NAME

       HTTP::Headers::Util - Header value parsing utility functions

VERSION

       version 6.14

SYNOPSIS

         use HTTP::Headers::Util qw(split_header_words);
         @values = split_header_words($h->header("Content-Type"));

DESCRIPTION

       This module provides a few functions that helps parsing and construction of valid HTTP
       header values.  None of the functions are exported by default.

       The following functions are available:

       split_header_words( @header_values )
           This function will parse the header values given as argument into a list of anonymous
           arrays containing key/value pairs.  The function knows how to deal with ",", ";" and
           "=" as well as quoted values after "=".  A list of space separated tokens are parsed
           as if they were separated by ";".

           If the @header_values passed as argument contains multiple values, then they are
           treated as if they were a single value separated by comma ",".

           This means that this function is useful for parsing header fields that follow this
           syntax (BNF as from the HTTP/1.1 specification, but we relax the requirement for
           tokens).

             headers           = #header
             header            = (token | parameter) *( [";"] (token | parameter))

             token             = 1*<any CHAR except CTLs or separators>
             separators        = "(" | ")" | "<" | ">" | "@"
                               | "," | ";" | ":" | "\" | <">
                               | "/" | "[" | "]" | "?" | "="
                               | "{" | "}" | SP | HT

             quoted-string     = ( <"> *(qdtext | quoted-pair ) <"> )
             qdtext            = <any TEXT except <">>
             quoted-pair       = "\" CHAR

             parameter         = attribute "=" value
             attribute         = token
             value             = token | quoted-string

           Each header is represented by an anonymous array of key/value pairs.  The keys will be
           all be forced to lower case.  The value for a simple token (not part of a parameter)
           is "undef".  Syntactically incorrect headers will not necessarily be parsed as you
           would want.

           This is easier to describe with some examples:

              split_header_words('foo="bar"; port="80,81"; DISCARD, BAR=baz');
              split_header_words('text/html; charset="iso-8859-1"');
              split_header_words('Basic realm="\\"foo\\\\bar\\""');

           will return

              [foo=>'bar', port=>'80,81', discard=> undef], [bar=>'baz' ]
              ['text/html' => undef, charset => 'iso-8859-1']
              [basic => undef, realm => "\"foo\\bar\""]

           If you don't want the function to convert tokens and attribute keys to lower case you
           can call it as "_split_header_words" instead (with a leading underscore).

       join_header_words( @arrays )
           This will do the opposite of the conversion done by split_header_words().  It takes a
           list of anonymous arrays as arguments (or a list of key/value pairs) and produces a
           single header value.  Attribute values are quoted if needed.

           Example:

              join_header_words(["text/plain" => undef, charset => "iso-8859/1"]);
              join_header_words("text/plain" => undef, charset => "iso-8859/1");

           will both return the string:

              text/plain; charset="iso-8859/1"

AUTHOR

       Gisle Aas <gisle@activestate.com>

COPYRIGHT AND LICENSE

       This software is copyright (c) 1994-2017 by Gisle Aas.

       This is free software; you can redistribute it and/or modify it under the same terms as
       the Perl 5 programming language system itself.