public override void Encrypt(Xp3Entry entry, long offset, byte[] values, int pos, int count)
{
throw new NotImplementedException (Strings.arcStrings.MsgEncNotImplemented);
// despite the fact that algorithm is symmetric, creating an archive without updating "list.bin"
// wouldn't make much sense
// Decrypt (entry, offset, values, pos, count);
}
public override void Decrypt(Xp3Entry entry, long offset, byte[] values, int pos, int count)
{
uint limit = GetEncryptionLimit (entry);
uint key = entry.Hash;
for (int i = 0; i < count && offset < limit; ++i, ++offset)
{
values[pos+i] ^= (byte)(offset ^ (key >> (((int)offset & 3) << 3)));
}
}
public override void Encrypt(Xp3Entry entry, long offset, byte[] values, int pos, int count)
{
Decrypt (entry, offset, values, pos, count);
}
public override void Decrypt(Xp3Entry entry, long offset, byte[] buffer, int pos, int count)
{
uint key = entry.Hash;
uint base_offset = GetBaseOffset (key);
if (offset < base_offset)
{
int base_length = Math.Min ((int)(base_offset - offset), count);
Decode (key, offset, buffer, pos, base_length);
offset += base_length;
pos += base_length;
count -= base_length;
}
if (count > 0)
{
key = (key >> 16) ^ key;
Decode (key, offset, buffer, pos, count);
}
}
public override byte Decrypt(Xp3Entry entry, long offset, byte value)
{
uint key = entry.Hash;
uint base_offset = GetBaseOffset (key);
if (offset >= base_offset)
{
key = (key >> 16) ^ key;
}
var buffer = new byte[1] { value };
Decode (key, offset, buffer, 0, 1);
return buffer[0];
}
uint GetEncryptionLimit(Xp3Entry entry)
{
uint limit;
if (EncryptionThresholdMap != null && EncryptionThresholdMap.TryGetValue (entry.Hash, out limit))
return limit;
else
return 0x200;
}