Add single-stream constructor to ROCS

SabreTools.IO.Test/ReadOnlyCompositeStreamTests.cs

@@ -35,6 +35,14 @@ namespace SabreTools.IO.Test
             Assert.Equal(0, stream.Position);
         }
 
+        [Fact]
+        public void SingleStreamConstructorTest()
+        {
+            var stream = new ReadOnlyCompositeStream(new MemoryStream(new byte[1024]));
+            Assert.Equal(1024, stream.Length);
+            Assert.Equal(0, stream.Position);
+        }
+
         [Fact]
         public void FilledArrayConstructorTest()
         {

SabreTools.IO/Streams/ReadOnlyCompositeStream.cs

@@ -69,6 +69,23 @@ namespace SabreTools.IO.Streams
             _position = 0;
         }
 
+        /// <summary>
+        /// Create a new ReadOnlyCompositeStream from a single Stream
+        /// </summary>
+        /// <param name="stream"></param>
+        public ReadOnlyCompositeStream(Stream stream)
+        {
+            _streams = [stream];
+            _length = 0;
+            _position = 0;
+
+            // Verify the stream and add to the length
+            if (!stream.CanRead || !stream.CanSeek)
+                throw new ArgumentException($"{nameof(stream)} needs to be readable and seekable");
+
+            _length += stream.Length;
+        }
+
         /// <summary>
         /// Create a new ReadOnlyCompositeStream from an existing collection of Streams
         /// </summary>