IndexedStructure

Libraries/Esiur/Data/IndexAttribute.cs

@@ -0,0 +1,29 @@
+using System;
+
+namespace Esiur.Data;
+
+/// <summary>
+/// Assigns a stable wire index to a field or property of a <see cref="IndexedStructure"/>.
+/// </summary>
+[AttributeUsage(AttributeTargets.Property | AttributeTargets.Field,
+                AllowMultiple = false, Inherited = true)]
+public sealed class IndexAttribute : Attribute
+{
+    /// <summary>
+    /// Gets or sets the byte-sized index used on the wire.
+    /// </summary>
+    public byte Index { get; set; }
+
+    public IndexAttribute()
+    {
+    }
+
+    public IndexAttribute(int index)
+    {
+        if (index < byte.MinValue || index > byte.MaxValue)
+            throw new ArgumentOutOfRangeException(nameof(index),
+                "A structure index must be between 0 and 255.");
+
+        Index = (byte)index;
+    }
+}