apewer-dotnet/Apewer/Externals/Compression/Zip/ZipOutputStream.cs

// ZipOutputStream.cs
//
// Copyright (C) 2001 Mike Krueger
// Copyright (C) 2004 John Reilly
//
// This file was translated from java, it was part of the GNU Classpath
// Copyright (C) 2001 Free Software Foundation, Inc.
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
//
// Linking this library statically or dynamically with other modules is
// making a combined work based on this library.  Thus, the terms and
// conditions of the GNU General Public License cover the whole
// combination.
// 
// As a special exception, the copyright holders of this library give you
// permission to link this library with independent modules to produce an
// executable, regardless of the license terms of these independent
// modules, and to copy and distribute the resulting executable under
// terms of your choice, provided that you also meet, for each linked
// independent module, the terms and conditions of the license of that
// module.  An independent module is a module which is not derived from
// or based on this library.  If you modify this library, you may extend
// this exception to your version of the library, but you are not
// obligated to do so.  If you do not wish to do so, delete this
// exception statement from your version.

// HISTORY
//	22-12-2009	Z-1649	Added AES support
//	22-02-2010	Z-1648	Zero byte entries would create invalid zip files

using System;
using System.IO;
using System.Collections;

using Externals.Compression.Checksums;
using Externals.Compression.Zip.Compression;
using Externals.Compression.Zip.Compression.Streams;

namespace Externals.Compression.Zip
{
    /// <summary>
    /// This is a DeflaterOutputStream that writes the files into a zip
    /// archive one after another.  It has a special method to start a new
    /// zip entry.  The zip entries contains information about the file name
    /// size, compressed size, CRC, etc.
    /// 
    /// It includes support for Stored and Deflated entries.
    /// This class is not thread safe.
    /// <br/>
    /// <br/>Author of the original java version : Jochen Hoenicke
    /// </summary>
    /// <example> This sample shows how to create a zip file
    /// <code>
    /// using System;
    /// using System.IO;
    /// 
    /// using Externals.Compression.Core;
    /// using Externals.Compression.Zip;
    /// 
    /// class MainClass
    /// {
    /// 	public static void Main(string[] args)
    /// 	{
    /// 		string[] filenames = Directory.GetFiles(args[0]);
    /// 		byte[] buffer = new byte[4096];
    /// 		
    /// 		using ( ZipOutputStream s = new ZipOutputStream(File.Create(args[1])) ) {
    /// 		
    /// 			s.SetLevel(9); // 0 - store only to 9 - means best compression
    /// 		
    /// 			foreach (string file in filenames) {
    /// 				ZipEntry entry = new ZipEntry(file);
    /// 				s.PutNextEntry(entry);
    ///
    /// 				using (FileStream fs = File.OpenRead(file)) {
    ///						StreamUtils.Copy(fs, s, buffer);
    /// 				}
    /// 			}
    /// 		}
    /// 	}
    /// }	
    /// </code>
    /// </example>
    internal class ZipOutputStream : DeflaterOutputStream
	{
		#region Constructors
		/// <summary>
		/// Creates a new Zip output stream, writing a zip archive.
		/// </summary>
		/// <param name="baseOutputStream">
		/// The output stream to which the archive contents are written.
		/// </param>
		public ZipOutputStream(Stream baseOutputStream)
			: base(baseOutputStream, new Deflater(Deflater.DEFAULT_COMPRESSION, true))
		{
		}

        /// <summary>
        /// Creates a new Zip output stream, writing a zip archive.
        /// </summary>
        /// <param name="baseOutputStream">The output stream to which the archive contents are written.</param>
        /// <param name="bufferSize">Size of the buffer to use.</param>
        public ZipOutputStream( Stream baseOutputStream, int bufferSize )
            : base(baseOutputStream, new Deflater(Deflater.DEFAULT_COMPRESSION, true), bufferSize)
        {
        }
        #endregion
		
		/// <summary>
		/// Gets a flag value of true if the central header has been added for this archive; false if it has not been added.
		/// </summary>
		/// <remarks>No further entries can be added once this has been done.</remarks>
		public bool IsFinished 
		{
			get {
				return entries == null;
			}
		}

