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(BURIKO): decode BSE-encrypted entries.

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This commit is contained in:
morkt 2017-12-30 06:40:47 +04:00
parent 5378499a8a
commit d6908c9e1e
1 changed files with 85 additions and 0 deletions
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85
ArcFormats/Ethornell/ArcBGI.cs
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@ -135,11 +135,57 @@ namespace GameRes.Formats.BGI
var res = AutoEntry.DetectFileType (signature);
if (res != null)
entry.Type = res.Type;
else if (file.View.AsciiEqual (entry.Offset, "BSE 1."))
entry.Type = "image";
else if (file.View.AsciiEqual (entry.Offset+4, "bw "))
entry.Type = "audio";
}
return new ArcFile (file, this, dir);
}
public override Stream OpenEntry (ArcFile arc, Entry entry)
{
if (entry.Size < 0x50 || !arc.File.View.AsciiEqual (entry.Offset, "BSE 1."))
return base.OpenEntry (arc, entry);
int version = arc.File.View.ReadUInt16 (entry.Offset+8);
if (version != 0x100 && version != 0x101)
return base.OpenEntry (arc, entry);
ushort checksum = arc.File.View.ReadUInt16 (entry.Offset+0xA);
uint key = arc.File.View.ReadUInt32 (entry.Offset+0xC);
var header = arc.File.View.ReadBytes (entry.Offset+0x10, 0x40);
if (0x101 == version)
DecryptBse (header, new BseGenerator101 (key));
else
DecryptBse (header, new BseGenerator100 (key));
var body = arc.File.CreateStream (entry.Offset+0x50, entry.Size-0x50);
return new PrefixStream (header, body);
}
void DecryptBse (byte[] data, IBseGenerator decoder)
{
var decoded = new bool[0x40];
for (int i = 0; i < decoded.Length; ++i)
{
int dst = decoder.NextKey() & 0x3F;
while (decoded[dst])
{
dst = (dst + 1) & 0x3F;
}
int shift = decoder.NextKey() & 7;
bool right_shift = (decoder.NextKey() & 1) == 0;
byte symbol = (byte)(data[dst] - decoder.NextKey());
if (right_shift)
{
data[dst] = Binary.RotByteR (symbol, shift);
}
else
{
data[dst] = Binary.RotByteL (symbol, shift);
}
decoded[dst] = true;
}
}
}
internal class BgiDecoderBase : MsbBitStream
@ -295,4 +341,43 @@ namespace GameRes.Formats.BGI
return dst_ptr;
}
}
internal interface IBseGenerator
{
int NextKey ();
}
internal class BseGenerator100 : IBseGenerator
{
int m_key;
public BseGenerator100 (uint key)
{
m_key = (int)key;
}
public int NextKey ()
{
uint v = (uint)(((m_key * 257 >> 8) + m_key * 97 + 23) ^ 0xA6CD9B75);
m_key = (int)Binary.RotR (v, 16);
return m_key;
}
}
internal class BseGenerator101 : IBseGenerator
{
int m_key;
public BseGenerator101 (uint key)
{
m_key = (int)key;
}
public int NextKey ()
{
uint v = (uint)((m_key * 127 >> 7) + m_key * 83 + 53) ^ 0xB97A7E5C;
m_key = (int)Binary.RotR (v, 16);
return m_key;
}
}
}