[BZip2] Enforce baseStream to be non-null in BZip2InputStream and BZi…

…p2OutputStream (constructor now throws an ArgumentNullException).

src/ICSharpCode.SharpZipLib/BZip2/BZip2InputStream.cs

@@ -66,7 +66,7 @@ during decompression.
 		int[][] perm = new int[BZip2Constants.GroupCount][];
 		int[] minLens = new int[BZip2Constants.GroupCount];
 
-		Stream baseStream;
+		readonly Stream baseStream;
 		bool streamEnd;
 
 		int currentChar = -1;
@@ -91,14 +91,18 @@ during decompression.
 		/// <param name="stream">Data source</param>
 		public BZip2InputStream(Stream stream)
 		{
+			if (stream == null)
+				throw new ArgumentNullException(nameof(stream));
 			// init arrays
 			for (int i = 0; i < BZip2Constants.GroupCount; ++i) {
 				limit[i] = new int[BZip2Constants.MaximumAlphaSize];
 				baseArray[i] = new int[BZip2Constants.MaximumAlphaSize];
 				perm[i] = new int[BZip2Constants.MaximumAlphaSize];
 			}
 
-			BsSetStream(stream);
+			baseStream = stream;
+			bsLive = 0;
+			bsBuff = 0;
 			Initialize();
 			InitBlock();
 			SetupBlock();
@@ -149,10 +153,10 @@ public override long Length {
 		}
 
 		/// <summary>
-		/// Gets or sets the streams position.
-		/// Setting the position is not supported and will throw a NotSupportException
+		/// Gets the current position of the stream.
+		/// Setting the position is not supported and will throw a NotSupportException.
 		/// </summary>
-		/// <exception cref="NotSupportedException">Any attempt to set the position</exception>
+		/// <exception cref="NotSupportedException">Any attempt to set the position.</exception>
 		public override long Position {
 			get {
 				return baseStream.Position;
@@ -167,9 +171,7 @@ public override long Position {
 		/// </summary>
 		public override void Flush()
 		{
-			if (baseStream != null) {
-				baseStream.Flush();
-			}
+			baseStream.Flush();
 		}
 
 		/// <summary>
@@ -250,7 +252,7 @@ public override int Read(byte[] buffer, int offset, int count)
 		/// </summary>
 		protected override void Dispose(bool disposing)
 		{
-			if (disposing && IsStreamOwner && (baseStream != null)) {
+			if (disposing && IsStreamOwner) {
 				baseStream.Dispose();
 			}
 		}
@@ -371,13 +373,6 @@ void Complete()
 			streamEnd = true;
 		}
 
-		void BsSetStream(Stream stream)
-		{
-			baseStream = stream;
-			bsLive = 0;
-			bsBuff = 0;
-		}
-
 		void FillBuffer()
 		{
 			int thech = 0;

src/ICSharpCode.SharpZipLib/BZip2/BZip2OutputStream.cs

@@ -100,7 +100,7 @@ The current block size is 100000 * this number.
 		int runLength;
 		uint blockCRC, combinedCRC;
 		int allowableBlockSize;
-		Stream baseStream;
+		readonly Stream baseStream;
 		bool disposed_;
 		#endregion
 
@@ -124,7 +124,13 @@ public BZip2OutputStream(Stream stream) : this(stream, 9)
 		/// </remarks>
 		public BZip2OutputStream(Stream stream, int blockSize)
 		{
-			BsSetStream(stream);
+			if (stream == null)
+				throw new ArgumentNullException(nameof(stream));
+
+			baseStream = stream;
+			bsLive = 0;
+			bsBuff = 0;
+			bytesOut = 0;
 
 			workFactor = 50;
 			if (blockSize > 9) {
@@ -528,14 +534,6 @@ void EndCompression()
 			BsFinishedWithStream();
 		}
 
-		void BsSetStream(Stream stream)
-		{
-			baseStream = stream;
-			bsLive = 0;
-			bsBuff = 0;
-			bytesOut = 0;
-		}
-
 		void BsFinishedWithStream()
 		{
 			while (bsLive > 0) {