You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: properties.go
    path of file: ./repos/learning/golang/practice/go-crontab/gopath/src/github.com/coreos/etcd/vendor/github.com/golang/protobuf/proto
    
    the code of the file until where you have to start completion: // Go support for Protocol Buffers - Google's data interchange format
//
// Copyright 2010 The Go Authors.  All rights reserved.
// https://github.com/golang/protobuf
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
//     * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
//     * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIB
    
func (p *Properties) Parse(s string) {
	// "bytes,49,opt,name=foo,def=hello!"
	fields := strings.Split(s, ",") // breaks def=, but handled below.
	if len(fields) < 2 {
		fmt.Fprintf(os.Stderr, "proto: tag has too few fields: %q\n", s)
		return
	}

	p.Wire = fields[0]
	switch p.Wire {
	case "varint":
		p.WireType = WireVarint
	case "fixed32":
		p.WireType = WireFixed32
	case "fixed64":
		p.WireType = WireFixed64
	case "zigzag32":
		p.WireType = WireVarint
	case "zigzag64":
		p.WireType = WireVarint
	case "bytes", "group":
		p.WireType = WireBytes
		// no numeric converter for non-numeric types
	default:
		fmt.Fprintf(os.Stderr, "proto: tag has unknown wire type: %q\n", s)
		return
	}

	var err error
	p.Tag, err = strconv.Atoi(fields[1])
	if err != nil {
		return
	}

outer:
	for i := 2; i < len(fields); i++ {
		f := fields[i]
		switch {
		case f == "req":
			p.Required = true
		case f == "opt":
			p.Optional = true
		case f == "rep":
			p.Repeated = true
		case f == "packed":
			p.Packed = true
		case strings.HasPrefix(f, "name="):
			p.OrigName = f[5:]
		case strings.HasPrefix(f, "json="):
			p.JSONName = f[5:]
		case strings.HasPrefix(f, "enum="):
			p.Enum = f[5:]
		case f == "proto3":
			p.proto3 = true
		case f == "oneof":
			p.oneof = true
		case strings.HasPrefix(f, "def="):
			p.HasDefault = true
			p.Default = f[4:] // rest of string
			if i+1 < len(fields) {
				// Commas aren't escaped, and def is always last.
				p.Default += "," + strings.Join(fields[i+1:], ",")
				break outer
			}
		}
	}
}