## $Id: Headers.pm,v 1.26 1996/09/16 12:49:47 aas Exp $package HTTP::Headers;=head1 NAMEHTTP::Headers - Class encapsulating HTTP Message headers=head1 SYNOPSIS require HTTP::Headers; $request = new HTTP::Headers;=head1 DESCRIPTIONThe C<HTTP::Headers> class encapsulates HTTP-style message headers.The headers consist of attribute-value pairs, which may be repeated,and which are printed in a particular order.Instances of this class are usually created as member variables of theC<HTTP::Request> and C<HTTP::Response> classes, internal to thelibrary.=head1 METHODS=cutrequire Carp;# Could not use the AutoLoader becase several of the method names are# not unique in the first 8 characters.#use SelfLoader;# "Good Practice" order of HTTP message headers:#    - General-Headers#    - Request-Headers#    - Response-Headers#    - Entity-Headers#    - Aditional Headers (§19.6.2)# (From draft-ietf-http-v11-spec-06, Jul 4, 1996)my @header_order = qw(   Cache-Control Connection Date Pragma Transfer-Encoding Upgrade Via   Accept Accept-Charset Accept-Encoding Accept-Language   Authorization From Host   If-Modified-Since If-Match If-None-Match If-Range If-Unmodified-Since   Max-Forwards Proxy-Authorization Range Referer User-Agent   Age Location Proxy-Authenticate Public Retry-After Server Vary   Warning WWW-Authenticate   Allow Content-Base Content-Encoding Content-Language Content-Length   Content-Location Content-MD5 Content-Range Content-Type   ETag Expires Last-Modified   Alternates Content-Version Derived-From Link URI);# Make alternative representations of @header_order.  This is used# for sorting and case matching.my $i = 0;my %header_order;my %standard_case;for (@header_order) {    my $lc = lc $_;    $header_order{$lc} = $i++;    $standard_case{$lc} = $_;}=head2 $h = new HTTP::HeadersConstructs a new C<HTTP::Headers> object.  You might pass some initialattribute-value pairs as parameters to the constructor.  I<E.g.>: $h = new HTTP::Headers     Date         => 'Thu, 03 Feb 1994 00:00:00 GMT',     Content_Type => 'text/html; version=3.2',     Content_Base => 'http://www.sn.no/';=cutsub new{    my($class) = shift;    my $self = bless {	'_header'   => { },    }, $class;    $self->header(@_); # set up initial headers    $self;}=head2 $h->header($field [=> $val],...)Get or set the value of a header.  The header field name is not casesensitive.  To make the life easier for perl users who wants to avoidquoting before the => operator, you can use '_' as a synonym for '-'in header names.The value argument may be a scalar or a reference to a list ofscalars. If the value argument is not defined, then the header is notmodified.The header() method accepts multiple ($field => $value) pairs.The list of previous values for the last $field is returned.  Only thefirst header value is returned in scalar context. $header->header(MIME_Version => '1.0',		 User_Agent   => 'My-Web-Client/0.01'); $header->header(Accept => "text/html, text/plain, image/*"); $header->header(Accept => [qw(text/html text/plain image/*)]); @accepts = $header->header('Accept');=cutsub header{    my $self = shift;    my($field, $val, @old);    while (($field, $val) = splice(@_, 0, 2)) {	@old = $self->_header($field, $val);    }    wantarray ? @old : $old[0];}sub _header{    my($self, $field, $val, $push) = @_;    $field =~ tr/_/-/;  # allow use of '_' as alternative to '-' in fields    # $push is only used interally sub push_header    Carp::croak('Need a field name') unless defined $field;    Carp::croak('Too many parameters') if @_ > 4;    my $lc_field = lc $field;    unless(defined $standard_case{$lc_field}) {	# generate a %stadard_case entry for this field	$field =~ s/\b(\w)/\u$1/g;	$standard_case{$lc_field} = $field;    }    my $this_header = \@{$self->{'_header'}{$lc_field}};    my @old = ();    if (!$push && defined $this_header) {	@old = @$this_header;  # save it so we can return it    }    if (defined $val) {	@$this_header = () unless $push;	if (!ref($val)) {	    # scalar: create list with single value	    push(@$this_header, $val);	} elsif (ref($val) eq 'ARRAY') {	    # list: copy list	    push(@$this_header, @$val);	} else {	    Carp::croak("Unexpected field value $val");	}    }    @old;}# Compare function which makes it easy to sort headers in the# recommended "Good Practice" order.sub _header_cmp{    # Unknown headers are assign a large value so that they are    # sorted last.  This also helps avoiding a warning from -w    # about comparing undefined values.    $header_order{$a} = 999 unless defined $header_order{$a};    $header_order{$b} = 999 unless defined $header_order{$b};    $header_order{$a} <=> $header_order{$b} || $a cmp $b;}=head2 $h->scan(\&doit)Apply a subroutine to each header in turn.  The callback routine iscalled with two parameters; the name of the field and a single value.If the header has more than one value, then the routine is called oncefor each value.  The field name passed to the callback routine hascase as suggested by HTTP Spec, and the headers will be visited in therecommended "Good Practice" order.=cutsub scan{    my($self, $sub) = @_;    my $field;    foreach $field (sort _header_cmp keys %{$self->{'_header'}} ) {	my $list = $self->{'_header'}{$field};	if (defined $list) {	    my $val;	    for $val (@$list) {		&$sub($standard_case{$field} || $field, $val);	    }	}    }}=head2 $h->as_string([$endl])Return the header fields as a formatted MIME header.  Since itinternally uses the C<scan()> method to build the string, the resultwill use case as suggested by HTTP Spec, and it will followrecommended "Good Practice" of ordering the header fieds.  Long headervalues are not folded. The optional parameter specifies the line ending sequence to use.  Thedefault is C<"\n">.  Embedded "\n" characters in the header will besubstitued with this line ending sequence.=cutsub as_string{    my($self, $endl) = @_;    $endl = "\n" unless defined $endl;    my @result = ();    $self->scan(sub {	my($field, $val) = @_;	if ($val =~ /\n/) {	    # must handle header values with embedded newlines with care	    $val =~ s/\s+$//;          # trailing newlines and space must go	    $val =~ s/\n\n+/\n/g;      # no empty lines	    $val =~ s/\n([^\040\t])/\n $1/g;  # intial space for continuation	    $val =~ s/\n/$endl/g;      # substitute with requested line ending	}	push(@result, "$field: $val");    });    join($endl, @result, '');}# The remaining functions should autoloaded only when needed# A bug in 5.002gamma makes it risky to have POD text inside the# autoloaded section of the code, so we keep the documentation before# the __DATA__ token.=head2 $h->push_header($field, $val)Add a new field value of the specified header.  The header field nameis not case sensitive.  The field need not already have avalue. Previous values for the same field are retained.  The argumentmay be a scalar or a reference to a list of scalars. $header->push_header(Accept => 'image/jpeg');=head2 $h->remove_header($field,...)This function removes the headers with the specified names.=head2 $h->cloneReturns a copy of this HTTP::Headers object.=head1 CONVENIENCE METHODSThe most frequently used headers can also be accessed through thefollowing convenience methods.  These methods can both be used to readand to set the value of a header.  The header value is set if you passan argument to the method.  The old header value is always returned.Methods that deal with dates/times always convert their value to systemtime (seconds since Jan 1, 1970) and they also expect this kind ofvalue when the header value is set.=head2 $h->dateThis header represents the date and time at which the message wasoriginated. I<E.g.>:  $h->date(time);  # set current date=head2 $h->expiresThis header gives the date and time after which the entity should beconsidered stale.=head2 $h->if_modified_sinceThis header is used to make a request conditional.  If the requestedresource has not been modified since the time specified in this field,then the server will return a C<"304 Not Modified"> response instead ofthe document itself.=head2 $h->last_modifiedThis header indicates the date and time at which the resource was lastmodified. I<E.g.>:  # check if document is more than 1 hour old  if ($h->last_modified < time - 60*60) {	...  }=head2 $h->content_typeThe Content-Type header field indicates the media type of the messagecontent. I<E.g.>:  $h->content_type('text/html');The value returned will be converted to lower case, and potentialparameters will be chopped off and returned as a separate value if inan array context.  This makes it safe to do the following:  if ($h->content_type eq 'text/html') {     # we enter this place even if the real header value happens to     # be 'TEXT/HTML; version=3.0'     ...  }=head2 $h->content_encodingThe Content-Encoding header field is used as a modifier to themedia type.  When present, its value indicates what additionalencoding mechanism has been applied to the resource.