public static BitWriter Write_MC(this BitWriter writer, int value)
{
var bytes = new List <int>();
var isNegative = false;
if (value < 0)
{
value *= -1;
isNegative = true;
}
while (value > 0)
{
var b = value & 0b01111111;
bytes.Add(b);
value >>= 7;
}
if (bytes.Count == 0)
{
// ensure there's at least one byte written; this happens if `value` is zero
bytes.Add(0);
}
// if last byte's 64 bit is set (which means it's necessary), add one more emtpy byte so it's not interpreted as a negative sign
if ((bytes[bytes.Count - 1] & 0x40) != 0)
{
bytes.Add(0);
}
for (int i = 0; i < bytes.Count; i++)
{
var b = bytes[i];
if (i == bytes.Count - 1)
{
// on last byte, set the negative bit
if (isNegative)
{
b |= 0x40;
}
}
else
{
// more bytes remain, set high bit
b |= 0b10000000;
}
writer.WriteByte((byte)b);
}
return(writer);
}
public void CopyTo(BitWriter other)
{
var bits = BitCount;
var bytes = this.AsBytes();
var spareBits = bits % 8;
var fullBytesCount = spareBits == 0 ? bytes.Length : bytes.Length - 1;
for (int i = 0; i < fullBytesCount; i++)
{
other.WriteByte(bytes[i]);
}
other.WriteBits(bytes[bytes.Length - 1], spareBits);
}
public void Write(BitWriter writer, bool writingSecondHeader = false)
{
writer.WriteByte(RecordNumber);
if (writingSecondHeader)
{
writer.Write_BL(Pointer);
writer.Write_BL(Length);
}
else
{
writer.WriteInt(Pointer);
writer.WriteInt(Length);
}
}
public static BitWriter Write_T(this BitWriter writer, string value)
{
if (value == null)
{
writer.Write_BS(0);
return(writer);
}
writer.Write_BS((short)value.Length);
foreach (var c in value)
{
writer.WriteByte((byte)c);
}
return(writer);
}
public static BitWriter Write_H(this BitWriter writer, DwgHandleReference handle)
{
var bytes = new Stack <byte>();
var offset = handle.HandleOrOffset;
while (offset != 0)
{
bytes.Push((byte)(offset & 0xFF));
offset >>= 8;
}
var header = (((int)handle.Code) << 4) | (bytes.Count & 0x0F);
writer.WriteByte((byte)header);
writer.WriteBytes(bytes);
return(writer);
}
public static BitWriter Write_BL(this BitWriter writer, int value)
{
if (value == 0)
{
writer.Write_BB(0b10);
}
else if (value >= 0 && value <= 255)
{
writer.Write_BB(0b01);
writer.WriteByte((byte)value);
}
else
{
writer.Write_BB(0b00);
writer.WriteInt(value);
}
return(writer);
}
public static BitWriter Write_BS(this BitWriter writer, short value)
{
if (value == 0)
{
writer.Write_BB(0b10);
}
else if (value == 256)
{
writer.Write_BB(0b11);
}
else if (value >= 0 && value <= 255)
{
writer.Write_BB(0b01);
writer.WriteByte((byte)value);
}
else
{
writer.Write_BB(0b00);
writer.WriteShort(value);
}
return(writer);
}
public static BitWriter Write_RC(this BitWriter writer, byte value)
{
writer.WriteByte(value);
return(writer);
}
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);
}
}