--- /dev/null
+package HTTP::Negotiate;
+
+$VERSION = "5.813";
+sub Version { $VERSION; }
+
+require 5.002;
+require Exporter;
+@ISA = qw(Exporter);
+@EXPORT = qw(choose);
+
+require HTTP::Headers;
+
+$DEBUG = 0;
+
+sub choose ($;$)
+{
+ my($variants, $request) = @_;
+ my(%accept);
+
+ unless (defined $request) {
+ # Create a request object from the CGI environment variables
+ $request = new HTTP::Headers;
+ $request->header('Accept', $ENV{HTTP_ACCEPT})
+ if $ENV{HTTP_ACCEPT};
+ $request->header('Accept-Charset', $ENV{HTTP_ACCEPT_CHARSET})
+ if $ENV{HTTP_ACCEPT_CHARSET};
+ $request->header('Accept-Encoding', $ENV{HTTP_ACCEPT_ENCODING})
+ if $ENV{HTTP_ACCEPT_ENCODING};
+ $request->header('Accept-Language', $ENV{HTTP_ACCEPT_LANGUAGE})
+ if $ENV{HTTP_ACCEPT_LANGUAGE};
+ }
+
+ # Get all Accept values from the request. Build a hash initialized
+ # like this:
+ #
+ # %accept = ( type => { 'audio/*' => { q => 0.2, mbx => 20000 },
+ # 'audio/basic' => { q => 1 },
+ # },
+ # language => { 'no' => { q => 1 },
+ # }
+ # );
+
+ $request->scan(sub {
+ my($key, $val) = @_;
+
+ my $type;
+ if ($key =~ s/^Accept-//) {
+ $type = lc($key);
+ }
+ elsif ($key eq "Accept") {
+ $type = "type";
+ }
+ else {
+ return;
+ }
+
+ $val =~ s/\s+//g;
+ my $default_q = 1;
+ for my $name (split(/,/, $val)) {
+ my(%param, $param);
+ if ($name =~ s/;(.*)//) {
+ for $param (split(/;/, $1)) {
+ my ($pk, $pv) = split(/=/, $param, 2);
+ $param{lc $pk} = $pv;
+ }
+ }
+ $name = lc $name;
+ if (defined $param{'q'}) {
+ $param{'q'} = 1 if $param{'q'} > 1;
+ $param{'q'} = 0 if $param{'q'} < 0;
+ }
+ else {
+ $param{'q'} = $default_q;
+
+ # This makes sure that the first ones are slightly better off
+ # and therefore more likely to be chosen.
+ $default_q -= 0.0001;
+ }
+ $accept{$type}{$name} = \%param;
+ }
+ });
+
+ # Check if any of the variants specify a language. We do this
+ # because it influences how we treat those without (they default to
+ # 0.5 instead of 1).
+ my $any_lang = 0;
+ for $var (@$variants) {
+ if ($var->[5]) {
+ $any_lang = 1;
+ last;
+ }
+ }
+
+ if ($DEBUG) {
+ print "Negotiation parameters in the request\n";
+ for $type (keys %accept) {
+ print " $type:\n";
+ for $name (keys %{$accept{$type}}) {
+ print " $name\n";
+ for $pv (keys %{$accept{$type}{$name}}) {
+ print " $pv = $accept{$type}{$name}{$pv}\n";
+ }
+ }
+ }
+ }
+
+ my @Q = (); # This is where we collect the results of the
+ # quality calculations
+
+ # Calculate quality for all the variants that are available.
+ for (@$variants) {
+ my($id, $qs, $ct, $enc, $cs, $lang, $bs) = @$_;
+ $qs = 1 unless defined $qs;
+ $ct = '' unless defined $ct;
+ $bs = 0 unless defined $bs;
+ $lang = lc($lang) if $lang; # lg tags are always case-insensitive
+ if ($DEBUG) {
+ print "\nEvaluating $id (ct='$ct')\n";
+ printf " qs = %.3f\n", $qs;
+ print " enc = $enc\n" if $enc && !ref($enc);
+ print " enc = @$enc\n" if $enc && ref($enc);
+ print " cs = $cs\n" if $cs;
+ print " lang = $lang\n" if $lang;
+ print " bs = $bs\n" if $bs;
+ }
+
+ # Calculate encoding quality
+ my $qe = 1;
+ # If the variant has no assigned Content-Encoding, or if no
+ # Accept-Encoding field is present, then the value assigned
+ # is "qe=1". If *all* of the variant's content encodings
+ # are listed in the Accept-Encoding field, then the value
+ # assigned is "qw=1". If *any* of the variant's content
+ # encodings are not listed in the provided Accept-Encoding
+ # field, then the value assigned is "qe=0"
+ if (exists $accept{'encoding'} && $enc) {
+ my @enc = ref($enc) ? @$enc : ($enc);
+ for (@enc) {
+ print "Is encoding $_ accepted? " if $DEBUG;
+ unless(exists $accept{'encoding'}{$_}) {
+ print "no\n" if $DEBUG;
+ $qe = 0;
+ last;
+ }
+ else {
+ print "yes\n" if $DEBUG;
+ }
+ }
+ }
+
+ # Calculate charset quality
+ my $qc = 1;
+ # If the variant's media-type has no charset parameter,
+ # or the variant's charset is US-ASCII, or if no Accept-Charset
+ # field is present, then the value assigned is "qc=1". If the
+ # variant's charset is listed in the Accept-Charset field,
+ # then the value assigned is "qc=1. Otherwise, if the variant's
+ # charset is not listed in the provided Accept-Encoding field,
+ # then the value assigned is "qc=0".
