zipfile.cs

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				baseStream.Seek(pos--, SeekOrigin.Begin);
			} while (ReadLeInt() != signature);
	
			return baseStream.Position;
		}
		
		/// <summary>
		/// Search for and read the central directory of a zip file filling the entries
		/// array.  This is called exactly once by the constructors.
		/// </summary>
		/// <exception cref="System.IO.IOException">
		/// An i/o error occurs.
		/// </exception>
		/// <exception cref="ICSharpCode.SharpZipLib.Zip.ZipException">
		/// The central directory is malformed or cannot be found
		/// </exception>
		void ReadEntries()
		{
			// Search for the End Of Central Directory.  When a zip comment is
			// present the directory may start earlier.
			// 
			// TODO: The search is limited to 64K which is the maximum size of a trailing comment field to aid speed.
			// This should be compatible with both SFX and ZIP files but has only been tested for Zip files
			// Need to confirm this is valid in all cases.
			// Could also speed this up by reading memory in larger blocks.			

			if (baseStream.CanSeek == false) {
				throw new ZipException("ZipFile stream must be seekable");
			}
			
			long locatedCentralDirOffset = LocateBlockWithSignature(ZipConstants.ENDSIG, baseStream.Length, ZipConstants.ENDHDR, 0xffff);
			if (locatedCentralDirOffset < 0) {
				throw new ZipException("Cannot find central directory");
			}

			int thisDiskNumber            = ReadLeShort();
			int startCentralDirDisk       = ReadLeShort();
			int entriesForThisDisk        = ReadLeShort();
			int entriesForWholeCentralDir = ReadLeShort();
			int centralDirSize            = ReadLeInt();
			int offsetOfCentralDir        = ReadLeInt();
			int commentSize               = ReadLeShort();
			
			byte[] zipComment = new byte[commentSize]; 
			baseStream.Read(zipComment, 0, zipComment.Length); 
			comment = ZipConstants.ConvertToString(zipComment); 
			
/* Its seems possible that this is too strict, more digging required.
			if (thisDiskNumber != 0 || startCentralDirDisk != 0 || entriesForThisDisk != entriesForWholeCentralDir) {
				throw new ZipException("Spanned archives are not currently handled");
			}
*/

			entries = new ZipEntry[entriesForWholeCentralDir];
			
			// SFX support, find the offset of the first entry vis the start of the stream
			// This applies to Zip files that are appended to the end of the SFX stub.
			// Zip files created by some archivers have the offsets altered to reflect the true offsets
			// and so dont require any adjustment here...
			if (offsetOfCentralDir < locatedCentralDirOffset - (4 + centralDirSize)) {
				offsetOfFirstEntry = locatedCentralDirOffset - (4 + centralDirSize + offsetOfCentralDir);
				if (offsetOfFirstEntry <= 0) {
					throw new ZipException("Invalid SFX file");
				}
			}

			baseStream.Seek(offsetOfFirstEntry + offsetOfCentralDir, SeekOrigin.Begin);
			
			for (int i = 0; i < entriesForThisDisk; i++) {
				if (ReadLeInt() != ZipConstants.CENSIG) {
					throw new ZipException("Wrong Central Directory signature");
				}
				
				int versionMadeBy      = ReadLeShort();
				int versionToExtract   = ReadLeShort();
				int bitFlags           = ReadLeShort();
				int method             = ReadLeShort();
				int dostime            = ReadLeInt();
				int crc                = ReadLeInt();
				int csize              = ReadLeInt();
				int size               = ReadLeInt();
				int nameLen            = ReadLeShort();
				int extraLen           = ReadLeShort();
				int commentLen         = ReadLeShort();
				
				int diskStartNo        = ReadLeShort();  // Not currently used
				int internalAttributes = ReadLeShort();  // Not currently used

				int externalAttributes = ReadLeInt();
				int offset             = ReadLeInt();
				
				byte[] buffer = new byte[Math.Max(nameLen, commentLen)];
				
				baseStream.Read(buffer, 0, nameLen);
				string name = ZipConstants.ConvertToString(buffer, nameLen);
				
				ZipEntry entry = new ZipEntry(name, versionToExtract, versionMadeBy);
				entry.CompressionMethod = (CompressionMethod)method;
				entry.Crc = crc & 0xffffffffL;
				entry.Size = size & 0xffffffffL;
				entry.CompressedSize = csize & 0xffffffffL;
				entry.Flags = bitFlags;
				entry.DosTime = (uint)dostime;
				
				if (extraLen > 0) {
					byte[] extra = new byte[extraLen];
					baseStream.Read(extra, 0, extraLen);
					entry.ExtraData = extra;
				}
				
				if (commentLen > 0) {
					baseStream.Read(buffer, 0, commentLen);
					entry.Comment = ZipConstants.ConvertToString(buffer, commentLen);
				}
				
				entry.ZipFileIndex           = i;
				entry.Offset                 = offset;
				entry.ExternalFileAttributes = externalAttributes;
				
				entries[i] = entry;
			}
		}
		
		/// <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()
		{
			entries = null;
			if ( isStreamOwner ) {
				lock(baseStream) {
					baseStream.Close();
				}
			}
		}
		
		/// <summary>
		/// Returns an enumerator for the Zip entries in this Zip file.
		/// </summary>
		/// <exception cref="InvalidOperationException">
		/// The Zip file has been closed.
		/// </exception>
		public IEnumerator GetEnumerator()
		{
			if (entries == null) {
				throw new InvalidOperationException("ZipFile has closed");
			}
			
			return new ZipEntryEnumeration(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="InvalidOperationException">
		/// The Zip file has been closed.
		/// </exception>
		public int FindEntry(string name, bool ignoreCase)
		{
			if (entries == null) {
				throw new InvalidOperationException("ZipFile has been closed");
			}
			
			for (int i = 0; i < entries.Length; i++) {
				if (string.Compare(name, entries[i].Name, ignoreCase) == 0) {
					return i;
				}
			}
			return -1;
		}
		
