Classes derived from Stream override ReadByte.

The Stream.ReadByte method is implemented by allocating a 1 byte buffer and calling into Read(byte[], int, int). Override ReadByte in derived classes to avoid needing to allocate this small temp buffer.

Also, fix some bugs in the stream implementations. Remove Write capability from MergedStream that didn't make sense. Add guards into SegmentStream to ensure reads and writes belonged to the segment - otherwise a reader or writer could access regions of the base stream that were outside the intended segment.

OpenRA.Game/Primitives/MergedStream.cs

@@ -9,6 +9,7 @@
  */
 #endregion
 
+using System;
 using System.IO;
 
 namespace OpenRA.Primitives
@@ -18,7 +19,7 @@ namespace OpenRA.Primitives
 		public Stream Stream1 { get; set; }
 		public Stream Stream2 { get; set; }
 
-		long VirtualLength { get; set; }
+		long VirtualLength { get; }
 		long position;
 
 		public MergedStream(Stream stream1, Stream stream2)
@@ -61,7 +62,21 @@ namespace OpenRA.Primitives
 
 		public override void SetLength(long value)
 		{
-			VirtualLength = value;
+			throw new NotSupportedException();
+		}
+
+		public override int ReadByte()
+		{
+			int value;
+
+			if (position >= Stream1.Length)
+				value = Stream2.ReadByte();
+			else
+				value = Stream1.ReadByte();
+
+			position++;
+
+			return value;
 		}
 
 		public override int Read(byte[] buffer, int offset, int count)
@@ -83,12 +98,14 @@ namespace OpenRA.Primitives
 			return bytesRead;
 		}
 
+		public override void WriteByte(byte value)
+		{
+			throw new NotSupportedException();
+		}
+
 		public override void Write(byte[] buffer, int offset, int count)
 		{
-			if (position >= Stream1.Length)
-				Stream2.Write(buffer, offset - (int)Stream1.Length, count);
-			else
-				Stream1.Write(buffer, offset, count);
+			throw new NotSupportedException();
 		}
 
 		public override bool CanRead
@@ -103,7 +120,7 @@ namespace OpenRA.Primitives
 
 		public override bool CanWrite
 		{
-			get { return Stream1.CanWrite && Stream2.CanWrite; }
+			get { return false; }
 		}
 
 		public override long Length