private Int32 _ExtractOne(Stream output)
{
Stream input = this.ArchiveStream;
// change for workitem 8098
input.Seek(this.FileDataPosition, SeekOrigin.Begin);
// workitem 10178
Ionic.Zip.SharedUtilities.Workaround_Ladybug318918(input);
// to validate the CRC.
Int32 CrcResult = 0;
byte[] bytes = new byte[BufferSize];
// The extraction process varies depending on how the entry was stored.
// It could have been encrypted, and it coould have been compressed, or both, or
// neither. So we need to check both the encryption flag and the compression flag,
// and take the proper action in all cases.
Int64 LeftToRead = (_CompressionMethod_FromZipFile == (short)CompressionMethod.Deflate)
? this.UncompressedSize
: this._CompressedFileDataSize;
// Get a stream that either decrypts or not.
_inputDecryptorStream = GetExtractDecryptor(input);
Stream input3 = GetExtractDecompressor( _inputDecryptorStream );
Int64 bytesWritten = 0;
// As we read, we maybe decrypt, and then we maybe decompress. Then we write.
using (var s1 = new Ionic.Zlib.CrcCalculatorStream(input3))
{
while (LeftToRead > 0)
{
//Console.WriteLine("ExtractOne: LeftToRead {0}", LeftToRead);
// Casting LeftToRead down to an int is ok here in the else clause,
// because that only happens when it is less than bytes.Length,
// which is much less than MAX_INT.
int len = (LeftToRead > bytes.Length) ? bytes.Length : (int)LeftToRead;
int n = s1.Read(bytes, 0, len);
// must check data read - essential for detecting corrupt zip files
_CheckRead(n);
output.Write(bytes, 0, n);
LeftToRead -= n;
bytesWritten += n;
// fire the progress event, check for cancels
OnExtractProgress(bytesWritten, UncompressedSize);
if (_ioOperationCanceled)
{
break;
}
}
CrcResult = s1.Crc;
}
return CrcResult;
}
