ZipFile.cs

using System;
using System.Collections;
using System.IO;
using System.Text;
using System.Globalization;
using System.Security.Cryptography;
using ICSharpCode.SharpZipLib.Encryption;
using ICSharpCode.SharpZipLib.Core;
using ICSharpCode.SharpZipLib.Checksum;
using ICSharpCode.SharpZipLib.Zip.Compression.Streams;
using ICSharpCode.SharpZipLib.Zip.Compression;

namespace ICSharpCode.SharpZipLib.Zip
{
	#region Keys Required Event Args
	/// <summary>
	/// Arguments used with KeysRequiredEvent
	/// </summary>
	public class KeysRequiredEventArgs : EventArgs
	{
		#region Constructors
		/// <summary>
		/// Initialise a new instance of <see cref="KeysRequiredEventArgs"></see>
		/// </summary>
		/// <param name="name">The name of the file for which keys are required.</param>
		public KeysRequiredEventArgs(string name)
		{
			fileName = name;
		}

		/// <summary>
		/// Initialise a new instance of <see cref="KeysRequiredEventArgs"></see>
		/// </summary>
		/// <param name="name">The name of the file for which keys are required.</param>
		/// <param name="keyValue">The current key value.</param>
		public KeysRequiredEventArgs(string name, byte[] keyValue)
		{
			fileName = name;
			key = keyValue;
		}

		#endregion
		#region Properties
		/// <summary>
		/// Gets the name of the file for which keys are required.
		/// </summary>
		public string FileName {
			get { return fileName; }
		}

		/// <summary>
		/// Gets or sets the key value
		/// </summary>
		public byte[] Key {
			get { return key; }
			set { key = value; }
		}
		#endregion

		#region Instance Fields
		string fileName;
		byte[] key;
		#endregion
	}
	#endregion

	#region Test Definitions
	/// <summary>
	/// The strategy to apply to testing.
	/// </summary>
	public enum TestStrategy
	{
		/// <summary>
		/// Find the first error only.
		/// </summary>
		FindFirstError,
		/// <summary>
		/// Find all possible errors.
		/// </summary>
		FindAllErrors,
	}

	/// <summary>
	/// The operation in progress reported by a <see cref="ZipTestResultHandler"/> during testing.
	/// </summary>
	/// <seealso cref="ZipFile.TestArchive(bool)">TestArchive</seealso>
	public enum TestOperation
	{
		/// <summary>
		/// Setting up testing.
		/// </summary>
		Initialising,

		/// <summary>
		/// Testing an individual entries header
		/// </summary>
		EntryHeader,

		/// <summary>
		/// Testing an individual entries data
		/// </summary>
		EntryData,

		/// <summary>
		/// Testing an individual entry has completed.
		/// </summary>
		EntryComplete,

		/// <summary>
		/// Running miscellaneous tests
		/// </summary>
		MiscellaneousTests,

		/// <summary>
		/// Testing is complete
		/// </summary>
		Complete,
	}

	/// <summary>
	/// Status returned returned by <see cref="ZipTestResultHandler"/> during testing.
	/// </summary>
	/// <seealso cref="ZipFile.TestArchive(bool)">TestArchive</seealso>
	public class TestStatus
	{
		#region Constructors
		/// <summary>
		/// Initialise a new instance of <see cref="TestStatus"/>
		/// </summary>
		/// <param name="file">The <see cref="ZipFile"/> this status applies to.</param>
		public TestStatus(ZipFile file)
		{
			file_ = file;
		}
		#endregion

		#region Properties

		/// <summary>
		/// Get the current <see cref="TestOperation"/> in progress.
		/// </summary>
		public TestOperation Operation {
			get { return operation_; }
		}

		/// <summary>
		/// Get the <see cref="ZipFile"/> this status is applicable to.
		/// </summary>
		public ZipFile File {
			get { return file_; }
		}

		/// <summary>
		/// Get the current/last entry tested.
		/// </summary>
		public ZipEntry Entry {
			get { return entry_; }
		}

		/// <summary>
		/// Get the number of errors detected so far.
		/// </summary>
		public int ErrorCount {
			get { return errorCount_; }
		}

		/// <summary>
		/// Get the number of bytes tested so far for the current entry.
		/// </summary>
		public long BytesTested {
			get { return bytesTested_; }
		}

