dart_wellen 0.1.1

Wellen bindings for ROHD with VCD, FST, and GHW reading and VCD writing.

dart_wellen

dart_wellen exposes the Rust Wellen waveform parser to Dart through Flutter Rust Bridge. It reads VCD, FST, and GHW waveforms and adapts them to the shared rohd_hierarchy and rohd_waveform contracts.

Capabilities

Operation	Native	WebAssembly
Read VCD, FST, or GHW from a file path	Yes	No
Read VCD, FST, or GHW from bytes	Yes	Yes
Query hierarchy and selected signal data	Yes	Yes
Write VCD	Yes	No
Write FST or GHW	No	No

Writing is deliberately separated from the cross-platform reader because it uses dart:io.

Installation

Add the package to a Dart or Flutter package:

dependencies:
  dart_wellen: ^0.1.1

The package owns its bridge version and matching artifacts. Prepared local packages and hosted archives include generated Dart bindings and the browser runtime under web/pkg. Git dependencies retrieve those same files from a checksummed CI bundle for the exact selected Git commit, without compiling dependencies:

python3 <resolved-dart_wellen-root>/tool/bridge_artifacts.py install

Python 3 is required. The installer verifies package/bridge versions and SHA-256 checksums. For Git installs it downloads the selected commit's CI-produced JSON metadata before its archive, checks the commit/version/profile/inventory, then verifies all downloaded bytes. Hosted and prepared local packages include this metadata as tool/bridge_artifacts.build.json and verify offline. Compiled-binary checksums are generated by the producer, not pinned from a different machine's build in the source contract. Missing metadata or an unavailable commit bundle fails explicitly. The same commit-based lookup applies to every branch, tag, and main. The producer's General workflow distributes bundles automatically after its build and browser tests succeed. No pub.dev publication or manual release is needed; GitHub prereleases are only the public file storage for CI output. Hosts copy web/pkg, including license notices, into ignored web staging output and load its JavaScript/WASM pair. They must not pin a separate bridge version or retain an older runtime when changing dependency sources. The packaged WASM profile is explicitly release, independent of whether the embedding Flutter application runs in debug or release mode.

Native applications additionally need a matching native library. Artifact production belongs to this repository, never an embedding application's build. See the consumer artifact release procedure.

Reading a Waveform

WellenReader is a convenience API for native, file-backed workflows:

import 'package:dart_wellen/dart_wellen.dart';

Future<void> inspectWaveform(String path) async {
  await WellenReader.init();
  final reader = WellenReader();

  try {
    final metadata = await reader.loadFile(path);
    final structure = await reader.getStructure();
    final signals = await reader.getSignalData(
      ['top.clk', 'top.counter'],
      startTime: 0,
      endTime: metadata.endTime,
    );

    print('${structure.modules.length} top-level modules');
    for (final waveform in signals) {
      print('${waveform.signalId}: ${waveform.data.length} changes');
    }
  } finally {
    await reader.close();
  }
}

WellenSignalWaveformApi implements the SignalWaveformApi contract used by ROHD viewers. Use loadFile on native platforms or loadBytes after the generated Wellen WebAssembly module has been initialized in a browser:

final api = WellenSignalWaveformApi();
await api.loadBytes(bytes, fileName: 'simulation.fst');

final hierarchy = await api.getModuleStructureOnly();
final waveforms = await api.getWaveformData(
  signalIds: ['top.clk'],
);

Only one waveform is held by the Rust bridge at a time. Creating multiple Dart reader or API objects does not create independent Rust waveform stores.

Writing VCD

Native code that writes waveforms must import the IO-specific library:

import 'package:dart_wellen/dart_wellen_io.dart';

• WellenWriter writes registered SignalOccurrence values directly to a VCD file.
• WellenWaveDumper provides a manual adapter that registers signals and records timestamped value changes.

The adapter is not automatically attached to the ROHD simulator. Callers must register signals and forward simulation changes themselves. Selecting WaveFormat.fst currently throws an unsupported-format error.

Repository Development

This package is a member of the ROHD Wave Viewer Pub workspace. From the repository root:

# Resolve the workspace.
flutter pub get

# Generate both Dart and Rust Flutter Rust Bridge bindings.
make dart

# Build native or WebAssembly bridge artifacts.
make rust-native
make wasm

# Run root and workspace-member tests.
make test

The generator configuration is packages/dart_wellen/flutter_rust_bridge.yaml. Generated Dart bindings are written to packages/dart_wellen/lib/src/rust/; the generated Rust counterpart is rust/wellen_bridge/src/frb_generated.rs. Do not invoke the generator with ad hoc output paths.

See ARCHITECTURE.md for package boundaries and the repository build guide for the complete build matrix.

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Copyright (C) 2024-2026 Intel Corporation SPDX-License-Identifier: BSD-3-Clause