signalk-server

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8zM97.2 352.9c-1.3 1-1 3.3 .7 5.2 1.6 1.6 3.9 2.3 5.2 1 1.3-1 1-3.3-.7-5.2-1.6-1.6-3.9-2.3-5.2-1zm-10.8-8.1c-.7 1.3 .3 2.9 2.3 3.9 1.6 1 3.6 .7 4.3-.7 .7-1.3-.3-2.9-2.3-3.9-2-.6-3.6-.3-4.3 .7zm32.4 35.6c-1.6 1.3-1 4.3 1.3 6.2 2.3 2.3 5.2 2.6 6.5 1 1.3-1.3 .7-4.3-1.3-6.2-2.2-2.3-5.2-2.6-6.5-1zm-11.4-14.7c-1.6 1-1.6 3.6 0 5.9 1.6 2.3 4.3 3.3 5.6 2.3 1.6-1.3 1.6-3.9 0-6.2-1.4-2.3-4-3.3-5.6-2z"></path></svg></a><a href="#" class="tsd-widget menu" id="tsd-toolbar-menu-trigger" data-toggle="menu" aria-label="Menu"><svg width="16" height="16" viewBox="0 0 16 16" fill="none" aria-hidden="true"><use href="../../../../assets/icons.svg#icon-menu"></use></svg></a></div></div></header><div class="container container-main"><div class="col-content"><div class="tsd-page-title"><ul class="tsd-breadcrumb" aria-label="Breadcrumb"><li><a href="../../../../Developing.html">Developing</a></li><li><a href="../../../Plugins.html">Plugins</a></li><li><a href="../../WASM_Plugins.html">WASM Plugins</a></li><li><a href="" aria-current="page">Go/TinyGo Plugins</a></li></ul></div><div class="tsd-panel tsd-typography"><h1 id="creating-gotinygo-plugins" class="tsd-anchor-link">Creating Go/TinyGo Plugins<a href="#creating-gotinygo-plugins" aria-label="Permalink" class="tsd-anchor-icon"><svg viewBox="0 0 24 24" aria-hidden="true"><use href="../../../../assets/icons.svg#icon-anchor"></use></svg></a></h1> Go plugins use TinyGo, a Go compiler designed for small environments including WebAssembly. <h2 id="step-1-install-tinygo" class="tsd-anchor-link">Step 1: Install TinyGo<a href="#step-1-install-tinygo" aria-label="Permalink" class="tsd-anchor-icon"><svg viewBox="0 0 24 24" aria-hidden="true"><use href="../../../../assets/icons.svg#icon-anchor"></use></svg></a></h2> Download from <a href="https://tinygo.org/getting-started/install/">https://tinygo.org/getting-started/install/</a> <pre><code class="bash"># Verify installation tinygo version </code><button type="button">Copy</button></pre> <h2 id="step-2-create-project-structure" class="tsd-anchor-link">Step 2: Create Project Structure<a href="#step-2-create-project-structure" aria-label="Permalink" class="tsd-anchor-icon"><svg viewBox="0 0 24 24" aria-hidden="true"><use href="../../../../assets/icons.svg#icon-anchor"></use></svg></a></h2> <pre><code>my-go-plugin/ ├── main.go # Plugin code ├── go.mod # Go module ├── package.json # npm package manifest ├── public/ # Static web assets (optional) │ └── index.html └── README.md </code><button>Copy</button></pre> <h2 id="step-3-create-gomod" class="tsd-anchor-link">Step 3: Create go.mod<a href="#step-3-create-gomod" aria-label="Permalink" class="tsd-anchor-icon"><svg viewBox="0 0 24 24" aria-hidden="true"><use href="../../../../assets/icons.svg#icon-anchor"></use></svg></a></h2> <pre><code class="go">module my-go-plugin go 1.21 </code><button type="button">Copy</button></pre> <h2 id="step-4-create-maingo" class="tsd-anchor-link">Step 4: Create main.go<a href="#step-4-create-maingo" aria-label="Permalink" class="tsd-anchor-icon"><svg viewBox="0 0 24 24" aria-hidden="true"><use href="../../../../assets/icons.svg#icon-anchor"></use></svg></a></h2> <pre><code class="go">package main import ( "encoding/json" "unsafe" ) // FFI