base32::core - Base32 encoding

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# base32::core(n) 0.1 tcllib "Base32 encoding"

## Name

base32::core - Expanding basic base32 maps

## Synopsis

- package require Tcl 8.4
- package require base32::core ?0.1?

- ::base32::core::define map forwvar backwvar ivar
- ::base32::core::valid string pattern mvar

## Description

This package provides generic commands for the construction of full base32 mappings from a basic mapping listing just the codes and associated characters. The full mappings, regular and inverse, created here map to and from bit sequences, and also handle the partial mappings at the end of a string.

This is in essence an internal package to be used by implementors of a base32 en- and decoder. A regular user has no need of this package at all.

## API

::base32::core::define map forwvar backwvar ivar

  This command computes full forward and backward (inverse) mappings from the basic map and stores them in the variables named by forwvar and backwvar resp. It also constructs a regexp pattern for the detection of invalid characters in supposedly base32 encoded input and stores it in the variable named by ivar.

::base32::core::valid string pattern mvar

  This command checks if the input string is a valid base32 encoded string, based on the pattern of invalid characters as generated by ::base32::core::define, and some other general rules.

  The result of the command is a boolean flag. Its value is True for a valid string, and False otherwise. In the latter case an error message describing the problem with the input is stored into the variable named by mvar. The variable is not touched if the input was found to be valid.

  The rules checked by the command, beyond rejection of bad characters, are:

  1. The length of the input is not a multiple of eight,

  2. The padding appears not at the end of input, but in the middle,

  3. The padding has not of length six, four, three, or one characters,

## Bugs, Ideas, Feedback

This document, and the package it describes, will undoubtedly contain bugs and other problems. Please report such in the category base32 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

base32

## Category

Text processing

## Copyright

Public domain