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1 | ;;; GNU Guix --- Functional package management for GNU |
2 | ;;; Copyright © 2012, 2014, 2017 Ludovic Courtès <ludo@gnu.org> | |
3 | ;;; | |
4 | ;;; This file is part of GNU Guix. | |
5 | ;;; | |
6 | ;;; GNU Guix is free software; you can redistribute it and/or modify it | |
7 | ;;; under the terms of the GNU General Public License as published by | |
8 | ;;; the Free Software Foundation; either version 3 of the License, or (at | |
9 | ;;; your option) any later version. | |
10 | ;;; | |
11 | ;;; GNU Guix is distributed in the hope that it will be useful, but | |
12 | ;;; WITHOUT ANY WARRANTY; without even the implied warranty of | |
13 | ;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
14 | ;;; GNU General Public License for more details. | |
15 | ;;; | |
16 | ;;; You should have received a copy of the GNU General Public License | |
17 | ;;; along with GNU Guix. If not, see <http://www.gnu.org/licenses/>. | |
18 | ||
19 | (define-module (guix base16) | |
20 | #:use-module (srfi srfi-1) | |
21 | #:use-module (srfi srfi-26) | |
22 | #:use-module (srfi srfi-60) | |
23 | #:use-module (rnrs bytevectors) | |
24 | #:use-module (ice-9 vlist) | |
25 | #:use-module (ice-9 format) | |
26 | #:export (bytevector->base16-string | |
27 | base16-string->bytevector)) | |
28 | \f | |
29 | ;;; | |
30 | ;;; Base 16. | |
31 | ;;; | |
32 | ||
33 | (define (bytevector->base16-string bv) | |
34 | "Return the hexadecimal representation of BV's contents." | |
35 | (define len | |
36 | (bytevector-length bv)) | |
37 | ||
38 | (let-syntax ((base16-chars (lambda (s) | |
39 | (syntax-case s () | |
40 | (_ | |
41 | (let ((v (list->vector | |
42 | (unfold (cut > <> 255) | |
43 | (lambda (n) | |
44 | (format #f "~2,'0x" n)) | |
45 | 1+ | |
46 | 0)))) | |
47 | v)))))) | |
48 | (define chars base16-chars) | |
49 | (let loop ((i len) | |
50 | (r '())) | |
51 | (if (zero? i) | |
52 | (string-concatenate r) | |
53 | (let ((i (- i 1))) | |
54 | (loop i | |
55 | (cons (vector-ref chars (bytevector-u8-ref bv i)) r))))))) | |
56 | ||
57 | (define base16-string->bytevector | |
58 | (let ((chars->value (fold (lambda (i r) | |
59 | (vhash-consv (string-ref (number->string i 16) | |
60 | 0) | |
61 | i r)) | |
62 | vlist-null | |
63 | (iota 16)))) | |
64 | (lambda (s) | |
65 | "Return the bytevector whose hexadecimal representation is string S." | |
66 | (define bv | |
67 | (make-bytevector (quotient (string-length s) 2) 0)) | |
68 | ||
69 | (string-fold (lambda (chr i) | |
70 | (let ((j (quotient i 2)) | |
71 | (v (and=> (vhash-assv chr chars->value) cdr))) | |
72 | (if v | |
73 | (if (zero? (logand i 1)) | |
74 | (bytevector-u8-set! bv j | |
75 | (arithmetic-shift v 4)) | |
76 | (let ((w (bytevector-u8-ref bv j))) | |
77 | (bytevector-u8-set! bv j (logior v w)))) | |
78 | (error "invalid hexadecimal character" chr))) | |
79 | (+ i 1)) | |
80 | 0 | |
81 | s) | |
82 | bv))) | |
83 |