Issue 122 streaming operation

MetadataExtractor.Tests/IO/StreamingIndexedCapturingReaderTest.cs

@@ -0,0 +1,107 @@
+#region License
+//
+// Copyright 2002-2017 Drew Noakes
+// Ported from Java to C# by Yakov Danilov for Imazen LLC in 2014
+//
+//    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.
+//
+// More information about this project is available at:
+//
+//    https://github.com/drewnoakes/metadata-extractor-dotnet
+//    https://drewnoakes.com/code/exif/
+//
+#endregion
+
+using System;
+using System.IO;
+using MetadataExtractor.IO;
+using Xunit;
+
+namespace MetadataExtractor.Tests.IO
+{
+    /// <summary>
+    /// Wrapper for MemoryStream that allows us to configure whether it is
+    /// seekable, and whether or not the Length property is supported.
+    /// </summary>
+    public class ConfigurableMemoryStream : MemoryStream
+    {
+        private bool _seekable;
+        private bool _lengthSupported;
+
+        public ConfigurableMemoryStream(byte[] buffer, bool seekable, bool lengthSupported) : base(buffer)
+        {
+            _seekable = seekable;
+            _lengthSupported = lengthSupported;
+        }
+
+        public override long Length
+        {
+            get
+            {
+                if (_lengthSupported)
+                {
+                    return base.Length;
+                }
+                else
+                {
+                    throw new NotSupportedException("Length property was disabled");
+                }
+            }
+        }
+
+        public override bool CanSeek => _seekable;
+    }
+
+    /// <summary>Unit tests for <see cref="IndexedCapturingReader"/>.</summary>
+    /// <author>Drew Noakes https://drewnoakes.com</author>
+    public abstract class StreamingIndexedCapturingReaderTestBase : IndexedReaderTestBase
+    {
+        [Fact]
+        public void ConstructWithNullBufferThrows()
+        {
+            // ReSharper disable once AssignNullToNotNullAttribute
+            Assert.Throws<ArgumentNullException>(() => new IndexedCapturingReader(null));
+        }
+    }
+
+    // Since the normal IndexedCapturingReaderTest uses MemoryStream, which both
+    // supports the Length property and is seekable, the following classes test
+    // the remaining permutations of options:
+    // 
+    // * non-seekable, has length
+    // * seekable, doesn't have length
+    // * non-seekable, doesn't have length
+    public sealed class NonSeekableLengthSupportedIndexedCapturingReaderTest : StreamingIndexedCapturingReaderTestBase
+    {
+        protected override IndexedReader CreateReader(params byte[] bytes)
+        {
+            return new IndexedCapturingReader(new ConfigurableMemoryStream(bytes, false, true));
+        }
+    }
+
+    public sealed class SeekableLengthUnsupportedIndexedCapturingReaderTest : StreamingIndexedCapturingReaderTestBase
+    {
+        protected override IndexedReader CreateReader(params byte[] bytes)
+        {
+            return new IndexedCapturingReader(new ConfigurableMemoryStream(bytes, true, false));
+        }
+    }
+
+    public sealed class NonSeekableLengthUnsupportedIndexedCapturingReaderTest : StreamingIndexedCapturingReaderTestBase
+    {
+        protected override IndexedReader CreateReader(params byte[] bytes)
+        {
+            return new IndexedCapturingReader(new ConfigurableMemoryStream(bytes, false, false));
+        }
+    }
+}