NAME

Blosxom::Header - Missing interface to modify HTTP headers

SYNOPSIS

# Object-oriented interface

use Blosxom::Header;

my $header = Blosxom::Header->instance;

$header->set(
    Status        => '304 Not Modified',
    Last_Modified => 'Wed, 23 Sep 2009 13:36:33 GMT',
);

my $status = $header->get( 'Status' );
my @deleted = $header->delete( qw/Content-Disposition Content-Length/ );

# Procedural interface

use Blosxom::Header qw/header_set header_get header_delete/;

header_set(
    Status        => '304 Not Modified',
    Last_Modified => 'Wed, 23 Sep 2009 13:36:33 GMT',
);

my $status = header_get( 'Status' );
my @deleted = header_delete( qw/Content-Disposition Content-Length/ );

DESCRIPTION

Provides Blosxom plugin developers with an interface to handle HTTP response headers.

BACKGROUND

Blosxom, an weblog application, globalizes $header which is a reference to a hash. This application passes $header to CGI::header() to generate HTTP headers.

package blosxom;
use strict;
use warnings;
use CGI qw/header/;

our $header = { -type => 'text/html' };

# Loads plugins

print header( $header );

Plugins may modify $header directly because the variable is global. On the other hand, header() doesn't care whether keys of $header are lowercased nor start with a dash. There is no agreement with how to normalize keys of $header.

HOW THIS MODULE NORMALIZES FIELD NAMES

To specify field names consistently, we need to normalize them. If you follow one of normalization rules, you can modify $header consistently. This module normalizes field names as follows.

Remember how Blosxom initializes $header:

$header = { -type => 'text/html' };

A key -type is starting with a dash and lowercased, and so this module follows the same rules:

'Status'  # not normalized
'status'  # not normalized
'-status' # normalized

How about Content-Length? It contains a dash. To avoid quoting when specifying hash keys, this module transliterates dashes into underscores in field names:

'Content-Length'  # not normalized
'-content-length' # not normalized
'-content_length' # normalized

If you follow the above normalization rule, you can modify $header directly. In other words, this module is compatible with the way modifying $header directly when you follow the above rule. Blosxom::Header::Fast explains the details.

VARIABLE

The following variable is exported on demand.

$Header

The same reference as Blosxom::Header->instance returns.

use Blosxom::Header qw/$Header/;

FUNCTIONS

The following functions are exported on demand.

@values = header_get( @fields )

A synonym for Blosxom::Header->instance->get().

header_set( $field => $value )

header_set( $f1 => $v2, $f2 => $v2, ... )

A synonym for Blosxom::Header->instance->set().

$bool = header_exists( $field )

A synonym for Blosxom::Header->instance->exists().

@deleted = header_delete( @fields )

A synonym for Blosxom::Header->instance->delete().

push_cookie( @cookies )

A synonym for Blosxom::Header->instance->push_cookie().

push_p3p( @tags )

A synonym for Blosxom::Header->instance->push_p3p().

header_push( Set_Cookie => @cookies )

header_push( P3P => @tags )

This function is obsolete and will be removed in 0.06. Use push_cookie() or push_p3p() instead.

header_push( Set_Cookie => @cookies );
header_push( P3P => @tags );
# become
push_cookie( @cookies );
push_p3p( @tags );

CLASS METHODS

$header = Blosxom::Header->instance: Returns a current Blosxom::Header object instance or create a new one.
$header = Blosxom::Header->has_instance: Returns a reference to any existing instance or undef if none is defined.

INSTANCE METHODS

$bool = $header->is_initialized

Returns a Boolean value telling whether $blosxom::header is initialized or not. Blosxom initializes the variable just before blosxom::generate() is called. If $bool was false, the following methods would throw exceptions.

Internally, this method is a shortcut for

$bool = ref $blosxom::header eq 'HASH';

$value = $header->get( $field )

@values = $header->get( @fields )

Returns the value of one or more header fields. Accepts a list of field names. $field isn't case-sensitive. You can use underscores as a replacement for dashes.

$header->set( $field => $value )

$header->set( $f1 => $v1, $f2 => $v2, ... )

Sets the value of one or more header fields. Accepts a list of named arguments.

The $value argument must be a plain string, except for when the Set-Cookie or P3P header is specified. In exceptional cases, $value may be a reference to an array.

$header->set(
    Set_Cookie => [ $cookie1, $cookie2 ],
    P3P        => [ 'CAO', 'DSP', 'LAW', 'CURa' ],
);

$bool = $header->exists( $field )

Returns a Boolean value telling whether the specified HTTP header exists.

@deleted = $header->delete( @fields )

Deletes the specified fields from HTTP headers. Returns values of deleted fields.

$header->push_cookie( @cookies )

Pushes the Set-Cookie headers onto HTTP headers. Accepts a list of cookies. Returns the number of the elements following the completed push_cookie().

# get values of Set-Cookie headers
my @cookies = $header->cookie; # ( 'foo', 'bar' )

# add Set-Cookie header
$header->push_cookie( 'baz' );

@cookies = $header->cookie; # ( 'foo', 'bar', 'baz' )

$header->push_p3p( @p3p )

Adds P3P tags to the P3P header. Accepts a list of P3P tags.

