Port ReadOnlyBitStream from Compression, add tests

SabreTools.IO.Test/ReadOnlyBitStreamTests.cs

@@ -0,0 +1,54 @@
+using System.IO;
+using SabreTools.IO.Streams;
+using Xunit;
+
+namespace SabreTools.IO.Test
+{
+    public class ReadOnlyBitStreamTests
+    {
+        [Fact]
+        public void DefaultConstructorTest()
+        {
+            var stream = new ReadOnlyBitStream(new MemoryStream());
+            Assert.Equal(0, stream.Length);
+            Assert.Equal(0, stream.Position);
+
+            stream = new ReadOnlyBitStream(new MemoryStream(new byte[16]));
+            Assert.Equal(16, stream.Length);
+            Assert.Equal(0, stream.Position);
+        }
+
+        [Fact]
+        public void ReadSingleBitTest()
+        {
+            byte[] data = [0b01010101];
+            var stream = new ReadOnlyBitStream(new MemoryStream(data));
+            byte? bit = stream.ReadBit();
+            Assert.NotNull(bit);
+            Assert.Equal((byte)0b00000001, bit);
+            Assert.Equal(1, stream.Position);
+        }
+
+        [Fact]
+        public void ReadBitsLSBTest()
+        {
+            byte[] data = [0b01010101, 0b01010101, 0b01010101, 0b01010101];
+            var stream = new ReadOnlyBitStream(new MemoryStream(data));
+            uint? bits = stream.ReadBitsLSB(4);
+            Assert.NotNull(bits);
+            Assert.Equal((byte)0b00000101, bits);
+            Assert.Equal(1, stream.Position);
+        }
+
+        [Fact]
+        public void ReadBitsMSBTest()
+        {
+            byte[] data = [0b01010101, 0b01010101, 0b01010101, 0b01010101];
+            var stream = new ReadOnlyBitStream(new MemoryStream(data));
+            uint? bits = stream.ReadBitsMSB(4);
+            Assert.NotNull(bits);
+            Assert.Equal((byte)0b00001010, bits);
+            Assert.Equal(1, stream.Position);
+        }
+    }
+}