LzssCodec

LZ10 / LZSS codec for Nintendo DS files.

This is the "Type 0x10" variant used in many DS ROMs and NARC archives. The format is a standard LZSS stream with a 4-byte header:

Byte 0      : 0x10  (magic / compression type)
Bytes 1–3   : uncompressed size as a 24-bit little-endian integer
Bytes 4+    : compressed data

Each group of up to 8 symbols is preceded by a flag byte whose bits are read MSB-first. A 0-bit means a literal byte follows; a 1-bit means a 2-byte back-reference follows:

[LLLL DDDD] [DDDDDDDD]
  L = (match length - 3)  stored in the high 4 bits   → lengths  3–18
  D = (match distance - 1) stored in the low 12 bits  → distance 1–4096