metadata: introduce protobuf structures

This commit adds in the metadata package. The primary purpose of this
package is to provide the on-disk metadata structures in the form of
protocol buffers. This includes:
	- Policy metadata structure
	- Protector metadata structure
	- Config file structure
	- All necessary sub-structures (wrapped keys, parameters, etc)

This commit also adds in an example usage of the Config structure, which
represents the structure of the global config file. All the package
does at this point is convert between the Config structure and a JSON
representation.

Here we introduce govendor, which is described more in the README. This
means we will have all of our Go dependencies in the vendor
subdirectory. This means we will have no Go source dependencies, only
dependencies on the build tools (Go and govendor). The README describes
this in detail.

Note that we commit the generated files.
  see: https://blog.golang.org/generate

Change-Id: Iaacd46666b5d3e4e865a0f4045dd63ed7e3d6f96

1 files changed, 45 insertions, 0 deletions

diff --git a/metadata/config.go b/metadata/config.go
new file mode 100644
index 0000000..1d73755
--- /dev/null
+++ b/metadata/config.go
@@ -0,0 +1,45 @@
+/*
+ * config.go - Parsing for our global config file. The file is simply the JSON
+ * output of the Config protocol buffer.
+ *
+ * Copyright 2017 Google Inc.
+ * Author: Joe Richey (joerichey@google.com)
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+
+// Package metadata contains all of the on disk structures.
+// These structures are definied in meatadata.proto. The package also
+// contains functions for reading and writing the Config file to disk
+// giving us a config file.
+package metadata
+
+//go:generate protoc --go_out=. metadata.proto
+import "github.com/golang/protobuf/jsonpb"
+
+// WriteConfig outputs the Config data as nicely formatted JSON
+func WriteConfig(config *Config) (string, error) {
+	m := jsonpb.Marshaler{
+		EmitDefaults: false,
+		EnumsAsInts:  false,
+		Indent:       "\t",
+		OrigName:     true,
+	}
+	return m.MarshalToString(config)
+}
+
+// ReadConfig writes the JSON data into the config structure
+func ReadConfig(input string) (*Config, error) {
+	config := new(Config)
+	return config, jsonpb.UnmarshalString(input, config)
+}