		/// <summary>
		/// Indexer property for ZipEntries
		/// </summary>
		[System.Runtime.CompilerServices.IndexerNameAttribute("EntryByIndex")]
		public ZipEntry this[int index] {
			get {
				return (ZipEntry) entries[index].Clone();	
			}
		}
		
		/// <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>
		/// The zip entry, or null if no entry with that name exists.
		/// </returns>
		/// <exception cref="InvalidOperationException">
		/// The Zip file has been closed.
		/// </exception>
		public ZipEntry GetEntry(string name)
		{
			if (entries == null) {
				throw new InvalidOperationException("ZipFile has been closed");
			}
			
			int index = FindEntry(name, true);
			return index >= 0 ? (ZipEntry) entries[index].Clone() : null;
		}
		/// <summary>
		/// Test an archive for integrity/validity
		/// </summary>
		/// <param name="testData">Perform low level data Crc check</param>
		/// <returns>true iff the test passes, false otherwise</returns>
		public bool TestArchive(bool testData)
		{
			bool result = true;
			try {
				for (int i = 0; i < Size; ++i) {
					long offset = TestLocalHeader(this[i], true, true);
					if (testData) {
						Stream entryStream = this.GetInputStream(this[i]);
						// TODO: events for updating info, recording errors etc
						Crc32 crc = new Crc32();
						byte[] buffer = new byte[4096];
						int bytesRead;
						while ((bytesRead = entryStream.Read(buffer, 0, buffer.Length)) > 0) {
							crc.Update(buffer, 0, bytesRead);
						}
	
						if (this[i].Crc != crc.Value) {
							result = false;
							// TODO: Event here....
							break; // Do all entries giving more info at some point?
						}
					}
				}
			}
			catch {
				result = false;
			}
			return result;
		}
	
		/// <summary>
		/// Test the local header against that provided from the central directory
		/// </summary>
		/// <param name="entry">
		/// The entry to test against
		/// </param>
		/// <param name="fullTest">
		/// If true be extremely picky about the testing, otherwise be relaxed
		/// </param>
		/// <param name="extractTest">
		/// Apply extra testing to see if the entry can be extracted by the library
		/// </param>
		/// <returns>The offset of the entries data in the file</returns>
		long TestLocalHeader(ZipEntry entry, bool fullTest, bool extractTest)
		{
			lock(baseStream) 
			{
				baseStream.Seek(offsetOfFirstEntry + entry.Offset, SeekOrigin.Begin);
				if (ReadLeInt() != ZipConstants.LOCSIG) {
					throw new ZipException("Wrong local header signature");
				}
				
				short shortValue = (short)ReadLeShort();	 // version required to extract
				if (extractTest == true && shortValue > ZipConstants.VERSION_MADE_BY) {
					throw new ZipException(string.Format("Version required to extract this entry not supported ({0})", shortValue));
				}

				short localFlags = (short)ReadLeShort();				  // general purpose bit flags.
				if (extractTest == true) {
					if ((localFlags & (int)(GeneralBitFlags.Patched | GeneralBitFlags.StrongEncryption | GeneralBitFlags.EnhancedCompress | GeneralBitFlags.HeaderMasked)) != 0) {
						throw new ZipException("The library doesnt support the zip version required to extract this entry");
					}
				}
					
				if (localFlags != entry.Flags) {
				   throw new ZipException("Central header/local header flags mismatch");
				}

				if (entry.CompressionMethod != (CompressionMethod)ReadLeShort()) {
				   throw new ZipException("Central header/local header compression method mismatch");
				}
	
				shortValue = (short)ReadLeShort();  // file time
				shortValue = (short)ReadLeShort();  // file date
	
				int intValue = ReadLeInt();         // Crc
	
				if (fullTest) {
					if ((localFlags & (int)GeneralBitFlags.Descriptor) == 0) {
						if (intValue != (int)entry.Crc) 
							throw new ZipException("Central header/local header crc mismatch");
					}
				}
	
				intValue = ReadLeInt();	   // compressed Size
				intValue = ReadLeInt();	   // uncompressed size
	
				// TODO: make test more correct...  can't compare lengths as was done originally as this can fail for MBCS strings
				// Assuming a code page at this point is not valid?  Best is to store the name length in the ZipEntry probably
				int storedNameLength = ReadLeShort();
				if (entry.Name.Length > storedNameLength) {
					throw new ZipException("file name length mismatch");
				}
					
				int extraLen = storedNameLength + ReadLeShort();
				return offsetOfFirstEntry + entry.Offset + ZipConstants.LOCHDR + extraLen;
			}
		}
		
		/// <summary>
		/// Checks, if the local header of the entry at index i matches the
		/// central directory, and returns the offset to the data.
		/// </summary>
		/// <returns>
		/// The start offset of the (compressed) data.
		/// </returns>
		/// <exception cref="System.IO.EndOfStreamException">
		/// The stream ends prematurely
		/// </exception>
		/// <exception cref="ICSharpCode.SharpZipLib.Zip.ZipException">
		/// The local header signature is invalid, the entry and central header file name lengths are different
		/// or the local and entry compression methods dont match
		/// </exception>
		long CheckLocalHeader(ZipEntry entry)
		{
			return TestLocalHeader(entry, false, true);
		}
		
		// Refactor this, its done elsewhere as well
		void ReadFully(Stream s, byte[] outBuf)
		{
			int off = 0;
			int len = outBuf.Length;