NAME

Mail::DKIM::TextWrap - text wrapping module written for use with DKIM

SYNOPSIS

  my $output = "";
  my $tw = Mail::DKIM::TextWrap->new(
                  Margin => 10,
                  Output => \$output,
              );
  $tw->add("Mary had a little lamb, whose fleece was white as snow.\n");
  $tw->finish;

  print $output;

DESCRIPTION

This is a general-purpose text-wrapping module that I wrote because I had some specific needs with Mail::DKIM that none of the contemporary text-wrapping modules offered.

Specifically, it offers the ability to change wrapping options in the middle of a paragraph. For instance, with a DKIM signature:

  DKIM-Signature: a=rsa; c=simple; h=first:second:third:fourth;
          b=Xr2mo2wmb1LZBwmEJElIPezal7wQQkRQ8WZtxpofkNmXTjXf8y2f0

the line-breaks can be inserted next to any of the colons of the h= tag, or any character of the b= tag. The way I implemented this was to serialize the signature one element at a time, changing the text-wrapping options at the start and end of each tag.

TEXT WRAPPING OPTIONS

Text wrapping options can be specified when calling new(), or by simply changing the property as needed. For example, to change the number of characters allowed per line:

  $tw->{Margin} = 20;

Break

a regular expression matching characters where a line break can be inserted. Line breaks are inserted AFTER a matching substring. The default is /\s/.

BreakBefore

a regular expression matching characters where a line break can be inserted. Line breaks are inserted BEFORE a matching substring. Usually, you want to use Break, rather than BreakBefore. The default is undef.

Margin

specifies how many characters to allow per line. The default is 72.

Separator

the text to insert when a linebreak is needed. The default is "\n". If you want to set a following-line indent (e.g. all lines but the first begin with four spaces), use something like "\n ".

Swallow

a regular expression matching characters that can be omitted when a line break occurs. For example, if you insert a line break between two words, then you are replacing a "space" with the line break, so you are omitting the space. On the other hand, if you insert a line break between two parts of a hyphenated word, then you are breaking at the hyphen, but you still want to display the hyphen. The default is /\s/.

CONSTRUCTOR

new() - create a new text-wrapping object

  my $tw = Mail::DKIM::TextWrap->new(
                      Output => \$output,
                      %wrapping_options,
                  );

The text-wrapping object encapsulates the current options and the current state of the text stream. In addition to specifying text wrapping options as described in the section above, the following options are recognized:

Output

a scalar reference, or a glob reference, to specify where the "wrapped" text gets output to. If not specified, the default of STDOUT is used.

METHODS

add() - process some text that can be wrapped

  $tw->add("Mary had a little lamb.\n");

You can add() all the text at once, or add() the text in parts by calling add() multiple times. If you are doing the latter, be aware that the text can be "wrapped" between add() calls, even if it does not match the "Break" pattern.

For example, given a margin of 12, this will not wrap

  $tw->add("Abcdefghijklmnopqrstuvwxyz");

but this will

  $tw->add("Abcdefgh");
  $tw->add("ijklmnop");
  $tw->add("qrstuvwxyz");

finish() - call when no more text is to be added

  $tw->finish;

Call this when finished adding text, so that any remaining text in TextWrap's buffers will be output.