Implements #64 by using Crockford Base32 to encode DOI suffix on 3_4 branch

cfg.d/z_datacitedoi.pl

@@ -134,6 +134,23 @@
 #Only useful for testing from "wrong" domain (eg an unregistered test server) should be undef for normal operation
 $c->{datacitedoi}{override_url} = undef;
 
+
+##########################################
+### Format of DOI to be generated      ###
+##########################################
+# A custom method can be defined to generate a DOI to your own spec. This could be a sub, or point
+# to an existing method in the Utils module, such as 'Cool DOIs' using Crockford Base32
+# (see https://datacite.org/blog/cool-dois/). NB the module Encode::Base32::Crockford must be installed
+# generate this style of DOI
+#$c->{datacitedoi}{generate_doi_override} = \&EPrints::DataCite::Utils::generate_doi_base32_crockford;
+# -or -
+#$c->{datacitedoi}{generate_doi_override} = sub
+#{
+#	my( $repo, $dataobj ) = @_;
+#	... generate the full DOI (including the prefix). See Utils.pm for inspiration.
+#	return $thisdoi;
+#}
+
 ##########################
 ##### When to coin ? #####
 ##########################

plugins/EPrints/DataCite/Utils.pm

@@ -6,20 +6,15 @@ use Encode;
 
 use strict;
 
-sub generate_doi
+sub generate_default_doi
 {
     my( $repository, $dataobj ) = @_;
 
-    if( $repository->can_call( "generate_doi_override" ) )
-    {
-        return $repository->call( "generate_doi_override", $repository, $dataobj );
-    }
-
     my $z_pad = $repository->get_conf( "datacitedoi", "zero_padding") || 0;
 
     my $id = $dataobj->id;
     $id  = sprintf( "%0" . $z_pad . "d" , $id );
-   
+
     if( $dataobj->get_dataset_id eq "document" )
     {
         my $eprintid = $dataobj->get_eprint->id;
@@ -38,8 +33,21 @@ sub generate_doi
     # construct the DOI string
     my $prefix = $repository->get_conf( "datacitedoi", "prefix" );
     my $thisdoi = $prefix.$delim1.$repository->get_conf( "datacitedoi", "repoid" ).$delim2.$id;
-
-    return $thisdoi;    
+
+    return $thisdoi;
+
+}
+
+sub generate_doi
+{
+    my( $repository, $dataobj ) = @_;
+
+    if( $repository->can_call( "datacitedoi", "generate_doi_override" ) )
+    {
+        return $repository->call( [ "datacitedoi", "generate_doi_override" ], $repository, $dataobj );
+    }
+
+    return generate_default_doi( $repository, $dataobj );
 }
 
 # reserve a doi, a.k.a create draft doi
@@ -290,4 +298,41 @@ sub create_related_identifier
     }
 }
 
+sub generate_doi_base32_crockford
+{
+	my( $repository, $dataobj ) = @_;
+
+	use Digest::MD5;
+	eval "use Encode::Base32::Crockford";
+	if($@) 
+	{
+		print STDERR "Unable to import Encode::Base32::Crockford\n";
+		return;
+	}
+
+	my( $delim1, $delim2 ) = @{$repository->get_conf( "datacitedoi", "delimiters" )};
+
+	# Get default DOI
+	my $thisdoi = generate_default_doi( $repository, $dataobj );
+
+	# Split to get out suffix and prefix
+	my ( $doi_prefix, $doi_suffix ) = split( $delim1, $thisdoi, 2 );
+
+	# Get first 15 hex chars of the MD5 digest of the original suffix (16 chars could cause integer overflow).
+	my $md5_hex = substr( Digest::MD5::md5_hex( $doi_suffix ), 0, 15 );
+
+	# Convert hex chars in decimal number and encode using Crockford Base32 and then lowercase the output for greater readability.
+	# Suppress "Hexadecimal number > 0xffffffff non-portable" warning
+	no warnings 'portable';
+	$doi_suffix = lc( Encode::Base32::Crockford::base32_encode(  hex( "0x". $md5_hex ) ) );
+
+	# Insert hyphen every 4 characters (last block may have 1,2 or 3 characters e.g. xxxx-xxxx-x)
+	$doi_suffix =~ s/(.{4})(?!$)/$1-/g;
+
+	# Put DOI back together gain
+	$thisdoi = $doi_prefix . $delim1 . $doi_suffix;
+
+	return $thisdoi;
+}
+
 1;