# get P3P tags
my @tags = $header->p3p; # ( 'CAO', 'DSP', 'LAW' )

# add P3P tags
$header->push_p3p( 'CURa' );

@tags = $header->p3p; # ( 'CAO', 'DSP', 'LAW', 'CURa' )

$header->clear

This will remove all header fields.

Internally, this method is a shortcut for

%{ $blosxom::header } = ( -type => q{} );

@fields = $header->field_names

Returns the list of distinct names for the fields present in the header. In scalar context return the number of distinct field names.

CONVENIENCE METHODS

The following methods were named after parameters recognized by CGI::header(). They can both be used to read and to set the value of an attribute. The value is set if you pass an argument to the method. If the given attribute wasn't defined then undef is returned.

$header->attachment

Can be used to turn the page into an attachment. Represents suggested name for the saved file.

$header->attachment( 'genome.jpg' );
my $attachment = $header->attachment; # genome.jpg

my $disposition = $header->get( 'Content-Disposition' );
# => 'attachment; filename="genome.jpg"'

$header->charset

Returns the upper-cased character set specified in the Content-Type header.

$charset = $header->charset; # UTF-8 (Readonly)

$header->cookie

Represents the Set-Cookie headers. The parameter can be an array.

$header->cookie( 'foo', 'bar' );
my @cookies = $header->cookie; # ( 'foo', 'bar' )

$header->expires

The Expires header gives the date and time after which the entity should be considered stale. You can specify an absolute or relative expiration interval. The following forms are all valid for this field:

$header->expires( '+30s' ); # 30 seconds from now
$header->expires( '+10m' ); # ten minutes from now
$header->expires( '+1h'  ); # one hour from now
$header->expires( '-1d'  ); # yesterday
$header->expires( 'now'  ); # immediately
$header->expires( '+3M'  ); # in three months
$header->expires( '+10y' ); # in ten years time

# at the indicated time & date
$header->expires( 'Thu, 25 Apr 1999 00:40:33 GMT' );

$header->nph

If set to a true value, will issue the correct headers to work with a NPH (no-parse-header) script:

$header->nph( 1 );

$header->p3p

Represents the P3P header. The parameter can be an array or a space-delimited string.

$header->p3p( qw/CAO DSP LAW CURa/ );
$header->p3p( 'CAO DSP LAW CURa' );

my @tags = $header->p3p; # ( 'CAO', 'DSP', 'LAW', 'CURa' )

In either case, the outgoing header will be formatted as:

P3P: policyref="/w3c/p3p.xml" CP="CAO DSP LAW CURa"

$header->status

Represents HTTP status code.

$header->status( 304 );
my $code = $header->status; # 304

cf.

$header->set( Status => '304 Not Modified' );
my $status = $header->get( 'Status' ); # 304 Not Modified

$header->target

Represents the Window-Target header.

$header->target( 'ResultsWindow' );
my $target = $header->target; # ResultsWindow

cf.

$header->set( Window_Target => 'ResultsWindow' );
$target = $header->get( 'Window-Target' ); # ResultsWindow

$header->type

The Content-Type header indicates the media type of the message content.

$header->type( 'text/plain; charset=utf-8' );

The above is a shortcut for

$header->set( Content_Type => 'text/plain; charset=utf-8' );

The value returned will be converted to lower case, and potential parameters will be chopped off and returned as a separate value if in an array context.

my $type = $header->type; # 'text/html'
my @type = $header->type; # ( 'text/html', 'charset=ISO-8859-1' )

cf.

my $content_type = $header->get( 'Content-Type' );
# => 'text/html; charset=ISO-8859-1'

If there is no such header field, then the empty string is returned. This makes it safe to do the following:

if ( $header->type eq 'text/html' ) {
    ...
}

DIAGNOSTICS

$blosxom::header hasn't been initialized yet: You attempted to modify $blosxom::header before the variable was initialized. See $header->is_initialized.
Useless use of %s with no values: You used the push_cookie() or push_p3p() method with no argument apart from the array, like $header->push_cookie() or $header->push_p3p().
Unknown status code "%d%d%d" passed to status(): The given status code is unknown to HTTP::Status.

DEPENDENCIES

Blosxom 2.0.0 or higher.

ACKNOWLEDGEMENT

Blosxom was written by Rael Dornfest. The Blosxom Development Team succeeded the maintenance.

BUGS AND LIMITATIONS

There are no known bugs in this module. Please report problems to ANAZAWA (anazawa@cpan.org). Patches are welcome.

AUTHOR

Ryo Anazawa (anazawa@cpan.org)

LICENSE AND COPYRIGHT

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

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

To install Blosxom::Header, copy and paste the appropriate command in to your terminal.

cpanm

cpanm Blosxom::Header

CPAN shell

perl -MCPAN -e shell
install Blosxom::Header

For more information on module installation, please visit the detailed CPAN module installation guide.

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