Exemplo n.º 1
0
        public ushort ComputeCrc(ushort initialValue = 0)
        {
            if (_crcStartValues.Count == 0)
            {
                throw new InvalidOperationException($"You must call {nameof(StartCrcCheck)}() first.");
            }

            var startOffset = _crcStartValues.Pop();
            var endOffset   = bitOffset == 0
                ? Offset
                : Offset + 1;

            return(BitReaderExtensions.ComputeCRC(Data, startOffset, endOffset - startOffset, initialValue));
        }
Exemplo n.º 2
0
 private void UpdateCrc(byte value)
 {
     CurrentCrcValue = BitReaderExtensions.ComputeCRC(value, CurrentCrcValue);
 }
Exemplo n.º 3
0
        internal void WriteSecondHeader(BitWriter writer, DwgHeaderVariables headerVariables, int pointer)
        {
            // write to memory the backtrack to fill in size and crc
            using (var ms = new MemoryStream())
            {
                var tempWriter = new BitWriter(ms);
                tempWriter.WriteBytes(SecondHeaderStartSentinel);

                var sizeOffset = tempWriter.Position;
                tempWriter.Write_RL(0); // size, filled in later
                tempWriter.Write_BL(pointer);
                tempWriter.WriteStringAscii(Version.VersionString(), nullTerminated: false);
                tempWriter.WriteBytes(new byte[] { 0, 0, 0, 0, 0, 0 }); // 6 zero bytes
                tempWriter.WriteBits(0x00000000, 4);                    // 4 zero bits
                tempWriter.WriteBytes(new byte[] { 0, 0 });             // 2 unknown bytes
                tempWriter.WriteBytes(SecondHeaderMidSentinel);

                tempWriter.WriteByte(5); // record locator count
                HeaderVariablesLocator.Write(tempWriter, writingSecondHeader: true);
                ClassSectionLocator.Write(tempWriter, writingSecondHeader: true);
                ObjectMapLocator.Write(tempWriter, writingSecondHeader: true);
                UnknownSection_R13C3AndLaterLocator.Write(tempWriter, writingSecondHeader: true);
                UnknownSection_PaddingLocator.Write(tempWriter, writingSecondHeader: true);

                tempWriter.Write_BS(14);
                headerVariables.NextAvailableHandle.WriteSecondHeader(tempWriter, 0);
                headerVariables.BlockControlObjectHandle.WriteSecondHeader(tempWriter, 1);
                headerVariables.LayerControlObjectHandle.WriteSecondHeader(tempWriter, 2);
                headerVariables.StyleObjectControlHandle.WriteSecondHeader(tempWriter, 3);
                headerVariables.LineTypeObjectControlHandle.WriteSecondHeader(tempWriter, 4);
                headerVariables.ViewControlObjectHandle.WriteSecondHeader(tempWriter, 5);
                headerVariables.UcsControlObjectHandle.WriteSecondHeader(tempWriter, 6);
                headerVariables.ViewPortControlObjectHandle.WriteSecondHeader(tempWriter, 7);
                headerVariables.AppIdControlObjectHandle.WriteSecondHeader(tempWriter, 8);
                headerVariables.DimStyleControlObjectHandle.WriteSecondHeader(tempWriter, 9);
                headerVariables.ViewPortEntityHeaderControlObjectHandle.WriteSecondHeader(tempWriter, 10);
                headerVariables.NamedObjectsDictionaryHandle.WriteSecondHeader(tempWriter, 11);
                headerVariables.MLineStyleDictionaryHandle.WriteSecondHeader(tempWriter, 12);
                headerVariables.GroupDictionaryHandle.WriteSecondHeader(tempWriter, 13);

                tempWriter.WriteByte(0); // unknown
                tempWriter.AlignByte();
                var crcOffset = tempWriter.Position;
                tempWriter.WriteShort(0); // CRC, filled in later

                if (Version == DwgVersionId.R14)
                {
                    // unknown garbage bytes
                    tempWriter.WriteBytes(new byte[] { 0, 0, 0, 0, 0, 0, 0, 0 });
                }

                tempWriter.WriteBytes(SecondHeaderEndSentinel);

                // get bytes of header
                var secondHeaderBytes = tempWriter.AsBytes();

                // fill in size
                var sizeBytes = BitConverter.GetBytes(secondHeaderBytes.Length - SecondHeaderStartSentinel.Length - SecondHeaderEndSentinel.Length);
                if (!BitConverter.IsLittleEndian)
                {
                    Array.Reverse(sizeBytes);
                }

                Array.Copy(sizeBytes, 0, secondHeaderBytes, sizeOffset, sizeBytes.Length);

                // fill in crc
                var crc      = BitReaderExtensions.ComputeCRC(secondHeaderBytes, sizeOffset, crcOffset - sizeOffset, DwgHeaderVariables.InitialCrcValue);
                var crcBytes = BitConverter.GetBytes(crc);
                if (!BitConverter.IsLittleEndian)
                {
                    Array.Reverse(crcBytes);
                }

                Array.Copy(crcBytes, 0, secondHeaderBytes, crcOffset, crcBytes.Length);

                // write to the real writer
                writer.WriteBytes(secondHeaderBytes);
            }
        }