static byte[] get_TTF_digest(OTFile f)
{
OTFont fn = f.GetFont(0);
Table_DSIG tDSIG = (Table_DSIG)fn.GetTable("DSIG");
DirectoryEntry deDSIG = null;
// sort table by offset
Dictionary <uint, int> offsetlookup = new Dictionary <uint, int>();
var list = new List <uint>();
for (ushort i = 0; i < fn.GetNumTables(); i++)
{
DirectoryEntry de = fn.GetDirectoryEntry(i);
offsetlookup.Add(de.offset, i);
list.Add(de.offset);
if ((string)de.tag == "DSIG")
{
deDSIG = de;
}
}
list.Sort();
// New offset table
var old_ot = fn.GetOffsetTable();
OffsetTable ot = new OffsetTable(old_ot.sfntVersion, (ushort)(old_ot.numTables - 1));
for (ushort i = 0; i < fn.GetNumTables(); i++)
{
DirectoryEntry oldde = fn.GetDirectoryEntry(i);
if ((string)oldde.tag != "DSIG")
{
DirectoryEntry de = new DirectoryEntry(oldde);
de.offset -= 16; // one less entry
if (de.offset > deDSIG.offset)
{
de.offset -= tDSIG.GetBuffer().GetPaddedLength();
}
ot.DirectoryEntries.Add(de);
}
}
hash.TransformBlock(ot.m_buf.GetBuffer(), 0, (int)ot.m_buf.GetLength(), ot.m_buf.GetBuffer(), 0);
for (int i = 0; i < ot.DirectoryEntries.Count; i++)
{
DirectoryEntry de = (DirectoryEntry)ot.DirectoryEntries[i];
hash.TransformBlock(de.m_buf.GetBuffer(), 0, (int)de.m_buf.GetLength(), de.m_buf.GetBuffer(), 0);
}
Table_head headTable = (Table_head)fn.GetTable("head");
// calculate the checksum
uint sum = 0;
sum += ot.CalcOffsetTableChecksum();
sum += ot.CalcDirectoryEntriesChecksum();
foreach (var key in list)
{
OTTable table = fn.GetTable((ushort)offsetlookup[key]);
if ((string)table.GetTag() != "DSIG")
{
sum += table.CalcChecksum();
}
}
Table_head.head_cache headCache = (Table_head.head_cache)headTable.GetCache();
// set the checkSumAdujustment field
headCache.checkSumAdjustment = 0xb1b0afba - sum;
Table_head newHead = (Table_head)headCache.GenerateTable();
foreach (var key in list)
{
OTTable table = fn.GetTable((ushort)offsetlookup[key]);
if ((string)table.GetTag() == "head")
{
table = newHead;
}
if ((string)table.GetTag() != "DSIG")
{
hash.TransformBlock(table.m_bufTable.GetBuffer(), 0, (int)table.GetBuffer().GetPaddedLength(),
table.m_bufTable.GetBuffer(), 0);
}
}
byte[] usFlag = { 0, 1 };
hash.TransformFinalBlock(usFlag, 0, 2);
return(hash.Hash);
}