Separate the codebase for XL and FS format.json related code (#5317)

cmd/format-meta.go

@@ -0,0 +1,52 @@
+/*
+ * Minio Cloud Storage, (C) 2017 Minio, Inc.
+ *
+ * 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 cmd
+
+// Format related consts
+const (
+	// Format config file carries backend format specific details.
+	formatConfigFile = "format.json"
+
+	// Format config tmp file carries backend format.
+	formatConfigFileTmp = "format.json.tmp"
+)
+
+const (
+	// Version of the formatMetaV1
+	formatMetaVersionV1 = "1"
+)
+
+// format.json currently has the format:
+// {
+//   "version": "1",
+//   "format": "XXXXX",
+//   "XXXXX": {
+//
+//   }
+// }
+// Here "XXXXX" depends on the backend, currently we have "fs" and "xl" implementations.
+// formatMetaV1 should be inherited by backend format structs. Please look at format-fs.go
+// and format-xl.go for details.
+
+// Ideally we will never have a situation where we will have to change the
+// fields of this struct and deal with related migration.
+type formatMetaV1 struct {
+	// Version of the format config.
+	Version string `json:"version"`
+	// Format indicates the backend format type, supports two values 'xl' and 'fs'.
+	Format string `json:"format"`
+}