		/// <summary>
		/// Get a value indicating wether the last entry test was valid.
		/// </summary>
		public bool EntryValid {
			get { return entryValid_; }
		}
		#endregion

		#region Internal API
		internal void AddError()
		{
			errorCount_++;
			entryValid_ = false;
		}

		internal void SetOperation(TestOperation operation)
		{
			operation_ = operation;
		}

		internal void SetEntry(ZipEntry entry)
		{
			entry_ = entry;
			entryValid_ = true;
			bytesTested_ = 0;
		}

		internal void SetBytesTested(long value)
		{
			bytesTested_ = value;
		}
		#endregion

		#region Instance Fields
		ZipFile file_;
		ZipEntry entry_;
		bool entryValid_;
		int errorCount_;
		long bytesTested_;
		TestOperation operation_;
		#endregion
	}

	/// <summary>
	/// Delegate invoked during <see cref="ZipFile.TestArchive(bool, TestStrategy, ZipTestResultHandler)">testing</see> if supplied indicating current progress and status.
	/// </summary>
	/// <remarks>If the message is non-null an error has occured.  If the message is null
	/// the operation as found in <see cref="TestStatus">status</see> has started.</remarks>
	public delegate void ZipTestResultHandler(TestStatus status, string message);
	#endregion

	#region Update Definitions
	/// <summary>
	/// The possible ways of <see cref="ZipFile.CommitUpdate()">applying updates</see> to an archive.
	/// </summary>
	public enum FileUpdateMode
	{
		/// <summary>
		/// Perform all updates on temporary files ensuring that the original file is saved.
		/// </summary>
		Safe,
		/// <summary>
		/// Update the archive directly, which is faster but less safe.
		/// </summary>
		Direct,
	}
	#endregion

	#region ZipFile Class
	/// <summary>
	/// This class represents a Zip archive.  You can ask for the contained
	/// entries, or get an input stream for a file entry.  The entry is
	/// automatically decompressed.
	/// 
	/// You can also update the archive adding or deleting entries.
	/// 
	/// This class is thread safe for input:  You can open input streams for arbitrary
	/// entries in different threads.
	/// <br/>
	/// <br/>Author of the original java version : Jochen Hoenicke
	/// </summary>
	/// <example>
	/// <code>
	/// using System;
	/// using System.Text;
	/// using System.Collections;
	/// using System.IO;
	/// 
	/// using ICSharpCode.SharpZipLib.Zip;
	/// 
	/// class MainClass
	/// {
	/// 	static public void Main(string[] args)
	/// 	{
	/// 		using (ZipFile zFile = new ZipFile(args[0])) {
	/// 			Console.WriteLine("Listing of : " + zFile.Name);
	/// 			Console.WriteLine("");
	/// 			Console.WriteLine("Raw Size    Size      Date     Time     Name");
	/// 			Console.WriteLine("--------  --------  --------  ------  ---------");
	/// 			foreach (ZipEntry e in zFile) {
	/// 				if ( e.IsFile ) {
	/// 					DateTime d = e.DateTime;
	/// 					Console.WriteLine("{0, -10}{1, -10}{2}  {3}   {4}", e.Size, e.CompressedSize,
	/// 						d.ToString("dd-MM-yy"), d.ToString("HH:mm"),
	/// 						e.Name);
	/// 				}
	/// 			}
	/// 		}
	/// 	}
	/// }
	/// </code>
	/// </example>
	public class ZipFile : IEnumerable, IDisposable
	{
		#region KeyHandling

		/// <summary>
		/// Delegate for handling keys/password setting during compresion/decompression.
		/// </summary>
		public delegate void KeysRequiredEventHandler(
			object sender,
			KeysRequiredEventArgs e
		);

		/// <summary>
		/// Event handler for handling encryption keys.
		/// </summary>
		public KeysRequiredEventHandler KeysRequired;

		/// <summary>
		/// Handles getting of encryption keys when required.
		/// </summary>
		/// <param name="fileName">The file for which encryption keys are required.</param>
		void OnKeysRequired(string fileName)
		{
			if (KeysRequired != null) {
				var krea = new KeysRequiredEventArgs(fileName, key);
				KeysRequired(this, krea);
				key = krea.Key;
			}
		}

