internal void Write(BitWriter writer)
{
writer.StartCrcCalculation();
writer.WriteStringAscii(Version.VersionString(), nullTerminated: false);
writer.WriteBytes(0, 0, 0, 0, 0);
if (Version == DwgVersionId.R14)
{
writer.WriteByte((byte)MaintenenceVersion);
}
else
{
writer.WriteByte(0);
}
writer.WriteByte(1);
writer.WriteInt(ImagePointer);
writer.WriteBytes(0, 0);
writer.WriteShort(CodePage);
writer.WriteInt(5); // 5 records
HeaderVariablesLocator.Write(writer);
ClassSectionLocator.Write(writer);
ObjectMapLocator.Write(writer);
UnknownSection_R13C3AndLaterLocator.Write(writer);
UnknownSection_PaddingLocator.Write(writer);
writer.WriteCrc(xorValue: 0x3CC4); // value for 5 records
writer.WriteBytes(HeaderSentinel);
}
private const int MaxSectionSizeBuffer = 10; // the maximum size of 2 MC values
public void Write(BitWriter writer)
{
void WriteSection(byte[] data)
{
writer.StartCrcCalculation(initialValue: DwgHeaderVariables.InitialCrcValue);
writer.WriteShortBigEndian((short)(data.Length + 2)); // account for crc
writer.WriteBytes(data);
writer.WriteCrc(writeCrcAsMsb: true);
}
// write in sections, each section is at most 2032 bytes, stop writing if remaining space is less than 10
var sectionStart = writer.Position;
var lastHandle = 0;
var lastLocation = 0;
var ms = new MemoryStream();
var sectionWriter = new BitWriter(ms);
foreach (var kvp in _handleOffsets.OrderBy(k => k.Key))
{
var sectionSize = writer.Position - sectionStart;
if (sectionSize >= MaxSectionSize - MaxSectionSizeBuffer)
{
// flush section
var sectionBytes = sectionWriter.AsBytes();
WriteSection(sectionBytes);
ms.Dispose();
ms = new MemoryStream();
sectionWriter = new BitWriter(ms);
sectionStart = writer.Position;
}
// now write the values
var handleDiff = kvp.Key - lastHandle;
var locationDiff = kvp.Value - lastLocation;
sectionWriter.Write_MC(handleDiff);
sectionWriter.Write_MC(locationDiff);
lastHandle = kvp.Key;
lastLocation = kvp.Value;
}
// flush the final section
var finalBytes = sectionWriter.AsBytes();
if (finalBytes.Length > 0)
{
WriteSection(finalBytes);
}
ms.Dispose();
// always finish with an empty section
WriteSection(new byte[0]);
}
internal void Write(BitWriter writer, DwgVersionId version)
{
writer.AlignByte();
using (var ms = new MemoryStream())
{
// write the variables to memory
var variableWriter = new BitWriter(ms);
WriteVariables(variableWriter, version);
var variableBytes = variableWriter.AsBytes();
// now write it all out
writer.WriteBytes(StartSentinel);
writer.StartCrcCalculation(initialValue: InitialCrcValue);
writer.Write_RL(variableBytes.Length);
writer.WriteBytes(variableBytes);
writer.WriteCrc();
writer.WriteBytes(EndSentinel);
}
}
internal static void Write(IList <DwgClassDefinition> classes, BitWriter writer)
{
writer.AlignByte();
using (var ms = new MemoryStream())
{
// write the classes to memory
var classWriter = new BitWriter(ms);
foreach (var c in classes)
{
c.Write(classWriter);
}
var classBytes = classWriter.AsBytes();
// now write it all out
writer.WriteBytes(StartSentinel);
writer.StartCrcCalculation(initialValue: DwgHeaderVariables.InitialCrcValue);
writer.Write_RL(classBytes.Length);
writer.WriteBytes(classBytes);
writer.WriteCrc();
writer.WriteBytes(EndSentinel);
}
}
