forked from mirrors/NBTExplorer
572 lines
19 KiB
C#
572 lines
19 KiB
C#
// Crc32.cs
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// ------------------------------------------------------------------
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//
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// Copyright (c) 2006-2009 Dino Chiesa and Microsoft Corporation.
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// All rights reserved.
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//
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// This code module is part of DotNetZip, a zipfile class library.
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//
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// ------------------------------------------------------------------
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//
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// This code is licensed under the Microsoft Public License.
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// See the file License.txt for the license details.
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// More info on: http://dotnetzip.codeplex.com
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//
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// ------------------------------------------------------------------
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//
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// last saved (in emacs):
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// Time-stamp: <2010-January-16 13:16:27>
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//
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// ------------------------------------------------------------------
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//
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// Implements the CRC algorithm, which is used in zip files. The zip format calls for
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// the zipfile to contain a CRC for the unencrypted byte stream of each file.
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//
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// It is based on example source code published at
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// http://www.vbaccelerator.com/home/net/code/libraries/CRC32/Crc32_zip_CRC32_CRC32_cs.asp
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//
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// This implementation adds a tweak of that code for use within zip creation. While
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// computing the CRC we also compress the byte stream, in the same read loop. This
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// avoids the need to read through the uncompressed stream twice - once to compute CRC
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// and another time to compress.
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//
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// ------------------------------------------------------------------
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using System;
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using Interop=System.Runtime.InteropServices;
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namespace Ionic.Zlib
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{
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/// <summary>
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/// Calculates a 32bit Cyclic Redundancy Checksum (CRC) using the same polynomial
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/// used by Zip. This type is used internally by DotNetZip; it is generally not used
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/// directly by applications wishing to create, read, or manipulate zip archive
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/// files.
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/// </summary>
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[Interop.GuidAttribute("ebc25cf6-9120-4283-b972-0e5520d0000C")]
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[Interop.ComVisible(true)]
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#if !NETCF
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[Interop.ClassInterface(Interop.ClassInterfaceType.AutoDispatch)]
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#endif
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public class CRC32
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{
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/// <summary>
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/// indicates the total number of bytes read on the CRC stream.
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/// This is used when writing the ZipDirEntry when compressing files.
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/// </summary>
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public Int64 TotalBytesRead
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{
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get
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{
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return _TotalBytesRead;
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}
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}
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/// <summary>
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/// Indicates the current CRC for all blocks slurped in.
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/// </summary>
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public Int32 Crc32Result
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{
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get
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{
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// return one's complement of the running result
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return unchecked((Int32)(~_RunningCrc32Result));
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}
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}
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/// <summary>
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/// Returns the CRC32 for the specified stream.
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/// </summary>
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/// <param name="input">The stream over which to calculate the CRC32</param>
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/// <returns>the CRC32 calculation</returns>
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public Int32 GetCrc32(System.IO.Stream input)
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{
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return GetCrc32AndCopy(input, null);
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}
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/// <summary>
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/// Returns the CRC32 for the specified stream, and writes the input into the
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/// output stream.
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/// </summary>
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/// <param name="input">The stream over which to calculate the CRC32</param>
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/// <param name="output">The stream into which to deflate the input</param>
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/// <returns>the CRC32 calculation</returns>
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public Int32 GetCrc32AndCopy(System.IO.Stream input, System.IO.Stream output)
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{
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if (input == null)
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throw new ZlibException("The input stream must not be null.");
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unchecked
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{
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//UInt32 crc32Result;
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//crc32Result = 0xFFFFFFFF;
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byte[] buffer = new byte[BUFFER_SIZE];
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int readSize = BUFFER_SIZE;
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_TotalBytesRead = 0;
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int count = input.Read(buffer, 0, readSize);
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if (output != null) output.Write(buffer, 0, count);
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_TotalBytesRead += count;
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while (count > 0)
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{
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SlurpBlock(buffer, 0, count);
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count = input.Read(buffer, 0, readSize);
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if (output != null) output.Write(buffer, 0, count);
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_TotalBytesRead += count;
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}
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return (Int32)(~_RunningCrc32Result);
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}
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}
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/// <summary>
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/// Get the CRC32 for the given (word,byte) combo. This is a computation
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/// defined by PKzip.