		/// <summary>
		/// Get/set the encryption key value.
		/// </summary>
		byte[] Key {
			get { return key; }
			set { key = value; }
		}

		/// <summary>
		/// Password to be used for encrypting/decrypting files.
		/// </summary>
		/// <remarks>Set to null if no password is required.</remarks>
		public string Password {
			set {
				if (string.IsNullOrEmpty(value)) {
					key = null;
				} else {
					rawPassword_ = value;
					key = PkzipClassic.GenerateKeys(ZipConstants.ConvertToArray(value));
				}
			}
		}

		/// <summary>
		/// Get a value indicating wether encryption keys are currently available.
		/// </summary>
		bool HaveKeys {
			get { return key != null; }
		}
		#endregion

		#region Constructors
		/// <summary>
		/// Opens a Zip file with the given name for reading.
		/// </summary>
		/// <param name="name">The name of the file to open.</param>
		/// <exception cref="ArgumentNullException">The argument supplied is null.</exception>
		/// <exception cref="IOException">
		/// An i/o error occurs
		/// </exception>
		/// <exception cref="ZipException">
		/// The file doesn't contain a valid zip archive.
		/// </exception>
		public ZipFile(string name)
		{
			if (name == null) {
				throw new ArgumentNullException(nameof(name));
			}

			name_ = name;

			baseStream_ = File.Open(name, FileMode.Open, FileAccess.Read, FileShare.Read);
			isStreamOwner = true;

			try {
				ReadEntries();
			} catch {
				DisposeInternal(true);
				throw;
			}
		}

		/// <summary>
		/// Opens a Zip file reading the given <see cref="FileStream"/>.
		/// </summary>
		/// <param name="file">The <see cref="FileStream"/> to read archive data from.</param>
		/// <exception cref="ArgumentNullException">The supplied argument is null.</exception>
		/// <exception cref="IOException">
		/// An i/o error occurs.
		/// </exception>
		/// <exception cref="ZipException">
		/// The file doesn't contain a valid zip archive.
		/// </exception>
		public ZipFile(FileStream file)
		{
			if (file == null) {
				throw new ArgumentNullException(nameof(file));
			}

			if (!file.CanSeek) {
				throw new ArgumentException("Stream is not seekable", nameof(file));
			}

			baseStream_ = file;
			name_ = file.Name;
			isStreamOwner = true;

			try {
				ReadEntries();
			} catch {
				DisposeInternal(true);
				throw;
			}
		}

		/// <summary>
		/// Opens a Zip file reading the given <see cref="Stream"/>.
		/// </summary>
		/// <param name="stream">The <see cref="Stream"/> to read archive data from.</param>
		/// <exception cref="IOException">
		/// An i/o error occurs
		/// </exception>
		/// <exception cref="ZipException">
		/// The stream doesn't contain a valid zip archive.<br/>
		/// </exception>
		/// <exception cref="ArgumentException">
		/// The <see cref="Stream">stream</see> doesnt support seeking.
		/// </exception>
		/// <exception cref="ArgumentNullException">
		/// The <see cref="Stream">stream</see> argument is null.
		/// </exception>
		public ZipFile(Stream stream)
		{
			if (stream == null) {
				throw new ArgumentNullException(nameof(stream));
			}

			if (!stream.CanSeek) {
				throw new ArgumentException("Stream is not seekable", nameof(stream));
			}

			baseStream_ = stream;
			isStreamOwner = true;

			if (baseStream_.Length > 0) {
				try {
					ReadEntries();
				} catch {
					DisposeInternal(true);
					throw;
				}
			} else {
				entries_ = new ZipEntry[0];
				isNewArchive_ = true;
			}
		}

		/// <summary>
		/// Initialises a default <see cref="ZipFile"/> instance with no entries and no file storage.
		/// </summary>
		internal ZipFile()
		{
			entries_ = new ZipEntry[0];
			isNewArchive_ = true;
		}

		#endregion

		#region Destructors and Closing
		/// <summary>
		/// Finalize this instance.
		/// </summary>
		~ZipFile()
		{
			Dispose(false);
		}

