[wasm] Wasm function imports.

I switched from a WasmImports object to a builder pattern:
module.instantiate().addMemory(...).addFunction(...).build();

Bug: https://github.com/dart-lang/sdk/issues/37882
Change-Id: I381aa0f7df1fa006ce8d051cd5b4a1bcc1835e46
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/167460
Reviewed-by: Ryan Macnak <rmacnak@google.com>
Commit-Queue: Liam Appelbe <liama@google.com>

DEPS

@@ -133,7 +133,7 @@ vars = {
   "quiver-dart_tag": "246e754fe45cecb6aa5f3f13b4ed61037ff0d784",
   "resource_rev": "f8e37558a1c4f54550aa463b88a6a831e3e33cd6",
   "root_certificates_rev": "7e5ec82c99677a2e5b95ce296c4d68b0d3378ed8",
-  "rust_revision": "cbe7c5ce705896d4e22bf6096590bc1f17993b78",
+  "rust_revision": "b7856f695d65a8ebc846754f97d15814bcb1c244",
   "shelf_static_rev": "v0.2.8",
   "shelf_packages_handler_tag": "2.0.0",
   "shelf_proxy_tag": "0.1.0+7",

pkg/wasm/lib/src/function.dart

@@ -28,8 +28,7 @@ class WasmFunction {
   }
 
   String toString() {
-    return "${wasmerValKindName(_returnType)} $_name" +
-        "(${_argTypes.map(wasmerValKindName).join(", ")})";
+    return WasmRuntime.getSignatureString(_name, _argTypes, _returnType);
   }
 
   bool _fillArg(dynamic arg, int i) {

pkg/wasm/lib/src/module.dart

@@ -19,9 +19,10 @@ class WasmModule {
     _module = WasmRuntime().compile(_store, data);
   }
 
-  /// Instantiate the module with the given imports.
-  WasmInstance instantiate(WasmImports imports) {
-    return WasmInstance(_store, _module, imports);
+  /// Returns a WasmInstanceBuilder that is used to add all the imports that the
+  /// module needs, and then instantiate it.
+  WasmInstanceBuilder instantiate() {
+    return WasmInstanceBuilder(this);
   }
 
   /// Create a new memory with the given number of initial pages, and optional
@@ -37,47 +38,166 @@ class WasmModule {
     var runtime = WasmRuntime();
     var imports = runtime.importDescriptors(_module);
     for (var imp in imports) {
-      var kind = wasmerExternKindName(imp.kind);
-      description.write('import $kind: ${imp.moduleName}::${imp.name}\n');
+      description.write("import $imp\n");
     }
     var exports = runtime.exportDescriptors(_module);
     for (var exp in exports) {
-      var kind = wasmerExternKindName(exp.kind);
-      description.write('export $kind: ${exp.name}\n');
+      description.write("export $exp\n");
     }
     return description.toString();
   }
 }
 
-/// WasmImports holds all the imports for a WasmInstance.
-class WasmImports {
-  Pointer<Pointer<WasmerExtern>> _imports;
-  int _capacity;
-  int _length;
+Pointer<WasmerTrap> _wasmFnImportTrampoline(Pointer<_WasmFnImport> imp,
+    Pointer<WasmerVal> args, Pointer<WasmerVal> results) {
+  try {
+    _WasmFnImport._call(imp, args, results);
+  } catch (e) {
+    // TODO: Use WasmerTrap to handle this case. For now just print the
+    // exception (if we ignore it, FFI will silently return a default result).
+    print(e);
+  }
+  return nullptr;
+}
 
-  /// Create an imports object.
-  WasmImports([this._capacity = 4])
-      : _imports = allocate<Pointer<WasmerExtern>>(count: _capacity),
-        _length = 0 {}
+void _wasmFnImportFinalizer(Pointer<_WasmFnImport> imp) {
+  _wasmFnImportToFn.remove(imp.address);
+  free(imp);
+}
 
