Crisis.Ionic.Zip.ZipEntry.SetInputAndFigureFileLength C# (CSharp) Метод

        private long SetInputAndFigureFileLength(ref Stream input)
        {
            long fileLength = -1L;
            // get the original stream:
            if (this._Source == ZipEntrySource.Stream)
            {
                PrepSourceStream();
                input = this._sourceStream;

                // Try to get the length, no big deal if not available.
                try { fileLength = this._sourceStream.Length; }
                catch (NotSupportedException) { }
            }
            else if (this._Source == ZipEntrySource.ZipFile)
            {
                // we are "re-streaming" the zip entry.
                string pwd = (_Encryption_FromZipFile == EncryptionAlgorithm.None) ? null : (this._Password ?? this._container.Password);
                this._sourceStream = InternalOpenReader(pwd);
                PrepSourceStream();
                input = this._sourceStream;
                fileLength = this._sourceStream.Length;
            }
            else if (this._Source == ZipEntrySource.JitStream)
            {
                // allow the application to open the stream
                if (this._sourceStream == null) _sourceStream = this._OpenDelegate(this.FileName);
                PrepSourceStream();
                input = this._sourceStream;
                try { fileLength = this._sourceStream.Length; }
                catch (NotSupportedException) { }
            }
            else if (this._Source == ZipEntrySource.FileSystem)
            {
                // workitem 7145
                FileShare fs = FileShare.ReadWrite;
#if !NETCF
                // FileShare.Delete is not defined for the Compact Framework
                fs |= FileShare.Delete;
#endif
                // workitem 8423
                input = File.Open(LocalFileName, FileMode.Open, FileAccess.Read, fs);
                fileLength = input.Length;
            }

            return fileLength;
        }