		/// <summary>
		/// Closes the ZipFile.  If the stream is <see cref="IsStreamOwner">owned</see> then this also closes the underlying input stream.
		/// Once closed, no further instance methods should be called.
		/// </summary>
		/// <exception cref="System.IO.IOException">
		/// An i/o error occurs.
		/// </exception>
		public void Close()
		{
			DisposeInternal(true);
			GC.SuppressFinalize(this);
		}

		#endregion

		#region Creators
		/// <summary>
		/// Create a new <see cref="ZipFile"/> whose data will be stored in a file.
		/// </summary>
		/// <param name="fileName">The name of the archive to create.</param>
		/// <returns>Returns the newly created <see cref="ZipFile"/></returns>
		/// <exception cref="ArgumentNullException"><paramref name="fileName"></paramref> is null</exception>
		public static ZipFile Create(string fileName)
		{
			if (fileName == null) {
				throw new ArgumentNullException(nameof(fileName));
			}

			FileStream fs = File.Create(fileName);

			var result = new ZipFile();
			result.name_ = fileName;
			result.baseStream_ = fs;
			result.isStreamOwner = true;
			return result;
		}

		/// <summary>
		/// Create a new <see cref="ZipFile"/> whose data will be stored on a stream.
		/// </summary>
		/// <param name="outStream">The stream providing data storage.</param>
		/// <returns>Returns the newly created <see cref="ZipFile"/></returns>
		/// <exception cref="ArgumentNullException"><paramref name="outStream"> is null</paramref></exception>
		/// <exception cref="ArgumentException"><paramref name="outStream"> doesnt support writing.</paramref></exception>
		public static ZipFile Create(Stream outStream)
		{
			if (outStream == null) {
				throw new ArgumentNullException(nameof(outStream));
			}

			if (!outStream.CanWrite) {
				throw new ArgumentException("Stream is not writeable", nameof(outStream));
			}

			if (!outStream.CanSeek) {
				throw new ArgumentException("Stream is not seekable", nameof(outStream));
			}

			var result = new ZipFile();
			result.baseStream_ = outStream;
			return result;
		}

		#endregion

		#region Properties
		/// <summary>
		/// Get/set a flag indicating if the underlying stream is owned by the ZipFile instance.
		/// If the flag is true then the stream will be closed when <see cref="Close">Close</see> is called.
		/// </summary>
		/// <remarks>
		/// The default value is true in all cases.
		/// </remarks>
		public bool IsStreamOwner {
			get { return isStreamOwner; }
			set { isStreamOwner = value; }
		}

		/// <summary>
		/// Get a value indicating wether
		/// this archive is embedded in another file or not.
		/// </summary>
		public bool IsEmbeddedArchive {
			// Not strictly correct in all circumstances currently
			get { return offsetOfFirstEntry > 0; }
		}

		/// <summary>
		/// Get a value indicating that this archive is a new one.
		/// </summary>
		public bool IsNewArchive {
			get { return isNewArchive_; }
		}

		/// <summary>
		/// Gets the comment for the zip file.
		/// </summary>
		public string ZipFileComment {
			get { return comment_; }
		}

		/// <summary>
		/// Gets the name of this zip file.
		/// </summary>
		public string Name {
			get { return name_; }
		}

		/// <summary>
		/// Gets the number of entries in this zip file.
		/// </summary>
		/// <exception cref="InvalidOperationException">
		/// The Zip file has been closed.
		/// </exception>
		[Obsolete("Use the Count property instead")]
		public int Size {
			get {
				return entries_.Length;
			}
		}

		/// <summary>
		/// Get the number of entries contained in this <see cref="ZipFile"/>.
		/// </summary>
		public long Count {
			get {
				return entries_.Length;
			}
		}

		/// <summary>
		/// Indexer property for ZipEntries
		/// </summary>
		[System.Runtime.CompilerServices.IndexerNameAttribute("EntryByIndex")]
		public ZipEntry this[int index] {
			get {
				return (ZipEntry)entries_[index].Clone();
			}
		}