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/// </summary>
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/// <param name="W">The word to start with.</param>
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/// <param name="B">The byte to combine it with.</param>
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/// <returns>The CRC-ized result.</returns>
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public Int32 ComputeCrc32(Int32 W, byte B)
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{
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return _InternalComputeCrc32((UInt32)W, B);
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}
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internal Int32 _InternalComputeCrc32(UInt32 W, byte B)
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{
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return (Int32)(crc32Table[(W ^ B) & 0xFF] ^ (W >> 8));
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}
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/// <summary>
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/// Update the value for the running CRC32 using the given block of bytes.
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/// This is useful when using the CRC32() class in a Stream.
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/// </summary>
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/// <param name="block">block of bytes to slurp</param>
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/// <param name="offset">starting point in the block</param>
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/// <param name="count">how many bytes within the block to slurp</param>
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public void SlurpBlock(byte[] block, int offset, int count)
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{
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if (block == null)
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throw new ZlibException("The data buffer must not be null.");
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for (int i = 0; i < count; i++)
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{
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int x = offset + i;
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_RunningCrc32Result = ((_RunningCrc32Result) >> 8) ^ crc32Table[(block[x]) ^ ((_RunningCrc32Result) & 0x000000FF)];
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}
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_TotalBytesRead += count;
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}
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// pre-initialize the crc table for speed of lookup.
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static CRC32()
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{
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unchecked
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{
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// PKZip specifies CRC32 with a polynomial of 0xEDB88320;
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// This is also the CRC-32 polynomial used bby Ethernet, FDDI,
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// bzip2, gzip, and others.
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// Often the polynomial is shown reversed as 0x04C11DB7.
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// For more details, see http://en.wikipedia.org/wiki/Cyclic_redundancy_check
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UInt32 dwPolynomial = 0xEDB88320;
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UInt32 i, j;
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crc32Table = new UInt32[256];
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UInt32 dwCrc;
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for (i = 0; i < 256; i++)
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{
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dwCrc = i;
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for (j = 8; j > 0; j--)
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{
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if ((dwCrc & 1) == 1)
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{
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dwCrc = (dwCrc >> 1) ^ dwPolynomial;
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}
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else
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{
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dwCrc >>= 1;
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}
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}
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crc32Table[i] = dwCrc;
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}
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}
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}
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private uint gf2_matrix_times(uint[] matrix, uint vec)
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{
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uint sum = 0;
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int i=0;
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while (vec != 0)
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{
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if ((vec & 0x01)== 0x01)
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sum ^= matrix[i];
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vec >>= 1;
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i++;
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}
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return sum;
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}
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private void gf2_matrix_square(uint[] square, uint[] mat)
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{
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for (int i = 0; i < 32; i++)
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square[i] = gf2_matrix_times(mat, mat[i]);
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}
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/// <summary>
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/// Combines the given CRC32 value with the current running total.
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/// </summary>
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/// <remarks>
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/// This is useful when using a divide-and-conquer approach to calculating a CRC.
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/// Multiple threads can each calculate a CRC32 on a segment of the data, and then
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/// combine the individual CRC32 values at the end.
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/// </remarks>
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/// <param name="crc">the crc value to be combined with this one</param>
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/// <param name="length">the length of data the CRC value was calculated on</param>
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public void Combine(int crc, int length)
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{
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uint[] even = new uint[32]; // even-power-of-two zeros operator
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uint[] odd = new uint[32]; // odd-power-of-two zeros operator
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if (length == 0)
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return;
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uint crc1= ~_RunningCrc32Result;
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uint crc2= (uint) crc;
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// put operator for one zero bit in odd
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odd[0] = 0xEDB88320; // the CRC-32 polynomial
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uint row = 1;
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for (int i = 1; i < 32; i++)
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{
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odd[i] = row;
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row <<= 1;
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}
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// put operator for two zero bits in even
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gf2_matrix_square(even, odd);
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// put operator for four zero bits in odd
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gf2_matrix_square(odd, even);
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uint len2 = (uint) length;
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// apply len2 zeros to crc1 (first square will put the operator for one
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// zero byte, eight zero bits, in even)
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do {
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// apply zeros operator for this bit of len2
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gf2_matrix_square(even, odd);
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if ((len2 & 1)== 1)
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crc1 = gf2_matrix_times(even, crc1);
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len2 >>= 1;
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if (len2 == 0)
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break;
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// another iteration of the loop with odd and even swapped
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gf2_matrix_square(odd, even);
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if ((len2 & 1)==1)
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crc1 = gf2_matrix_times(odd, crc1);
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len2 >>= 1;
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} while (len2 != 0);
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crc1 ^= crc2;
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_RunningCrc32Result= ~crc1;
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//return (int) crc1;
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return;
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}
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// private member vars
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private Int64 _TotalBytesRead;
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private static readonly UInt32[] crc32Table;
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private const int BUFFER_SIZE = 8192;
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private UInt32 _RunningCrc32Result = 0xFFFFFFFF;
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}
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/// <summary>
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/// A Stream that calculates a CRC32 (a checksum) on all bytes read,
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/// or on all bytes written.
