ascii85 - Text encoding & decoding binary data

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# ascii85(n) 1.0 tcllib "Text encoding & decoding binary data"

## Name

ascii85 - ascii85-encode/decode binary data

## Synopsis

- package require Tcl 8.4
- package require ascii85 ?1.0?

- ::ascii85::encode ?-maxlen maxlen? ?-wrapchar wrapchar? string
- ::ascii85::decode string

## Description

This package provides procedures to encode binary data into ascii85 and back.

::ascii85::encode ?-maxlen maxlen? ?-wrapchar wrapchar? string

  Ascii85 encodes the given binary string and returns the encoded result. Inserts the character wrapchar every maxlen characters of output. wrapchar defaults to newline. maxlen defaults to 76.

  Note well: If your string is not simple ascii you should fix the string encoding before doing ascii85 encoding. See the examples.

  The command will throw an error for negative values of maxlen, or if maxlen is not an integer number.

::ascii85::decode string

  Ascii85 decodes the given string and returns the binary data. The decoder ignores whitespace in the string, as well as tabs and newlines.

## EXAMPLES

    % ascii85::encode "Hello, world"
    87cURD_*#TDfTZ)

    % ascii85::encode [string repeat xyz 24]
    G^4U[H$X^\H?a^]G^4U[H$X^\H?a^]G^4U[H$X^\H?a^]G^4U[H$X^\H?a^]G^4U[H$X^\H?a^]G
    ^4U[H$X^\H?a^]
    % ascii85::encode -wrapchar "" [string repeat xyz 24]
    G^4U[H$X^\H?a^]G^4U[H$X^\H?a^]G^4U[H$X^\H?a^]G^4U[H$X^\H?a^]G^4U[H$X^\H?a^]G^4U[H$X^\H?a^]

    # NOTE: ascii85 encodes BINARY strings.
    % set chemical [encoding convertto utf-8 "C\u2088H\u2081\u2080N\u2084O\u2082"]
    % set encoded [ascii85::encode $chemical]
    6fN]R8E,5Pidu\UiduhZidua
    % set caffeine [encoding convertfrom utf-8 [ascii85::decode $encoded]]

## References

1. http://en.wikipedia.org/wiki/Ascii85

2. Postscript Language Reference Manual, 3rd Edition, page 131. http://www.adobe.com/devnet/postscript/pdfs/PLRM.pdf

## Bugs, Ideas, Feedback

This document, and the package it describes, will undoubtedly contain bugs and other problems. Please report such in the category base64 of the Tcllib Trackers. Please also report any ideas for enhancements you may have for either package and/or documentation.

When proposing code changes, please provide unified diffs, i.e the output of diff -u.

Note further that attachments are strongly preferred over inlined patches. Attachments can be made by going to the Edit form of the ticket immediately after its creation, and then using the left-most button in the secondary navigation bar.

## Keywords

ascii85, encoding

## Category

Text processing

## Copyright

Copyright © 2010, Emiliano Gavilán