+ if (exists $accept{'charset'} && $cs && $cs ne 'us-ascii' ) {
+ $qc = 0 unless $accept{'charset'}{$cs};
+ }
+
+ # Calculate language quality
+ my $ql = 1;
+ if ($lang && exists $accept{'language'}) {
+ my @lang = ref($lang) ? @$lang : ($lang);
+ # If any of the variant's content languages are listed
+ # in the Accept-Language field, the the value assigned is
+ # the largest of the "q" parameter values for those language
+ # tags.
+ my $q = undef;
+ for (@lang) {
+ next unless exists $accept{'language'}{$_};
+ my $this_q = $accept{'language'}{$_}{'q'};
+ $q = $this_q unless defined $q;
+ $q = $this_q if $this_q > $q;
+ }
+ if(defined $q) {
+ $DEBUG and print " -- Exact language match at q=$q\n";
+ }
+ else {
+ # If there was no exact match and at least one of
+ # the Accept-Language field values is a complete
+ # subtag prefix of the content language tag(s), then
+ # the "q" parameter value of the largest matching
+ # prefix is used.
+ $DEBUG and print " -- No exact language match\n";
+ my $selected = undef;
+ for $al (keys %{ $accept{'language'} }) {
+ if (index($al, "$lang-") == 0) {
+ # $lang starting with $al isn't enough, or else
+ # Accept-Language: hu (Hungarian) would seem
+ # to accept a document in hup (Hupa)
+ $DEBUG and print " -- $al ISA $lang\n";
+ $selected = $al unless defined $selected;
+ $selected = $al if length($al) > length($selected);
+ }
+ else {
+ $DEBUG and print " -- $lang isn't a $al\n";
+ }
+ }
+ $q = $accept{'language'}{$selected}{'q'} if $selected;
+
+ # If none of the variant's content language tags or
+ # tag prefixes are listed in the provided
+ # Accept-Language field, then the value assigned
+ # is "ql=0.001"
+ $q = 0.001 unless defined $q;
+ }
+ $ql = $q;
+ }
+ else {
+ $ql = 0.5 if $any_lang && exists $accept{'language'};
+ }
+
+ my $q = 1;
+ my $mbx = undef;
+ # If no Accept field is given, then the value assigned is "q=1".
+ # If at least one listed media range matches the variant's media
+ # type, then the "q" parameter value assigned to the most specific
+ # of those matched is used (e.g. "text/html;version=3.0" is more
+ # specific than "text/html", which is more specific than "text/*",
+ # which in turn is more specific than "*/*"). If not media range
+ # in the provided Accept field matches the variant's media type,
+ # then the value assigned is "q=0".
