Imported Upstream version 4.3.2.467

Former-commit-id: 9c2cb47f45fa221e661ab616387c9cda183f283d

mcs/class/System.Threading.Tasks.Dataflow/CoreFxSources/Base/DataflowMessageHeader.cs

@@ -0,0 +1,92 @@
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+// =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+//
+// DataflowMessageHeader.cs
+//
+//
+// A container of data attributes passed between dataflow blocks.
+//
+// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
+
+using System.Diagnostics;
+using System.Diagnostics.Contracts;
+using System.Threading.Tasks.Dataflow.Internal;
+
+namespace System.Threading.Tasks.Dataflow
+{
+    /// <summary>Provides a container of data attributes for passing between dataflow blocks.</summary>
+    [DebuggerDisplay("Id = {Id}")]
+    public struct DataflowMessageHeader : IEquatable<DataflowMessageHeader>
+    {
+        /// <summary>The message ID. Needs to be unique within the source.</summary>
+        private readonly long _id;
+
+        /// <summary>Initializes the <see cref="DataflowMessageHeader"/> with the specified attributes.</summary>
+        /// <param name="id">The ID of the message. Must be unique within the originating source block. Need not be globally unique.</param>
+        public DataflowMessageHeader(Int64 id)
+        {
+            if (id == default(long)) throw new ArgumentException(SR.Argument_InvalidMessageId, "id");
+            Contract.EndContractBlock();
+
+            _id = id;
+        }
+
+        /// <summary>Gets the validity of the message.</summary>
+        /// <returns>True if the ID of the message is different from 0. False if the ID of the message is 0</returns>
+        public Boolean IsValid { get { return _id != default(long); } }
+
+        /// <summary>Gets the ID of the message within the source.</summary>
+        /// <returns>The ID contained in the <see cref="DataflowMessageHeader"/> instance.</returns>
+        public Int64 Id { get { return _id; } }
+
+        // These overrides are required by the FX API Guidelines.
+        // NOTE: When these overrides are present, the compiler doesn't complain about statements 
+        // like 'if (struct == null) ...' which will result in incorrect behavior at runtime.
+        // The product code should not use them. Instead, it should compare the Id properties.
+        // To verify that, every once in a while, comment out this region and build the product. 
+        #region Comparison Operators
+        /// <summary>Checks two <see cref="DataflowMessageHeader"/> instances for equality by ID without boxing.</summary>
+        /// <param name="other">Another <see cref="DataflowMessageHeader"/> instance.</param>
+        /// <returns>True if the instances are equal. False otherwise.</returns>
+        public bool Equals(DataflowMessageHeader other)
+        {
+            return this == other;
+        }
+
+        /// <summary>Checks boxed <see cref="DataflowMessageHeader"/> instances for equality by ID.</summary>
+        /// <param name="obj">A boxed <see cref="DataflowMessageHeader"/> instance.</param>
+        /// <returns>True if the instances are equal. False otherwise.</returns>
+        public override bool Equals(object obj)
+        {
+            return obj is DataflowMessageHeader && this == (DataflowMessageHeader)obj;
+        }
+
+        /// <summary>Generates a hash code for the <see cref="DataflowMessageHeader"/> instance.</summary>
+        /// <returns>Hash code.</returns>
+        public override int GetHashCode()
+        {
+            return (int)Id;
+        }
+
+        /// <summary>Checks two <see cref="DataflowMessageHeader"/> instances for equality by ID.</summary>
+        /// <param name="left">A <see cref="DataflowMessageHeader"/> instance.</param>
+        /// <param name="right">A <see cref="DataflowMessageHeader"/> instance.</param>
+        /// <returns>True if the instances are equal. False otherwise.</returns>
+        public static bool operator ==(DataflowMessageHeader left, DataflowMessageHeader right)
+        {
+            return left.Id == right.Id;
+        }
+
+        /// <summary>Checks two <see cref="DataflowMessageHeader"/> instances for non-equality by ID.</summary>
+        /// <param name="left">A <see cref="DataflowMessageHeader"/> instance.</param>
+        /// <param name="right">A <see cref="DataflowMessageHeader"/> instance.</param>
+        /// <returns>True if the instances are not equal. False otherwise.</returns>
+        public static bool operator !=(DataflowMessageHeader left, DataflowMessageHeader right)
+        {
+            return left.Id != right.Id;
+        }
+        #endregion
+    }
+}