Memfrob
November 10, 2020
We give a function that performs encryption, and leave it to the reader to wrap that in a function that handles files:
(define (memfrob str)
(define (frob c)
(integer->char (bitwise-xor (char->integer c) 42)))
(list->string (map frob (string->list str))))
> (memfrob (memfrob "Programming Praxis"))
"Programming Praxis"
You can run the program at http://ideone.com/RnJDWB.
A quick solution using standard Scheme:
(import (scheme base) (scheme write) (only (srfi 60) bitwise-xor) (only (org eip10 okmij myenv) assert)) (define (memfrob-byte byt) (bitwise-xor byt 42)) (assert (equal? '(42 0 43 41) (map memfrob-byte '(0 42 1 3)))) (define (memfrob-bytevector bytvec) (let* ((n (bytevector-length bytvec)) (r (make-bytevector n))) (do ((i 0 (+ i 1))) ((>= i n) r) (bytevector-u8-set! r i (memfrob-byte (bytevector-u8-ref bytvec i)))))) (assert (equal? #u8(42 0 43 41) (memfrob-bytevector #u8(0 42 1 3)))) (define (memfrob-string str) (utf8->string (memfrob-bytevector (string->utf8 str)))) (assert (string=? "Hello, World!" (memfrob-string (memfrob-string "Hello, World!"))))In Python:
def memfrob(msg): return bytes(c ^ 42 for c in msg)Input argument must be a bytes-like object.