Initial checkin of gRPC to third_party/

third_party/grpc/src/csharp/Grpc.Core/ContextPropagationToken.cs

Index: third_party/grpc/src/csharp/Grpc.Core/ContextPropagationToken.cs
diff --git a/third_party/grpc/src/csharp/Grpc.Core/ContextPropagationToken.cs b/third_party/grpc/src/csharp/Grpc.Core/ContextPropagationToken.cs
new file mode 100644
index 0000000000000000000000000000000000000000..c0f638f837d18f67946769f59af829e5da698ab0
--- /dev/null
+++ b/third_party/grpc/src/csharp/Grpc.Core/ContextPropagationToken.cs
@@ -0,0 +1,170 @@
+#region Copyright notice and license
+
+// Copyright 2015-2016, Google Inc.
+// All rights reserved.
+//
+// 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 CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#endregion
+
+using System;
+using System.Threading;
+
+using Grpc.Core.Internal;
+using Grpc.Core.Utils;
+
+namespace Grpc.Core
+{
+    /// <summary>
+    /// Token for propagating context of server side handlers to child calls.
+    /// In situations when a backend is making calls to another backend,
+    /// it makes sense to propagate properties like deadline and cancellation 
+    /// token of the server call to the child call.
+    /// The gRPC native layer provides some other contexts (like tracing context) that
+    /// are not accessible to explicitly C# layer, but this token still allows propagating them.
+    /// </summary>
+    public class ContextPropagationToken
+    {
+        /// <summary>
+        /// Default propagation mask used by C core.
+        /// </summary>
+        private const ContextPropagationFlags DefaultCoreMask = (ContextPropagationFlags)0xffff;
+
+        /// <summary>
+        /// Default propagation mask used by C# - we want to propagate deadline 
+        /// and cancellation token by our own means.
+        /// </summary>
+        internal const ContextPropagationFlags DefaultMask = DefaultCoreMask
+            & ~ContextPropagationFlags.Deadline & ~ContextPropagationFlags.Cancellation;
+
+        readonly CallSafeHandle parentCall;
+        readonly DateTime deadline;
+        readonly CancellationToken cancellationToken;
+        readonly ContextPropagationOptions options;
+
+        internal ContextPropagationToken(CallSafeHandle parentCall, DateTime deadline, CancellationToken cancellationToken, ContextPropagationOptions options)
+        {
+            this.parentCall = GrpcPreconditions.CheckNotNull(parentCall);
+            this.deadline = deadline;
+            this.cancellationToken = cancellationToken;
+            this.options = options ?? ContextPropagationOptions.Default;
+        }
+
+        /// <summary>
+        /// Gets the native handle of the parent call.
+        /// </summary>
+        internal CallSafeHandle ParentCall
+        {
+            get
+            {
+                return this.parentCall;
+            }
+        }
+
+        /// <summary>
+        /// Gets the parent call's deadline.
+        /// </summary>
+        internal DateTime ParentDeadline
+        {
+            get
+            {
+                return this.deadline;
+            }
+        }
+
+        /// <summary>
+        /// Gets the parent call's cancellation token.
+        /// </summary>
+        internal CancellationToken ParentCancellationToken
+        {
+            get
+            {
+                return this.cancellationToken;
+            }
+        }
+
+        /// <summary>
+        /// Get the context propagation options.
+        /// </summary>
+        internal ContextPropagationOptions Options
+        {
+            get
+            {
+                return this.options;
+            }
+        }
+    }
+
+    /// <summary>
+    /// Options for <see cref="ContextPropagationToken"/>.
+    /// </summary>
+    public class ContextPropagationOptions
+    {
+        /// <summary>
+        /// The context propagation options that will be used by default.
+        /// </summary>
+        public static readonly ContextPropagationOptions Default = new ContextPropagationOptions();
+
+        bool propagateDeadline;
+        bool propagateCancellation;
+
+        /// <summary>
+        /// Creates new context propagation options.
+        /// </summary>
+        /// <param name="propagateDeadline">If set to <c>true</c> parent call's deadline will be propagated to the child call.</param>
+        /// <param name="propagateCancellation">If set to <c>true</c> parent call's cancellation token will be propagated to the child call.</param>
+        public ContextPropagationOptions(bool propagateDeadline = true, bool propagateCancellation = true)
+        {
+            this.propagateDeadline = propagateDeadline;
+            this.propagateCancellation = propagateCancellation;
+        }
+            
+        /// <summary><c>true</c> if parent call's deadline should be propagated to the child call.</summary>
+        public bool IsPropagateDeadline
+        {
+            get { return this.propagateDeadline; }
+        }
+
+        /// <summary><c>true</c> if parent call's cancellation token should be propagated to the child call.</summary>
+        public bool IsPropagateCancellation
+        {
+            get { return this.propagateCancellation; }
+        }
+    }
+
+    /// <summary>
+    /// Context propagation flags from grpc/grpc.h.
+    /// </summary>
+    [Flags]
+    internal enum ContextPropagationFlags
+    {
+        Deadline = 1,
+        CensusStatsContext = 2,
+        CensusTracingContext = 4,
+        Cancellation = 8
+    }
+}