=head2 $h->content_lengthA decimal number indicating the size in bytes of the message content.=head2 $h->titleThe title of the document.  In libwww-perl this header will beinitialized automatically from the E<lt>TITLE>...E<lt>/TITLE> elementof HTML documents.  I<This header is no longer part of the HTTPstandard.>=head2 $h->user_agentThis header field is used in request messages and contains informationabout the user agent originating the request.  I<E.g.>:  $h->user_agent('Mozilla/1.2');=head2 $h->serverThe server header field contains information about the software beingused by the originating server program handling the request.=head2 $h->fromThis header should contain an Internet e-mail address for the humanuser who controls the requesting user agent.  The address should bemachine-usable, as defined by RFC822.  E.g.:  $h->from('Gisle Aas <aas@sn.no>');=head2 $h->refererUsed to specify the address (URI) of the document from which therequested resouce address was obtained.=head2 $h->www_authenticateThis header must be included as part of a "401 Unauthorized" response.The field value consist of a challenge that indicates theauthentication scheme and parameters applicable to the requested URI.=head2 $h->authorizationA user agent that wishes to authenticate itself with a server, may doso by including this header.=head2 $h->authorization_basicThis method is used to get or set an authorization header that use the"Basic Authentication Scheme".  In array context it will return twovalues; the user name and the password.  In scalar context it willreturn I<"uname:password"> as a single string value.When used to set the header value, it expects two arguments.  I<E.g.>:  $h->authorization_basic($uname, $password);=cut1;#__DATA__sub clone{    my $self = shift;    my $clone = new HTTP::Headers;    $self->scan(sub { $clone->push_header(@_);} );    $clone;}sub push_header{    Carp::croak('Usage: $h->push_header($field, $val)') if @_ != 3;    shift->_header(@_, 'PUSH');}sub remove_header{    my($self, @fields) = @_;    my $field;    foreach $field (@fields) {	$field =~ tr/_/-/;	delete $self->{'_header'}{lc $field};    }}# Convenience access functionssub _date_header{    require HTTP::Date;    my($self, $header, $time) = @_;    my($old) = $self->_header($header);    if (defined $time) {	$self->_header($header, HTTP::Date::time2str($time));    }    HTTP::Date::str2time($old);}sub date              { shift->_date_header('Date',              @_); }sub expires           { shift->_date_header('Expires',           @_); }sub if_modified_since { shift->_date_header('If-Modified-Since', @_); }sub last_modified     { shift->_date_header('Last-Modified',     @_); }# This is used as a private LWP extention.  The Client-Date header is# added as a timestamp to a response when it has been received.sub client_date       { shift->_date_header('Client-Date',       @_); }# The retry_after field is dual format (can also be a expressed as# number of seconds from now), so we don't provide an easy way to# access it until we have know how both these interfaces can be# addressed.#sub retry_after       { shift->_date_header('Retry-After',       @_); }sub content_type      {  my $ct = (shift->_header('Content-Type', @_))[0];  return '' unless defined $ct;  my @ct = split(/\s*;\s*/, lc($ct));  wantarray ? @ct : $ct[0];}sub title             { (shift->_header('Title',            @_))[0] }sub content_encoding  { (shift->_header('Content-Encoding', @_))[0] }sub content_length    { (shift->_header('Content-Length',   @_))[0] }sub user_agent        { (shift->_header('User-Agent',       @_))[0] }sub server            { (shift->_header('Server',           @_))[0] }sub from              { (shift->_header('From',             @_))[0] }sub referer           { (shift->_header('Referer',          @_))[0] }sub www_authenticate  { (shift->_header('WWW-Authenticate', @_))[0] }sub authorization     { (shift->_header('Authorization',    @_))[0] }sub authorization_basic {    require MIME::Base64;    my($self, $user, $passwd) = @_;    my($old) = $self->_header('Authorization');    if (defined $user) {	$passwd = '' unless defined $passwd;	$self->_header('Authorization',		       'Basic ' . MIME::Base64::encode("$user:$passwd", ''));    }    if (defined $old && $old =~ s/^\s*Basic\s+//) {	my $val = MIME::Base64::decode($old);	return $val unless wantarray;	return split(/:/, $val, 2);    }    undef;}1;