		#endregion

		#region Input Handling
		/// <summary>
		/// Gets an enumerator for the Zip entries in this Zip file.
		/// </summary>
		/// <returns>Returns an <see cref="IEnumerator"/> for this archive.</returns>
		/// <exception cref="ObjectDisposedException">
		/// The Zip file has been closed.
		/// </exception>
		public IEnumerator GetEnumerator()
		{
			if (isDisposed_) {
				throw new ObjectDisposedException("ZipFile");
			}

			return new ZipEntryEnumerator(entries_);
		}

		/// <summary>
		/// Return the index of the entry with a matching name
		/// </summary>
		/// <param name="name">Entry name to find</param>
		/// <param name="ignoreCase">If true the comparison is case insensitive</param>
		/// <returns>The index position of the matching entry or -1 if not found</returns>
		/// <exception cref="ObjectDisposedException">
		/// The Zip file has been closed.
		/// </exception>
		public int FindEntry(string name, bool ignoreCase)
		{
			if (isDisposed_) {
				throw new ObjectDisposedException("ZipFile");
			}

			// TODO: This will be slow as the next ice age for huge archives!
			for (int i = 0; i < entries_.Length; i++) {
				if (string.Compare(name, entries_[i].Name, ignoreCase, CultureInfo.InvariantCulture) == 0) {
					return i;
				}
			}
			return -1;
		}

		/// <summary>
		/// Searches for a zip entry in this archive with the given name.
		/// String comparisons are case insensitive
		/// </summary>
		/// <param name="name">
		/// The name to find. May contain directory components separated by slashes ('/').
		/// </param>
		/// <returns>
		/// A clone of the zip entry, or null if no entry with that name exists.
		/// </returns>
		/// <exception cref="ObjectDisposedException">
		/// The Zip file has been closed.
		/// </exception>
		public ZipEntry GetEntry(string name)
		{
			if (isDisposed_) {
				throw new ObjectDisposedException("ZipFile");
			}

			int index = FindEntry(name, true);
			return (index >= 0) ? (ZipEntry)entries_[index].Clone() : null;
		}

		/// <summary>
		/// Gets an input stream for reading the given zip entry data in an uncompressed form.
		/// Normally the <see cref="ZipEntry"/> should be an entry returned by GetEntry().
		/// </summary>
		/// <param name="entry">The <see cref="ZipEntry"/> to obtain a data <see cref="Stream"/> for</param>
		/// <returns>An input <see cref="Stream"/> containing data for this <see cref="ZipEntry"/></returns>
		/// <exception cref="ObjectDisposedException">
		/// The ZipFile has already been closed
		/// </exception>
		/// <exception cref="ICSharpCode.SharpZipLib.Zip.ZipException">
		/// The compression method for the entry is unknown
		/// </exception>
		/// <exception cref="IndexOutOfRangeException">
		/// The entry is not found in the ZipFile
		/// </exception>
		public Stream GetInputStream(ZipEntry entry)
		{
			if (entry == null) {
				throw new ArgumentNullException(nameof(entry));
			}

			if (isDisposed_) {
				throw new ObjectDisposedException("ZipFile");
			}

			long index = entry.ZipFileIndex;
			if ((index < 0) || (index >= entries_.Length) || (entries_[index].Name != entry.Name)) {
				index = FindEntry(entry.Name, true);
				if (index < 0) {
					throw new ZipException("Entry cannot be found");
				}
			}
			return GetInputStream(index);
		}

		/// <summary>
		/// Creates an input stream reading a zip entry
		/// </summary>
		/// <param name="entryIndex">The index of the entry to obtain an input stream for.</param>
		/// <returns>
		/// An input <see cref="Stream"/> containing data for this <paramref name="entryIndex"/>
		/// </returns>
		/// <exception cref="ObjectDisposedException">
		/// The ZipFile has already been closed
		/// </exception>
		/// <exception cref="ICSharpCode.SharpZipLib.Zip.ZipException">
		/// The compression method for the entry is unknown
		/// </exception>
		/// <exception cref="IndexOutOfRangeException">
		/// The entry is not found in the ZipFile
		/// </exception>
		public Stream GetInputStream(long entryIndex)
		{
			if (isDisposed_) {
				throw new ObjectDisposedException("ZipFile");
			}

			long start = LocateEntry(entries_[entryIndex]);
			CompressionMethod method = entries_[entryIndex].CompressionMethod;
			Stream result = new PartialInputStream(this, start, entries_[entryIndex].CompressedSize);

			if (entries_[entryIndex].IsCrypted == true) {
				result = CreateAndInitDecryptionStream(result, entries_[entryIndex]);
				if (result == null) {
					throw new ZipException("Unable to decrypt this entry");
				}
			}

