1 files changed, 250 insertions, 0 deletions

diff --git a/src/dtf/WixToolset.Dtf.Compression.Zip/CrcStream.cs b/src/dtf/WixToolset.Dtf.Compression.Zip/CrcStream.cs
new file mode 100644
index 00000000..c645ecc1
--- /dev/null
+++ b/src/dtf/WixToolset.Dtf.Compression.Zip/CrcStream.cs
@@ -0,0 +1,250 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolset.Dtf.Compression.Zip
+{
+    using System;
+    using System.IO;
+    using System.Diagnostics.CodeAnalysis;
+
+    /// <summary>
+    /// Wraps a source stream and calcaluates a CRC over all bytes that are read or written.
+    /// </summary>
+    /// <remarks>
+    /// The CRC algorithm matches that used in the standard ZIP file format.
+    /// </remarks>
+    [SuppressMessage("Microsoft.Naming", "CA1704:IdentifiersShouldBeSpelledCorrectly", MessageId = "Crc")]
+    public class CrcStream : Stream
+    {
+        private Stream source;
+        private uint crc;
+
+        /// <summary>
+        /// Creates a new CrcStream instance from a source stream.
+        /// </summary>
+        /// <param name="source">Underlying stream where bytes will be read from or written to.</param>
+        public CrcStream(Stream source)
+        {
+            this.source = source;
+        }
+
+        /// <summary>
+        /// Gets the current CRC over all bytes that have been read or written
+        /// since this instance was created.
+        /// </summary>
+        [SuppressMessage("Microsoft.Naming", "CA1704:IdentifiersShouldBeSpelledCorrectly", MessageId = "Crc")]
+        public uint Crc
+        {
+            get
+            {
+                return this.crc;
+            }
+        }
+
+        /// <summary>
+        /// Gets the underlying stream that this stream reads from or writes to.
+        /// </summary>
+        public Stream Source
+        {
+            get
+            {
+                return this.source;
+            }
+        }
+
+        /// <summary>
+        /// Gets a value indicating whether the source stream supports reading.
+        /// </summary>
+        /// <value>true if the stream supports reading; otherwise, false.</value>
+        public override bool CanRead
+        {
+            get
+            {
+                return this.source.CanRead;
+            }
+        }
+
+        /// <summary>
+        /// Gets a value indicating whether the source stream supports writing.
+        /// </summary>
+        /// <value>true if the stream supports writing; otherwise, false.</value>
+        public override bool CanWrite
+        {
+            get
+            {
+                return this.source.CanWrite;
+            }
+        }
+
+        /// <summary>
+        /// Gets a value indicating whether the source stream supports seeking.
+        /// </summary>
+        /// <value>true if the stream supports seeking; otherwise, false.</value>
+        public override bool CanSeek
+        {
+            get
+            {
+                return this.source.CanSeek;
+            }
+        }
+
+        /// <summary>
+        /// Gets the length of the source stream.
+        /// </summary>
+        public override long Length
+        {
+            get
+            {
+                return this.source.Length;
+            }
+        }
+
+        /// <summary>
+        /// Gets or sets the position of the source stream.
+        /// </summary>
+        public override long Position
+        {
+            get
+            {
+                return this.source.Position;
+            }
+
+            set
+            {
+                this.source.Position = value;
+            }
+        }
+
+        /// <summary>
+        /// Sets the position within the source stream.
+        /// </summary>
+        /// <param name="offset">A byte offset relative to the origin parameter.</param>
+        /// <param name="origin">A value of type SeekOrigin indicating
+        /// the reference point used to obtain the new position.</param>
+        /// <returns>The new position within the source stream.</returns>
+        /// <remarks>
+        /// Note the CRC is only calculated over bytes that are actually read or
+        /// written, so any bytes skipped by seeking will not contribute to the CRC.
+        /// </remarks>
+        public override long Seek(long offset, SeekOrigin origin)
+        {
+            return this.source.Seek(offset, origin);
+        }
+
+        /// <summary>
+        /// Sets the length of the source stream.
