Electronics Workbench Decoder and Encoder

Interop tools for Electronics Workbench / Multisim / Ultiboard binary formats. The goal: get designs and part databases out of EW into mainstream representations (and back, where the format permits).

• ewd — decode an EW file into JSON or XML, picking the right decoder by reading the file's magic bytes.
• ewe — encode the text-form back into an EW binary the original software can re-open. Currently supports compressed-XML; .prj Jet database encode is deferred (see below).

Supported formats

compressed-xml (ewprj, multisim)

PKWare DCL Implode (ASCII literal mode, large dictionary) wrapped in a small container: a magic-string header, a 64-bit LE total decompressed length, then a sequence of (decompressed_length: u32, compressed_length: u32, pkware_implode_block) sections. Multisim chunks big files into 900 000-decompressed-byte sections; ewe mirrors that.

Decode and encode are both supported. A decode/encode/decode round-trip on every sample tested produces byte-identical XML, and the resulting files are accepted by ewd.

mdb (.prj, .usr)

NI ships part libraries and project component databases as Microsoft Access Jet 3 / Jet 4 files (despite the .prj / .usr extensions). ewd reads them via mdb-reader and emits a single JSON document with every table:

{
  "format": "mdb",
  "source": "Stocked.prj",
  "tables": {
    "SYS_COMPONENT": {
      "columns": [{ "name": "Component_ID", "type": "long" }, ...],
      "rows": [{ "Component_ID": 17, "Component_Name": "BD9763FVM", ... }, ...]
    },
    ...
  }
}

Dates become ISO 8601 strings; binary blob fields (ole columns) become { "_bytes": "base64", "value": "..." } envelopes so the data survives a JSON round-trip.

Encode is a deliberately narrow byte-patch path, not a real Jet writer. Reimplementing Access's storage engine (page splits, B-tree index maintenance, free-space tracking, MSysObjects invariants) is out of scope for this project — ewd/ewe exist to move data out of Electronics Workbench, not to clone Microsoft's database engine.

What ewe does on an mdb input today:

1. You decode with ewd to produce <file>.prj.json.

2. You edit the JSON in your text editor (or with a script).

3. You run ewe edited.json. It diffs the edited JSON against the original .prj, then for each changed cell where:

   • the column is text or memo,
   • the new value has the same byte length as the old,
   • the old value appears exactly once in the file,

   it overwrites the bytes in place. Anything that violates those constraints is skipped, and --verbose prints the reason per cell.

This is enough for the typical vendor / price / MPN editing workflow because those values are usually unique and you usually substitute one same-length identifier for another. It is not a general-purpose editor and we don't intend to grow it into one.

If you want general-purpose .prj edit support

Not planned in this repo. The clean way to add it is a separate, optional, Windows-only tool that drives Microsoft's own Access engine:

• ACE OLE DB Provider (Microsoft.ACE.OLEDB.12.0 / 16.0) — free Redistributable from Microsoft, reads & writes both .mdb and .accdb.
• Access ODBC driver — same engine, ODBC interface. Pair with node-odbc (N-API native addon) and issue plain SQL: UPDATE SYS_USER_DATA SET USER_DEFINED_7 = ? WHERE Component_ID = ?. The diff logic we already have for edited-JSON → changed-cells would generate those statements directly.
• Jet OLE DB 4.0 — older, 32-bit only, still works for Jet 3 .mdb files like NI's .prj.

That path requires Windows + a driver install and so deliberately lives outside this cross-platform repo's CI. The current byte-patch encode covers the vendor/price editing case; for anything harder, route through Access (or the ACE driver, or DAO/ADO) instead of expecting ewe to grow into a full Jet writer.

Format detection

ewd identifies the format by reading the magic bytes at the start of the file, so the filename extension can be anything (renamed files, no extension, .dat, etc.). It then dispatches to the right decoder.

ewe infers the format from the output filename's extension; pass --format <key> to override for non-standard extensions. Out-of-range Multisim versions (e.g. .ms9 or future .ms20+) need an explicit --format multisim.

Install

Requires bun (≥ 1.0).

bun install

Decode

bun run ewd --verbose ./samples/Temp.ewprj ./samples/Design1.ms14
bun run ewd --verbose ./samples/Stocked.prj          # writes Stocked.prj.json

For each input, writes <filename>.xml (compressed-xml) or <filename>.json (mdb) next to it.

Options:

• -v, --verbose — log per-section progress
• -c, --concurrent — decode multiple files in parallel
• positional args — files to decode

Encode

Compressed-XML (greenfield encode from .xml)

bun run ewe --verbose ./samples/Temp.ewprj.xml
# or with explicit output:
bun run ewe --output ./out.ewprj ./samples/Temp.ewprj.xml
# or force a format on a non-standard extension:
bun run ewe --format multisim --output ./out.dat ./samples/Design1.ms14.xml

By default, strips a trailing .xml from each input to derive the output path. Format is inferred from the output extension (see the table above).

MDB in-place edits from .json

# Decode first to produce the editable JSON.
bun run ewd ./samples/Stocked.prj
# Edit ./samples/Stocked.prj.json in your editor / script.
# Then re-encode: ewe diffs vs the original and writes a patched copy.
bun run ewe --verbose ./samples/Stocked.prj.json
# -> samples/Stocked.prj.patched.prj

ewe recognizes .json inputs and routes them through the in-place edit path. The original .prj location is taken from the JSON's source field (or --source <path> to override). The patched copy goes to <source>.patched.prj (or --output <path> to override).

Each --verbose run prints N applied, M skipped and lists every skipped change with its reason. Skipped changes leave the file untouched at that cell.

Options

• -v, --verbose — log progress
• -c, --concurrent — encode multiple files in parallel
• -o, --output <path> — explicit output path (single-input only)
• -s, --source <path> — for MDB JSON inputs: override the source .prj
• -f, --format <key> — for compressed-XML: force a format (ewprj or multisim)
• positional args — XML or JSON files to encode

Compression ratio caveat

ewe uses node-pkware's implode for compression. The repetition search isn't quite as sophisticated as the original PKWare DCL implementation Multisim itself uses — re-encoded files are roughly 2× the size of the originals (e.g. 9 KB .ewprj round-trips to 20 KB). The output is still valid PKWare DCL Implode: round-trips are byte-identical on every sample tested, and the resulting files are accepted by ewd.

This is a substantial improvement over the previous baseline (7-10× bloat) thanks to fixes in the v5-fix branch of the cinderblock/node-pkware fork — see plans/jet-in-place-edit.md context and the fork's v5-fix branch for the specific bugs that were patched.

Tests

bun test

Covers the format registry (extension matching, header detection including the Jet magic prefix with leading NUL bytes, on-disk detection), encoder filename helpers, mdb value normalization (Date → ISO, OLE blobs → base64), and compressed-xml round-trip integration (tiny .ewprj, tiny .ms14, multi-block payload that spans more than one PKWare section, and an empty payload).

Development

bun run dev:ewd --verbose ./samples/Temp.ewprj
bun run dev:ewe --verbose ./samples/Temp.ewprj.xml

Both use bun --watch for fast reload on source changes.

Lint, format, and typecheck

bun run check        # biome lint + format check (no changes)
bun run check:fix    # apply all safe fixes
bun run format       # format only
bun run typecheck    # tsc --noEmit

CI on push/PR runs check, typecheck, and test on Ubuntu and Windows.