-  /// Returns the number of imports.
-  int get length => _length;
+final _wasmFnImportTrampolineNative = Pointer.fromFunction<
+    Pointer<WasmerTrap> Function(Pointer<_WasmFnImport>, Pointer<WasmerVal>,
+        Pointer<WasmerVal>)>(_wasmFnImportTrampoline);
+final _wasmFnImportToFn = <int, Function>{};
+final _wasmFnImportFinalizerNative =
+    Pointer.fromFunction<Void Function(Pointer<_WasmFnImport>)>(
+        _wasmFnImportFinalizer);
+
+class _WasmFnImport extends Struct {
+  @Int32()
+  external int numArgs;
+
+  @Int32()
+  external int returnType;
+
+  static void _call(Pointer<_WasmFnImport> imp, Pointer<WasmerVal> rawArgs,
+      Pointer<WasmerVal> rawResult) {
+    Function fn = _wasmFnImportToFn[imp.address] as Function;
+    var args = [];
+    for (var i = 0; i < imp.ref.numArgs; ++i) {
+      args.add(rawArgs[i].toDynamic);
+    }
+    var result = Function.apply(fn, args);
+    switch (imp.ref.returnType) {
+      case WasmerValKindI32:
+        rawResult.ref.i32 = result;
+        break;
+      case WasmerValKindI64:
+        rawResult.ref.i64 = result;
+        break;
+      case WasmerValKindF32:
+        rawResult.ref.f32 = result;
+        break;
+      case WasmerValKindF64:
+        rawResult.ref.f64 = result;
+        break;
+      case WasmerValKindVoid:
+      // Do nothing.
+    }
+  }
+}
+
+/// WasmInstanceBuilder is used collect all the imports that a WasmModule
+/// requires before it is instantiated.
+class WasmInstanceBuilder {
+  WasmModule _module;
+  late List<WasmImportDescriptor> _importDescs;
+  Map<String, int> _importIndex;
+  late Pointer<Pointer<WasmerExtern>> _imports;
+
+  WasmInstanceBuilder(this._module) : _importIndex = {} {
+    _importDescs = WasmRuntime().importDescriptors(_module._module);
+    _imports = allocate<Pointer<WasmerExtern>>(count: _importDescs.length);
+    for (var i = 0; i < _importDescs.length; ++i) {
+      var imp = _importDescs[i];
+      _importIndex["${imp.moduleName}::${imp.name}"] = i;
+      _imports[i] = nullptr;
+    }
+  }
+
+  int _getIndex(String moduleName, String name) {
+    var index = _importIndex["${moduleName}::${name}"];
+    if (index == null) {
+      throw Exception("Import not found: ${moduleName}::${name}");
+    } else if (_imports[index] != nullptr) {
+      throw Exception("Import already filled: ${moduleName}::${name}");
+    } else {
+      return index;
+    }
+  }
+
+  /// Add a WasmMemory to the imports.
+  WasmInstanceBuilder addMemory(
+      String moduleName, String name, WasmMemory memory) {
+    var index = _getIndex(moduleName, name);
+    var imp = _importDescs[index];
+    if (imp.kind != WasmerExternKindMemory) {
+      throw Exception("Import is not a memory: $imp");
+    }
+    _imports[index] = WasmRuntime().memoryToExtern(memory._mem);
+    return this;
+  }
+
+  /// Add a function to the imports.
+  WasmInstanceBuilder addFunction(String moduleName, String name, Function fn) {
+    var index = _getIndex(moduleName, name);
+    var imp = _importDescs[index];
+    var runtime = WasmRuntime();
+
+    if (imp.kind != WasmerExternKindFunction) {
+      throw Exception("Import is not a function: $imp");
+    }
+
+    var argTypes = runtime.getArgTypes(imp.funcType);
+    var returnType = runtime.getReturnType(imp.funcType);
+    var wasmFnImport = allocate<_WasmFnImport>();
+    wasmFnImport.ref.numArgs = argTypes.length;
+    wasmFnImport.ref.returnType = returnType;
+    _wasmFnImportToFn[wasmFnImport.address] = fn;
+    var fnImp = runtime.newFunc(
+        _module._store,
+        imp.funcType,
+        _wasmFnImportTrampolineNative,
+        wasmFnImport,
+        _wasmFnImportFinalizerNative);
+    _imports[index] = runtime.functionToExtern(fnImp);
+    return this;
+  }
+
+  /// Build the module instance.
+  WasmInstance build() {
+    for (var i = 0; i < _importDescs.length; ++i) {
+      if (_imports[i] == nullptr) {
+        throw Exception("Missing import: ${_importDescs[i]}");
+      }
+    }
+    return WasmInstance(_module, _imports);
+  }
 }
 
 /// WasmInstance is an instantiated WasmModule.
 class WasmInstance {
-  Pointer<WasmerStore> _store;
-  Pointer<WasmerModule> _module;
+  WasmModule _module;
   Pointer<WasmerInstance> _instance;
   Pointer<WasmerMemory>? _exportedMemory;
   Map<String, WasmFunction> _functions = {};
 
-  WasmInstance(this._store, this._module, WasmImports imports)
+  WasmInstance(this._module, Pointer<Pointer<WasmerExtern>> imports)
       : _instance = WasmRuntime()
-            .instantiate(_store, _module, imports._imports, imports.length) {
+            .instantiate(_module._store, _module._module, imports) {
     var runtime = WasmRuntime();
     var exports = runtime.exports(_instance);
-    var exportDescs = runtime.exportDescriptors(_module);
+    var exportDescs = runtime.exportDescriptors(_module._module);
     assert(exports.ref.length == exportDescs.length);
     for (var i = 0; i < exports.ref.length; ++i) {
       var e = exports.ref.data[i];

pkg/wasm/lib/src/runtime.dart

@@ -20,6 +20,18 @@ class WasmImportDescriptor {
   String name;
   Pointer<WasmerFunctype> funcType;
   WasmImportDescriptor(this.kind, this.moduleName, this.name, this.funcType);
+
+  String toString() {
+    var kindName = wasmerExternKindName(kind);
+    if (kind == WasmerExternKindFunction) {
+      var runtime = WasmRuntime();
+      var sig = WasmRuntime.getSignatureString("${moduleName}::${name}",
+          runtime.getArgTypes(funcType), runtime.getReturnType(funcType));
+      return "$kindName: $sig";
+    } else {
+      return "$kindName: ${moduleName}::${name}";
+    }
+  }
 }
 
 class WasmExportDescriptor {
@@ -27,6 +39,18 @@ class WasmExportDescriptor {
   String name;
   Pointer<WasmerFunctype> funcType;
   WasmExportDescriptor(this.kind, this.name, this.funcType);
+
+  String toString() {
+    var kindName = wasmerExternKindName(kind);
+    if (kind == WasmerExternKindFunction) {
+      var runtime = WasmRuntime();
+      var sig = WasmRuntime.getSignatureString(
+          name, runtime.getArgTypes(funcType), runtime.getReturnType(funcType));
+      return "$kindName: $sig";
+    } else {
+      return "$kindName: ${name}";
+    }
+  }
 }
 