		/// <summary>
		/// Set the zip file comment.
		/// </summary>
		/// <param name="comment">
		/// The comment text for the entire archive.
		/// </param>
		/// <exception name ="ArgumentOutOfRangeException">
		/// The converted comment is longer than 0xffff bytes.
		/// </exception>
		public void SetComment(string comment)
		{
			// TODO: Its not yet clear how to handle unicode comments here.
			byte[] commentBytes = ZipConstants.ConvertToArray(comment);
			if (commentBytes.Length > 0xffff) {
				throw new ArgumentOutOfRangeException("comment");
			}
			zipComment = commentBytes;
		}
		
		/// <summary>
		/// Sets the compression level.  The new level will be activated
		/// immediately.
		/// </summary>
		/// <param name="level">The new compression level (1 to 9).</param>
		/// <exception cref="ArgumentOutOfRangeException">
		/// Level specified is not supported.
		/// </exception>
		/// <see cref="Externals.Compression.Zip.Compression.Deflater"/>
		public void SetLevel(int level)
		{
			deflater_.SetLevel(level);
			defaultCompressionLevel = level;
		}
		
		/// <summary>
		/// Get the current deflater compression level
		/// </summary>
		/// <returns>The current compression level</returns>
		public int GetLevel()
		{
			return deflater_.GetLevel();
		}

		/// <summary>
		/// Get / set a value indicating how Zip64 Extension usage is determined when adding entries.
		/// </summary>
		/// <remarks>Older archivers may not understand Zip64 extensions.
		/// If backwards compatability is an issue be careful when adding <see cref="ZipEntry.Size">entries</see> to an archive.
		/// Setting this property to off is workable but less desirable as in those circumstances adding a file
		/// larger then 4GB will fail.</remarks>
		public UseZip64 UseZip64
		{
			get { return useZip64_; }
			set { useZip64_ = value; }
		}
		
		/// <summary>
		/// Write an unsigned short in little endian byte order.
		/// </summary>
		private void WriteLeShort(int value)
		{
			unchecked {
				baseOutputStream_.WriteByte((byte)(value & 0xff));
				baseOutputStream_.WriteByte((byte)((value >> 8) & 0xff));
			}
		}
		
		/// <summary>
		/// Write an int in little endian byte order.
		/// </summary>
		private void WriteLeInt(int value)
		{
			unchecked {
				WriteLeShort(value);
				WriteLeShort(value >> 16);
			}
		}
		
		/// <summary>
		/// Write an int in little endian byte order.
		/// </summary>
		private void WriteLeLong(long value)
		{
			unchecked {
				WriteLeInt((int)value);
				WriteLeInt((int)(value >> 32));
			}
		}
		
		/// <summary>
		/// Starts a new Zip entry. It automatically closes the previous
		/// entry if present.
		/// All entry elements bar name are optional, but must be correct if present.
		/// If the compression method is stored and the output is not patchable
		/// the compression for that entry is automatically changed to deflate level 0
		/// </summary>
		/// <param name="entry">
		/// the entry.
		/// </param>
		/// <exception cref="System.ArgumentNullException">
		/// if entry passed is null.
		/// </exception>
		/// <exception cref="System.IO.IOException">
		/// if an I/O error occured.
		/// </exception>
		/// <exception cref="System.InvalidOperationException">
		/// if stream was finished
		/// </exception>
		/// <exception cref="ZipException">
		/// Too many entries in the Zip file<br/>
		/// Entry name is too long<br/>
		/// Finish has already been called<br/>
		/// </exception>
		public void PutNextEntry(ZipEntry entry)
		{
			if ( entry == null ) {
				throw new ArgumentNullException("entry");
			}

			if (entries == null) {
				throw new InvalidOperationException("ZipOutputStream was finished");
			}
			
			if (curEntry != null) {
				CloseEntry();
			}

			if (entries.Count == int.MaxValue) {
				throw new ZipException("Too many entries for Zip file");
			}
			
