HTTP-Negotiate-6.00/000755 000765 000024 00000000000 11532551114 014377 5ustar00gislestaff000000 000000 HTTP-Negotiate-6.00/Changes000644 000765 000024 00000000533 11532551074 015700 0ustar00gislestaff000000 000000 _______________________________________________________________________________ 2011-02-27 HTTP-Negotiate 6.00 Initial release of HTTP-Negotiate as a separate distribution. There are no code changes besides incrementing the version number since libwww-perl-5.837. The HTTP::Negotiate module used to be bundled with the libwww-perl distribution. HTTP-Negotiate-6.00/lib/000755 000765 000024 00000000000 11532551114 015145 5ustar00gislestaff000000 000000 HTTP-Negotiate-6.00/Makefile.PL000644 000765 000024 00000002131 11532551067 016355 0ustar00gislestaff000000 000000 #!perl -w require 5.008008; use strict; use ExtUtils::MakeMaker; WriteMakefile( NAME => 'HTTP::Negotiate', VERSION_FROM => 'lib/HTTP/Negotiate.pm', ABSTRACT_FROM => 'lib/HTTP/Negotiate.pm', AUTHOR => 'Gisle Aas ', LICENSE => "perl", MIN_PERL_VERSION => 5.008008, PREREQ_PM => { 'HTTP::Headers' => 6, }, META_MERGE => { resources => { repository => 'http://github.com/gisle/libwww-perl', MailingList => 'mailto:libwww@perl.org', } }, ); BEGIN { # compatibility with older versions of MakeMaker my $developer = -f ".gitignore"; my %mm_req = ( LICENCE => 6.31, META_MERGE => 6.45, META_ADD => 6.45, MIN_PERL_VERSION => 6.48, ); undef(*WriteMakefile); *WriteMakefile = sub { my %arg = @_; for (keys %mm_req) { unless (eval { ExtUtils::MakeMaker->VERSION($mm_req{$_}) }) { warn "$_ $@" if $developer; delete $arg{$_}; } } ExtUtils::MakeMaker::WriteMakefile(%arg); }; } HTTP-Negotiate-6.00/MANIFEST000644 000765 000024 00000000254 11532551114 015531 0ustar00gislestaff000000 000000 Changes lib/HTTP/Negotiate.pm Makefile.PL MANIFEST This list of files README t/negotiate.t META.yml Module meta-data (added by MakeMaker) HTTP-Negotiate-6.00/META.yml000644 000765 000024 00000001252 11532551114 015650 0ustar00gislestaff000000 000000 --- #YAML:1.0 name: HTTP-Negotiate version: 6.00 abstract: choose a variant to serve author: - Gisle Aas license: perl distribution_type: module configure_requires: ExtUtils::MakeMaker: 0 build_requires: ExtUtils::MakeMaker: 0 requires: HTTP::Headers: 6 perl: 5.008008 resources: MailingList: mailto:libwww@perl.org repository: http://github.com/gisle/libwww-perl no_index: directory: - t - inc generated_by: ExtUtils::MakeMaker version 6.56 meta-spec: url: http://module-build.sourceforge.net/META-spec-v1.4.html version: 1.4 HTTP-Negotiate-6.00/README000644 000765 000024 00000017124 11532551073 015270 0ustar00gislestaff000000 000000 NAME HTTP::Negotiate - choose a variant to serve 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); DESCRIPTION This module provides a complete implementation of the HTTP content negotiation algorithm specified in 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). *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 `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(). 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 `undef' instead. identifier This is a string that you use as the name for the variant. This identifier for the preferred variants returned by choose(). qs This is a number between 0.000 and 1.000 that describes the "source quality". This is what 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". 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 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 content-charset This is the character set used when the variant contains text. The charset value should generally be `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 content-language This describes one or more languages that are used in the variant. Language is described like this in 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 content-length This is the number of bytes used to represent the content. ACCEPT HEADERS The following Accept* headers can be used for describing content preferences in a request (This description is an edited extract from draft-ietf-http-v11-spec-00.ps): 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" 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 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 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). 