+        /// </summary>
+        /// <param name="value">The desired length of the
+        /// stream in bytes.</param>
+        public override void SetLength(long value)
+        {
+            this.source.SetLength(value);
+        }
+
+        /// <summary>
+        /// Reads a sequence of bytes from the source stream and advances
+        /// the position within the stream by the number of bytes read.
+        /// </summary>
+        /// <param name="buffer">An array of bytes. When this method returns, the buffer
+        /// contains the specified byte array with the values between offset and
+        /// (offset + count - 1) replaced by the bytes read from the current source.</param>
+        /// <param name="offset">The zero-based byte offset in buffer at which to begin
+        /// storing the data read from the current stream.</param>
+        /// <param name="count">The maximum number of bytes to be read from the current stream.</param>
+        /// <returns>The total number of bytes read into the buffer. This can be less
+        /// than the number of bytes requested if that many bytes are not currently available,
+        /// or zero (0) if the end of the stream has been reached.</returns>
+        public override int Read(byte[] buffer, int offset, int count)
+        {
+            count = this.source.Read(buffer, offset, count);
+            this.UpdateCrc(buffer, offset, count);
+            return count;
+        }
+
+        /// <summary>
+        /// Writes a sequence of bytes to the source stream and advances the
+        /// current position within this stream by the number of bytes written.
+        /// </summary>
+        /// <param name="buffer">An array of bytes. This method copies count
+        /// bytes from buffer to the current stream.</param>
+        /// <param name="offset">The zero-based byte offset in buffer at which
+        /// to begin copying bytes to the current stream.</param>
+        /// <param name="count">The number of bytes to be written to the
+        /// current stream.</param>
+        public override void Write(byte[] buffer, int offset, int count)
+        {
+            this.source.Write(buffer, offset, count);
+            this.UpdateCrc(buffer, offset, count);
+        }
+
+        /// <summary>
+        /// Flushes the source stream.
+        /// </summary>
+        public override void Flush()
+        {
+            this.source.Flush();
+        }
+
+        /// <summary>
+        /// Closes the underlying stream.
+        /// </summary>
+        public override void Close()
+        {
+            this.source.Close();
+            base.Close();
+        }
+
+        /// <summary>
+        /// Updates the CRC with a range of bytes that were read or written.
+        /// </summary>
+        private void UpdateCrc(byte[] buffer, int offset, int count)
+        {
+            this.crc = ~this.crc;
+            for( ; count > 0; count--, offset++)
+            {
+                this.crc = (this.crc >> 8) ^
+                    CrcStream.crcTable[(this.crc  & 0xFF) ^ buffer[offset]];
+            }
+            this.crc = ~this.crc;
+        }
+
+        private static uint[] crcTable = MakeCrcTable();
+
+        /// <summary>
+        /// Computes a table that speeds up calculation of the CRC.
+        /// </summary>
+        private static uint[] MakeCrcTable()
+        {
+            const uint poly = 0x04C11DB7u;
+            uint[] crcTable = new uint[256];
+            for(uint n = 0; n < 256; n++)
+            {
+                uint c = CrcStream.Reflect(n, 8);
+                c = c << 24;
+                for(uint k = 0; k < 8; k++)
+                {
+                    c = (c << 1) ^ ((c & 0x80000000u) != 0 ? poly : 0);
+                }
+                crcTable[n] = CrcStream.Reflect(c, 32);
+            }
+            return crcTable;
+        }
+
+        /// <summary>
+        /// Reflects the ordering of certain number of bits. For exmample when reflecting
+        /// one byte, bit one is swapped with bit eight, bit two with bit seven, etc.
+        /// </summary>
+        private static uint Reflect(uint value, int bits)
+        {
+            for (int i = 0; i < bits / 2; i++)
+            {
+                uint leftBit = 1u << (bits - 1 - i);
+                uint rightBit = 1u << i;
+                if (((value & leftBit) != 0) != ((value & rightBit) != 0))
+                {
+                    value ^= leftBit | rightBit;
+                }
+            }
+            return value;
+        }
+    }
+}