			CompressionMethod method = entry.CompressionMethod;
			int compressionLevel = defaultCompressionLevel;
			
			// Clear flags that the library manages internally
			entry.Flags &= (int)GeneralBitFlags.UnicodeText;
			patchEntryHeader = false;

			bool headerInfoAvailable;

			// No need to compress - definitely no data.
			if (entry.Size == 0)
			{
				entry.CompressedSize = entry.Size;
				entry.Crc = 0;
				method = CompressionMethod.Stored;
				headerInfoAvailable = true;
			}
			else
			{
				headerInfoAvailable = (entry.Size >= 0) && entry.HasCrc;

				// Switch to deflation if storing isnt possible.
				if (method == CompressionMethod.Stored)
				{
					if (!headerInfoAvailable)
					{
						if (!CanPatchEntries)
						{
							// Can't patch entries so storing is not possible.
							method = CompressionMethod.Deflated;
							compressionLevel = 0;
						}
					}
					else // entry.size must be > 0
					{
						entry.CompressedSize = entry.Size;
						headerInfoAvailable = entry.HasCrc;
					}
				}
			}

			if (headerInfoAvailable == false) {
				if (CanPatchEntries == false) {
					// Only way to record size and compressed size is to append a data descriptor
					// after compressed data.

					// Stored entries of this form have already been converted to deflating.
					entry.Flags |= 8;
				} else {
					patchEntryHeader = true;
				}
			}
			
			if (Password != null) {
				entry.IsCrypted = true;
				if (entry.Crc < 0) {
					// Need to append a data descriptor as the crc isnt available for use
					// with encryption, the date is used instead.  Setting the flag
					// indicates this to the decompressor.
					entry.Flags |= 8;
				}
			}

			entry.Offset = offset;
			entry.CompressionMethod = (CompressionMethod)method;
			
			curMethod = method;
			sizePatchPos = -1;
			
			if ( (useZip64_ == UseZip64.On) || ((entry.Size < 0) && (useZip64_ == UseZip64.Dynamic)) ) {
				entry.ForceZip64();
			}

			// Write the local file header
			WriteLeInt(ZipConstants.LocalHeaderSignature);
			
			WriteLeShort(entry.Version);
			WriteLeShort(entry.Flags);
			WriteLeShort((byte)entry.CompressionMethodForHeader);
			WriteLeInt((int)entry.DosTime);

			// TODO: Refactor header writing.  Its done in several places.
			if (headerInfoAvailable == true) {
				WriteLeInt((int)entry.Crc);
				if ( entry.LocalHeaderRequiresZip64 ) {
					WriteLeInt(-1);
					WriteLeInt(-1);
				}
				else {
					WriteLeInt(entry.IsCrypted ? (int)entry.CompressedSize + ZipConstants.CryptoHeaderSize : (int)entry.CompressedSize);
					WriteLeInt((int)entry.Size);
				}
			} else {
				if (patchEntryHeader) {
					crcPatchPos = baseOutputStream_.Position;
				}
				WriteLeInt(0);	// Crc
				
				if ( patchEntryHeader ) {
					sizePatchPos = baseOutputStream_.Position;
				}

				// For local header both sizes appear in Zip64 Extended Information
				if ( entry.LocalHeaderRequiresZip64 || patchEntryHeader ) {
					WriteLeInt(-1);
					WriteLeInt(-1);
				}
				else {
					WriteLeInt(0);	// Compressed size
					WriteLeInt(0);	// Uncompressed size
				}
			}

			byte[] name = ZipConstants.ConvertToArray(entry.Flags, entry.Name);
			
			if (name.Length > 0xFFFF) {
				throw new ZipException("Entry name too long.");
			}

