Crisis.Ionic.Zip.ZipEntry.ProcessExtraFieldZip64 C# (CSharp) Method

        private int ProcessExtraFieldZip64(byte[] buffer, int j, Int16 dataSize, long posn)
        {
            // The PKWare spec says that any of {UncompressedSize, CompressedSize,
            // RelativeOffset} exceeding 0xFFFFFFFF can lead to the ZIP64 header,
            // and the ZIP64 header may contain one or more of those.  If the
            // values are present, they will be found in the prescribed order.
            // There may also be a 4-byte "disk start number."
            // This means that the DataSize must be 28 bytes or less.

            this._InputUsesZip64 = true;

            // workitem 7941: check datasize before reading.
            if (dataSize > 28)
                throw new BadReadException(String.Format("  Inconsistent size (0x{0:X4}) for ZIP64 extra field at position 0x{1:X16}",
                                                         dataSize, posn));
            int remainingData = dataSize;

            var slurp = new Func<Int64>( () => {
                    if (remainingData < 8)
                        throw new BadReadException(String.Format("  Missing data for ZIP64 extra field, position 0x{0:X16}", posn));
                    var x = BitConverter.ToInt64(buffer, j);
                    j+= 8;
                    remainingData -= 8;
                    return x;
                });

            if (this._UncompressedSize == 0xFFFFFFFF)
                this._UncompressedSize = slurp();

            if (this._CompressedSize == 0xFFFFFFFF)
                this._CompressedSize = slurp();

            if (this._RelativeOffsetOfLocalHeader == 0xFFFFFFFF)
                this._RelativeOffsetOfLocalHeader = slurp();

            // Ignore anything else. Potentially there are 4 more bytes for the
            // disk start number.  DotNetZip currently doesn't handle multi-disk
            // archives.
            return j;
        }