
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(set5! (lambda (bv offset value)
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(setq! bv offset 1 6 value)))
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(set6! (lambda (bv offset value)
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(setq! bv offset 6 8 (bit-field value 0 2))
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(or (= (+ 1 offset) (bytevector-length bv))
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(setq! bv (+ 1 offset) 0 3 (bit-field value 2 5)))))
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(set7! (lambda (bv offset value)
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(setq! bv offset 3 8 value)))
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(sets (vector set0! set1! set2! set3! set4! set5! set6! set7!)))
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(lambda (bv index value)
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"Set the INDEXth quintet of BV to VALUE, assuming quintets start from
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the least-significant bits."
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(let ((p (vector-ref sets (modulo index 8))))
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(p bv (quotient (* index 5) 8) (logand value #x1f))))))
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(define (base32-string-unfold f s)
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"Given procedure F which, when applied to a character, returns the
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corresponding quintet, return the bytevector corresponding to string S."
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(define len (string-length s))
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(let ((bv (make-bytevector (quotient (* len 5) 8))))
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(string-fold (lambda (chr index)
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(bytevector-quintet-set! bv index (f chr))
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(+ 1 index))
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0
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s)
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bv))
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(define (base32-string-unfold-right f s)
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"Given procedure F which, when applied to a character, returns the
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corresponding quintet, return the bytevector corresponding to string S,
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starting from the right of S."
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(define len (string-length s))
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(let ((bv (make-bytevector (quotient (* len 5) 8))))
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(string-fold-right (lambda (chr index)
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(bytevector-quintet-set-right! bv index (f chr))
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(+ 1 index))
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0
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s)
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bv))
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;; Invalid base32 character error condition when decoding base32.
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(define-condition-type &invalid-base32-character &error
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invalid-base32-character?
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(character invalid-base32-character-value)
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(string invalid-base32-character-string))
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(define (make-base32-string->bytevector base32-string-unfold base32-chars)
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(let ((char->value (let loop ((i 0)
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(v vlist-null))
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(if (= i (vector-length base32-chars))
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v
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(loop (+ 1 i)
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(vhash-consv (vector-ref base32-chars i)
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i v))))))
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(lambda (s)
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"Return the binary representation of base32 string S as a bytevector."
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(base32-string-unfold (lambda (chr)
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(or (and=> (vhash-assv chr char->value) cdr)
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(raise (condition
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(&invalid-base32-character
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(character chr)
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(string s))))))
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s))))
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(define base32-string->bytevector
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(make-base32-string->bytevector base32-string-unfold %rfc4648-base32-chars))
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(define nix-base32-string->bytevector
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(make-base32-string->bytevector base32-string-unfold-right %nix-base32-chars))
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;;; base32.scm ends here
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