public static void PatchSyslinux_3_72(PartitionDeviceDriver partitionDevice, FatFileSystem fat)
{
// Locate ldlinux.sys file for patching
string filename = "ldlinux.sys";
string name = (Path.GetFileNameWithoutExtension(filename) + Path.GetExtension(filename).PadRight(4).Substring(0, 4)).ToUpper();
var location = fat.FindEntry(name);
if (location.IsValid)
{
// Read boot sector
var bootSector = new DataBlock(partitionDevice.ReadBlock(0, 1));
// Set the first sector location of the file
bootSector.SetUInt(0x1F8, fat.GetSectorByCluster(location.FirstCluster));
// Change jump address
bootSector.SetUInt(0x01, 0x58);
// Write back patched boot sector
partitionDevice.WriteBlock(0, 1, bootSector.Data);
// Get the file size & number of sectors used
uint fileSize = fat.GetFileSize(location.DirectorySector, location.DirectorySectorIndex);
uint sectorCount = (fileSize + 511) >> 9;
uint[] sectors = new uint[65];
uint nsec = 0;
// Create list of the first 65 sectors of the file
for (uint cluster = location.FirstCluster; ((cluster != 0) & (nsec <= 64)); cluster = fat.GetNextCluster(cluster))
{
uint sec = fat.GetSectorByCluster(cluster);
for (uint s = 0; s < fat.SectorsPerCluster; s++)
{
sectors[nsec++] = sec + s;
}
}
// Read the first cluster of the file
var firstCluster = new DataBlock(fat.ReadCluster(location.FirstCluster));
uint patchArea = 0;
// Search for 0x3EB202FE (magic)
for (patchArea = 0; (firstCluster.GetUInt(patchArea) != 0x3EB202FE) && (patchArea < fat.ClusterSizeInBytes); patchArea += 4)
{
;
}
patchArea = patchArea + 8;
if (patchArea < fat.ClusterSizeInBytes)
{
// Set up the totals
firstCluster.SetUShort(patchArea, (ushort)(fileSize >> 2));
firstCluster.SetUShort(patchArea + 2, (ushort)(sectorCount - 1));
// Clear sector entries
firstCluster.Fill(patchArea + 8, 0, 64 * 4);
// Set sector entries
for (nsec = 0; nsec < 64; nsec++)
{
firstCluster.SetUInt(patchArea + 8 + (nsec * 4), sectors[nsec + 1]);
}
// Clear out checksum
firstCluster.SetUInt(patchArea + 4, 0);
// Write back the updated cluster
fat.WriteCluster(location.FirstCluster, firstCluster.Data);
// Re-Calculate checksum by opening the file
var file = new FatFileStream(fat, location);
uint csum = 0x3EB202FE;
for (uint index = 0; index < (file.Length >> 2); index++)
{
uint value = (uint)file.ReadByte() | ((uint)file.ReadByte() << 8) | ((uint)file.ReadByte() << 16) | ((uint)file.ReadByte() << 24);
csum -= value;
}
// Set the checksum
firstCluster.SetUInt(patchArea + 4, csum);
// Write patched cluster back to disk
fat.WriteCluster(location.FirstCluster, firstCluster.Data);
}
}
}
