--- /dev/null
+#
+# is_domain_name.rb
+#
+
+module Puppet::Parser::Functions
+ newfunction(:is_domain_name, :type => :rvalue, :doc => <<-EOS
+Returns true if the string passed to this function is a syntactically correct domain name.
+ EOS
+ ) do |arguments|
+
+ if (arguments.size != 1) then
+ raise(Puppet::ParseError, "is_domain_name(): Wrong number of arguments "+
+ "given #{arguments.size} for 1")
+ end
+
+ # Only allow string types
+ return false unless arguments[0].is_a?(String)
+
+ domain = arguments[0].dup
+
+ # Limits (rfc1035, 3.1)
+ domain_max_length=255
+ label_min_length=1
+ label_max_length=63
+
+ # Allow ".", it is the top level domain
+ return true if domain == '.'
+
+ # Remove the final dot, if present.
+ domain.chomp!('.')
+
+ # Check the whole domain
+ return false if domain.empty?
+ return false if domain.length > domain_max_length
+
+ # The top level domain must be alphabetic if there are multiple labels.
+ # See rfc1123, 2.1
+ return false if domain.include? '.' and not /\.[A-Za-z]+$/.match(domain)
+
+ # Check each label in the domain
+ labels = domain.split('.')
+ vlabels = labels.each do |label|
+ break if label.length < label_min_length
+ break if label.length > label_max_length
+ break if label[-1..-1] == '-'
+ break if label[0..0] == '-'
+ break unless /^[a-z\d-]+$/i.match(label)
+ end
+ return vlabels == labels
+
+ end
+end
+
+# vim: set ts=2 sw=2 et :