			switch (method) {
				case CompressionMethod.Stored:
					// read as is.
					break;

				case CompressionMethod.Deflated:
					// No need to worry about ownership and closing as underlying stream close does nothing.
					result = new InflaterInputStream(result, new Inflater(true));
					break;

				default:
					throw new ZipException("Unsupported compression method " + method);
			}

			return result;
		}

		#endregion

		#region Archive Testing
		/// <summary>
		/// Test an archive for integrity/validity
		/// </summary>
		/// <param name="testData">Perform low level data Crc check</param>
		/// <returns>true if all tests pass, false otherwise</returns>
		/// <remarks>Testing will terminate on the first error found.</remarks>
		public bool TestArchive(bool testData)
		{
			return TestArchive(testData, TestStrategy.FindFirstError, null);
		}

		/// <summary>
		/// Test an archive for integrity/validity
		/// </summary>
		/// <param name="testData">Perform low level data Crc check</param>
		/// <param name="strategy">The <see cref="TestStrategy"></see> to apply.</param>
		/// <param name="resultHandler">The <see cref="ZipTestResultHandler"></see> handler to call during testing.</param>
		/// <returns>true if all tests pass, false otherwise</returns>
		/// <exception cref="ObjectDisposedException">The object has already been closed.</exception>
		public bool TestArchive(bool testData, TestStrategy strategy, ZipTestResultHandler resultHandler)
		{
			if (isDisposed_) {
				throw new ObjectDisposedException("ZipFile");
			}

			var status = new TestStatus(this);

			if (resultHandler != null) {
				resultHandler(status, null);
			}

			HeaderTest test = testData ? (HeaderTest.Header | HeaderTest.Extract) : HeaderTest.Header;

			bool testing = true;

			try {
				int entryIndex = 0;

				while (testing && (entryIndex < Count)) {
					if (resultHandler != null) {
						status.SetEntry(this[entryIndex]);
						status.SetOperation(TestOperation.EntryHeader);
						resultHandler(status, null);
					}

					try {
						TestLocalHeader(this[entryIndex], test);
					} catch (ZipException ex) {
						status.AddError();

						if (resultHandler != null) {
							resultHandler(status,
								string.Format("Exception during test - '{0}'", ex.Message));
						}

						testing &= strategy != TestStrategy.FindFirstError;
					}

					if (testing && testData && this[entryIndex].IsFile) {
						if (resultHandler != null) {
							status.SetOperation(TestOperation.EntryData);
							resultHandler(status, null);
						}

						var crc = new Crc32();

						using (Stream entryStream = this.GetInputStream(this[entryIndex])) {

							byte[] buffer = new byte[4096];
							long totalBytes = 0;
							int bytesRead;
							while ((bytesRead = entryStream.Read(buffer, 0, buffer.Length)) > 0) {
								crc.Update(buffer, 0, bytesRead);

								if (resultHandler != null) {
									totalBytes += bytesRead;
									status.SetBytesTested(totalBytes);
									resultHandler(status, null);
								}
							}
						}

						if (this[entryIndex].Crc != crc.Value) {
							status.AddError();

							if (resultHandler != null) {
								resultHandler(status, "CRC mismatch");
							}

							testing &= strategy != TestStrategy.FindFirstError;
						}

						if ((this[entryIndex].Flags & (int)GeneralBitFlags.Descriptor) != 0) {
							var helper = new ZipHelperStream(baseStream_);
							var data = new DescriptorData();
							helper.ReadDataDescriptor(this[entryIndex].LocalHeaderRequiresZip64, data);
							if (this[entryIndex].Crc != data.Crc) {
								status.AddError();
							}

							if (this[entryIndex].CompressedSize != data.CompressedSize) {
								status.AddError();
							}

							if (this[entryIndex].Size != data.Size) {
								status.AddError();
							}
						}
					}

					if (resultHandler != null) {
						status.SetOperation(TestOperation.EntryComplete);
						resultHandler(status, null);
					}

					entryIndex += 1;
				}

				if (resultHandler != null) {
					status.SetOperation(TestOperation.MiscellaneousTests);
					resultHandler(status, null);
				}

