New function parse_host_mac_ip_list().

This adds a function for parsing a simple line-based file format for
specifying MAC and IP addresses for hosts, returning a data structure
suitable for the networking::hostsfile::hostentries definition.

lib/puppet/parser/functions/parse_host_mac_ip_list.rb

+# Copyright (C) 2020 Thomas Bellman.
+# Licensed under the GNU LGPL v3+; see the README file for more information.
+
+
+module Puppet::Parser::Functions
+    newfunction(:parse_host_mac_ip_list, :type => :rvalue, :doc => '
+	Parse lines of hostnames, MAC addresses and IP addresses.
+
+	This function parses lines containing hostname, MAC address, and IP
+	address(es), returning a hash mapping from hostname to a records
+	(in the form of hashes) with the MAC and IP addresses.	The single
+	parameter is a string, or (nested) list of strings, containing
+	lines.	Each line should be on the format
+
+	    NAME	MACADDR		[IPADDR ...]
+
+	i.e, a name, a MAC address, and zero, one or more IP addresses, all
+	separated by horizontal whitespace.
+
+	The return value is a hash with the host names as keys, and the
+	value for each host being a hash with two items, "ip" and "mac".
+	Each of those will be a list of strings.  The special value "-" (a
+	single dash and nothing else) in the MAC address column means there
+	is no MAC address, and the "mac" element will be the empty list.
+
+	Blank lines are ignored.  Lines starting with a hash sign ("#") are
+	comments, and are also skipped
+
+	The intent is to have simple text files with one line per host,
+	that can be used as source for generating HOSTS.TXT (/etc/hosts)
+	files and DHCP configuration files.  This function parses such
+	files into a data structure that is easy to use in ERB templates
+	generating such files.
+
+	Example input:
+
+	    # A simple comment line
+	    foo		012345-6789ab	192.0.2.6
+	    fie		-		192.0.2.7  2001:db8:1::7
+	    fum		cdef-0123-4567
+
+	This will be parsed into the hash
+
+	    {
+		"foo" => {
+			"mac" => [ "012345-6789ab" ],
+			"ip"  => [ "192.0.2.6" ],
+		},
+		"fie" => {
+			"mac" => [ ],
+			"ip"  => [ "192.0.2.7", "2001:db8:1::7" ],
+		},
+		"fum" => {
+			"mac" => [ "cdef-0123-4567" ],
+			"ip"  => [ ],
+		},
+	    }
+
+	Hostnames, MAC addresses and IP addresses in the input are not
+	validated for correctness.  Multiple lines using the same hostname
+	are not permitted.
+    ') \
+    do |args|
+	if args.length != 1
+	    raise(Puppet::ParseError,
+		  "parse_host_mac_ip_list(): Wrong number of arguments")
+	end
+	lines = [args[0]].flatten.join("\n").split("\n")
+	# Skip blank lines and comments
+	lines = lines.select {|l|
+	    l = l.strip
+	    l != "" and l[0] != "#"
+	}
+
+	hosts = { }
+	lines.each do |l|
+	    hostname,macs,*ips = l.split()
+	    macs = (macs == "-") ? [] : [macs]
+	    if hosts.has_key?(hostname)
+		raise(Puppet::ParseError,
+		      "parse_host_mac_ip_list(): Duplicate host name, `#{hostname}'")
+	    end
+	    hosts[hostname] = { 'ip' => ips, 'mac' => [macs].flatten }
+	end
+	return hosts
+    end
+end