.AUP File Type Decryptor and Viewer

Fully local, client-side tool for (en/de)crypting / (de)compressing the reverse-engineered file format for the custom .aup type files, which are used for packing game asset files for the MMORPG "Dragon Soul" (DragonSoul).

More about Dragon Soul and my game file preservation archive for it:
https://archive.org/details/Dragon-Soul-DragonSoul-MMORPG-Client

• Decrypts/decompresses custom packed Dragon Soul .aup files
• Supports previewing PNG, JPG, BMP, TGA, DDS, custom game icons, WAV, Chinese encoded text (GB18030), ASCII, Hex
• Batch export with folder structure preservation
• Arrow key file list navigation
• TO DO: Encrypts/compresses raw files into the .aup format (bit-perfect)

This is an unofficial fan project not affiliated with the original developers; all Dragon Soul assets and intellectual property belong to their respective owners.

Licensed under the MIT License.

Version: 1.0.0

Project source code: github.com/PredatorIWD/.AUP-File-Type-Decryptor-and-Viewer

DECRYPTION ALGORITHM (LZSS Variant)

The .aup files use a custom implementation of LZSS (Lempel-Ziv-Storer-Szymanski) compression based on a ring buffer dictionary.

1. HEADER:
   - First 4 bytes (Little Endian Integer) indicate the uncompressed size.

2. BIT STREAM:
   - The stream is read bit-by-bit (MSB first).
   - It maintains a 16384 byte (0x4000) Ring Buffer (History).
   - Initial Buffer Index: 1

3. COMMANDS:
   BIT = 1 (LITERAL BIT):
       - Read next 8 bits as a raw byte.
       - Append to Output.
       - Write to Ring Buffer.
       - Increment Buffer Index (wrapping at 0x3FFF).

   BIT = 0 (MATCH BIT):
       - Read next 14 bits = Offset (Absolute position in Ring Buffer).
       - If Offset = 0, Stop (End of File).
       - Read next 4 bits = Length.
       - Actual Length = Length + 3.
       - Iterate [Actual Length] times:
           - Read byte from Ring Buffer at [(Offset + i) & 0x3FFF].
           - Append byte to Output.
           - Write byte to Ring Buffer.
           - Increment Buffer Index (wrapping at 0x3FFF).