 class WasmRuntime {
@@ -57,8 +81,10 @@ class WasmRuntime {
   late WasmerExterntypeAsFunctypeFn _externtype_as_functype;
   late WasmerExterntypeDeleteFn _externtype_delete;
   late WasmerExterntypeKindFn _externtype_kind;
+  late WasmerFuncAsExternFn _func_as_extern;
   late WasmerFuncCallFn _func_call;
   late WasmerFuncDeleteFn _func_delete;
+  late WasmerFuncNewWithEnvFn _func_new_with_env;
   late WasmerFunctypeDeleteFn _functype_delete;
   late WasmerFunctypeParamsFn _functype_params;
   late WasmerFunctypeResultsFn _functype_results;
@@ -72,6 +98,7 @@ class WasmRuntime {
   late WasmerInstanceDeleteFn _instance_delete;
   late WasmerInstanceExportsFn _instance_exports;
   late WasmerInstanceNewFn _instance_new;
+  late WasmerMemoryAsExternFn _memory_as_extern;
   late WasmerMemoryDataFn _memory_data;
   late WasmerMemoryDataSizeFn _memory_data_size;
   late WasmerMemoryDeleteFn _memory_delete;
@@ -199,11 +226,16 @@ class WasmRuntime {
         WasmerExterntypeDeleteFn>('wasm_externtype_delete');
     _externtype_kind = _lib.lookupFunction<NativeWasmerExterntypeKindFn,
         WasmerExterntypeKindFn>('wasm_externtype_kind');
+    _func_as_extern =
+        _lib.lookupFunction<NativeWasmerFuncAsExternFn, WasmerFuncAsExternFn>(
+            'wasm_func_as_extern');
     _func_call = _lib.lookupFunction<NativeWasmerFuncCallFn, WasmerFuncCallFn>(
         'wasm_func_call');
     _func_delete =
         _lib.lookupFunction<NativeWasmerFuncDeleteFn, WasmerFuncDeleteFn>(
             'wasm_func_delete');
+    _func_new_with_env = _lib.lookupFunction<NativeWasmerFuncNewWithEnvFn,
+        WasmerFuncNewWithEnvFn>('wasm_func_new_with_env');
     _functype_delete = _lib.lookupFunction<NativeWasmerFunctypeDeleteFn,
         WasmerFunctypeDeleteFn>('wasm_functype_delete');
     _functype_params = _lib.lookupFunction<NativeWasmerFunctypeParamsFn,
@@ -235,6 +267,8 @@ class WasmRuntime {
     _instance_new =
         _lib.lookupFunction<NativeWasmerInstanceNewFn, WasmerInstanceNewFn>(
             'wasm_instance_new');
+    _memory_as_extern = _lib.lookupFunction<NativeWasmerMemoryAsExternFn,
+        WasmerMemoryAsExternFn>('wasm_memory_as_extern');
     _memory_data =
         _lib.lookupFunction<NativeWasmerMemoryDataFn, WasmerMemoryDataFn>(
             'wasm_memory_data');
@@ -363,20 +397,8 @@ class WasmRuntime {
     return imps;
   }
 
-  Pointer<WasmerInstance> instantiate(
-      Pointer<WasmerStore> store,
-      Pointer<WasmerModule> module,
-      Pointer<Pointer<WasmerExtern>> imports,
-      int numImports) {
-    var importsVec = allocate<WasmerImporttypeVec>();
-    _module_imports(module, importsVec);
-    if (importsVec.ref.length != numImports) {
-      throw Exception(
-          "Wrong number of imports. Expected ${importsVec.ref.length} but " +
-              "found $numImports.");
-    }
-    free(importsVec);
-
+  Pointer<WasmerInstance> instantiate(Pointer<WasmerStore> store,
+      Pointer<WasmerModule> module, Pointer<Pointer<WasmerExtern>> imports) {
     var instancePtr = _instance_new(store, module, imports, nullptr);
     if (instancePtr == nullptr) {
       throw Exception("Wasm module instantiation failed");
@@ -399,6 +421,10 @@ class WasmRuntime {
     return _extern_as_func(extern);
   }
 
+  Pointer<WasmerExtern> functionToExtern(Pointer<WasmerFunc> func) {
+    return _func_as_extern(func);
+  }
+
   List<int> getArgTypes(Pointer<WasmerFunctype> funcType) {
     var types = <int>[];
     var args = _functype_params(funcType);
@@ -427,6 +453,10 @@ class WasmRuntime {
     return _extern_as_memory(extern);
   }
 
