Successful type descriptor embed

Author: surma

read_data.js

@@ -0,0 +1,17 @@
+const fs = require("fs/promises");
+
+async function main() {
+  const b = await fs.readFile(process.argv[2]);
+  const { instance } = await WebAssembly.instantiate(b);
+  const ptr = instance.exports.__asbind_type_data.value;
+  const dv = new DataView(instance.exports.memory.buffer);
+  const strLen = dv.getUint32(ptr - 4, true);
+  const strView = new Uint16Array(
+    instance.exports.memory.buffer,
+    ptr,
+    strLen / Uint16Array.BYTES_PER_ELEMENT
+  );
+  const str = new TextDecoder("utf-16le").decode(strView);
+  console.log({ str });
+}
+main();

transform.js

@@ -0,0 +1,70 @@
+const { Transform } = require("assemblyscript/cli/transform");
+const assemblyscript = require("assemblyscript");
+
+function isInternalElement(element) {
+  return element.internalName.startsWith("~");
+}
+
+function elementHasFlag(el, flag) {
+  return (el.flags & flag) != 0;
+}
+
+function typeName(type) {
+  return type.name.text ?? type.name.identifier.text;
+}
+
+const marker = "__asbind_type_data";
+
+class AsBindTransform extends Transform {
+  afterInitialize(program) {
+    const exportedFunctions = [...program.elementsByDeclaration.values()]
+      .filter(el =>
+        elementHasFlag(el, assemblyscript.CommonFlags.MODULE_EXPORT)
+      )
+      .filter(el => !isInternalElement(el))
+      .filter(
+        el =>
+          el.declaration.kind === assemblyscript.NodeKind.FUNCTIONDECLARATION
+      );
+    const importedFunctions = [...program.elementsByDeclaration.values()]
+      .filter(el => elementHasFlag(el, assemblyscript.CommonFlags.DECLARE))
+      .filter(el => !isInternalElement(el))
+      .filter(
+        v => v.declaration.kind === assemblyscript.NodeKind.FUNCTIONDECLARATION
+      );
+    const typeData = {
+      importedFunction: Object.fromEntries(
+        importedFunctions.map(func => [
+          func.name,
+          {
+            returnType: typeName(func.declaration.signature.returnType),
+            parameters: func.declaration.signature.parameters.map(parameter =>
+              typeName(parameter.type)
+            )
+          }
+        ])
+      ),
+      exportedFunctions: Object.fromEntries(
+        exportedFunctions.map(func => [
+          func.name,
+          {
+            returnType: typeName(func.declaration.signature.returnType),
+            parameters: func.declaration.signature.parameters.map(parameter =>
+              typeName(parameter.type)
+            )
+          }
+        ])
+      )
+    };
+    const typeDataExport = [...program.elementsByDeclaration.values()].find(
+      v => v.name === marker
+    );
+    if (!typeDataExport) {
+      throw Error("Could not find type data export");
+    }
+    typeDataExport.declaration.initializer = new assemblyscript.StringLiteralExpression(
+      JSON.stringify(typeData)
+    );
+  }
+}
+module.exports = AsBindTransform;