private bool CalculateLayer2Checksum(string filename, int OffsetLayer2, bool forceSilent)
{
bool Layer2ChecksumValid = false;
uint checksum0 = 0;
uint checksum1 = 0;
uint sum0 = 0;
uint matrix_dimension = 0;
uint partial_address = 0;
uint x = 0;
/*
Get 0x100 byte buffer from CHPTR – CHPTR + 0xFF
Because level 1 is in that area level1 must be correct first
Prepare coded_buffer (0x100 buffer from chptr) with loop: coded_buffer(x) = (buffer (x) + 0xD6) xor 0x21
(add 0xd6 to every byte of buffer, then xor it by 0x21)
[ 1 indexed, not 0 indexed ]
So, 0x101 byte buffer with first byte ignored (convention)
* */
byte[] coded_buffer = readdatafromfile(filename, OffsetLayer2, 0x100);
for (int i = 0; i < coded_buffer.Length; i++)
{
byte b = coded_buffer[i];
b += 0xD6;
b ^= 0x21;
coded_buffer[i] = b;
//Console.Write(b.ToString("X2") + " ");
}
//logger.Debug("");
byte[] complete_file = readdatafromfile(filename, 0, m_currentfile_size);
int index = 0;
bool chk_found = false;
while (index < 0x100 && !chk_found)
{
if ((coded_buffer[index] == 0xFB) && (coded_buffer[index + 6] == 0xFC) && (coded_buffer[index + 0x0C] == 0xFD))
{
sum0 = ((uint)coded_buffer[index + 1] * 0x01000000 + (uint)coded_buffer[index + 2] * 0x010000 + (uint)coded_buffer[index + 3] * 0x100 + (uint)coded_buffer[index + 4]);
matrix_dimension = (uint)coded_buffer[index + 7] * 0x01000000 + (uint)coded_buffer[index + 8] * 0x010000 + (uint)coded_buffer[index + 9] * 0x100 + (uint)coded_buffer[index + 10];
partial_address = (uint)coded_buffer[index + 0x0d] * 0x01000000 + (uint)coded_buffer[index + 0x0e] * 0x010000 + (uint)coded_buffer[index + 0x0F] * 0x100 + (uint)coded_buffer[index + 0x10];
if (matrix_dimension >= 0x020000)
{
checksum0 = 0;
x = partial_address /*+ 1*/;
while (x < (matrix_dimension - 4))
{
checksum0 = checksum0 + (uint)complete_file[x];
x++;
}
checksum0 = checksum0 + (uint)complete_file[matrix_dimension - 1];
checksum1 = 0;
x = partial_address /*+ 1*/;
while (x < (matrix_dimension - 4))
{
checksum1 = checksum1 + (uint)complete_file[x] * 0x01000000 + (uint)complete_file[x + 1] * 0x10000 + (uint)complete_file[x + 2] * 0x100 + (uint)complete_file[x + 3];
x = x + 4;
}
if ((checksum0 & 0xFFF00000) != (sum0 & 0xFFF00000))
{
checksum0 = checksum1;
}
if (checksum0 != sum0)
{
//MessageBox.Show("Layer 2 checksum was invalid, should be updated!");
if (m_appSettings.AutoChecksum || forceSilent)
{
byte[] checksum_to_file = new byte[4];
checksum_to_file[0] = Convert.ToByte((checksum0 >> 24) & 0x000000FF);
checksum_to_file[1] = Convert.ToByte((checksum0 >> 16) & 0x000000FF);
checksum_to_file[2] = Convert.ToByte((checksum0 >> 8) & 0x000000FF);
checksum_to_file[3] = Convert.ToByte((checksum0) & 0x000000FF);
checksum_to_file[0] = Convert.ToByte(((checksum_to_file[0] ^ 0x21) - (byte)0xD6) & 0x000000FF);
checksum_to_file[1] = Convert.ToByte(((checksum_to_file[1] ^ 0x21) - (byte)0xD6) & 0x000000FF);
checksum_to_file[2] = Convert.ToByte(((checksum_to_file[2] ^ 0x21) - (byte)0xD6) & 0x000000FF);
checksum_to_file[3] = Convert.ToByte(((checksum_to_file[3] ^ 0x21) - (byte)0xD6) & 0x000000FF);
//CreateBinaryBackup();
savedatatobinary(index + OffsetLayer2 + 1, 4, checksum_to_file, filename, false);
Layer2ChecksumValid = true;
}
else
{
frmChecksum frmchecksum = new frmChecksum();
frmchecksum.Layer = "Checksum validation Layer 2";
string layer2file = sum0.ToString("X8");
string layer2calc = checksum0.ToString("X8");
frmchecksum.FileChecksum = layer2file;
frmchecksum.RealChecksum = layer2calc;
if (frmchecksum.ShowDialog() == DialogResult.OK)
{
byte[] checksum_to_file = new byte[4];
