Common Lisp Package: S-BASE64

An implementation of standard Base64 encoding and decoding

README:

S-BASE64

A Common Lisp implementation of Base64 Encoding/Decoding

S-BASE64 is an open source Common Lisp implementation of Base64 encoding and decoding. Base64 encoding is a technique to encode binary data in a portable, safe printable, 7-bit ASCII format. For a general introduction, please consult the Wikipedia article on Base64.

This simple package is used as a building block in a number of other open source projects e.g. the KPAX web development framework.

Contents

Features

S-BASE64 can:

  • convert a Base64 encoded character input stream into a decoded binary output stream
  • convert a binary output stream into a Base64 encoded character output stream
  • convert a Base64 encoded character input stream into a byte array
  • convert a byte array into a Base64 encoded character output stream
  • optionally break lines at 76 characters

Status

S-BASE64 is considered stable code.

News

October 2005 - Created as a separate project.

Platforms

S-BASE64 is written in ANSI standard Common Lisp and should be portable across any CL implementation.

Installation

The S-BASE64 package is loaded using ASDF. There is an excellent tutorial on ASDF to get you started.

$ cd apps/asdf/systems/  
$ ln -s ~/darcs/s-base64/s-base64.asd .  
$ cd ~  
$ /Applications/LispWorks/lispworks-tty  
LispWorks(R): The Common Lisp Programming Environment  
Copyright (C) 1987-2005 LispWorks Ltd.  All rights reserved.  
Version 4.4.5  
Saved by sven as lispworks-tty, at 26 Oct 2005 11:53  
User sven on voyager.local  
; Loading text file /Applications/LispWorks/Library/lib/4-4-0-0/config/siteinit.lisp  
;  Loading text file /Applications/LispWorks/Library/lib/4-4-0-0/private-patches/load.lisp  
; Loading text file /Users/sven/.lispworks  
;  Loading text file /Users/sven/apps/asdf/init-asdf.lisp  
;   Loading fasl file /Users/sven/apps/asdf/asdf.nfasl  
;Pushed #P"/Users/sven/apps/asdf/systems/" onto ASDF central registry  
 
CL-USER 1 > (asdf:oos 'asdf:load-op :s-base64)  
; Loading /Applications/LispWorks/Library/lib/4-4-0-0/load-on-demand/ccl/xp-fancyformat.nfasl on demand...  
; loading system definition from  
; /Users/sven/apps/asdf/systems/s-base64.asd into  
; #<The ASDF787 package, 0/16 internal, 0/16 external>  
; Loading text file /Users/sven/darcs/s-base64/s-base64.asd  
; registering # as S-BASE64  
;;; Compiling file /Users/sven/darcs/s-base64/src/package.lisp ...  
...  
; Loading fasl file /Users/sven/darcs/s-base64/src/package.nfasl  
;;; Compiling file /Users/sven/darcs/s-base64/src/base64.lisp ...  
...  
; Loading fasl file /Users/sven/darcs/s-base64/src/base64.nfasl 

Example of setting up and using ASDF to compile and load the package

Usage

To encode you start with either a binary input stream or a byte array and write to a character output stream. To decode you start from a character input stream and write to a binary output stream or return a byte array. You can use the standard CL marcros WITH-OUTPUT-TO-STRING of WITH-INPUT-FROM-STRING to convert to and from a string. The following listener transcript show how to compute the second example from RFC 3548, section 7:

CL-USER 1 > (in-package :s-base64)  
#<The S-BASE64 package, 50/128 internal, 4/16 external>  
 
S-BASE64 2 > (setf bytes #(#x14 #xfb #x9c #x03 #xd9))  
#(20 251 156 3 217)  
 
S-BASE64 3 > (with-output-to-string (out)  
               (encode-base64-bytes bytes out))  
"FPucA9k="  
 
S-BASE64 4 > (with-input-from-string (in *)  
               (decode-base64-bytes in))  
#(20 251 156 3 217) 

Example Base64 Encoding and Decoding

API Reference

There is automatically generated API Referencedocumentation available for the S-BASE64 package in doc/API.html.

Mailinglist

The KPAX mailing list is used for this project.

Changelog

Release Notes:

  • release 1: moved S-BASE64 into a seperate project under a new structure

TODO

There is a variant of Base64 encoding used for URL's and filenames that could be implemented.

FAQ

Nothing appropriate.

Bugs

Illegal input results in generic low-level CL conditions rather than a more meaningful high-level application specific condition.

Authors

S-BASE64 was written by Sven Van Caekenberghe.

Maintainers

S-BASE64 is being maintained by Sven Van Caekenberghe.

License

You are granted the rights to distribute and use this software as governed by the terms of the Lisp Lesser General Public License (http://opensource.franz.com/preamble.html), also known as the LLGPL.

History

S-BASE64 was originally part of KPAX and became a separate project in October 2005.

References

The following RFC's can be considered as definitions of Base64 Encoding:

Copyright © 2002-2006 Sven Van Caekenberghe, Beta Nine BVBA. All Right Reserved.

FUNCTION

Public

DECODE-BASE64 (IN OUT)

Decode a base64 encoded character input stream into a binary output stream

DECODE-BASE64-BYTES (STREAM)

Decode a base64 encoded character stream, returns a byte array

ENCODE-BASE64 (IN OUT &OPTIONAL (BREAK-LINES T))

Encode a binary input stream into a base64 encoded character output stream

ENCODE-BASE64-BYTES (ARRAY STREAM &OPTIONAL (BREAK-LINES T))

Encode a byte array into a base64b encoded character stream

Private

Undocumented

CORE-DECODE-BASE64 (CHAR1 CHAR2 CHAR3 CHAR4)

CORE-ENCODE-BASE64 (BYTE1 BYTE2 BYTE3)

SKIP-BASE64-WHITESPACE (STREAM)

VARIABLE

Private

Undocumented

+BASE64-ALPHABET+

+INVERSE-BASE64-ALPHABET+