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. AUTHOR Gisle Aas HTTP-Negotiate-6.00/t/000755 000765 000024 00000000000 11532551114 014642 5ustar00gislestaff000000 000000 HTTP-Negotiate-6.00/t/negotiate.t000644 000765 000024 00000005045 11532551073 017016 0ustar00gislestaff000000 000000 #!perl -w use Test; plan tests => 5; use HTTP::Request; use HTTP::Negotiate; # ID QS Content-Type Encoding Char-Set Lang Size $variants = [ ['var1', 0.950, 'text/plain', ['uuencode', 'compress'], 'iso-8859-2', 'se', 400], ['var2', 1.000, 'text/html;version=2.0', 'gzip', 'iso-8859-1', 'en', 3000], ['var3', 0.333, 'image/gif', undef, undef, undef, 43555], ]; # First we try a request with not accept headers $request = new HTTP::Request 'GET', 'http://localhost/'; @a = choose($variants, $request); show_res(@a); expect(\@a, [['var2' => 1], ['var1' => 0.95], ['var3' => 0.333] ] ); $a = choose($variants, $request); print "The chosen one is '$a'\n"; ok($a, "var2"); #------------------ $request = new HTTP::Request 'GET', 'http://localhost/'; $request->header('Accept', 'text/plain; q=0.55, image/gif; mbx=10000'); $request->push_header('Accept', 'text/*; q=0.25'); $request->header('Accept-Language', 'no, en'); $request->header('Accept-Charset', 'iso-8859-1'); $request->header('Accept-Encoding', 'gzip'); @a = choose($variants, $request); show_res(@a); expect(\@a, [['var2' => 0.25], ['var1' => 0], ['var3' => 0] ] ); $variants = [ ['var-en', undef, 'text/html', undef, undef, 'en', undef], ['var-de', undef, 'text/html', undef, undef, 'de', undef], ['var-ES', undef, 'text/html', undef, undef, 'ES', undef], ['provoke-warning', undef, undef, undef, undef, 'x-no-content-type', undef], ]; $HTTP::Negotiate::DEBUG=1; $ENV{HTTP_ACCEPT_LANGUAGE}='DE,en,fr;Q=0.5,es;q=0.1'; $a = choose($variants); ok($a, 'var-de'); $variants = [ [ 'Canadian English' => 1.0, 'text/html', undef, undef, 'en-CA', undef ], [ 'Generic English' => 1.0, 'text/html', undef, undef, 'en', undef ], [ 'Non-Specific' => 1.0, 'text/html', undef, undef, undef, undef ], ]; $ENV{HTTP_ACCEPT_LANGUAGE}='en-US'; $a = choose($variants); ok($a, 'Generic English'); #------------------ sub expect { my($res, $exp) = @_; do { $a = shift @$res; $b = shift @$exp; last if defined($a) ne defined($b); if (defined($a)) { ($va, $qa) = @$a; ($vb, $qb) = @$b; if ($va ne $vb) { print "$va == $vb ?\n"; ok(0); return; } if (abs($qa - $qb) > 0.002) { print "$qa ~= $qb ?\n"; ok(0); return; } } } until (!defined($a) || !defined($b)); ok(defined($a), defined($b)); } sub show_res { print "-------------\n"; for (@_) { printf "%-6s %.3f\n", @$_; } print "-------------\n"; } HTTP-Negotiate-6.00/lib/HTTP/000755 000765 000024 00000000000 11532551114 015724 5ustar00gislestaff000000 000000 HTTP-Negotiate-6.00/lib/HTTP/Negotiate.pm000644 000765 000024 00000037363 11532551074 020222 0ustar00gislestaff000000 000000 package HTTP::Negotiate; $VERSION = "6.00"; 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 = HTTP::Headers->new; $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 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: (['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 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 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 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 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: 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): =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 =cut