Google Api

Yavsc/GoogleApiSupport/Google.Apis/Util/Store/NullDataStore.cs

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+/*
+Copyright 2017 Google 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.
+*/
+
+using System.Threading.Tasks;
+
+namespace Google.Apis.Util.Store
+{
+    /// <summary>
+    /// A null datastore. Nothing is stored, nothing is retrievable.
+    /// </summary>
+    public class NullDataStore : IDataStore
+    {
+        private static readonly Task s_completedTask = CompletedTask<int>();
+
+        private static Task<T> CompletedTask<T>()
+        {
+            var tcs = new TaskCompletionSource<T>();
+            tcs.SetResult(default(T));
+            return tcs.Task;
+        }
+
+        /// <summary>
+        /// Construct a new null datastore, that stores nothing.
+        /// </summary>
+        public NullDataStore()
+        {
+        }
+
+        /// <inheritdoc/>
+        public Task ClearAsync() => s_completedTask;
+
+        /// <inheritdoc/>
+        public Task DeleteAsync<T>(string key) => s_completedTask;
+
+        /// <summary>
+        /// Asynchronously returns the stored value for the given key or <c>null</c> if not found.
+        /// This implementation of <see cref="IDataStore"/> will always return a completed task
+        /// with a result of <c>null</c>. 
+        /// </summary>
+        /// <typeparam name="T">The type to retrieve from the data store.</typeparam>
+        /// <param name="key">The key to retrieve its value.</param>
+        /// <returns>Always <c>null</c>.</returns>
+        public Task<T> GetAsync<T>(string key) => CompletedTask<T>();
+
+        /// <summary>
+        /// Asynchronously stores the given value for the given key (replacing any existing value).
+        /// This implementation of <see cref="IDataStore"/> does not store the value,
+        /// and will not return it in future calls to <see cref="GetAsync{T}(string)"/>. 
+        /// </summary>
+        /// <typeparam name="T">The type to store in the data store.</typeparam>
+        /// <param name="key">The key.</param>
+        /// <param name="value">The value.</param>
+        /// <returns>A task that completes immediately.</returns>
+        public Task StoreAsync<T>(string key, T value) => s_completedTask;
+    }
+}