Add options to control compression when writing

MatFileHandler.Tests/MatFileWriterTests.cs

@@ -376,13 +376,17 @@ namespace MatFileHandler.Tests
             }
         }
 
-        private void MatCompareWithTestData(string factoryName, string testName, IMatFile actual)
+        private void CompareTestDataWithWritingOptions(
+            IMatFile expected,
+            IMatFile actual,
+            MatFileWriterOptions? maybeOptions)
         {
-            var expected = GetMatTestData(factoryName)[testName];
             byte[] buffer;
             using (var stream = new MemoryStream())
             {
-                var writer = new MatFileWriter(stream);
+                var writer = maybeOptions is MatFileWriterOptions options
+                    ? new MatFileWriter(stream, options)
+                    : new MatFileWriter(stream);
                 writer.Write(actual);
                 buffer = stream.ToArray();
             }
@@ -394,6 +398,20 @@ namespace MatFileHandler.Tests
             }
         }
 
+        private void MatCompareWithTestData(string factoryName, string testName, IMatFile actual)
+        {
+            var expected = GetMatTestData(factoryName)[testName];
+            CompareTestDataWithWritingOptions(expected, actual, null);
+            CompareTestDataWithWritingOptions(
+                expected,
+                actual,
+                new MatFileWriterOptions { UseCompression = CompressionUsage.Always });
+            CompareTestDataWithWritingOptions(
+                expected,
+                actual,
+                new MatFileWriterOptions { UseCompression = CompressionUsage.Never });
+        }
+
         private ComplexOf<T>[] CreateComplexLimits<T>(T[] limits)
           where T : struct
         {

MatFileHandler/CompressionUsage.cs

@@ -0,0 +1,20 @@
+// Copyright 2017 Alexander Luzgarev
+
+namespace MatFileHandler
+{
+    /// <summary>
+    /// Describes compression usage strategy for writing files.
+    /// </summary>
+    public enum CompressionUsage
+    {
+        /// <summary>
+        /// Never use compression.
+        /// </summary>
+        Never,
+
+        /// <summary>
+        /// Always use compression.
+        /// </summary>
+        Always,
+    }
+}

MatFileHandler/MatFileWriter.cs

@@ -15,13 +15,27 @@ namespace MatFileHandler
     /// </summary>
     public class MatFileWriter
     {
+        private readonly MatFileWriterOptions _options;
+
         /// <summary>
-        /// Initializes a new instance of the <see cref="MatFileWriter"/> class with a stream.
+        /// Initializes a new instance of the <see cref="MatFileWriter"/> class with a stream and default options.
         /// </summary>
         /// <param name="stream">Output stream.</param>
         public MatFileWriter(Stream stream)
         {
             Stream = stream;
+            _options = MatFileWriterOptions.Default;
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="MatFileWriter"/> class with a stream.
+        /// </summary>
+        /// <param name="stream">Output stream.</param>
+        /// <param name="options">Options to use for file writing.</param>
+        public MatFileWriter(Stream stream, MatFileWriterOptions options)
+        {
+            Stream = stream;
+            _options = options;
         }
 
         private Stream Stream { get; }
@@ -38,7 +52,17 @@ namespace MatFileHandler
                 WriteHeader(writer, header);
                 foreach (var variable in file.Variables)
                 {
-                    WriteCompressedVariable(writer, variable);
+                    switch (_options.UseCompression)
+                    {
+                        case CompressionUsage.Always:
+                            WriteCompressedVariable(writer, variable);
+                            break;
+                        case CompressionUsage.Never:
+                            WriteVariable(writer, variable);
+                            break;
+                        default:
+                            throw new ArgumentOutOfRangeException();
+                    }
                 }
             }
         }

MatFileHandler/MatFileWriterOptions.cs

@@ -0,0 +1,23 @@
+// Copyright 2017 Alexander Luzgarev
+
+namespace MatFileHandler
+{
+    /// <summary>
+    /// Options for writing .mat files.
+    /// </summary>
+    public struct MatFileWriterOptions
+    {
+        /// <summary>
+        /// Gets default options.
+        /// </summary>
+        public static MatFileWriterOptions Default => new MatFileWriterOptions
+        {
+            UseCompression = CompressionUsage.Always,
+        };
+
+        /// <summary>
+        /// Gets or sets a value indicating whether to compress all variables when writing the file.
+        /// </summary>
+        public CompressionUsage UseCompression { get; set; }
+    }
+}