				// TODO: the 'Corrina Johns' test where local headers are missing from
				// the central directory.  They are therefore invisible to many archivers.
			} catch (Exception ex) {
				status.AddError();

				if (resultHandler != null) {
					resultHandler(status, string.Format("Exception during test - '{0}'", ex.Message));
				}
			}

			if (resultHandler != null) {
				status.SetOperation(TestOperation.Complete);
				status.SetEntry(null);
				resultHandler(status, null);
			}

			return (status.ErrorCount == 0);
		}

		[Flags]
		enum HeaderTest
		{
			Extract = 0x01,     // Check that this header represents an entry whose data can be extracted
			Header = 0x02,     // Check that this header contents are valid
		}

		/// <summary>
		/// Test a local header against that provided from the central directory
		/// </summary>
		/// <param name="entry">
		/// The entry to test against
		/// </param>
		/// <param name="tests">The type of <see cref="HeaderTest">tests</see> to carry out.</param>
		/// <returns>The offset of the entries data in the file</returns>
		long TestLocalHeader(ZipEntry entry, HeaderTest tests)
		{
			lock (baseStream_) {
				bool testHeader = (tests & HeaderTest.Header) != 0;
				bool testData = (tests & HeaderTest.Extract) != 0;

				baseStream_.Seek(offsetOfFirstEntry + entry.Offset, SeekOrigin.Begin);
				if ((int)ReadLEUint() != ZipConstants.LocalHeaderSignature) {
					throw new ZipException(string.Format("Wrong local header signature @{0:X}", offsetOfFirstEntry + entry.Offset));
				}

				var extractVersion = (short)(ReadLEUshort() & 0x00ff);
				var localFlags = (short)ReadLEUshort();
				var compressionMethod = (short)ReadLEUshort();
				var fileTime = (short)ReadLEUshort();
				var fileDate = (short)ReadLEUshort();
				uint crcValue = ReadLEUint();
				long compressedSize = ReadLEUint();
				long size = ReadLEUint();
				int storedNameLength = ReadLEUshort();
				int extraDataLength = ReadLEUshort();

				byte[] nameData = new byte[storedNameLength];
				StreamUtils.ReadFully(baseStream_, nameData);

				byte[] extraData = new byte[extraDataLength];
				StreamUtils.ReadFully(baseStream_, extraData);

				var localExtraData = new ZipExtraData(extraData);

				// Extra data / zip64 checks
				if (localExtraData.Find(1)) {
					// 2010-03-04 Forum 10512: removed checks for version >= ZipConstants.VersionZip64
					// and size or compressedSize = MaxValue, due to rogue creators.

					size = localExtraData.ReadLong();
					compressedSize = localExtraData.ReadLong();

					if ((localFlags & (int)GeneralBitFlags.Descriptor) != 0) {
						// These may be valid if patched later
						if ((size != -1) && (size != entry.Size)) {
							throw new ZipException("Size invalid for descriptor");
						}

						if ((compressedSize != -1) && (compressedSize != entry.CompressedSize)) {
							throw new ZipException("Compressed size invalid for descriptor");
						}
					}
				} else {
					// No zip64 extra data but entry requires it.
					if ((extractVersion >= ZipConstants.VersionZip64) &&
						(((uint)size == uint.MaxValue) || ((uint)compressedSize == uint.MaxValue))) {
						throw new ZipException("Required Zip64 extended information missing");
					}
				}

				if (testData) {
					if (entry.IsFile) {
						if (!entry.IsCompressionMethodSupported()) {
							throw new ZipException("Compression method not supported");
						}

						if ((extractVersion > ZipConstants.VersionMadeBy)
							|| ((extractVersion > 20) && (extractVersion < ZipConstants.VersionZip64))) {
							throw new ZipException(string.Format("Version required to extract this entry not supported ({0})", extractVersion));
						}

						if ((localFlags & (int)(GeneralBitFlags.Patched | GeneralBitFlags.StrongEncryption | GeneralBitFlags.EnhancedCompress | GeneralBitFlags.HeaderMasked)) != 0) {
							throw new ZipException("The library does not support the zip version required to extract this entry");
						}
					}
				}

				if (testHeader) {
					if ((extractVersion <= 63) &&   // Ignore later versions as we dont know about them..
						(extractVersion != 10) &&
						(extractVersion != 11) &&