			ZipExtraData ed = new ZipExtraData(entry.ExtraData);

			if (entry.LocalHeaderRequiresZip64) {
				ed.StartNewEntry();
				if (headerInfoAvailable) {
					ed.AddLeLong(entry.Size);
					ed.AddLeLong(entry.CompressedSize);
				}
				else {
					ed.AddLeLong(-1);
					ed.AddLeLong(-1);
				}
				ed.AddNewEntry(1);

				if ( !ed.Find(1) ) {
					throw new ZipException("Internal error cant find extra data");
				}
				
				if ( patchEntryHeader ) {
					sizePatchPos = ed.CurrentReadIndex;
				}
			}
			else {
				ed.Delete(1);
			}

#if !NET_1_1 && !NETCF_2_0
			if (entry.AESKeySize > 0) {
				AddExtraDataAES(entry, ed);
			}
#endif
			byte[] extra = ed.GetEntryData();

			WriteLeShort(name.Length);
			WriteLeShort(extra.Length);

			if ( name.Length > 0 ) {
				baseOutputStream_.Write(name, 0, name.Length);
			}
			
			if ( entry.LocalHeaderRequiresZip64 && patchEntryHeader ) {
				sizePatchPos += baseOutputStream_.Position;
			}

			if ( extra.Length > 0 ) {
				baseOutputStream_.Write(extra, 0, extra.Length);
			}
			
			offset += ZipConstants.LocalHeaderBaseSize + name.Length + extra.Length;
			// Fix offsetOfCentraldir for AES
			if (entry.AESKeySize > 0)
				offset += entry.AESOverheadSize;
			
			// Activate the entry.
			curEntry = entry;
			crc.Reset();
			if (method == CompressionMethod.Deflated) {
				deflater_.Reset();
				deflater_.SetLevel(compressionLevel);
			}
			size = 0;

			if (entry.IsCrypted) {
#if !NET_1_1 && !NETCF_2_0
				if (entry.AESKeySize > 0) {
					WriteAESHeader(entry);
				} else
#endif
				{
					if (entry.Crc < 0) {			// so testing Zip will says its ok
						WriteEncryptionHeader(entry.DosTime << 16);
					} else {
						WriteEncryptionHeader(entry.Crc);
					}
				}
			}
		}
		
		/// <summary>
		/// Closes the current entry, updating header and footer information as required
		/// </summary>
		/// <exception cref="System.IO.IOException">
		/// An I/O error occurs.
		/// </exception>
		/// <exception cref="System.InvalidOperationException">
		/// No entry is active.
		/// </exception>
		public void CloseEntry()
		{
			if (curEntry == null) {
				throw new InvalidOperationException("No open entry");
			}

			long csize = size;
			
			// First finish the deflater, if appropriate
			if (curMethod == CompressionMethod.Deflated) {
				if (size >= 0) {
					base.Finish();
					csize = deflater_.TotalOut;
				}
				else {
					deflater_.Reset();
				}
			}

			// Write the AES Authentication Code (a hash of the compressed and encrypted data)
			if (curEntry.AESKeySize > 0) {
				baseOutputStream_.Write(AESAuthCode, 0, 10);
			}

			if (curEntry.Size < 0) {
				curEntry.Size = size;
			} else if (curEntry.Size != size) {
				throw new ZipException("size was " + size + ", but I expected " + curEntry.Size);
			}
			
			if (curEntry.CompressedSize < 0) {
				curEntry.CompressedSize = csize;
			} else if (curEntry.CompressedSize != csize) {
				throw new ZipException("compressed size was " + csize + ", but I expected " + curEntry.CompressedSize);
			}
			
			if (curEntry.Crc < 0) {
				curEntry.Crc = crc.Value;
			} else if (curEntry.Crc != crc.Value) {
				throw new ZipException("crc was " + crc.Value +	", but I expected " + curEntry.Crc);
			}
			
			offset += csize;

			if (curEntry.IsCrypted) {
				if (curEntry.AESKeySize > 0) {
					curEntry.CompressedSize += curEntry.AESOverheadSize;
					
				} else {
					curEntry.CompressedSize += ZipConstants.CryptoHeaderSize;
				}
			}
				
