Format DENC (D? ENCrypt)

Binary format that contains data that can be compressed.

Specification

Offset	Size	Description
0x00	4	Stamp `DENC`
0x04	4	Decompressed size
0x08	4	Compression algorithm
0x0C	4	Compressed size
0x10	-	Data

The possible values for the compression algorithm field are:

\0: not implemented in this game but it is detected as a valid case.
NULL: data is not compressed.
RLE : data is compressed with RLE variant.
LZSS: data is compressed with a LZSS variant.
BPE : Not implemented in this game.
ZSKP: data is compressed with ZSKP.
LSKP: data is compressed with LSKP.
RNGE: data is compressed with RNGE.
SOA : Not implemented in this game.

Null compression

Data is not compressed. The processing subroutine in overlay 48 at 0x020d314c.

RLE compression

TODO: Analyze code. The decompression subroutine is in overlay 48 at 0x020d320c.

LZSS compression

The compression algorithm has two mode of operation. The compressed data starts with a token that contains the operation mode and information. The first bit of the token decides the operation:

If the first bit of the token is 0, copy a sequence of input bytes to the output. The token is 8-bits with the following format:

Bits	Explanation
0	`0` for copy operation
1-7	Number of bytes to copy from input to output

If the first bit of the token is 1, copy a sequence of bytes from a previous position of the output to the current position. The token is 16-bits (read a second byte and combine). The format is:

Bits	Explanation
0	`1` for repeat decompressed data
1-11	Number of bytes to go back in output (max 2048 bytes)
12-15	Number of bytes to copy starting with 2 (2-18 bytes)

The decompression subroutine is in overlay 48 at 0x020d3330.

BPE compression

The game Layton London Life does not implement this compression.

ZSKP compression

TODO: Analyze code. The decompression subroutine is in overlay 48 at 0x020d3580.

LSKP compression

TODO: Analyze code. The decompression subroutine is in overlay 48 at 0x020d366c.

RNGE compression

TODO: Analyze code. The decompression subroutine is in overlay 48 at 0x020d3744.

SOA compression