// Parses the format 4 cmap table
// Refer to https://www.microsoft.com/typography/otspec/cmap.htm to learn about how this format is organized
private void ParseFormat4(byte[] source, ref uint offset, List <GlyphModel> allChars)
{
CmapFormat4Header header = ParseCmapFormat4Header(source, ref offset);
int segCount = (int)header.segCountX2 / 2;
ushort[] endCountArray = ReadUshortArrayAndIncreaseIndex(segCount, source, ref offset, sizeof(ushort));
ushort reservedPad = ReadDataAndIncreaseIndex <ushort>(source, ref offset, sizeof(ushort));
ushort[] startCountArray = ReadUshortArrayAndIncreaseIndex(segCount, source, ref offset, sizeof(ushort));
short[] idDeltaArray = ReadShortArrayAndIncreaseIndex(segCount, source, ref offset, sizeof(short));
uint idRangeTableOffset = offset;
ushort[] idRangeTable = ReadUshortArrayAndIncreaseIndex(segCount, source, ref offset, sizeof(ushort));
for (byte i = 0; i < startCountArray.Length - 1; i++)
{
if (idRangeTable[i] == 0)
{
for (uint j = startCountArray[i]; j <= endCountArray[i]; j++)
{
GlyphModel newChar = new GlyphModel();
newChar.CodePoint = j;
newChar.GlyphID = (ushort)(j + idDeltaArray[i]);
byte[] byteJ = BitConverter.GetBytes(j);
newChar.Definition = Encoding.UTF32.GetString(byteJ);
if (!allChars.Contains(newChar))
{
allChars.Add(newChar);
}
}
}
else
{
uint glyphIdOffset = idRangeTableOffset + idRangeTable[i] + (uint)(i * 2);
for (uint j = startCountArray[i]; j <= endCountArray[i]; j++)
{
ushort gID = ReadDataAndIncreaseIndex <ushort>(source, ref glyphIdOffset, sizeof(ushort));
GlyphModel newChar = new GlyphModel();
newChar.CodePoint = j;
newChar.GlyphID = gID;
byte[] byteJ = BitConverter.GetBytes(j);
newChar.Definition = Encoding.UTF32.GetString(byteJ);
if (!allChars.Contains(newChar))
{
allChars.Add(newChar);
}
}
}
}
}
// Reads through the header information of the cmap format 4 table
private CmapFormat4Header ParseCmapFormat4Header(byte[] source, ref uint offset)
{
CmapFormat4Header header = new CmapFormat4Header();
header.format = ReadDataAndIncreaseIndex <ushort>(source, ref offset, sizeof(ushort));
Debug.Assert(header.format == 4);
header.length = ReadDataAndIncreaseIndex <ushort>(source, ref offset, sizeof(ushort));
header.language = ReadDataAndIncreaseIndex <ushort>(source, ref offset, sizeof(ushort));
header.segCountX2 = ReadDataAndIncreaseIndex <ushort>(source, ref offset, sizeof(ushort));
header.searchRange = ReadDataAndIncreaseIndex <ushort>(source, ref offset, sizeof(ushort));
header.entrySelector = ReadDataAndIncreaseIndex <ushort>(source, ref offset, sizeof(ushort));
header.rangeShift = ReadDataAndIncreaseIndex <ushort>(source, ref offset, sizeof(ushort));
return(header);
}