NAME

Text::Conceal - conceal and recover interface for text processing

SYNOPSIS

    use Text::Conceal;
    my $conceal = Text::Conceal->new(
        length => \&sub,
        match  => qr/regex/,
        );
    $conceal->encode(@args);
    $_ = foo(@args);
    $conceal->decode($_);

VERSION

Version 1.03

DESCRIPTION

This is a general interface to transform text data into desirable form, and recover the result after the process.

For example, Text::Tabs does not take care of Asian wide characters to calculate string width. So next program does not work as we wish.

    use Text::Tabs;
    print expand <>;

In this case, make conceal object with length function which can correctly handle wide character width, and the pattern of string to be concealed.

    use Text::Conceal;
    use Text::VisualWidth::PP;
    my $conceal = Text::Conceal->new(
        length => \&Text::VisualWidth::PP::width,
        match  => qr/\P{ASCII}+/,
    );

Then next program encode data, call expand() function, and recover the result into original text.

    my @lines = <>;
    $conceal->encode(@lines);
    my @expanded = expand @lines;
    $conceal->decode(@expanded);
    print @expanded;

Be aware that encode and decode method alter the values of given arguments. Because they return results as a list too, this can be done more simply.

    print $conceal->decode(expand($conceal->encode(<>)));

Next program implements ANSI terminal sequence aware expand command.

    use Text::ANSI::Fold::Util qw(ansi_width);

    my $conceal = Text::Conceal->new(
        length => \&ansi_width,
        match  => qr/[^\t\n]+/,
    );
    while (<>) {
        print $conceal->decode(expand($conceal->encode($_)));
    }

Calling decode method with many arguments is not a good idea, since replacement cycle is performed against all entries. So collect them into single chunk if possible.

    print $conceal->decode(join '', @expanded);

METHODS

new

Create conceal object. Takes following parameters.

length => function

Function to calculate text width. Default is length.

match => regex

Specify text area to be replaced. Default is qr/.+/s.

max => number

When the maximum number of replacement is known, give it by max parameter to avoid unnecessary work.

test => regex or sub

Specify regex or subroutine to test if the argument is to be processed or not. Default is undef, and all arguments will be subject to replace.

except => string

Text concealing is done by replacing text with different string which can not be found in any arguments. This parameter gives additional string which also to be taken care of.

visible => number (default 0)

0

With default value 0, this module uses characters in the range:

    [0x01 => 0x07], [0x10 => 0x1f], [0x21 => 0x7e], [0x81 => 0xfe]

1

Use printable characters first, then use non-printable characters.

    [0x21 => 0x7e], [0x01 => 0x07], [0x10 => 0x1f], [0x81 => 0xfe]

2

Use only printable characters.

    [0x21 => 0x7e]

ordered => bool (default 1)

Ensures that the parameters given and the order in which they appear in the output do not change. The default is set to 1; if set to 0, it will be handled correctly even if they appear in a different order, a behavior that may lead to instability.

duplicate => bool (default 0)

It is assumed that the string before conversion appears only once after the process. Therefore, if the same string appears a second time, the conversion fails. By setting this parameter to 1, it is possible to allow a string to appear multiple times. However, doing so will increase the probability of failure if a large number of strings are attempted to be converted.

encode

decode

Encode/Decode arguments and return them. Given arguments will be altered.

LIMITATION

All arguments given to encode method have to appear in the same order in the pre-decode string. If you want to convert unordered output, set the ordered parameter to 0. However, if a large number of short items are included, you may get unexpected results.

Each argument can be shorter than the original, or it can even disappear.

If an argument is trimmed down to single byte in a result, and it have to be recovered to wide character, it is replaced by single space.

Replacement string is made of characters those are not found in any arguments. So if they contains all characters in the given range, encode stop to work. It requires at least two.

Minimum two characters are enough to produce correct result if all arguments will appear in the same order. However, if even single item is missing, it won't work correctly. Using three characters, one continuous missing is allowed. Less characters, more confusion.

SEE ALSO

Text::VisualPrintf, https://github.com/tecolicom/Text-VisualPrintf

This module is originally implemented as a part of Text::VisualPrintf module.

Text::ANSI::Printf, https://github.com/tecolicom/Text-ANSI-Printf

AUTHOR

Kazumasa Utashiro

LICENSE

Copyright 2020-2023 Kazumasa Utashiro.

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

cpanm Text::Conceal

perl -MCPAN -e shell
install Text::Conceal