internal static DwgHeaderVariables Parse(BitReader reader, DwgVersionId version)
{
var header = new DwgHeaderVariables();
reader.ValidateSentinel(StartSentinel);
reader.StartCrcCheck();
var size = reader.Read_RL();
var startOffset = reader.Offset;
header.ReadVariables(reader, version);
reader.AlignToByte();
var unreadByteCount = Math.Max(startOffset + size - reader.Offset, 0);
var unreadBytes = reader.ReadBytes(unreadByteCount);
reader.ValidateCrc(initialValue: InitialCrcValue);
reader.ValidateSentinel(EndSentinel);
return(header);
}
internal static int ReadSecondHeader(BitReader reader, int byteCount)
{
var handleBytes = reader.ReadBytes(byteCount);
if (!BitConverter.IsLittleEndian)
{
Array.Reverse(handleBytes);
}
var handle = 0;
foreach (var b in handleBytes)
{
handle = (handle << 8) + b;
}
return(handle);
}
internal static DwgFileHeader Parse(BitReader reader)
{
reader.StartCrcCheck();
var versionString = reader.ReadStringAscii(6);
var version = DwgVersionIdExtensions.VersionIdFromString(versionString);
var unknown1 = reader.ReadBytes(6);
var maintVer = 0;
if (version == DwgVersionId.R14)
{
maintVer = unknown1[5];
}
var marker = reader.ReadByte();
if (marker != 1)
{
throw new DwgReadException("Expected value of 1 at offset 13.");
}
var imagePointer = reader.ReadInt();
var unknown2 = reader.ReadBytes(2);
var codePage = reader.ReadShort();
var header = new DwgFileHeader(version, maintVer, imagePointer, codePage);
var recordLocatorCount = reader.ReadInt();
for (int i = 0; i < recordLocatorCount; i++)
{
var locator = DwgSectionLocator.Parse(reader);
switch (i)
{
case 0:
header.HeaderVariablesLocator = locator;
break;
case 1:
header.ClassSectionLocator = locator;
break;
case 2:
header.ObjectMapLocator = locator;
break;
case 3:
header.UnknownSection_R13C3AndLaterLocator = locator;
break;
case 4:
header.UnknownSection_PaddingLocator = locator;
break;
}
}
ushort crcXorValue;
switch (recordLocatorCount)
{
case 0:
case 1:
case 2:
crcXorValue = 0;
break;
case 3:
crcXorValue = 0xAD98;
break;
case 4:
crcXorValue = 0x8101;
break;
case 5:
crcXorValue = 0x3CC4;
break;
case 6:
crcXorValue = 0x8461;
break;
default:
throw new DwgReadException("Unsupported record locator count.");
}
reader.ValidateCrc(xorValue: crcXorValue);
reader.ValidateSentinel(HeaderSentinel);
return(header);
}
internal static DwgImageData Parse(BitReader reader)
{
var imageData = new DwgImageData();
reader.ValidateSentinel(StartSentinel);
var overallSize = reader.Read_RL();
var startOffset = reader.Offset;
var imageCount = reader.Read_RC();
var headerStart = 0;
var headerSize = 0;
var bmpStart = 0;
var bmpSize = 0;
var wmfStart = 0;
var wmfSize = 0;
for (int i = 0; i < imageCount; i++)
{
var code = reader.Read_RC();
var start = reader.Read_RL();
var size = reader.Read_RL();
switch (code)
{
case 1:
headerStart = start;
headerSize = size;
break;
case 2:
bmpStart = start;
bmpSize = size;
break;
case 3:
wmfStart = start;
wmfSize = size;
break;
}
}
if (headerSize > 0)
{
if (reader.Offset != headerStart)
{
throw new DwgReadException("Unexpected image data header start.");
}
imageData.HeaderData = reader.ReadBytes(headerSize);
}
if (bmpSize > 0)
{
if (reader.Offset != bmpStart)
{
throw new DwgReadException("Unexpected BMP data start.");
}
imageData.BmpData = reader.ReadBytes(bmpSize);
}
if (wmfSize > 0)
{
if (reader.Offset != wmfStart)
{
throw new DwgReadException("Unexpected WMF data start.");
}
imageData.WmfData = reader.ReadBytes(wmfSize);
}
var endOffset = reader.Offset;
var readBytes = endOffset - startOffset;
if (readBytes != overallSize)
{
throw new DwgReadException($"Invalid count of read image data bytes. Expected: {overallSize}, Actual: {readBytes}");
}
reader.ValidateSentinel(EndSentinel);
return(imageData);
}
public static byte[] Read_Bytes(this BitReader reader, int count)
{
return(reader.ReadBytes(count));
}
