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#lang typed/racket
;;; Copyright 2011, Matthias Andreas Benkard.
;;;
;;;-----------------------------------------------------------------------------
;;; This program is free software: you can redistribute it and/or modify
;;; it under the terms of the GNU Affero 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 Affero General Public License for more details.
;;;
;;; You should have received a copy of the GNU Affero General Public License
;;; along with this program. If not, see <http://www.gnu.org/licenses/>.
;;;-----------------------------------------------------------------------------
;;;
(provide integer->bytes
integer->bytes/size
bytes->integer
bytes->integer/le
pad-bytes
Justification
Endianness
bytes-xor)
(define-type Justification (U 'left 'right))
(define-type Endianness (U 'little-endian 'big-endian))
(define: (integer->bytes [x : Exact-Nonnegative-Integer]
[endianness : Endianness])
: Bytes
(let: loop : Bytes
([acc : (Listof Byte) (list)]
[x : Exact-Nonnegative-Integer x])
(if (zero? x)
(list->bytes (if (eq? endianness 'big-endian)
acc
(reverse acc)))
(loop (cons (bitwise-and #xff x) acc)
(arithmetic-shift x -8)))))
(define: (integer->bytes/size [x : Exact-Nonnegative-Integer]
[endianness : Endianness]
[size : Exact-Nonnegative-Integer])
: Bytes
(pad-bytes (integer->bytes x endianness)
size
#x0
(if (eq? endianness 'big-endian)
'right
'left)))
(define: (bytes->integer [b : Bytes]) : Exact-Nonnegative-Integer
(for/fold: ([n : Exact-Nonnegative-Integer 0])
([byte : Byte (in-bytes b)])
(bitwise-ior (arithmetic-shift n 8)
byte)))
(define: (bytes->integer/le [b : Bytes]) : Exact-Nonnegative-Integer
(for/fold: ([n : Exact-Nonnegative-Integer 0])
([byte : Byte (in-bytes b)]
[i : Integer (in-naturals)])
(bitwise-ior (arithmetic-shift byte (* i 8))
n)))
(define: (pad-bytes [b : Bytes]
[s : Exact-Nonnegative-Integer]
[fill : Byte]
[justify : Justification])
: Bytes
(if (>= (bytes-length b) s)
b
(let* ([delta (- s (bytes-length b))]
[padding (make-bytes delta fill)])
(if (eq? justify 'left)
(bytes-append b padding)
(bytes-append padding b)))))
(define: (bytes-xor [a : Bytes] [b : Bytes]) : Bytes
(list->bytes
(reverse
(for/fold: ([acc : (Listof Byte) (list)])
([x : Byte (in-bytes a)]
[y : Byte (in-bytes b)])
(cons (bitwise-xor x y) acc)))))
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