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/// </summary>
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///
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/// <remarks>
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/// <para>
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/// This class can be used to verify the CRC of a ZipEntry when
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/// reading from a stream, or to calculate a CRC when writing to a
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/// stream. The stream should be used to either read, or write, but
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/// not both. If you intermix reads and writes, the results are not
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/// defined.
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/// </para>
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///
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/// <para>
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/// This class is intended primarily for use internally by the
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/// DotNetZip library.
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/// </para>
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/// </remarks>
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public class CrcCalculatorStream : System.IO.Stream, System.IDisposable
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{
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private static readonly Int64 UnsetLengthLimit = -99;
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internal System.IO.Stream _innerStream;
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private CRC32 _Crc32;
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private Int64 _lengthLimit = -99;
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private bool _leaveOpen;
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/// <summary>
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/// Gets the total number of bytes run through the CRC32 calculator.
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/// </summary>
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///
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/// <remarks>
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/// This is either the total number of bytes read, or the total number of bytes
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/// written, depending on the direction of this stream.
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/// </remarks>
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public Int64 TotalBytesSlurped
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{
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get { return _Crc32.TotalBytesRead; }
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}
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/// <summary>
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/// The default constructor.
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/// </summary>
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/// <remarks>
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/// Instances returned from this constructor will leave the underlying stream
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/// open upon Close().
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/// </remarks>
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/// <param name="stream">The underlying stream</param>
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public CrcCalculatorStream(System.IO.Stream stream)
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: this(true, CrcCalculatorStream.UnsetLengthLimit, stream)
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{
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}
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/// <summary>
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/// The constructor allows the caller to specify how to handle the underlying
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/// stream at close.
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/// </summary>
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/// <param name="stream">The underlying stream</param>
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/// <param name="leaveOpen">true to leave the underlying stream
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/// open upon close of the CrcCalculatorStream.; false otherwise.</param>
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public CrcCalculatorStream(System.IO.Stream stream, bool leaveOpen)
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: this(leaveOpen, CrcCalculatorStream.UnsetLengthLimit, stream)
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{
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}
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/// <summary>
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/// A constructor allowing the specification of the length of the stream to read.
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/// </summary>
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/// <remarks>
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/// Instances returned from this constructor will leave the underlying stream open
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/// upon Close().
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/// </remarks>
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/// <param name="stream">The underlying stream</param>
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/// <param name="length">The length of the stream to slurp</param>
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public CrcCalculatorStream(System.IO.Stream stream, Int64 length)
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: this(true, length, stream)
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{
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if (length < 0)
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throw new ArgumentException("length");
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}
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/// <summary>
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/// A constructor allowing the specification of the length of the stream to
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/// read, as well as whether to keep the underlying stream open upon Close().
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/// </summary>
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/// <param name="stream">The underlying stream</param>
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/// <param name="length">The length of the stream to slurp</param>
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/// <param name="leaveOpen">true to leave the underlying stream
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/// open upon close of the CrcCalculatorStream.; false otherwise.</param>
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public CrcCalculatorStream(System.IO.Stream stream, Int64 length, bool leaveOpen)
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: this(leaveOpen, length, stream)
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{
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if (length < 0)
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throw new ArgumentException("length");
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}
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// This ctor is private - no validation is done here. This is to allow the use
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// of a (specific) negative value for the _lengthLimit, to indicate that there
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// is no length set. So we validate the length limit in those ctors that use an
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// explicit param, otherwise we don't validate, because it could be our special
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// value.
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private CrcCalculatorStream(bool leaveOpen, Int64 length, System.IO.Stream stream)
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: base()
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{
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_innerStream = stream;
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_Crc32 = new CRC32();
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_lengthLimit = length;
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_leaveOpen = leaveOpen;
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}
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/// <summary>
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/// Provides the current CRC for all blocks slurped in.