			// Patch the header if possible
			if (patchEntryHeader) {
				patchEntryHeader = false;

				long curPos = baseOutputStream_.Position;
				baseOutputStream_.Seek(crcPatchPos, SeekOrigin.Begin);
				WriteLeInt((int)curEntry.Crc);
				
				if ( curEntry.LocalHeaderRequiresZip64 ) {
					
					if ( sizePatchPos == -1 ) {
						throw new ZipException("Entry requires zip64 but this has been turned off");
					}
					
					baseOutputStream_.Seek(sizePatchPos, SeekOrigin.Begin);
					WriteLeLong(curEntry.Size);
					WriteLeLong(curEntry.CompressedSize);
				}
				else {
					WriteLeInt((int)curEntry.CompressedSize);
					WriteLeInt((int)curEntry.Size);
				}
				baseOutputStream_.Seek(curPos, SeekOrigin.Begin);
			}

			// Add data descriptor if flagged as required
			if ((curEntry.Flags & 8) != 0) {
				WriteLeInt(ZipConstants.DataDescriptorSignature);
				WriteLeInt(unchecked((int)curEntry.Crc));
				
				if ( curEntry.LocalHeaderRequiresZip64 ) {
					WriteLeLong(curEntry.CompressedSize);
					WriteLeLong(curEntry.Size);
					offset += ZipConstants.Zip64DataDescriptorSize;
				}
				else {
					WriteLeInt((int)curEntry.CompressedSize);
					WriteLeInt((int)curEntry.Size);
					offset += ZipConstants.DataDescriptorSize;
				}
			}
			
			entries.Add(curEntry);
			curEntry = null;
		}
		
		void WriteEncryptionHeader(long crcValue)
		{
			offset += ZipConstants.CryptoHeaderSize;
			
			InitializePassword(Password);
			
			byte[] cryptBuffer = new byte[ZipConstants.CryptoHeaderSize];
			Random rnd = new Random();
			rnd.NextBytes(cryptBuffer);
			cryptBuffer[11] = (byte)(crcValue >> 24);
			
			EncryptBlock(cryptBuffer, 0, cryptBuffer.Length);
			baseOutputStream_.Write(cryptBuffer, 0, cryptBuffer.Length);
		}

#if !NET_1_1 && !NETCF_2_0
		private static void AddExtraDataAES(ZipEntry entry, ZipExtraData extraData) {

			// Vendor Version: AE-1 IS 1. AE-2 is 2. With AE-2 no CRC is required and 0 is stored.
			const int VENDOR_VERSION = 2;
			// Vendor ID is the two ASCII characters "AE".
			const int VENDOR_ID = 0x4541; //not 6965;
			extraData.StartNewEntry();
			// Pack AES extra data field see http://www.winzip.com/aes_info.htm
			//extraData.AddLeShort(7);							// Data size (currently 7)
			extraData.AddLeShort(VENDOR_VERSION);				// 2 = AE-2
			extraData.AddLeShort(VENDOR_ID);					// "AE"
			extraData.AddData(entry.AESEncryptionStrength);		//  1 = 128, 2 = 192, 3 = 256
			extraData.AddLeShort((int)entry.CompressionMethod); // The actual compression method used to compress the file
			extraData.AddNewEntry(0x9901);
		}

		// Replaces WriteEncryptionHeader for AES
		//
		private void WriteAESHeader(ZipEntry entry) {
			byte[] salt;
			byte[] pwdVerifier;
			InitializeAESPassword(entry, Password, out salt, out pwdVerifier);
			// File format for AES:
			// Size (bytes)   Content
			// ------------   -------
			// Variable       Salt value
			// 2              Password verification value
			// Variable       Encrypted file data
			// 10             Authentication code
			//
			// Value in the "compressed size" fields of the local file header and the central directory entry
			// is the total size of all the items listed above. In other words, it is the total size of the
			// salt value, password verification value, encrypted data, and authentication code.
			baseOutputStream_.Write(salt, 0, salt.Length);
			baseOutputStream_.Write(pwdVerifier, 0, pwdVerifier.Length);
		}
#endif