+  Pointer<WasmerExtern> memoryToExtern(Pointer<WasmerMemory> memory) {
+    return _memory_as_extern(memory);
+  }
+
   Pointer<WasmerMemory> newMemory(
       Pointer<WasmerStore> store, int pages, int? maxPages) {
     var limPtr = allocate<WasmerLimits>();
@@ -456,4 +486,20 @@ class WasmRuntime {
   Uint8List memoryView(Pointer<WasmerMemory> memory) {
     return _memory_data(memory).asTypedList(_memory_data_size(memory));
   }
+
+  Pointer<WasmerFunc> newFunc(
+      Pointer<WasmerStore> store,
+      Pointer<WasmerFunctype> funcType,
+      Pointer func,
+      Pointer env,
+      Pointer finalizer) {
+    return _func_new_with_env(
+        store, funcType, func.cast(), env.cast(), finalizer.cast());
+  }
+
+  static String getSignatureString(
+      String name, List<int> argTypes, int returnType) {
+    return "${wasmerValKindName(returnType)} $name" +
+        "(${argTypes.map(wasmerValKindName).join(", ")})";
+  }
 }

pkg/wasm/lib/src/tools/generate_ffi_boilerplate.py

@@ -283,9 +283,12 @@ WASM_API_EXTERN wasm_memory_pages_t wasm_memory_size(const wasm_memory_t*);
 WASM_API_EXTERN bool wasm_memory_grow(wasm_memory_t*, wasm_memory_pages_t delta);
 WASM_API_EXTERN wasm_externkind_t wasm_extern_kind(const wasm_extern_t*);
 WASM_API_EXTERN wasm_func_t* wasm_extern_as_func(wasm_extern_t*);
+WASM_API_EXTERN wasm_extern_t* wasm_func_as_extern(wasm_func_t*);
 WASM_API_EXTERN wasm_memory_t* wasm_extern_as_memory(wasm_extern_t*);
+WASM_API_EXTERN wasm_extern_t* wasm_memory_as_extern(wasm_memory_t*);
 WASM_API_EXTERN const wasm_valtype_vec_t* wasm_functype_params(const wasm_functype_t*);
 WASM_API_EXTERN const wasm_valtype_vec_t* wasm_functype_results(const wasm_functype_t*);
+WASM_API_EXTERN own wasm_func_t* wasm_func_new_with_env( wasm_store_t*, const wasm_functype_t* type, void* fn, void* env, void *finalizer);
 WASM_API_EXTERN own wasm_trap_t* wasm_func_call(const wasm_func_t*, const wasm_val_t args[], wasm_val_t results[]);
 WASM_API_EXTERN wasm_valkind_t wasm_valtype_kind(const wasm_valtype_t*);
 '''

pkg/wasm/lib/src/tools/runtime_template.dart

@@ -18,6 +18,18 @@ class WasmImportDescriptor {
   String name;
   Pointer<WasmerFunctype> funcType;
   WasmImportDescriptor(this.kind, this.moduleName, this.name, this.funcType);
+
+  String toString() {
+    var kindName = wasmerExternKindName(kind);
+    if (kind == WasmerExternKindFunction) {
+      var runtime = WasmRuntime();
+      var sig = WasmRuntime.getSignatureString("${moduleName}::${name}",
+          runtime.getArgTypes(funcType), runtime.getReturnType(funcType));
+      return "$kindName: $sig";
+    } else {
+      return "$kindName: ${moduleName}::${name}";
+    }
+  }
 }
 
 class WasmExportDescriptor {
@@ -25,6 +37,18 @@ class WasmExportDescriptor {
   String name;
   Pointer<WasmerFunctype> funcType;
   WasmExportDescriptor(this.kind, this.name, this.funcType);
+
+  String toString() {
+    var kindName = wasmerExternKindName(kind);
+    if (kind == WasmerExternKindFunction) {
+      var runtime = WasmRuntime();
+      var sig = WasmRuntime.getSignatureString(
+          name, runtime.getArgTypes(funcType), runtime.getReturnType(funcType));
+      return "$kindName: $sig";
+    } else {
+      return "$kindName: ${name}";
+    }
+  }
 }
 
 class WasmRuntime {
@@ -147,20 +171,8 @@ class WasmRuntime {
     return imps;
   }
 
-  Pointer<WasmerInstance> instantiate(
-      Pointer<WasmerStore> store,
-      Pointer<WasmerModule> module,
-      Pointer<Pointer<WasmerExtern>> imports,
-      int numImports) {
-    var importsVec = allocate<WasmerImporttypeVec>();
-    _module_imports(module, importsVec);
-    if (importsVec.ref.length != numImports) {
-      throw Exception(
-          "Wrong number of imports. Expected ${importsVec.ref.length} but " +
-              "found $numImports.");
-    }
-    free(importsVec);
-
+  Pointer<WasmerInstance> instantiate(Pointer<WasmerStore> store,
+      Pointer<WasmerModule> module, Pointer<Pointer<WasmerExtern>> imports) {
     var instancePtr = _instance_new(store, module, imports, nullptr);
     if (instancePtr == nullptr) {
       throw Exception("Wasm module instantiation failed");
@@ -183,6 +195,10 @@ class WasmRuntime {
     return _extern_as_func(extern);
   }
 
+  Pointer<WasmerExtern> functionToExtern(Pointer<WasmerFunc> func) {
+    return _func_as_extern(func);
+  }
+
   List<int> getArgTypes(Pointer<WasmerFunctype> funcType) {
     var types = <int>[];
     var args = _functype_params(funcType);
@@ -211,6 +227,10 @@ class WasmRuntime {
     return _extern_as_memory(extern);
   }
 