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/// </summary>
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public Int32 Crc
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{
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get { return _Crc32.Crc32Result; }
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}
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/// <summary>
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/// Indicates whether the underlying stream will be left open when the
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/// CrcCalculatorStream is Closed.
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/// </summary>
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public bool LeaveOpen
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{
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get { return _leaveOpen; }
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set { _leaveOpen = value; }
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}
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/// <summary>
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/// Read from the stream
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/// </summary>
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/// <param name="buffer">the buffer to read</param>
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/// <param name="offset">the offset at which to start</param>
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/// <param name="count">the number of bytes to read</param>
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/// <returns>the number of bytes actually read</returns>
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public override int Read(byte[] buffer, int offset, int count)
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{
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int bytesToRead = count;
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// Need to limit the # of bytes returned, if the stream is intended to have
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// a definite length. This is especially useful when returning a stream for
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// the uncompressed data directly to the application. The app won't
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// necessarily read only the UncompressedSize number of bytes. For example
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// wrapping the stream returned from OpenReader() into a StreadReader() and
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// calling ReadToEnd() on it, We can "over-read" the zip data and get a
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// corrupt string. The length limits that, prevents that problem.
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if (_lengthLimit != CrcCalculatorStream.UnsetLengthLimit)
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{
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if (_Crc32.TotalBytesRead >= _lengthLimit) return 0; // EOF
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Int64 bytesRemaining = _lengthLimit - _Crc32.TotalBytesRead;
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if (bytesRemaining < count) bytesToRead = (int)bytesRemaining;
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}
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int n = _innerStream.Read(buffer, offset, bytesToRead);
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if (n > 0) _Crc32.SlurpBlock(buffer, offset, n);
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return n;
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}
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/// <summary>
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/// Write to the stream.
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/// </summary>
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/// <param name="buffer">the buffer from which to write</param>
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/// <param name="offset">the offset at which to start writing</param>
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/// <param name="count">the number of bytes to write</param>
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public override void Write(byte[] buffer, int offset, int count)
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{
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if (count > 0) _Crc32.SlurpBlock(buffer, offset, count);
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_innerStream.Write(buffer, offset, count);
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}
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/// <summary>
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/// Indicates whether the stream supports reading.
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/// </summary>
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public override bool CanRead
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{
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get { return _innerStream.CanRead; }
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}
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/// <summary>
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/// Indicates whether the stream supports seeking.
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/// </summary>
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public override bool CanSeek
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{
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get { return _innerStream.CanSeek; }
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}
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/// <summary>
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/// Indicates whether the stream supports writing.
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/// </summary>
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public override bool CanWrite
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{
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get { return _innerStream.CanWrite; }
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}
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/// <summary>
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/// Flush the stream.
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/// </summary>
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public override void Flush()
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{
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_innerStream.Flush();
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}
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/// <summary>
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/// Not implemented.
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/// </summary>
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public override long Length
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{
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get
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{
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if (_lengthLimit == CrcCalculatorStream.UnsetLengthLimit)
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return _innerStream.Length;
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else return _lengthLimit;
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}
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}
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/// <summary>
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/// Not implemented.
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/// </summary>
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public override long Position
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{
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get { return _Crc32.TotalBytesRead; }
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set { throw new NotImplementedException(); }
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}
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/// <summary>
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/// Not implemented.
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/// </summary>
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/// <param name="offset">N/A</param>
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/// <param name="origin">N/A</param>
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/// <returns>N/A</returns>
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public override long Seek(long offset, System.IO.SeekOrigin origin)
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{
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throw new NotImplementedException();
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}
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/// <summary>
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/// Not implemented.
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/// </summary>
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/// <param name="value">N/A</param>
|
|
public override void SetLength(long value)
|
|
{
|
|
throw new NotImplementedException();
|
|
}
|
|
|
|
|
|
void IDisposable.Dispose()
|
|
{
|
|
Close();
|
|
}
|
|
|
|
/// <summary>
|
|
/// Closes the stream.
|
|
/// </summary>
|
|
public override void Close()
|
|
{
|
|
base.Close();
|
|
if (!_leaveOpen)
|
|
_innerStream.Close();
|
|
}
|
|
|
|
}
|
|
}
|