Handle passing in custom memory (#281)

taybenlor · Oct 12, 2023 · 78a1f1b · 78a1f1b
1 parent 6751758
commit 78a1f1b
Show file tree

Hide file tree

Showing 2 changed files with 23 additions and 19 deletions.
diff --git a/packages/wasi/README.md b/packages/wasi/README.md
@@ -80,19 +80,22 @@ const wasi = new WASI({
   },
 });
 
+const myMemory = new WebAssembly.Memory({ initial: 32, maximum: 10000 });
+
 // Then instantiate your binary with the imports provided by the wasi object
-const wasm = await WebAssembly.instantiateStreaming(
-  fetch("/binary.wasm"),
-  {
-    ...wasi.getImportObject(),
-
-    // Your own custom imports (e.g. memory)
-    {env: {memory: new WebAssembly.Memory({ initial: 32, maximum: 10000 })}}
-  }
-);
-
-// Finally start the WASI binary
-const result = wasi.start(wasm);
+const wasm = await WebAssembly.instantiateStreaming(fetch("/binary.wasm"), {
+  ...wasi.getImportObject(),
+
+  // Your own custom imports (e.g. custom memory)
+  env: {
+    memory: myMemory,
+  },
+});
+
+// Finally start the WASI binary (with the custom memory)
+const result = wasi.start(wasm, {
+  memory: myMemory,
+});
 ```
 
 ## Using the WASIWorker

diff --git a/packages/wasi/lib/wasi/wasi.ts b/packages/wasi/lib/wasi/wasi.ts
@@ -81,15 +81,16 @@ export class WASI implements SnapshotPreview1 {
     };
   }
 
-  // Internal initialization
-  private init(wasm: WebAssembly.WebAssemblyInstantiatedSource) {
+  start(
+    wasm: WebAssembly.WebAssemblyInstantiatedSource,
+    options: {
+      memory?: WebAssembly.Memory;
+    } = {}
+  ): WASIExecutionResult {
     this.instance = wasm.instance;
     this.module = wasm.module;
-    this.memory = this.instance.exports.memory as WebAssembly.Memory;
-  }
-
-  start(wasm: WebAssembly.WebAssemblyInstantiatedSource): WASIExecutionResult {
-    this.init(wasm);
+    this.memory =
+      options.memory ?? (this.instance.exports.memory as WebAssembly.Memory);
 
     const entrypoint = this.instance.exports._start as () => void;
     try {