Title here
Summary here
Base64 Encoding in Scheme
Our program demonstrates base64 encoding and decoding in Scheme. Here’s the full source code:
(import (scheme base)
(scheme write)
(srfi 60)) ; for base64 encoding/decoding
(define (main)
; Here's the string we'll encode/decode.
(define data "abc123!?$*&()'-=@~")
; Scheme doesn't have built-in base64 support, so we use SRFI 60.
; This encodes using the standard base64 encoder.
(define sEnc (base64-encode-string data))
(display sEnc)
(newline)
; Decoding the base64 string
(define sDec (base64-decode-string sEnc))
(display sDec)
(newline)
(newline)
; Scheme doesn't have a built-in URL-safe base64 encoder,
; so we'll use a custom function to replace characters
(define (url-safe-base64 str)
(string-map (lambda (c)
(case c
((#\+) #\-)
((#\/) #\_)
(else c)))
str))
; This encodes using a URL-compatible base64 format
(define uEnc (url-safe-base64 (base64-encode-string data)))
(display uEnc)
(newline)
; Decoding the URL-safe base64 string
(define (url-safe-base64-decode str)
(base64-decode-string
(string-map (lambda (c)
(case c
((#\-) #\+)
((#\_) #\/)
(else c)))
str)))
(define uDec (url-safe-base64-decode uEnc))
(display uDec)
(newline))
(main)To run the program, save it as base64-encoding.scm and use your Scheme interpreter. For example, if you’re using Chez Scheme:
$ scheme --script base64-encoding.scm
YWJjMTIzIT8kKiYoKSctPUB+
abc123!?$*&()'-=@~
YWJjMTIzIT8kKiYoKSctPUB-
abc123!?$*&()'-=@~Note that Scheme doesn’t have built-in base64 encoding/decoding, so we use SRFI 60 for standard base64. For URL-safe base64, we implement custom functions to replace the characters that differ between standard and URL-safe base64 encodings.
The string encodes to slightly different values with the standard and URL-safe base64 encoders (trailing + vs -), but they both decode to the original string as desired.