+ if (exists $accept{'type'} && $ct) {
+ # First we clean up our content-type
+ $ct =~ s/\s+//g;
+ my $params = "";
+ $params = $1 if $ct =~ s/;(.*)//;
+ my($type, $subtype) = split("/", $ct, 2);
+ my %param = ();
+ for $param (split(/;/, $params)) {
+ my($pk,$pv) = split(/=/, $param, 2);
+ $param{$pk} = $pv;
+ }
+
+ my $sel_q = undef;
+ my $sel_mbx = undef;
+ my $sel_specificness = 0;
+
+ ACCEPT_TYPE:
+ for $at (keys %{ $accept{'type'} }) {
+ print "Consider $at...\n" if $DEBUG;
+ my($at_type, $at_subtype) = split("/", $at, 2);
+ # Is it a match on the type
+ next if $at_type ne '*' && $at_type ne $type;
+ next if $at_subtype ne '*' && $at_subtype ne $subtype;
+ my $specificness = 0;
+ $specificness++ if $at_type ne '*';
+ $specificness++ if $at_subtype ne '*';
+ # Let's see if content-type parameters also match
+ while (($pk, $pv) = each %param) {
+ print "Check if $pk = $pv is true\n" if $DEBUG;
+ next unless exists $accept{'type'}{$at}{$pk};
+ next ACCEPT_TYPE
+ unless $accept{'type'}{$at}{$pk} eq $pv;
+ print "yes it is!!\n" if $DEBUG;
+ $specificness++;
+ }
+ print "Hurray, type match with specificness = $specificness\n"
+ if $DEBUG;
+
+ if (!defined($sel_q) || $sel_specificness < $specificness) {
+ $sel_q = $accept{'type'}{$at}{'q'};
+ $sel_mbx = $accept{'type'}{$at}{'mbx'};
+ $sel_specificness = $specificness;
+ }
+ }
+ $q = $sel_q || 0;
+ $mbx = $sel_mbx;
+ }
+
+ my $Q;
+ if (!defined($mbx) || $mbx >= $bs) {
+ $Q = $qs * $qe * $qc * $ql * $q;
+ }
+ else {
+ $Q = 0;
+ print "Variant's size is too large ==> Q=0\n" if $DEBUG;
+ }
+
+ if ($DEBUG) {
+ $mbx = "undef" unless defined $mbx;
+ printf "Q=%.4f", $Q;
+ print " (q=$q, mbx=$mbx, qe=$qe, qc=$qc, ql=$ql, qs=$qs)\n";
+ }
+
+ push(@Q, [$id, $Q, $bs]);
+ }
+
+
+ @Q = sort { $b->[1] <=> $a->[1] || $a->[2] <=> $b->[2] } @Q;
+
+ return @Q if wantarray;
+ return undef unless @Q;
+ return undef if $Q[0][1] == 0;
+ $Q[0][0];
+}
+
+1;
+
+__END__
+
+
+=head1 NAME
+
+HTTP::Negotiate - choose a variant to serve
+
+=head1 SYNOPSIS
+
+ use HTTP::Negotiate qw(choose);
+
+ # ID QS Content-Type Encoding Char-Set Lang Size
+ $variants =
+ [['var1', 1.000, 'text/html', undef, 'iso-8859-1', 'en', 3000],
+ ['var2', 0.950, 'text/plain', 'gzip', 'us-ascii', 'no', 400],
+ ['var3', 0.3, 'image/gif', undef, undef, undef, 43555],
+ ];
+
+ @preferred = choose($variants, $request_headers);
+ $the_one = choose($variants);
+
+=head1 DESCRIPTION
+
+This module provides a complete implementation of the HTTP content
+negotiation algorithm specified in F<draft-ietf-http-v11-spec-00.ps>
+chapter 12. Content negotiation allows for the selection of a
+preferred content representation based upon attributes of the
+negotiable variants and the value of the various Accept* header fields
+in the request.
+
+The variants are ordered by preference by calling the function
+choose().
+
+The first parameter is reference to an array of the variants to
+choose among.
+Each element in this array is an array with the values [$id, $qs,
+$content_type, $content_encoding, $charset, $content_language,
+$content_length] whose meanings are described
+below. The $content_encoding and $content_language can be either a
+single scalar value or an array reference if there are several values.
+
+The second optional parameter is either a HTTP::Headers or a HTTP::Request
+object which is searched for "Accept*" headers. If this
+parameter is missing, then the accept specification is initialized
+from the CGI environment variables HTTP_ACCEPT, HTTP_ACCEPT_CHARSET,
+HTTP_ACCEPT_ENCODING and HTTP_ACCEPT_LANGUAGE.
+
+In an array context, choose() returns a list of [variant
+identifier, calculated quality, size] tuples. The values are sorted by
+quality, highest quality first. If the calculated quality is the same
+for two variants, then they are sorted by size (smallest first). I<E.g.>:
+
+ (['var1', 1, 2000], ['var2', 0.3, 512], ['var3', 0.3, 1024]);
+
+Note that also zero quality variants are included in the return list
+even if these should never be served to the client.
+
+In a scalar context, it returns the identifier of the variant with the
+highest score or C<undef> if none have non-zero quality.
+
+If the $HTTP::Negotiate::DEBUG variable is set to TRUE, then a lot of
+noise is generated on STDOUT during evaluation of choose().
+
+=head1 VARIANTS
+
+A variant is described by a list of the following values. If the
+attribute does not make sense or is unknown for a variant, then use
+C<undef> instead.
