Refactor storage class well-know values. (#929)

I will need the well-known values separated from the
BucketMetadata. Part of the changes for #537.

Author: coryan

google/cloud/storage/CMakeLists.txt

@@ -183,6 +183,7 @@ add_library(storage_client
             well_known_parameters.h
             retry_policy.h
             status.h
+            storage_class.h
             version.h
             version.cc)
 target_link_libraries(storage_client
@@ -260,6 +261,7 @@ set(storage_client_unit_tests
     object_metadata_test.cc
     object_test.cc
     retry_policy_test.cc
+    storage_class_test.cc
     storage_client_options_test.cc
     link_test.cc)
 

google/cloud/storage/bucket_metadata.cc

@@ -214,12 +214,6 @@ std::ostream& operator<<(std::ostream& os, BucketMetadata const& rhs) {
   return os;
 }
 
-constexpr char BucketMetadata::STORAGE_CLASS_STANDARD[];
-constexpr char BucketMetadata::STORAGE_CLASS_MULTI_REGIONAL[];
-constexpr char BucketMetadata::STORAGE_CLASS_REGIONAL[];
-constexpr char BucketMetadata::STORAGE_CLASS_NEARLINE[];
-constexpr char BucketMetadata::STORAGE_CLASS_COLDLINE[];
-constexpr char BucketMetadata::STORAGE_CLASS_DURABLE_REDUCED_AVAILABILITY[];
 }  // namespace STORAGE_CLIENT_NS
 }  // namespace storage
 }  // namespace cloud

google/cloud/storage/bucket_metadata.h

@@ -393,14 +393,6 @@ class BucketMetadata : private internal::CommonMetadata<BucketMetadata> {
   bool operator==(BucketMetadata const& rhs) const;
   bool operator!=(BucketMetadata const& rhs) const { return not(*this == rhs); }
 
-  constexpr static char STORAGE_CLASS_STANDARD[] = "STANDARD";
-  constexpr static char STORAGE_CLASS_MULTI_REGIONAL[] = "MULTI_REGIONAL";
-  constexpr static char STORAGE_CLASS_REGIONAL[] = "REGIONAL";
-  constexpr static char STORAGE_CLASS_NEARLINE[] = "NEARLINE";
-  constexpr static char STORAGE_CLASS_COLDLINE[] = "COLDLINE";
-  constexpr static char STORAGE_CLASS_DURABLE_REDUCED_AVAILABILITY[] =
-      "DURABLE_REDUCED_AVAILABILITY";
-
  private:
   friend std::ostream& operator<<(std::ostream& os, BucketMetadata const& rhs);
   // Keep the fields in alphabetical order.

google/cloud/storage/bucket_metadata_test.cc

@@ -13,6 +13,7 @@
 // limitations under the License.
 
 #include "google/cloud/storage/bucket_metadata.h"
+#include "google/cloud/storage/storage_class.h"
 #include <gmock/gmock.h>
 
 namespace google {
@@ -174,7 +175,7 @@ TEST(BucketMetadataTest, Parse) {
   EXPECT_EQ(123456789, actual.project_number());
   EXPECT_EQ("https://www.googleapis.com/storage/v1/b/test-bucket",
             actual.self_link());
-  EXPECT_EQ(BucketMetadata::STORAGE_CLASS_STANDARD, actual.storage_class());
+  EXPECT_EQ(storage_class::Standard(), actual.storage_class());
   // Use `date -u +%s --date='2018-05-19T19:31:14Z'` to get the magic number:
   auto magic_timestamp = 1526758274L;
   using std::chrono::duration_cast;

google/cloud/storage/storage_class.h

@@ -0,0 +1,67 @@
+// Copyright 2018 Google LLC
+//
+// 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.
+
+#ifndef GOOGLE_CLOUD_CPP_GOOGLE_CLOUD_STORAGE_STORAGE_CLASS_H_
+#define GOOGLE_CLOUD_CPP_GOOGLE_CLOUD_STORAGE_STORAGE_CLASS_H_
+
+#include "google/cloud/storage/version.h"
+
+namespace google {
+namespace cloud {
+namespace storage {
+inline namespace STORAGE_CLIENT_NS {
+/**
+ * Define functions with the well-know storage classes.
+ *
+ * These functions are provided to avoid typos when setting or comparing storage
+ * classes.
+ */
+namespace storage_class {
+char const* Standard() {
+  static constexpr char kStorageClass[] = "STANDARD";
+  return kStorageClass;
+}
+
+char const* MultiRegional() {
+  static constexpr char kStorageClass[] = "MULTI_REGIONAL";
+  return kStorageClass;
+}
+
+char const* Regional() {
+  static constexpr char kStorageClass[] = "REGIONAL";
+  return kStorageClass;
+}
+
+char const* Nearline() {
+  static constexpr char kStorageClass[] = "NEARLINE";
+  return kStorageClass;
+}
+
+char const* Coldline() {
+  static constexpr char kStorageClass[] = "COLDLINE";
+  return kStorageClass;
+}
+
+char const* DurableReducedAvailability() {
+  static constexpr char kStorageClass[] = "DURABLE_REDUCED_AVAILABILITY";
+  return kStorageClass;
+}
+
+}  // namespace storage_class
+}  // namespace STORAGE_CLIENT_NS
+}  // namespace storage
+}  // namespace cloud
+}  // namespace google
+
+#endif  // GOOGLE_CLOUD_CPP_GOOGLE_CLOUD_STORAGE_STORAGE_CLASS_H_

google/cloud/storage/storage_class_test.cc

@@ -0,0 +1,41 @@
+// Copyright 2018 Google LLC
+//
+// 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.
+
+#include "google/cloud/storage/storage_class.h"
+#include <gmock/gmock.h>
+
+namespace google {
+namespace cloud {
+namespace storage {
+inline namespace STORAGE_CLIENT_NS {
+namespace storage_class {
+namespace {
+
+/// @test Verify the values for the storage class functions.
+TEST(StorageClassTest, Values) {
+  EXPECT_EQ(std::string("STANDARD"), Standard());
+  EXPECT_EQ(std::string("MULTI_REGIONAL"), MultiRegional());
+  EXPECT_EQ(std::string("REGIONAL"), Regional());
+  EXPECT_EQ(std::string("NEARLINE"), Nearline());
+  EXPECT_EQ(std::string("COLDLINE"), Coldline());
+  EXPECT_EQ(std::string("DURABLE_REDUCED_AVAILABILITY"),
+            DurableReducedAvailability());
+}
+
+}  // namespace
+}  // namespace storage_class
+}  // namespace STORAGE_CLIENT_NS
+}  // namespace storage
+}  // namespace cloud
+}  // namespace google

google/cloud/storage/storage_client.bzl

@@ -51,6 +51,7 @@ storage_client_HDRS = [
     "well_known_parameters.h",
     "retry_policy.h",
     "status.h",
+    "storage_class.h",
     "version.h",
 ]
 

google/cloud/storage/storage_client_unit_tests.bzl

@@ -33,6 +33,7 @@ storage_client_unit_tests = [
     "object_metadata_test.cc",
     "object_test.cc",
     "retry_policy_test.cc",
+    "storage_class_test.cc",
     "storage_client_options_test.cc",
     "link_test.cc",
 ]