SwiftJWW

📖 Documentation: https://secondmouseau.github.io/SwiftJWW/

A native-Swift reader for JWW — the native drawing format of Jw_cad, the free 2D CAD program widely used in Japan — plus a jww2dxf command-line converter.

JWW is an MFC CArchive-serialized binary file (JwwData. magic, a version, a large version-gated document header, then an MFC object array of entities). SwiftJWW reads the geometry — lines, arcs/circles/ellipses, points, and text — and converts it to DXF.

• Pure Swift, no third-party dependencies.
• Clean-room port of the documented JWW byte layout (the published jwdatafmt spec + LibreCAD's jwwlib as the reference reader). Validated byte-for-byte against the reference reader on real drawings: identical entity counts and bounding boxes.

Install

dependencies: [
    .package(url: "https://github.com/SecondMouseAU/SwiftJWW.git", from: "1.0.0"),
],
// target:
.target(name: "YourTarget", dependencies: [.product(name: "SwiftJWW", package: "SwiftJWW")]),

CLI

swift run jww2dxf drawing.jww            # → drawing.dxf
swift run jww2dxf drawing.jww out.dxf

Library

import SwiftJWW

let dwg = try JWW.read(contentsOf: url)
print(dwg.version, dwg.counts.line, dwg.counts.arc, dwg.bounds as Any)

for e in dwg.entities {
    switch e {
    case let .line(a, b, layer, color):  …
    case let .arc(center, radius, start, sweep, tilt, ratio, full, layer, color):  …
    case let .point(at, layer, color):  …
    case let .text(at, height, width, angleRad, raw, layer, color):  …   // `raw` is CP932 bytes
    }
}

let dxf = DXFWriter.string(dwg)          // or DXFWriter.write(dwg, to: url)

JWW.looksLikeJWW(data) sniffs the JwwData. signature.

Scope & notes

Covers lines, arcs/circles/ellipses, points, text, block definitions + inserts, and dimensions. Block definitions become DXF BLOCKs and inserts become INSERTs (Drawing.blocks holds the defs by number); dimensions are decomposed into their drawn parts (dimension line, value text, witness lines, arrows). Text is decoded to Unicode at read time (Entity.text.string) from the file's CP932 (Shift-JIS) bytes via JWW.decodeCP932, and the DXF writer emits non-ASCII as \U+XXXX escapes so Japanese renders in AutoCAD / LibreCAD regardless of code page. (CP932 decoding uses CoreFoundation — reliable on Apple platforms; on Linux it falls back and Japanese may not decode, but geometry still converts.)

Block/dimension support is validated on synthetic fixtures and is structurally correct against the documented format; the line/arc/point/text core is additionally validated byte-for-byte against the reference reader on real drawings.

DWG output is out of scope (proprietary); produce DXF here and convert to DWG downstream (e.g. the free ODA File Converter) if needed.

License

MIT. JWW and Jw_cad are the work of their respective authors; the reference jwwlib is part of LibreCAD (GPL). This is a clean-room reimplementation of the format — no jwwlib code is included.