		/// <summary>
		/// Writes the given buffer to the current entry.
		/// </summary>
		/// <param name="buffer">The buffer containing data to write.</param>
		/// <param name="offset">The offset of the first byte to write.</param>
		/// <param name="count">The number of bytes to write.</param>
		/// <exception cref="ZipException">Archive size is invalid</exception>
		/// <exception cref="System.InvalidOperationException">No entry is active.</exception>
		public override void Write(byte[] buffer, int offset, int count)
		{
			if (curEntry == null) {
				throw new InvalidOperationException("No open entry.");
			}
			
			if ( buffer == null ) {
				throw new ArgumentNullException("buffer");
			}
			
			if ( offset < 0 ) {
#if NETCF_1_0
				throw new ArgumentOutOfRangeException("offset");
#else
				throw new ArgumentOutOfRangeException("offset", "Cannot be negative");
#endif
			}

			if ( count < 0 ) {
#if NETCF_1_0
				throw new ArgumentOutOfRangeException("count");
#else
				throw new ArgumentOutOfRangeException("count", "Cannot be negative");
#endif
			}

			if ( (buffer.Length - offset) < count ) {
				throw new ArgumentException("Invalid offset/count combination");
			}
			
			crc.Update(buffer, offset, count);
			size += count;
			
			switch (curMethod) {
				case CompressionMethod.Deflated:
					base.Write(buffer, offset, count);
					break;
				
				case CompressionMethod.Stored:
					if (Password != null) {
						CopyAndEncrypt(buffer, offset, count);
					} else {
						baseOutputStream_.Write(buffer, offset, count);
					}
					break;
			}
		}
		
		void CopyAndEncrypt(byte[] buffer, int offset, int count)
		{
			const int CopyBufferSize = 4096;
			byte[] localBuffer = new byte[CopyBufferSize];
			while ( count > 0 ) {
				int bufferCount = (count < CopyBufferSize) ? count : CopyBufferSize;
				
				Array.Copy(buffer, offset, localBuffer, 0, bufferCount);
				EncryptBlock(localBuffer, 0, bufferCount);
				baseOutputStream_.Write(localBuffer, 0, bufferCount);
				count -= bufferCount;
				offset += bufferCount;
			}
		}
		
		/// <summary>
		/// Finishes the stream.  This will write the central directory at the
		/// end of the zip file and flush the stream.
		/// </summary>
		/// <remarks>
		/// This is automatically called when the stream is closed.
		/// </remarks>
		/// <exception cref="System.IO.IOException">
		/// An I/O error occurs.
		/// </exception>
		/// <exception cref="ZipException">
		/// Comment exceeds the maximum length<br/>
		/// Entry name exceeds the maximum length
		/// </exception>
		public override void Finish()
		{
			if (entries == null)  {
				return;
			}
			
			if (curEntry != null) {
				CloseEntry();
			}
			
			long numEntries = entries.Count;
			long sizeEntries = 0;
			
			foreach (ZipEntry entry in entries) {
				WriteLeInt(ZipConstants.CentralHeaderSignature); 
				WriteLeShort(ZipConstants.VersionMadeBy);
				WriteLeShort(entry.Version);
				WriteLeShort(entry.Flags);
				WriteLeShort((short)entry.CompressionMethodForHeader);
				WriteLeInt((int)entry.DosTime);
				WriteLeInt((int)entry.Crc);

				if ( entry.IsZip64Forced() || 
					(entry.CompressedSize >= uint.MaxValue) )
				{
					WriteLeInt(-1);
				}
				else {
					WriteLeInt((int)entry.CompressedSize);
				}

				if ( entry.IsZip64Forced() ||
					(entry.Size >= uint.MaxValue) )
				{
					WriteLeInt(-1);
				}
				else {
					WriteLeInt((int)entry.Size);
				}

				byte[] name = ZipConstants.ConvertToArray(entry.Flags, entry.Name);
				
				if (name.Length > 0xffff) {
					throw new ZipException("Name too long.");
				}
				
				ZipExtraData ed = new ZipExtraData(entry.ExtraData);

				if ( entry.CentralHeaderRequiresZip64 ) {
					ed.StartNewEntry();
					if ( entry.IsZip64Forced() ||
						(entry.Size >= 0xffffffff) )
					{
						ed.AddLeLong(entry.Size);
					}

