fix: Handle array segments correctly

Fixes #209

Signed-off-by: Jon Skeet <[email protected]>

Author: jskeet

src/CloudNative.CloudEvents/Core/BinaryDataUtilities.cs

@@ -106,7 +106,9 @@ public static async Task CopyToStreamAsync(ReadOnlyMemory<byte> source, Stream d
         public static byte[] AsArray(ReadOnlyMemory<byte> memory)
         {
             var segment = GetArraySegment(memory);
-            return segment.Offset == 0 || segment.Count == memory.Length
+            // We probably don't actually need to check the offset: if the count is the same as the length,
+            // I can't see how the offset can be non-zero. But it doesn't *hurt* as a check.
+            return segment.Offset == 0 && segment.Count == segment.Array.Length
                 ? segment.Array
                 : memory.ToArray();
         }

test/CloudNative.CloudEvents.UnitTests/Core/BinaryDataUtilitiesTest.cs

@@ -0,0 +1,33 @@
+// Copyright 2022 Cloud Native Foundation. 
+// Licensed under the Apache 2.0 license.
+// See LICENSE file in the project root for full license information.
+
+using System;
+using System.Linq;
+using Xunit;
+
+namespace CloudNative.CloudEvents.Core.UnitTests
+{
+    public class BinaryDataUtilitiesTest
+    {
+        [Fact]
+        public void AsArray_ReturningOriginal()
+        {
+            byte[] original = { 1, 2, 3, 4, 5 };
+            var segment = new ArraySegment<byte>(original);
+            Assert.Same(original, BinaryDataUtilities.AsArray(segment));
+        }
+
+        [Theory]
+        [InlineData(0)]
+        [InlineData(1)]
+        public void AsArray_FromPartialSegment(int offset)
+        {
+            byte[] original = { 1, 2, 3, 4, 5 };
+            var segment = new ArraySegment<byte>(original, offset, 4);
+            var actual = BinaryDataUtilities.AsArray(segment);
+            Assert.True(actual.SequenceEqual(segment));
+            Assert.NotSame(original, actual);
+        }
+    }
+}