Initial commit - WPinternals 2.6

DiscUtils/Compression/ZlibStream.cs

@@ -0,0 +1,237 @@
+//
+// 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;
+    using System.IO;
+    using System.IO.Compression;
+
+    /// <summary>
+    /// Implementation of the Zlib compression algorithm.
+    /// </summary>
+    /// <remarks>Only decompression is currently implemented.</remarks>
+    public class ZlibStream : Stream
+    {
+        private Stream _stream;
+        private CompressionMode _mode;
+        private DeflateStream _deflateStream;
+        private Adler32 _adler32;
+
+        /// <summary>
+        /// Initializes a new instance of the ZlibStream class.
+        /// </summary>
+        /// <param name="stream">The stream to compress of decompress.</param>
+        /// <param name="mode">Whether to compress or decompress.</param>
+        /// <param name="leaveOpen">Whether closing this stream should leave <c>stream</c> open.</param>
+        public ZlibStream(Stream stream, CompressionMode mode, bool leaveOpen)
+        {
+            _stream = stream;
+            _mode = mode;
+
+            if (mode == CompressionMode.Decompress)
+            {
+                // We just sanity check against expected header values...
+                byte[] headerBuffer = Utilities.ReadFully(stream, 2);
+                ushort header = Utilities.ToUInt16BigEndian(headerBuffer, 0);
+
+                if ((header % 31) != 0)
+                {
+                    throw new IOException("Invalid Zlib header found");
+                }
+
+                if ((header & 0x0F00) != (8 << 8))
+                {
+                    throw new NotSupportedException("Zlib compression not using DEFLATE algorithm");
+                }
+
+                if ((header & 0x0020) != 0)
+                {
+                    throw new NotSupportedException("Zlib compression using preset dictionary");
+                }
+            }
+            else
+            {
+                ushort header =
+                    (8 << 8)    // DEFLATE
+                    | (7 << 12) // 32K window size
+                    | 0x80;     // Default algorithm
+                header |= (ushort)(31 - (header % 31));
+
+                byte[] headerBuffer = new byte[2];
+                Utilities.WriteBytesBigEndian(header, headerBuffer, 0);
+                stream.Write(headerBuffer, 0, 2);
+            }
+
+            _deflateStream = new DeflateStream(stream, mode, leaveOpen);
+            _adler32 = new Adler32();
+        }
+
+        /// <summary>
+        /// Gets whether the stream can be read.
+        /// </summary>
+        public override bool CanRead
+        {
+            get { return _deflateStream.CanRead; }
+        }
+
+        /// <summary>
+        /// Gets whether the stream pointer can be changed.
+        /// </summary>
+        public override bool CanSeek
+        {
+            get { return false; }
+        }
+
+        /// <summary>
+        /// Gets whether the stream can be written to.
+        /// </summary>
+        public override bool CanWrite
+        {
+            get { return _deflateStream.CanWrite; }
+        }
+
+        /// <summary>
+        /// Gets the length of the stream.
+        /// </summary>
+        public override long Length
+        {
+            get { throw new NotSupportedException(); }
+        }
+
+        /// <summary>
+        /// Gets and sets the stream position.
+        /// </summary>
+        public override long Position
+        {
+            get { throw new NotSupportedException(); }
+            set { throw new NotSupportedException(); }
+        }
+
+        /// <summary>
+        /// Closes the stream.
+        /// </summary>
+        public override void Close()
+        {
+            if (_mode == CompressionMode.Decompress)
+            {
+                // Can only check Adler checksum on seekable streams.  Since DeflateStream
+                // aggresively caches input, it normally has already consumed the footer.
+                if (_stream.CanSeek)
+                {
+                    _stream.Seek(-4, SeekOrigin.End);
+                    byte[] footerBuffer = Utilities.ReadFully(_stream, 4);
+                    if (Utilities.ToInt32BigEndian(footerBuffer, 0) != _adler32.Value)
+                    {
+                        throw new InvalidDataException("Corrupt decompressed data detected");
+                    }
+                }
+
+                _deflateStream.Close();
+            }
+            else
+            {
+                _deflateStream.Close();
+
+                byte[] footerBuffer = new byte[4];
+                Utilities.WriteBytesBigEndian(_adler32.Value, footerBuffer, 0);
+                _stream.Write(footerBuffer, 0, 4);
+            }
+        }
+
+        /// <summary>
+        /// Flushes the stream.
+        /// </summary>
+        public override void Flush()
+        {
+            _deflateStream.Flush();
+        }
+
+        /// <summary>
+        /// Reads data from the stream.
+        /// </summary>
+        /// <param name="buffer">The buffer to populate.</param>
+        /// <param name="offset">The first byte to write.</param>
+        /// <param name="count">The number of bytes requested.</param>
+        /// <returns>The number of bytes read.</returns>
+        public override int Read(byte[] buffer, int offset, int count)
+        {
+            CheckParams(buffer, offset, count);
+
+            int numRead = _deflateStream.Read(buffer, offset, count);
+            _adler32.Process(buffer, offset, numRead);
+            return numRead;
+        }
+
+        /// <summary>
+        /// Seeks to a new position.
+        /// </summary>
+        /// <param name="offset">Relative position to seek to.</param>
+        /// <param name="origin">The origin of the seek.</param>
+        /// <returns>The new position.</returns>
+        public override long Seek(long offset, SeekOrigin origin)
+        {
+            throw new NotSupportedException();
+        }
+
+        /// <summary>
+        /// Changes the length of the stream.
+        /// </summary>
+        /// <param name="value">The new desired length of the stream.</param>
+        public override void SetLength(long value)
+        {
+            throw new NotSupportedException();
+        }
+
+        /// <summary>
+        /// Writes data to the stream.
+        /// </summary>
+        /// <param name="buffer">Buffer containing the data to write.</param>
+        /// <param name="offset">Offset of the first byte to write.</param>
+        /// <param name="count">Number of bytes to write.</param>
+        public override void Write(byte[] buffer, int offset, int count)
+        {
+            CheckParams(buffer, offset, count);
+
+            _adler32.Process(buffer, offset, count);
+            _deflateStream.Write(buffer, offset, count);
+        }
+
+        private static void CheckParams(byte[] buffer, int offset, int count)
+        {
+            if (buffer == null)
+            {
+                throw new ArgumentNullException("buffer");
+            }
+
+            if (offset < 0 || offset > buffer.Length)
+            {
+                throw new ArgumentException("Offset outside of array bounds", "offset");
+            }
+
+            if (count < 0 || offset + count > buffer.Length)
+            {
+                throw new ArgumentException("Array index out of bounds", "count");
+            }
+        }
+    }
+}