Imports from Signal K host //go:wasmimport env sk_debug func sk_debug(ptr *byte, len uint32) //go:wasmimport env sk_set_status func sk_set_status(ptr *byte, len uint32) //go:wasmimport env sk_set_error func sk_set_error(ptr *byte, len uint32) //go:wasmimport env sk_handle_message func sk_handle_message(ptr *byte, len uint32) // Helper wrappers func debug(msg string) { if len(msg) > 0 { sk_debug(unsafe.StringData(msg), uint32(len(msg))) } } func setStatus(msg string) { if len(msg) > 0 { sk_set_status(unsafe.StringData(msg), uint32(len(msg))) } } func handleMessage(msg string) { if len(msg) > 0 { sk_handle_message(unsafe.StringData(msg), uint32(len(msg))) } } // Memory allocation for string passing //export allocate func allocate(size uint32) *byte { buf := make([]byte, size) return &buf[0] } //export deallocate func deallocate(ptr *byte, size uint32) { // With leaking GC, memory is reclaimed when module unloads } // Plugin exports //export plugin_id func plugin_id(outPtr *byte, maxLen uint32) int32 { return writeString("my-go-plugin", outPtr, maxLen) } //export plugin_name func plugin_name(outPtr *byte, maxLen uint32) int32 { return writeString("My Go Plugin", outPtr, maxLen) } //export plugin_schema func plugin_schema(outPtr *byte, maxLen uint32) int32 { schema := `{"type":"object","properties":{}}` return writeString(schema, outPtr, maxLen) } //export plugin_start func plugin_start(configPtr *byte, configLen uint32) int32 { debug("Go plugin starting") setStatus("Running") // Emit a test delta delta := `{"updates":[{"values":[{"path":"test.goPlugin","value":"hello from Go"}]}]}` handleMessage(delta) return 0 } //export plugin_stop func plugin_stop() int32 { debug("Go plugin stopped") setStatus("Stopped") return 0 } // Helper: write string to output buffer func writeString(s string, ptr *byte, maxLen uint32) int32 { bytes := []byte(s) length := len(bytes) if uint32(length) > maxLen { length = int(maxLen) } dst := unsafe.Slice(ptr, length) copy(dst, bytes[:length]) return int32(length) } // Required for TinyGo WASM func main() {} </code><button type="button">Copy</button></pre> <h2 id="step-5-create-packagejson" class="tsd-anchor-link">Step 5: Create package.json<a href="#step-5-create-packagejson" aria-label="Permalink" class="tsd-anchor-icon"><svg viewBox="0 0 24 24" aria-hidden="true"><use href="../../../../assets/icons.svg#icon-anchor"></use></svg></a></h2> <pre><code class="json">{ "name": "my-go-wasm-plugin", "version": "0.1.0", "description": "My Go WASM plugin", "keywords": ["signalk-wasm-plugin"], "wasmManifest": "plugin.wasm", "wasmCapabilities": { "dataRead": true, "dataWrite": true, "storage": "vfs-only" } } </code><button type="button">Copy</button></pre> <blockquote> Note: The package name can be anything - there's no requirement for <code>@signalk/</code> scope. The <code>wasmManifest</code> field is what identifies this as a WASM plugin. </blockquote> <h2 id="step-6-build" class="tsd-anchor-link">Step 6: Build<a href="#step-6-build" aria-label="Permalink" class="tsd-anchor-icon"><svg viewBox="0 0 24 24" aria-hidden="true"><use href="../../../../assets/icons.svg#icon-anchor"></use></svg></a></h2> <pre><code class="bash"># Release build (smaller, optimized) tinygo build -o plugin.wasm -target=wasip1 -gc=leaking -no-debug main.go # Debug build (for development) tinygo build -o plugin.wasm -target=wasip1 main.go </code><button type="button">Copy</button></pre> <h2 id="step-7-install" class="tsd-anchor-link">Step 7: Install<a href="#step-7-install" aria-label="Permalink" class="tsd-anchor-icon"><svg viewBox="0 0 24 24" aria-hidden="true"><use href="../../../../assets/icons.svg#icon-anchor"></use></svg></a></h2> Option 1: Symlink (Recommended for Development) <pre><code class="bash">cd ~/.signalk/node_modules ln -s /path/to/your/my-go-wasm-plugin my-go-wasm-plugin </code><button type="button">Copy</button></pre> Option 2: Direct Copy <pre><code class="bash">mkdir -p ~/.signalk/node_modules/my-go-wasm-plugin cp plugin.wasm package.json ~/.signalk/node_modules/my-go-wasm-plugin/ </code><button type="button">Copy</button></pre> <h2 id="go-ffi-interface-reference" class="tsd-anchor-link">Go FFI Interface Reference<a href="#go-ffi-interface-reference" aria-label="Permalink" class="tsd-anchor-icon"><svg viewBox="0 0 24 24" aria-hidden="true"><use href="../../../../assets/icons.svg#icon-anchor"></use></svg></a></h2> Signal K provides these FFI imports in the <code>env</code> module: <table> <thead> <tr> <th>Function</th> <th>Parameters</th> <th>Description</th> </tr> </thead> <tbody> <tr> <td><code>sk_debug</code></td> <td><code>(ptr, len)</code></td> <td>Log debug message</td> </tr> <tr> <td><code>sk_set_status</code></td> <td><code>(ptr, len)</code></td> <td>Set plugin status</td> </tr> <tr> <td><code>sk_set_error</code></td> <td><code>(ptr, len)</code></td> <td>Set error message</td> </tr> <tr> <td><code>sk_handle_message</code></td> <td><code>(ptr, len)</code></td> <td>Emit delta message</td> </tr> <tr> <td><code>sk_register_resource_provider</code></td> <td><code>(ptr, len)</code></td> <td>Register as resource provider</td> </tr> </tbody> </table> <h2 id="required-plugin-exports" class="tsd-anchor-link">Required Plugin Exports<a href="#required-plugin-exports" aria-label="Permalink" class="tsd-anchor-icon"><svg viewBox="0 0 24 24" aria-hidden="true"><use href="../../../../assets/icons.svg#icon-anchor"></use></svg></a></h2> Your plugin MUST export: <table> <thead> <tr> <th>Export</th> <th>Signature</th> <th>Description</th> </tr> </thead> <tbody> <tr> <td><code>plugin_id</code></td> <td><code>(out_ptr, max_len) -> len</code></td> <td>Return plugin ID</td> </tr> <tr> <td><code>plugin_name</code></td> <td><code>(out_ptr, max_len) -> len</code></td> <td>Return plugin name</td> </tr> <tr> <td><code>plugin_schema</code></td> <td><code>(out_ptr, max_len) -> len</code></td> <td>Return JSON schema</td> </tr> <tr> <td><code>plugin_start</code></td> <td><code>(config_ptr, config_len) -> status</code></td> <td>Start plugin</td> </tr> <tr> <td><code>plugin_stop</code></td> <td><code>() -> status</code></td> <td>Stop plugin</td> </tr> <tr> <td><code>allocate</code></td> <td><code>(size) -> ptr</code></td> <td>Allocate memory</td> </tr> <tr> <td><code>deallocate</code></td> <td><code>(ptr, size)</code></td> <td>Free memory</td> </tr> </tbody> </table> <h2 id="optional-plugin-exports" class="tsd-anchor-link">Optional Plugin Exports<a href="#optional-plugin-exports" aria-label="Permalink" class="tsd-anchor-icon"><svg viewBox="0 0 24 24" aria-hidden="true"><use href="../../../../assets/icons.svg#icon-anchor"></use></svg></a></h2> Your plugin MAY export: <table> <thead> <tr> <th>Export</th> <th>Signature</th> <th>Description</th> </tr> </thead> <tbody> <tr> <td><code>poll</code></td> <td><code>() -> status</code></td> <td>Called every 1 second while plugin is running. Useful for polling hardware, sockets, or external systems. Return 0 for success, non-zero for errors.