checksum_to_file[0] = Convert.ToByte((checksum0 >> 24) & 0x000000FF);
checksum_to_file[1] = Convert.ToByte((checksum0 >> 16) & 0x000000FF);
checksum_to_file[2] = Convert.ToByte((checksum0 >> 8) & 0x000000FF);
checksum_to_file[3] = Convert.ToByte((checksum0) & 0x000000FF);
checksum_to_file[0] = Convert.ToByte(((checksum_to_file[0] ^ 0x21) - (byte)0xD6) & 0x000000FF);
checksum_to_file[1] = Convert.ToByte(((checksum_to_file[1] ^ 0x21) - (byte)0xD6) & 0x000000FF);
checksum_to_file[2] = Convert.ToByte(((checksum_to_file[2] ^ 0x21) - (byte)0xD6) & 0x000000FF);
checksum_to_file[3] = Convert.ToByte(((checksum_to_file[3] ^ 0x21) - (byte)0xD6) & 0x000000FF);
//CreateBinaryBackup();
savedatatobinary(index + OffsetLayer2 + 1, 4, checksum_to_file, filename, true);
Layer2ChecksumValid = true;
coded_buffer[index/* + 1*/] = Convert.ToByte((checksum0 >> 24) & 0x000000FF);
coded_buffer[index/* + 2*/] = Convert.ToByte((checksum0 >> 16) & 0x000000FF);
coded_buffer[index/* + 3*/] = Convert.ToByte((checksum0 >> 8) & 0x000000FF);
coded_buffer[index/* + 4*/] = Convert.ToByte((checksum0) & 0x000000FF);
for (int i = 0; i < 4; i++)
{
//TODO: Actually update the file!!!
//complete_file[i + index + OffsetLayer2] = Convert.ToByte((coded_buffer[index + i] ^ 0x21) - 0xD6);
}
// checksum is ready
}
else
{
Layer2ChecksumValid = false;
}
}
}
else
{
Layer2ChecksumValid = true;
}
chk_found = true;
}
}
index++;
}
if (!chk_found)
{
//MessageBox.Show("Layer 2 checksum could not be calculated [ file incompatible ]");
}
return Layer2ChecksumValid;
}
private void UpdateChecksum(string filename, bool forceSilent)
{
int m_ChecksumAreaOffset = GetChecksumAreaOffset(filename);
if (m_ChecksumAreaOffset > m_currentfile_size) return;
bool do_layer2 = true;
bool _layer1Valid = false;
bool _layer2Valid = false;
barChecksumInfo.Caption = "Checksum: validating...";
System.Windows.Forms.Application.DoEvents();
//logger.Debug("Checksum area offset: " + m_ChecksumAreaOffset.ToString("X8"));
byte[] hash = CalculateLayer1ChecksumMD5(filename, m_ChecksumAreaOffset, forceSilent);
// compare hash to bytes after checksumareaoffset
byte[] layer1checksuminfile = readdatafromfile(filename, m_ChecksumAreaOffset + 2, 16);
if (!CompareByteArray(hash, layer1checksuminfile))
{
//CreateBinaryBackup();
//savedatatobinary(m_ChecksumAreaOffset + 2, 16, hash, filename);
if (m_appSettings.AutoChecksum || forceSilent)
{
savedatatobinary(m_ChecksumAreaOffset + 2, 16, hash, filename, false);
_layer1Valid = true;
do_layer2 = true;
}
else
{
frmChecksum frmchecksum = new frmChecksum();
frmchecksum.Layer = "Checksum validation Layer 1";
string layer1file = string.Empty;
string layer1calc = string.Empty;
for (int i = 0; i < layer1checksuminfile.Length; i++)
{
layer1file += layer1checksuminfile[i].ToString("X2") + " ";
layer1calc += hash[i].ToString("X2") + " ";
}
frmchecksum.FileChecksum = layer1file;
frmchecksum.RealChecksum = layer1calc;
if (frmchecksum.ShowDialog() == DialogResult.OK)
{
savedatatobinary(m_ChecksumAreaOffset + 2, 16, hash, filename, false);
_layer1Valid = true;
do_layer2 = true;
}
else
{
do_layer2 = false;
}
}
}
else
{
_layer1Valid = true;
}
if (do_layer2)
{
if (CalculateLayer2Checksum(filename, m_ChecksumAreaOffset, forceSilent))
{
_layer2Valid = true;
}
else
{
_layer2Valid = false;
}
}
// show result in statusbar
if (_layer1Valid && _layer2Valid)
{
barChecksumInfo.Caption = "Checksum: OK";
}
else if (!_layer1Valid)
{
barChecksumInfo.Caption = "Checksum: Layer 1 invalid";
}
else if (!_layer2Valid)
{
barChecksumInfo.Caption = "Checksum: Layer 2 invalid";
}
}