jill-data-formats

name

jill-data-formats

description

Use when reading, parsing, writing, dumping, or debugging any Jill of the Jungle data file (DMA, SHA, JN, MAC, CFG, VCL, CMF/DDT, Crunched Screen Image) or when reasoning about its byte layout, flag bits, object iTypes, savegame structure, palette handling, or per-file quirks. Examples: "why is this DMA entry parsing wrong?", "add a SHA tile dumper", "what's the layout of the JN object record?", "is the player object always first?", "decode dan.cmf", "parse the VCL sound table", "port the Crunched Screen Image renderer".

Jill of the Jungle Data Formats

Single source of truth for byte-level layout of every Jill of the Jungle data file: docs/port/00-format-reference.md. That file cites the upstream ModdingWiki pages and is updated when new porting questions surface. This skill is a router into it plus the quirks/gotchas that bite porters most often.

When to use

Trigger on any of:

• Touching crates/openjill-data/ (or any module that reads/writes original Jill bytes).
• Adding or fixing a parser, dumper, or extractor.
• Designing types that mirror an on-disk record.
• Debugging why parsed data disagrees with the original game.
• Answering "what does this byte mean?" / "what is the layout of …?".
• Auditing endianness, offsets, masks, or string encoding for any of DMA, SHA, JN (*.JN[123]), MAC, CFG, VCL, CMF (*.DDT), or Crunched Screen Image streams.

Workflow

1. Open docs/port/00-format-reference.md.
2. Jump to the section for the format in question (anchors below).
3. Re-read the per-file quirks subsection — most parser bugs live there.
4. Cross-check against existing Rust code in crates/openjill-data/<format>.rs
   (parser already exists for: DMA, VCL-text, CFG, SHA, JN).
5. For new behavior, prefer extending the existing parser to introducing
   a parallel one. Match the wiki's field names (iType, lPointer, etc.)
   so the code maps 1:1 onto the reference.