+  Pointer<WasmerExtern> memoryToExtern(Pointer<WasmerMemory> memory) {
+    return _memory_as_extern(memory);
+  }
+
   Pointer<WasmerMemory> newMemory(
       Pointer<WasmerStore> store, int pages, int? maxPages) {
     var limPtr = allocate<WasmerLimits>();
@@ -240,4 +260,20 @@ class WasmRuntime {
   Uint8List memoryView(Pointer<WasmerMemory> memory) {
     return _memory_data(memory).asTypedList(_memory_data_size(memory));
   }
+
+  Pointer<WasmerFunc> newFunc(
+      Pointer<WasmerStore> store,
+      Pointer<WasmerFunctype> funcType,
+      Pointer func,
+      Pointer env,
+      Pointer finalizer) {
+    return _func_new_with_env(
+        store, funcType, func.cast(), env.cast(), finalizer.cast());
+  }
+
+  static String getSignatureString(
+      String name, List<int> argTypes, int returnType) {
+    return "${wasmerValKindName(returnType)} $name" +
+        "(${argTypes.map(wasmerValKindName).join(", ")})";
+  }
 }

pkg/wasm/lib/src/tools/wasmer_api_template.dart

@@ -86,6 +86,19 @@ class WasmerVal extends Struct {
   bool get isI64 => kind == WasmerValKindI64;
   bool get isF32 => kind == WasmerValKindF32;
   bool get isF64 => kind == WasmerValKindF64;
+
+  dynamic get toDynamic {
+    switch (kind) {
+      case WasmerValKindI32:
+        return i32;
+      case WasmerValKindI64:
+        return i64;
+      case WasmerValKindF32:
+        return f32;
+      case WasmerValKindF64:
+        return f64;
+    }
+  }
 }
 
 // wasmer_limits_t

pkg/wasm/lib/src/wasmer_api.dart

@@ -88,6 +88,19 @@ class WasmerVal extends Struct {
   bool get isI64 => kind == WasmerValKindI64;
   bool get isF32 => kind == WasmerValKindF32;
   bool get isF64 => kind == WasmerValKindF64;
+
+  dynamic get toDynamic {
+    switch (kind) {
+      case WasmerValKindI32:
+        return i32;
+      case WasmerValKindI64:
+        return i64;
+      case WasmerValKindF32:
+        return f32;
+      case WasmerValKindF64:
+        return f64;
+    }
+  }
 }
 
 // wasmer_limits_t
@@ -316,6 +329,12 @@ typedef NativeWasmerExterntypeKindFn = Uint8 Function(
     Pointer<WasmerExterntype>);
 typedef WasmerExterntypeKindFn = int Function(Pointer<WasmerExterntype>);
 
+// wasm_func_as_extern
+typedef NativeWasmerFuncAsExternFn = Pointer<WasmerExtern> Function(
+    Pointer<WasmerFunc>);
+typedef WasmerFuncAsExternFn = Pointer<WasmerExtern> Function(
+    Pointer<WasmerFunc>);
+
 // wasm_func_call
 typedef NativeWasmerFuncCallFn = Pointer<WasmerTrap> Function(
     Pointer<WasmerFunc>, Pointer<WasmerVal>, Pointer<WasmerVal>);
@@ -326,6 +345,20 @@ typedef WasmerFuncCallFn = Pointer<WasmerTrap> Function(
 typedef NativeWasmerFuncDeleteFn = Void Function(Pointer<WasmerFunc>);
 typedef WasmerFuncDeleteFn = void Function(Pointer<WasmerFunc>);
 
+// wasm_func_new_with_env
+typedef NativeWasmerFuncNewWithEnvFn = Pointer<WasmerFunc> Function(
+    Pointer<WasmerStore>,
+    Pointer<WasmerFunctype>,
+    Pointer<Void>,
+    Pointer<Void>,
+    Pointer<Void>);
+typedef WasmerFuncNewWithEnvFn = Pointer<WasmerFunc> Function(
+    Pointer<WasmerStore>,
+    Pointer<WasmerFunctype>,
+    Pointer<Void>,
+    Pointer<Void>,
+    Pointer<Void>);
+
 // wasm_functype_delete
 typedef NativeWasmerFunctypeDeleteFn = Void Function(Pointer<WasmerFunctype>);
 typedef WasmerFunctypeDeleteFn = void Function(Pointer<WasmerFunctype>);
@@ -406,6 +439,12 @@ typedef WasmerInstanceNewFn = Pointer<WasmerInstance> Function(
     Pointer<Pointer<WasmerExtern>>,
     Pointer<Pointer<WasmerTrap>>);
 
+// wasm_memory_as_extern
+typedef NativeWasmerMemoryAsExternFn = Pointer<WasmerExtern> Function(
+    Pointer<WasmerMemory>);
+typedef WasmerMemoryAsExternFn = Pointer<WasmerExtern> Function(
+    Pointer<WasmerMemory>);
+
 // wasm_memory_data
 typedef NativeWasmerMemoryDataFn = Pointer<Uint8> Function(
     Pointer<WasmerMemory>);

tests/lib/wasm/basic_test.dart

@@ -20,7 +20,7 @@ void main() {
     0x7e, 0x0b,
   ]);
 
-  var inst = WasmModule(data).instantiate(WasmImports());
+  var inst = WasmModule(data).instantiate().build();
   var fn = inst.lookupFunction("square");
   int n = fn(1234);
 

tests/lib/wasm/fn_call_error_test.dart

@@ -20,7 +20,7 @@ void main() {
     0x7e, 0x0b,
   ]);
 
