private void DecryptEntry(byte[] data, uint key1, uint key2, DpkEntry entry)
{
for (uint i = 0; i < data.Length; ++i)
{
data[i] ^= (byte)(key1 + (key1 >> 8));
data[i] -= (byte)entry.Hash;
key1 += key2;
}
}
public override ArcFile TryOpen(ArcView file)
{
var header = new byte[8];
if (8 != file.View.Read(8, header, 0, 8))
{
return(null);
}
byte last = header[7];
for (int i = 0; i < 8; i++)
{
header[i] ^= (byte)(i - 8);
}
int data_offset = LittleEndian.ToInt32(header, 0);
if (data_offset <= 16 || data_offset >= file.MaxOffset)
{
return(null);
}
int index_length = data_offset - 16;
var index = new byte[index_length];
if (index_length != file.View.Read(16, index, 0, (uint)index_length))
{
return(null);
}
DecryptIndex(index, 16, index_length, last);
int count = LittleEndian.ToInt32(index, 0);
if (count <= 0 || count > 0xfffff)
{
return(null);
}
var options = Query <DpkOptions> (arcStrings.ArcEncryptedNotice);
var name_bytes = new byte[0x20];
var dir = new List <Entry> (count);
int base_offset = 4 + count * 4;
for (int i = 0; i < count; ++i)
{
var index_offset = base_offset + LittleEndian.ToInt32(index, 4 + i * 4);
int name_begin = index_offset + 0x0c;
int name_end = Array.IndexOf(index, (byte)0, name_begin);
if (-1 == name_end)
{
name_end = index.Length;
}
if (name_end == name_begin)
{
continue;
}
if ('z' == index[name_end - 1])
{
--name_end; // strip 'z' from file extensions
}
int name_length = name_end - name_begin;
var name = Encodings.cp932.GetString(index, name_begin, name_length);
if (name_length > name_bytes.Length)
{
name_bytes = new byte[name_length];
}
// shift-jis characters sequence may contain '\\' that is not a path delimiter
string name_base = Path.GetFileName(name);
name_length = Encodings.cp932.GetBytes(name_base, 0, name_base.Length, name_bytes, 0);
uint size = LittleEndian.ToUInt32(index, index_offset + 4);
var entry = new DpkEntry
{
Name = name,
Type = FormatCatalog.Instance.GetTypeFromName(name),
Hash = GetNameHash(name_bytes, 0, name_length, options.Key1, options.Key2, size),
Offset = data_offset + LittleEndian.ToUInt32(index, index_offset),
Size = size,
};
if (!entry.CheckPlacement(file.MaxOffset))
{
return(null);
}
dir.Add(entry);
}
if (0 == dir.Count)
{
return(null);
}
return(new DpkArchive(file, this, dir, options));
}