Rob Mueller
and 1 contributors

NAME

HTML::GenerateUtil - Routines useful when generating HTML output

SYNOPSIS

  use HTML::GenerateUtil qw(escape_html generate_attributes generate_tag escape_uri :consts $H div);

    my $Html = "text < with > things & that need \x{1234} escaping";
    $Html = escape_html($Html);

  Or

    escape_html($Html, EH_INPLACE);

  Also

    my $Attr = generate_attributes({ href => 'http://...', title => 'blah' });
    $Html = "<a $Attr>$Html</a>";

  But even better

    $Html = generate_tag('a', { href => 'http://...', title => 'blah' }, $Html, 0);

  Also you might want something like

    my $URI = 'http://host/?' . join ";", map { $_ => escape_uri($Params{$_}) } keys %Params;
    $Html = generate_tag('a', { href => $URI }, $Html, 0);

  You can shortcut that by importing a function, or using the autoloading $H object

    div({ class => [ qw(a b) ] }, "div content");
    $H->a({ href => $URI  }, "text", GT_ADDNEWLINE);

  Or the newer (>= 1.20) $E object with more smarts

    $E->tr(
      [
        \$E->th("row 1 heading with <>& nasties"),
        \$E->td( { class => "someclassforeachrow" },
          "column 1",
          \"column <b>2</b> with trusted html",
        )
      ], [
        \$E->th(\"row 2 heading with <b>trusted</b> html"),
        \$E->td(
          "column 1",
          \"column <b>2</b> with trusted html",
        )
      ]
    )

DESCRIPTION

Provides a number of functions that make generating HTML output easier and faster. All written in XS for speed.

CONTEXT

When creating a web application in perl, you've got a couple of main choices on how to actually generate the HTML that gets output:

  • Programatically generating the HTML in perl

  • Using some template system for the HTML and inserting the data calculated in perl as appropriate

Your actual application, experience and environment will generally determine which is the best way to.

If you go the programatic route, then you generally need some way of generating the actual HTML output in perl. Again, there's generally a couple of ways of doing this.

  • Just joining together text strings in perl as appropriate.

      Eg. $link = "<a href="$ref">$text</a>";
  • Or using some function module like CGI

      Eg. $line = a({ href => $ref }, $text);
  • More complex object systems like HTML::Table

The first seems easy, but it gets harder when you have to manually escape each string to avoid placing special HTML chars (eg <, etc) in strings like $text above.

With the CGI, most of this is automatically taken care of, and most strings are automatically escaped to replace special HTML chars with their entity equivalents.

While this is nice, CGI is written in pure perl, and can end up being a bit slow, especially if you already have a fast system that generates pages very heavy in tags (eg lots of table elements, links, etc)

That's where this module comes it. It provides functions useful for escaping html and generating HTML tags, but it's all written in XS to be very fast. It's also fully UTF-8 aware.

FUNCTIONS

escape_html($Str [, $Mode ])

Escapes the contents of $Str to change the chars [<>&"] to '&lt;', '&gt;', '&amp;' and '&quot;' repectively.

$Mode is an optional bit field with the additional options or'd together:

  • EH_INPLACE - modify in-place, otherwise return new copy

  • EH_LFTOBR - convert \n to <br>

  • EH_SPTONBSP - convert ' ' to ' &nbsp;'

  • EH_LEAVEKNOWN - if & is followed by text that looks like an entity reference (eg &#1234; or &#x1ab2; or &nbsp;) then it's left unescaped

Useful for turning text into similar to <pre> form without actually being in <pre> tags

generate_attributes($HashRef)

Turns the contents of $HashRef of the form:

  {
    aaa => 'bbb',
    ccc => undef
  }

Into a string of the form:

  q{aaa="bbb" ccc}

Useful for generating HTML tags. The values of each hash entry are escaped with escape_html() before being added to the final string.

If you want to use a raw value unescaped, pass it as a scalar ref with a single item. Eg.

  {
    aaa => \'<blah>',
    bbb => '<blah>'
  }

Is turned into:

  q{aaa="<blah>" bbb="&lt;blah&gt;"}

If the value is an array ref, then the individual items are joined together with a space separator. Eg.

  {
    class => [ 'class1', 'class2', \'<blah>' ],
    aaa => 'bbb'
  }

Is turned into:

  q{aaa="bbb" class="class1 class2 <blah>"}

If the value is a hash ref, then the individual keys are joined together with a space separator. Eg.