-  var inst = WasmModule(data).instantiate(WasmImports());
+  var inst = WasmModule(data).instantiate().build();
   var fn = inst.lookupFunction("square");
 
   Expect.throwsArgumentError(() => fn());

tests/lib/wasm/fn_import_error_test.dart

@@ -5,7 +5,7 @@
 // Test errors thrown by function imports.
 
 import "package:expect/expect.dart";
-import "dart:wasm";
+import "package:wasm/wasm.dart";
 import "dart:typed_data";
 
 void main() {
@@ -25,36 +25,27 @@ void main() {
   ]);
 
   var mod = WasmModule(data);
-  var imp = WasmImports()
-    ..addFunction<Int64 Function(Int32, Int64, Float, Double)>(
-        "env", "someFn", (num a, num b, num c, num d) => 123);
-  mod.instantiate(imp);
 
-  imp = WasmImports();
-  Expect.throwsArgumentError(() => mod.instantiate(imp));
+  // Valid instantiation.
+  var inst = mod.instantiate()
+    .addFunction(
+        "env", "someFn", (int a, int b, num c, double d) => 123).build();
 
-  imp = WasmImports()
-    ..addFunction<Int64 Function(Int32)>("env", "someFn", (num a) => 123);
-  Expect.throwsArgumentError(() => mod.instantiate(imp));
+  // Missing imports.
+  Expect.throws(() => mod.instantiate().build(), (Exception e) => "$e".contains("Missing import"));
 
-  imp = WasmImports()
-    ..addFunction<Double Function(Int32, Int64, Float, Double)>(
-        "env", "someFn", (num a, num b, num c, num d) => 123);
-  Expect.throwsArgumentError(() => mod.instantiate(imp));
+  // Wrong kind of import.
+  Expect.throws(() => mod.instantiate().addMemory("env", "someFn", mod.createMemory(10)), (Exception e) => "$e".contains("Import is not a memory"));
 
-  imp = WasmImports()
-    ..addFunction<Int64 Function(Int32, Int64, Float, Float)>(
-        "env", "someFn", (num a, num b, num c, num d) => 123);
-  Expect.throwsArgumentError(() => mod.instantiate(imp));
+  // Wrong namespace.
+  Expect.throws(() => mod.instantiate().addFunction("foo", "someFn", (int a, int b, num c, double d) => 123).build(), (Exception e) => "$e".contains("Import not found"));
 
-  Expect.throwsArgumentError(() => WasmImports()
-    ..addFunction<dynamic Function(Int32, Int64, Float, Double)>(
-        "env", "someFn", (num a, num b, num c, num d) => 123));
+  // Wrong name.
+  Expect.throws(() => mod.instantiate().addFunction("env", "otherFn", (int a, int b, num c, double d) => 123).build(), (Exception e) => "$e".contains("Import not found"));
 
-  Expect.throwsArgumentError(() => WasmImports()
-    ..addFunction<Int64 Function(Int32, Int64, dynamic, Double)>(
-        "env", "someFn", (num a, num b, num c, num d) => 123));
-
-  imp = WasmImports()..addGlobal<Int64>("env", "someFn", 123, false);
-  Expect.throwsArgumentError(() => mod.instantiate(imp));
+  // Already filled.
+  Expect.throws(() => mod.instantiate()
+    .addFunction("env", "someFn", (int a, int b, num c, double d) => 123)
+    .addFunction("env", "someFn", (int a, int b, num c, double d) => 456)
+    .build(), (Exception e) => "$e".contains("Import already filled"));
 }

tests/lib/wasm/fn_import_test.dart

@@ -5,7 +5,7 @@
 // Test that we can load a wasm module, find a function, and call it.
 
 import "package:expect/expect.dart";
-import "dart:wasm";
+import "package:wasm/wasm.dart";
 import "dart:typed_data";
 
 void main() {
@@ -25,13 +25,13 @@ void main() {
   int report_x = -1;
   int report_y = -1;
 
-  var inst = WasmModule(data).instantiate(WasmImports()
-    ..addFunction<Void Function(Int64, Int64)>("env", "report", (int x, int y) {
+  var inst = WasmModule(data).instantiate()
+    .addFunction("env", "report", (int x, int y) {
       report_x = x;
       report_y = y;
-    }));
-  var fn = inst.lookupFunction<Void Function()>("reportStuff");
-  fn.call([]);
+    }).build();
+  var fn = inst.lookupFunction("reportStuff");
+  fn();
   Expect.equals(report_x, 123);
   Expect.equals(report_y, 456);
 }

tests/lib/wasm/hello_world_test.dart

@@ -5,7 +5,7 @@
 // Test for hello world built using emscripten with WASI.
 
 import "package:expect/expect.dart";
-import "dart:wasm";
+import "package:wasm/wasm.dart";
 import "dart:typed_data";
 
 void main() {
@@ -169,7 +169,7 @@ void main() {
     0x0b, 0x05, 0x0a, 0xff, 0xff, 0xff, 0xff,
   ]);
 
