Initial commit - WPinternals 2.6

DiscUtils/Compression/BigEndianBitStream.cs

@@ -0,0 +1,95 @@
+//
+// Copyright (c) 2008-2011, Kenneth Bell
+//
+// Permission is hereby granted, free of charge, to any person obtaining a
+// copy of this software and associated documentation files (the "Software"),
+// to deal in the Software without restriction, including without limitation
+// the rights to use, copy, modify, merge, publish, distribute, sublicense,
+// and/or sell copies of the Software, and to permit persons to whom the
+// Software is furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+//
+
+namespace DiscUtils.Compression
+{
+    using System.IO;
+
+    /// <summary>
+    /// Converts a byte stream into a bit stream.
+    /// </summary>
+    internal class BigEndianBitStream : BitStream
+    {
+        private Stream _byteStream;
+
+        private uint _buffer;
+        private int _bufferAvailable;
+
+        private byte[] _readBuffer = new byte[2];
+
+        public BigEndianBitStream(Stream byteStream)
+        {
+            _byteStream = byteStream;
+        }
+
+        public override int MaxReadAhead
+        {
+            get { return 16; }
+        }
+
+        public override uint Read(int count)
+        {
+            if (count > 16)
+            {
+                uint result = Read(16) << (count - 16);
+                return result | Read(count - 16);
+            }
+
+            EnsureBufferFilled();
+
+            _bufferAvailable -= count;
+
+            uint mask = (uint)((1 << count) - 1);
+
+            return (uint)((_buffer >> _bufferAvailable) & mask);
+        }
+
+        public override uint Peek(int count)
+        {
+            EnsureBufferFilled();
+
+            uint mask = (uint)((1 << count) - 1);
+
+            return (uint)((_buffer >> (_bufferAvailable - count)) & mask);
+        }
+
+        public override void Consume(int count)
+        {
+            EnsureBufferFilled();
+
+            _bufferAvailable -= count;
+        }
+
+        private void EnsureBufferFilled()
+        {
+            if (_bufferAvailable < 16)
+            {
+                _readBuffer[0] = 0;
+                _readBuffer[1] = 0;
+                _byteStream.Read(_readBuffer, 0, 2);
+
+                _buffer = (uint)((uint)(_buffer << 16) | (uint)(_readBuffer[0] << 8) | (uint)_readBuffer[1]);
+                _bufferAvailable += 16;
+            }
+        }
+    }
+}