private static void ReplaceEntry(DrpFileEntry entry, byte[] replaceWith)
{
var before = entry.GetData().Length;
var after = replaceWith.Length;
entry.SetData(replaceWith);
var msg = $"Replaced: {entry.FileName}.";
if (before != after)
{
msg += $" {before}->{after}";
}
Console.WriteLine(msg);
}
private static void WriteEntry(this BinaryWriter bw, DrpFileEntry entry, bool encrypted, ReadOnlySpan <byte> table)
{
Debug.WriteLine($"Writing entry at 0x0{bw.BaseStream.Position:X}.");
var h = entry.Header;
var seed = entry.GetChecksum();
ReadOnlySpan <byte> payload = entry.GetData();
h.CompressedSize = h.DecompressedSize = payload.Length;
if (entry.Compressed)
{
payload = Oodle.Compress(payload, out int size);
h.CompressedSize = 4 + size;
Debug.Assert((payload.Length & 3) == 0);
}
var nameSize = (entry.FileName.Length | 3) + 1; // next multiple of 4
var dataSize = (h.CompressedSize + 3) & ~3; // roundup multiple of 4
h.SizeTotal = 0x18 + nameSize + dataSize;
bw.Write(seed);
if (encrypted)
{
var rng = XorShiftUtil.GetEncryptionRng(seed, table);
bw.Write(rng.GetNext(uint.MaxValue) ^ h.Magic);
bw.Write(rng.GetNext(uint.MaxValue) ^ (uint)h.SizeTotal);
bw.Write(rng.GetNext(uint.MaxValue) ^ h.Extension);
bw.Write(rng.GetNext(uint.MaxValue) ^ (uint)h.CompressedSize);
bw.Write(rng.GetNext(uint.MaxValue) ^ (uint)h.DecompressedSize);
Span <byte> temp = stackalloc byte[4];
var fn = entry.FileName;
int ctr = 0;
foreach (var c in fn)
{
temp[ctr++] = (byte)c;
if (ctr != 4)
{
continue;
}
bw.Write(rng.GetNext(uint.MaxValue) ^ BitConverter.ToUInt32(temp));
temp.Clear();
ctr = 0;
}
if (ctr == 0)
{
bw.Write(rng.GetNext(uint.MaxValue) ^ 0u);
}
else
{
bw.Write(rng.GetNext(uint.MaxValue) ^ BitConverter.ToUInt32(temp));
}
var asUint = MemoryMarshal.Cast <byte, uint>(payload);
if (entry.Compressed)
{
bw.Write(rng.GetNext(uint.MaxValue) ^ DrpFileHeader.CompressedDataMagic);
}
foreach (var u32 in asUint)
{
bw.Write(rng.GetNext(uint.MaxValue) ^ u32);
}
var slice = payload[(asUint.Length * 4)..];