maolan-plugin-host

Out-of-process plugin host for the Maolan DAW.

This crate provides both a library and a standalone binary that loads and runs audio plugins inside isolated processes. The DAW communicates with each host over shared memory and lightweight event channels, giving robust sandboxing: a crashing plugin does not bring down the session.

Supported formats

How it works

1. The DAW spawns maolan-plugin-host as a separate process for every plugin instance.
2. Both sides open a shared-memory segment and a pair of event pipes (Unix) or named events (Windows).
3. Audio buffers, parameter changes, and MIDI events are exchanged through the shared-memory protocol defined in maolan-plugin-protocol.
4. If the plugin crashes or hangs, the DAW can terminate the host process and recover without affecting the rest of the project.

Binary usage

Plugin hosting mode

The DAW normally invokes the binary automatically, but the command-line interface looks like this:

maolan-plugin-host <format> <plugin-path> <shm-name> <instance-id> <d2h-fd> <h2d-fd> [sample-rate buffer-size num-inputs num-outputs]

• format – clap, vst3, or lv2.
• plugin-path – Path to the plugin library. For CLAP you can select a specific plugin inside the factory with path#plugin_id or path::plugin_id.
• shm-name – Name of the shared-memory segment created by the DAW.
• instance-id – Unique identifier for this instance.
• d2h-fd / h2d-fd – File descriptors (Unix) or event names (Windows) used for the event channel.
• Optional VST3/LV2 arguments: sample-rate, buffer-size, num-inputs, num-outputs.

Scan mode

Discover plugins and dump their metadata to JSON:

maolan-plugin-host --scan --format <format> --path <plugin-path> [--output <json-path>]

Example:

maolan-plugin-host --scan --format clap --path /usr/lib/clap --output clap-index.json

Library usage

Add the crate to your Cargo.toml:

[dependencies]
maolan-plugin-host = "0.0.1"

The library re-exports maolan_plugin_protocol and exposes the following modules:

• clap – Low-level CLAP C FFI bindings and host extension helpers.
• host – Shared-memory runtime that drives a plugin instance.
• lv2 – LV2 host implementation (Unix only).
• scan – Plugin scanner and metadata serialization.
• paths – Standard plugin installation paths for each platform.
• util – Small helpers such as SimpleMutex and AudioPort.
• vst3 – VST3 bindings and helpers.
• vst3_lv2_host – VST3/LV2 specific runtime loop and GUI support.

Most users will only need the binary; the library API is intended for the Maolan engine and advanced integrations.

Building

Requires Rust 1.85+ (2024 edition).

cargo build --release

Platform-specific dependencies

• Linux / FreeBSD
  • liblilv / lv2 development libraries (for LV2 support)
  • libsuil and X11 development libraries (for LV2/VST3 GUI support)
• Windows
  • No extra system libraries required.

License

BSD-2-Clause. See Cargo.toml for the full license identifier.