From bae21c2bd9b182b6b6bc7810e5e9daf424ebab7c Mon Sep 17 00:00:00 2001
From: Pali <pali@cpan.org>
Date: Sat, 18 Feb 2017 20:58:16 +0100
Subject: [PATCH] Email::MIME::Header: Add function set_class_for_header

It will safely without overwriting modify hash: %Email::MIME::Header::header_to_class_map
---
 lib/Email/MIME.pm        | 4 +++-
 lib/Email/MIME/Header.pm | 8 ++++++++
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/lib/Email/MIME.pm b/lib/Email/MIME.pm
index e206fe8..cf50e1d 100644
--- a/lib/Email/MIME.pm
+++ b/lib/Email/MIME.pm
@@ -908,7 +908,9 @@ This method returns an object representation of the header value.  It instances
 new object via method C<from_mime_string> of specified class.  Input argument
 for that class method is list of the raw MIME-encoded values.  If class argument
 is not specified then class name is taken from the hash
-C<%Email::MIME::Header::header_to_class_map> via key field.
+C<%Email::MIME::Header::header_to_class_map> via key field.  Use function
+C<Email::MIME::Header::set_class_for_header($class, $field)> for adding new
+mapping.
 
 =method parts
 
diff --git a/lib/Email/MIME/Header.pm b/lib/Email/MIME/Header.pm
index 3aa09b2..4cfbec5 100644
--- a/lib/Email/MIME/Header.pm
+++ b/lib/Email/MIME/Header.pm
@@ -106,4 +106,12 @@ sub _maybe_decode {
   return;
 }
 
+sub set_class_for_header {
+  my ($class, $header) = @_;
+  $header = lc $header;
+  Carp::croak("Class for header '$header' is already set") if defined $header_to_class_map{$header};
+  $header_to_class_map{$header} = $class;
+  return;
+}
+
 1;