</td> </tr> <tr> <td><code>http_endpoints</code></td> <td><code>() -> json</code></td> <td>Return JSON array of HTTP endpoint definitions</td> </tr> <tr> <td><code>delta_handler</code></td> <td><code>(delta_ptr, delta_len)</code></td> <td>Receives Signal K deltas as JSON strings. Called for every delta emitted by the server.</td> </tr> </tbody> </table> <h2 id="tinygo-limitations" class="tsd-anchor-link">TinyGo Limitations<a href="#tinygo-limitations" aria-label="Permalink" class="tsd-anchor-icon"><svg viewBox="0 0 24 24" aria-hidden="true"><use href="../../../../assets/icons.svg#icon-anchor"></use></svg></a></h2> TinyGo is a subset of Go. Notable limitations: <ul> <li>No reflection (limited <code>encoding/json</code> support)</li> <li>No goroutines with WASI Preview 1</li> <li>Garbage collector options: <code>leaking</code> (recommended), <code>conservative</code></li> <li>Some standard library packages unavailable</li> </ul> See <a href="https://tinygo.org/docs/reference/lang-support/">https://tinygo.org/docs/reference/lang-support/</a> for details. <h2 id="additional-resources" class="tsd-anchor-link">Additional Resources<a href="#additional-resources" aria-label="Permalink" class="tsd-anchor-icon"><svg viewBox="0 0 24 24" aria-hidden="true"><use href="../../../../assets/icons.svg#icon-anchor"></use></svg></a></h2> See the example-routes-waypoints plugin in <code>examples/wasm-plugins/example-routes-waypoints/</code> for a complete resource provider plugin. </div></div><div class="col-sidebar"><div class="page-menu"><details open class="tsd-accordion tsd-page-navigation"><summary class="tsd-accordion-summary"><svg width="20" height="20" viewBox="0 0 24 24" fill="none" aria-hidden="true"><use href="../../../../assets/icons.svg#icon-chevronDown"></use></svg><h3>On This Page</h3></summary><div class="tsd-accordion-details"><a href="#step-1-install-tinygo">Step 1: Install TinyGo</a><a href="#step-2-create-project-structure">Step 2: Create Project Structure</a><a href="#step-3-create-gomod">Step 3: Create go.mod</a><a href="#step-4-create-maingo">Step 4: Create main.go</a><a href="#step-5-create-packagejson">Step 5: Create package.json</a><a href="#step-6-build">Step 6: Build</a><a href="#step-7-install">Step 7: Install</a><a href="#go-ffi-interface-reference">Go FFI Interface Reference</a><a href="#required-plugin-exports">Required Plugin Exports</a><a href="#optional-plugin-exports">Optional Plugin Exports</a><a href="#tinygo-limitations">TinyGo Limitations</a><a href="#additional-resources">Additional Resources</a></div></details></div><div class="site-menu"><nav class="tsd-navigation"><a href="../../../../modules.html">Signal K</a><ul class="tsd-small-nested-navigation" id="tsd-nav-container"><li>Loading...</li></ul></nav></div></div></div><footer>Generated using <a href="https://typedoc.org/" target="_blank">TypeDoc</a></footer><div class="overlay"></div></body></html>