					if ( entry.IsZip64Forced() ||
						(entry.CompressedSize >= 0xffffffff) )
					{
						ed.AddLeLong(entry.CompressedSize);
					}

					if ( entry.Offset >= 0xffffffff )
					{
						ed.AddLeLong(entry.Offset);
					}

					ed.AddNewEntry(1);
				}
				else {
					ed.Delete(1);
				}

#if !NET_1_1 && !NETCF_2_0
				if (entry.AESKeySize > 0) {
					AddExtraDataAES(entry, ed);
				}
#endif
				byte[] extra = ed.GetEntryData();
				
				byte[] entryComment = 
					(entry.Comment != null) ? 
					ZipConstants.ConvertToArray(entry.Flags, entry.Comment) :
					new byte[0];

				if (entryComment.Length > 0xffff) {
					throw new ZipException("Comment too long.");
				}
				
				WriteLeShort(name.Length);
				WriteLeShort(extra.Length);
				WriteLeShort(entryComment.Length);
				WriteLeShort(0);	// disk number
				WriteLeShort(0);	// internal file attributes
									// external file attributes

				if (entry.ExternalFileAttributes != -1) {
					WriteLeInt(entry.ExternalFileAttributes);
				} else {
					if (entry.IsDirectory) {                         // mark entry as directory (from nikolam.AT.perfectinfo.com)
						WriteLeInt(16);
					} else {
						WriteLeInt(0);
					}
				}

				if ( entry.Offset >= uint.MaxValue ) {
					WriteLeInt(-1);
				}
				else {
					WriteLeInt((int)entry.Offset);
				}
				
				if ( name.Length > 0 ) {
					baseOutputStream_.Write(name,    0, name.Length);
				}

				if ( extra.Length > 0 ) {
					baseOutputStream_.Write(extra,   0, extra.Length);
				}

				if ( entryComment.Length > 0 ) {
					baseOutputStream_.Write(entryComment, 0, entryComment.Length);
				}

				sizeEntries += ZipConstants.CentralHeaderBaseSize + name.Length + extra.Length + entryComment.Length;
			}
			
			using ( ZipHelperStream zhs = new ZipHelperStream(baseOutputStream_) ) {
				zhs.WriteEndOfCentralDirectory(numEntries, sizeEntries, offset, zipComment);
			}

			entries = null;
		}
		
		#region Instance Fields
		/// <summary>
		/// The entries for the archive.
		/// </summary>
		ArrayList entries  = new ArrayList();
		
		/// <summary>
		/// Used to track the crc of data added to entries.
		/// </summary>
		Crc32 crc = new Crc32();
		
		/// <summary>
		/// The current entry being added.
		/// </summary>
		ZipEntry  curEntry;
		
		int defaultCompressionLevel = Deflater.DEFAULT_COMPRESSION;
		
		CompressionMethod curMethod = CompressionMethod.Deflated;

		/// <summary>
		/// Used to track the size of data for an entry during writing.
		/// </summary>
		long size;
		
		/// <summary>
		/// Offset to be recorded for each entry in the central header.
		/// </summary>
		long offset;
		
		/// <summary>
		/// Comment for the entire archive recorded in central header.
		/// </summary>
		byte[] zipComment = new byte[0];
		
		/// <summary>
		/// Flag indicating that header patching is required for the current entry.
		/// </summary>
		bool patchEntryHeader;
		
		/// <summary>
		/// Position to patch crc
		/// </summary>
		long crcPatchPos = -1;
		
		/// <summary>
		/// Position to patch size.
		/// </summary>
		long sizePatchPos = -1;

		// Default is dynamic which is not backwards compatible and can cause problems
		// with XP's built in compression which cant read Zip64 archives.
		// However it does avoid the situation were a large file is added and cannot be completed correctly.
		// NOTE: Setting the size for entries before they are added is the best solution!
		UseZip64 useZip64_ = UseZip64.Dynamic;
		#endregion
	}
}