-  WasmMemory mem = null;
+  late WasmMemory mem;
   String out = "";
   var getI32 = (int p) {
     // Read a little-endian I32.
@@ -180,26 +180,26 @@ void main() {
     }
     return n;
   };
-  var inst = WasmModule(data).instantiate(WasmImports()
-    ..addFunction<Int32 Function(Int32, Int32, Int32, Int32)>(
-        "wasi_unstable", "fd_write",
-        (int fd, int iovs, int iovs_len, int unused) {
-      // iovs points to an array of length iovs_len. Each element is two I32s,
-      // a char* and a length.
-      String o = "";
-      for (var i = 0; i < iovs_len; ++i) {
-        var str = getI32(iovs + 8 * i);
-        var len = getI32(iovs + 4 + 8 * i);
-        for (var j = 0; j < len; ++j) {
-          o += String.fromCharCode(mem[str + j]);
-        }
+  var inst = WasmModule(data)
+      .instantiate()
+      .addFunction("wasi_unstable", "fd_write",
+          (int fd, int iovs, int iovs_len, int unused) {
+    // iovs points to an array of length iovs_len. Each element is two I32s,
+    // a char* and a length.
+    String o = "";
+    for (var i = 0; i < iovs_len; ++i) {
+      var str = getI32(iovs + 8 * i);
+      var len = getI32(iovs + 4 + 8 * i);
+      for (var j = 0; j < len; ++j) {
+        o += String.fromCharCode(mem[str + j]);
       }
-      out += o;
-      return o.length;
-    }));
+    }
+    out += o;
+    return o.length;
+  }).build();
   mem = inst.memory;
 
-  var fn = inst.lookupFunction<Void Function()>("_start");
-  fn.call([]);
+  var fn = inst.lookupFunction("_start");
+  fn();
   Expect.equals("hello, world!\n", out);
 }

tests/lib/wasm/numerics_test.dart

@@ -29,7 +29,7 @@ void main() {
     0x01, 0x92, 0x0b,
   ]);
 
-  var inst = WasmModule(data).instantiate(WasmImports());
+  var inst = WasmModule(data).instantiate().build();
   var addI64 = inst.lookupFunction("addI64");
   var addI32 = inst.lookupFunction("addI32");
   var addF64 = inst.lookupFunction("addF64");

tests/lib/wasm/void_test.dart

@@ -25,7 +25,7 @@ void main() {
     0x80, 0x08, 0x0b, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
   ]);
 
-  var inst = WasmModule(data).instantiate(WasmImports());
+  var inst = WasmModule(data).instantiate().build();
   var setFn = inst.lookupFunction("set");
   var getFn = inst.lookupFunction("get");
   Expect.isNull(setFn(123, 456));

tests/lib_2/wasm/basic_test.dart

@@ -20,7 +20,7 @@ void main() {
     0x7e, 0x0b,
   ]);
 
-  var inst = WasmModule(data).instantiate(WasmImports());
+  var inst = WasmModule(data).instantiate().build();
   var fn = inst.lookupFunction("square");
   int n = fn(1234);
 

tests/lib_2/wasm/fn_call_error_test.dart

@@ -20,7 +20,7 @@ void main() {
     0x7e, 0x0b,
   ]);
 
-  var inst = WasmModule(data).instantiate(WasmImports());
+  var inst = WasmModule(data).instantiate().build();
   var fn = inst.lookupFunction("square");
 
   Expect.throwsArgumentError(() => fn());

tests/lib_2/wasm/fn_import_error_test.dart

@@ -5,7 +5,7 @@
 // Test errors thrown by function imports.
 
 import "package:expect/expect.dart";
-import "dart:wasm";
+import "package:wasm/wasm.dart";
 import "dart:typed_data";
 
 void main() {
@@ -25,36 +25,27 @@ void main() {
   ]);
 
   var mod = WasmModule(data);
-  var imp = WasmImports()
-    ..addFunction<Int64 Function(Int32, Int64, Float, Double)>(
-        "env", "someFn", (num a, num b, num c, num d) => 123);
-  mod.instantiate(imp);
 
-  imp = WasmImports();
-  Expect.throwsArgumentError(() => mod.instantiate(imp));
+  // Valid instantiation.
+  var inst = mod.instantiate()
+    .addFunction(
+        "env", "someFn", (int a, int b, num c, double d) => 123).build();
 
-  imp = WasmImports()
-    ..addFunction<Int64 Function(Int32)>("env", "someFn", (num a) => 123);
-  Expect.throwsArgumentError(() => mod.instantiate(imp));
+  // Missing imports.
+  Expect.throws(() => mod.instantiate().build(), (Exception e) => "$e".contains("Missing import"));
 
-  imp = WasmImports()
-    ..addFunction<Double Function(Int32, Int64, Float, Double)>(
-        "env", "someFn", (num a, num b, num c, num d) => 123);
-  Expect.throwsArgumentError(() => mod.instantiate(imp));
+  // Wrong kind of import.
+  Expect.throws(() => mod.instantiate().addMemory("env", "someFn", mod.createMemory(10)), (Exception e) => "$e".contains("Import is not a memory"));
 
-  imp = WasmImports()
-    ..addFunction<Int64 Function(Int32, Int64, Float, Float)>(
-        "env", "someFn", (num a, num b, num c, num d) => 123);
-  Expect.throwsArgumentError(() => mod.instantiate(imp));
+  // Wrong namespace.
+  Expect.throws(() => mod.instantiate().addFunction("foo", "someFn", (int a, int b, num c, double d) => 123).build(), (Exception e) => "$e".contains("Import not found"));
 
