HTTP::Headers::Util

Section: User Contributed Perl Documentation (3)
Updated: 2021-03-08
Page Index

NAME

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

VERSION

version 6.29

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