  {
    class => { class1 => 1, class2 => 2 ],
    aaa => 'bbb'
  }

Is turned into:

  q{aaa="bbb" class="class2 class1"}

Keys are always escaped since you can't have a scalar reference as a key.

generate_tag($Tag, $AttrHashRef, $Value, $Mode)

Creates an HTML tag of the basic form:

  <$Tag %$AttrHashRef>$Value</$Tag>

If $AttrHashRef is undef, then no attributes are created. Otherwise generate_attributes() is called to stringify the hash ref.

If $Value is undef, then no $Value is included, and no </$Tag> is added.

$Mode is a bit field with the additional options:

  • GT_ESCAPEVAL - call escape_html on $Value

  • GT_ADDNEWLINE - append \n to output of string

  • GT_CLOSETAG - close the tag (eg <tag />). This should really only be used when $Value is undef, otherwise you'll end up with something like <tag />value</tag>, which is probably not what you want

escape_uri($Uri, [ $Mode, $EscapeChars ])

Escape unsafe characters in a uri.

This escapes all characters not in the unreserved character set. As a regexp that is:

  [^A-Za-z0-9\-_.!~*'()]

or

  [\x00-\x1F "#$%&+,/:;<=>?@\[\]^`{}|\\\x7f-\xff];

And always any characters > 127. See below for more details.

Some other things to note:

  • The escaping assumes all strings with char codes > 127 are to be represeted as encoded utf-8 octets. That is it first turns off any utf-8 bit on the string, and then encodes each byte to it's corresponding octet.

  • When encoding a uri with parameters, you'll probably want to encode each parameter first and then join it to the final string, something like:

      my %uri_params = ( ... )
      my $uri = "http://hostname.com/somepath/?" .
        join ";",
        map { $_ . "=" . escape_uri($uri_params{$_}) } 
        keys %uri_params;

    Assuming your keys don't have any unreserved characters in them, a common practice in many peoples design.

    Doing something like:

      my $uri = escape_uri("http://hostname.com/somepath/?a=p1");

    Will escape the '?', not giving you what you expect at the other end.

$Mode is a bit field with the additional options:

  • EU_INPLACE - modify in-place, otherwise return new copy

$EscapeChars is optional characters to escape instead of default set

If supplied, only these characters (and always any ctrl or 8-bit characters) are escaped rather than the unreserved set above.

OBJECTS

$H

Shortcut object you can call to generate tags.

Basically a lightweight wrapper around generate_tag. Attribute hash ref at start is optional. Doesn't escape any values by default.

Examples:

  $H->tag()                 -> '<tag>'
  $H->tag({a=>"b"})         -> '<tag a="b">'
  $H->tag("text")           -> '<tag>text</tag>'
  $H->tag({a=>"b"}, "text") -> '<tag a="b">text</tag>'
  $H->tag({a=>"b"}, "t<>t") -> '<tag a="b">t<>t</tag>'
  $H->tag({a=>"b"}, "t<>t", GT_ESCAPEVAL)
                            -> '<tag a="b">t&lt;&gt;t</tag>'
$E

Shortcut object you can call to generate tags.

More heavy weight than $H, but has extra smarts

  • Optional attribute hash ref at start

  • By default escapes all values. Use scalar ref to not escape value

  • Multiple parameters generate multiple tags

  • Array ref item concatenates all values in array ref

To pass flags to generate_tag or escape_html, add _gtflags or _ehflags item to initial attributes hash.

Examples:

  $E->tag()                   -> '<tag>'
  $E->tag({a=>"b"})           -> '<tag a="b">'
  $E->tag("text")             -> '<tag>text</tag>'
  $E->tag("t<>t")             -> '<tag>t&lt;&gt;t</tag>'
  $E->tag("t<",\"t<boo>")     -> '<tag>t&lt</tag><tag>t<boo></tag>'
  $H->tag({a=>"b"},"c","<")   -> '<tag a="b">c</tag><tag a="b">&lt;</tag>'
  $H->tag(["a","2"])          -> '<tag>a2</tag>'
  $H->tag(["t<", \"t<boo>"])  -> '<tag>t&lt;t<boo></tag>'

BUGS AND LIMITATIONS

The EH_LEAVEKNOWN option is just heuristic, and accepts anything that even looks like an entity reference, even if it isn't a correct one. I'm not sure if this is a security issue or not.

SEE ALSO

Apache::Util, HTML::Entities, CGI

Latest news/details can also be found at:

http://cpan.robm.fastmail.fm/htmlgenerateutil/

Available on github at:

https://github.com/robmueller/html-generateutil/

AUTHOR

Rob Mueller <cpan@robm.fastmail.fm>

COPYRIGHT AND LICENSE

Copyright (C) 2004-2014 by FastMail Pty Ltd

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