-  Expect.throwsArgumentError(() => WasmImports()
-    ..addFunction<dynamic Function(Int32, Int64, Float, Double)>(
-        "env", "someFn", (num a, num b, num c, num d) => 123));
+  // Wrong name.
+  Expect.throws(() => mod.instantiate().addFunction("env", "otherFn", (int a, int b, num c, double d) => 123).build(), (Exception e) => "$e".contains("Import not found"));
 
-  Expect.throwsArgumentError(() => WasmImports()
-    ..addFunction<Int64 Function(Int32, Int64, dynamic, Double)>(
-        "env", "someFn", (num a, num b, num c, num d) => 123));
-
-  imp = WasmImports()..addGlobal<Int64>("env", "someFn", 123, false);
-  Expect.throwsArgumentError(() => mod.instantiate(imp));
+  // Already filled.
+  Expect.throws(() => mod.instantiate()
+    .addFunction("env", "someFn", (int a, int b, num c, double d) => 123)
+    .addFunction("env", "someFn", (int a, int b, num c, double d) => 456)
+    .build(), (Exception e) => "$e".contains("Import already filled"));
 }

tests/lib_2/wasm/fn_import_test.dart

@@ -5,7 +5,7 @@
 // Test that we can load a wasm module, find a function, and call it.
 
 import "package:expect/expect.dart";
-import "dart:wasm";
+import "package:wasm/wasm.dart";
 import "dart:typed_data";
 
 void main() {
@@ -25,13 +25,13 @@ void main() {
   int report_x = -1;
   int report_y = -1;
 
-  var inst = WasmModule(data).instantiate(WasmImports()
-    ..addFunction<Void Function(Int64, Int64)>("env", "report", (int x, int y) {
+  var inst = WasmModule(data).instantiate()
+    .addFunction("env", "report", (int x, int y) {
       report_x = x;
       report_y = y;
-    }));
-  var fn = inst.lookupFunction<Void Function()>("reportStuff");
-  fn.call([]);
+    }).build();
+  var fn = inst.lookupFunction("reportStuff");
+  fn();
   Expect.equals(report_x, 123);
   Expect.equals(report_y, 456);
 }

tests/lib_2/wasm/hello_world_test.dart

@@ -5,7 +5,7 @@
 // Test for hello world built using emscripten with WASI.
 
 import "package:expect/expect.dart";
-import "dart:wasm";
+import "package:wasm/wasm.dart";
 import "dart:typed_data";
 
 void main() {
@@ -180,26 +180,26 @@ void main() {
     }
     return n;
   };
-  var inst = WasmModule(data).instantiate(WasmImports()
-    ..addFunction<Int32 Function(Int32, Int32, Int32, Int32)>(
-        "wasi_unstable", "fd_write",
-        (int fd, int iovs, int iovs_len, int unused) {
-      // iovs points to an array of length iovs_len. Each element is two I32s,
-      // a char* and a length.
-      String o = "";
-      for (var i = 0; i < iovs_len; ++i) {
-        var str = getI32(iovs + 8 * i);
-        var len = getI32(iovs + 4 + 8 * i);
-        for (var j = 0; j < len; ++j) {
-          o += String.fromCharCode(mem[str + j]);
-        }
+  var inst = WasmModule(data)
+      .instantiate()
+      .addFunction("wasi_unstable", "fd_write",
+          (int fd, int iovs, int iovs_len, int unused) {
+    // iovs points to an array of length iovs_len. Each element is two I32s,
+    // a char* and a length.
+    String o = "";
+    for (var i = 0; i < iovs_len; ++i) {
+      var str = getI32(iovs + 8 * i);
+      var len = getI32(iovs + 4 + 8 * i);
+      for (var j = 0; j < len; ++j) {
+        o += String.fromCharCode(mem[str + j]);
       }
-      out += o;
-      return o.length;
-    }));
+    }
+    out += o;
+    return o.length;
+  }).build();
   mem = inst.memory;
 
-  var fn = inst.lookupFunction<Void Function()>("_start");
-  fn.call([]);
+  var fn = inst.lookupFunction("_start");
+  fn();
   Expect.equals("hello, world!\n", out);
 }

tests/lib_2/wasm/numerics_test.dart

@@ -29,7 +29,7 @@ void main() {
     0x01, 0x92, 0x0b,
   ]);
 
-  var inst = WasmModule(data).instantiate(WasmImports());
+  var inst = WasmModule(data).instantiate().build();
   var addI64 = inst.lookupFunction("addI64");
   var addI32 = inst.lookupFunction("addI32");
   var addF64 = inst.lookupFunction("addF64");

tests/lib_2/wasm/void_test.dart

@@ -25,7 +25,7 @@ void main() {
     0x80, 0x08, 0x0b, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
   ]);
 
-  var inst = WasmModule(data).instantiate(WasmImports());
+  var inst = WasmModule(data).instantiate().build();
   var setFn = inst.lookupFunction("set");
   var getFn = inst.lookupFunction("get");
   Expect.isNull(setFn(123, 456));

third_party/wasmer/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "wasmer"
-version = "1.0.0-alpha3"
+version = "1.0.0-alpha4"
 
 [lib]
 name = "wasmer"
@@ -8,6 +8,6 @@ crate-type = ["dylib"]
 path = "wasmer.rs"
 
 [dependencies.wasmer-c-api]
-version = "1.0.0-alpha3"
+version = "1.0.0-alpha4"
 default-features = false
 features = ["jit", "cranelift", "wasi"]