+
+=over 3
+
+=item identifier
+
+This is a string that you use as the name for the variant. This
+identifier for the preferred variants returned by choose().
+
+=item qs
+
+This is a number between 0.000 and 1.000 that describes the "source
+quality". This is what F<draft-ietf-http-v11-spec-00.ps> says about this
+value:
+
+Source quality is measured by the content provider as representing the
+amount of degradation from the original source. For example, a
+picture in JPEG form would have a lower qs when translated to the XBM
+format, and much lower qs when translated to an ASCII-art
+representation. Note, however, that this is a function of the source
+- an original piece of ASCII-art may degrade in quality if it is
+captured in JPEG form. The qs values should be assigned to each
+variant by the content provider; if no qs value has been assigned, the
+default is generally "qs=1".
+
+=item content-type
+
+This is the media type of the variant. The media type does not
+include a charset attribute, but might contain other parameters.
+Examples are:
+
+ text/html
+ text/html;version=2.0
+ text/plain
+ image/gif
+ image/jpg
+
+=item content-encoding
+
+This is one or more content encodings that has been applied to the
+variant. The content encoding is generally used as a modifier to the
+content media type. The most common content encodings are:
+
+ gzip
+ compress
+
+=item content-charset
+
+This is the character set used when the variant contains text.
+The charset value should generally be C<undef> or one of these:
+
+ us-ascii
+ iso-8859-1 ... iso-8859-9
+ iso-2022-jp
+ iso-2022-jp-2
+ iso-2022-kr
+ unicode-1-1
+ unicode-1-1-utf-7
+ unicode-1-1-utf-8
+
+=item content-language
+
+This describes one or more languages that are used in the variant.
+Language is described like this in F<draft-ietf-http-v11-spec-00.ps>: A
+language is in this context a natural language spoken, written, or
+otherwise conveyed by human beings for communication of information to
+other human beings. Computer languages are explicitly excluded.
+
+The language tags are defined by RFC 3066. Examples
+are:
+
+ no Norwegian
+ en International English
+ en-US US English
+ en-cockney
+
+=item content-length
+
+This is the number of bytes used to represent the content.
+
+=back
+
+=head1 ACCEPT HEADERS
+
+The following Accept* headers can be used for describing content
+preferences in a request (This description is an edited extract from
+F<draft-ietf-http-v11-spec-00.ps>):
+
+=over 3
+
+=item Accept
+
+This header can be used to indicate a list of media ranges which are
+acceptable as a response to the request. The "*" character is used to
+group media types into ranges, with "*/*" indicating all media types
+and "type/*" indicating all subtypes of that type.
+
+The parameter q is used to indicate the quality factor, which
+represents the user's preference for that range of media types. The
+parameter mbx gives the maximum acceptable size of the response
+content. The default values are: q=1 and mbx=infinity. If no Accept
+header is present, then the client accepts all media types with q=1.
+
+For example:
+
+ Accept: audio/*;q=0.2;mbx=200000, audio/basic
+
+would mean: "I prefer audio/basic (of any size), but send me any audio
+type if it is the best available after an 80% mark-down in quality and
+its size is less than 200000 bytes"
+
+
+=item Accept-Charset
+
+Used to indicate what character sets are acceptable for the response.
+The "us-ascii" character set is assumed to be acceptable for all user
+agents. If no Accept-Charset field is given, the default is that any
+charset is acceptable. Example:
+
+ Accept-Charset: iso-8859-1, unicode-1-1
+
+
+=item Accept-Encoding
+
+Restricts the Content-Encoding values which are acceptable in the
+response. If no Accept-Encoding field is present, the server may
+assume that the client will accept any content encoding. An empty
+Accept-Encoding means that no content encoding is acceptable. Example:
+
+ Accept-Encoding: compress, gzip
+
+
+=item Accept-Language
+
+This field is similar to Accept, but restricts the set of natural
+languages that are preferred in a response. Each language may be
+given an associated quality value which represents an estimate of the
+user's comprehension of that language. For example:
+
+ Accept-Language: no, en-gb;q=0.8, de;q=0.55
+
+would mean: "I prefer Norwegian, but will accept British English (with
+80% comprehension) or German (with 55% comprehension).
+
+=back
+
+
+=head1 COPYRIGHT
+
+Copyright 1996,2001 Gisle Aas.
+
+This library is free software; you can redistribute it and/or
+modify it under the same terms as Perl itself.
+
+=head1 AUTHOR
+
+Gisle Aas <gisle@aas.no>
+
+=cut
projects / dh-make-perl / blobdiff