Reduce calls to get array length

Author: bpcreech

src/py_mini_racer/_abstract_context.py

@@ -78,6 +78,10 @@ def array_insert(
     ) -> None:
         pass
 
+    @abstractmethod
+    def array_push(self, arr: JSArray, new_val: PythonJSConvertedTypes) -> None:
+        pass
+
     @abstractmethod
     def call_function(
         self,

src/py_mini_racer/_context.py

@@ -199,6 +199,15 @@ def array_insert(
             )
         ).to_python_or_raise()
 
+    def array_push(self, arr: JSArray, new_val: PythonJSConvertedTypes) -> None:
+        arr_handle = python_to_value_handle(self, arr)
+        new_val_handle = python_to_value_handle(self, new_val)
+
+        # Convert the value just to convert any exceptions (and GC the result)
+        self._wrap_raw_handle(
+            self._get_dll().mr_array_push(self._ctx, arr_handle.raw, new_val_handle.raw)
+        ).to_python_or_raise()
+
     def call_function(
         self,
         func: JSFunction,

src/py_mini_racer/_dll.py

@@ -134,6 +134,9 @@ def _build_dll_handle(dll_path: Path) -> ctypes.CDLL:  # noqa: PLR0915
     ]
     handle.mr_splice_array.restype = RawValueHandle
 
+    handle.mr_array_push.argtypes = [ctypes.c_uint64, RawValueHandle, RawValueHandle]
+    handle.mr_array_push.restype = RawValueHandle
+
     handle.mr_call_function.argtypes = [
         ctypes.c_uint64,
         RawValueHandle,

src/py_mini_racer/_objects.py

@@ -132,7 +132,10 @@ def insert(self, index: int, new_obj: PythonJSConvertedTypes) -> None:
 
     def __iter__(self) -> Iterator[PythonJSConvertedTypes]:
         for i in range(len(self)):
-            yield self[i]
+            yield self._ctx.get_object_item(self, i)
+
+    def append(self, value: PythonJSConvertedTypes) -> None:
+        self._ctx.array_push(self, value)
 
 
 class JSFunctionImpl(JSMappedObjectImpl, JSFunction):

src/v8_py_frontend/context.cc

@@ -277,6 +277,29 @@ auto Context::SpliceArray(BinaryValueHandle* obj_handle,
           .get());
 }
 
+auto Context::ArrayPush(BinaryValueHandle* obj_handle,
+                        BinaryValueHandle* new_val_handle)
+    -> BinaryValueHandle* {
+  auto obj_hc = MakeHandleConverter(obj_handle, "Bad handle: obj");
+  if (!obj_hc) {
+    return obj_hc.GetErrorHandle();
+  }
+
+  auto new_val_hc = MakeHandleConverter(new_val_handle, "Bad handle: new_val");
+  if (!new_val_hc) {
+    return new_val_hc.GetErrorHandle();
+  }
+
+  return bv_registry_.Remember(
+      isolate_manager_
+          .Run([this, obj_ptr = obj_hc.GetPtr(),
+                new_val_ptr = new_val_hc.GetPtr()](v8::Isolate* isolate) {
+            return object_manipulator_.Push(isolate, obj_ptr.get(),
+                                            new_val_ptr.get());
+          })
+          .get());
+}
+
 void Context::FreeBinaryValue(BinaryValueHandle* val) {
   bv_registry_.Forget(val);
 }

src/v8_py_frontend/context.h

@@ -60,6 +60,8 @@ class Context {
                    int32_t start,
                    int32_t delete_count,
                    BinaryValueHandle* new_val_handle) -> BinaryValueHandle*;
+  auto ArrayPush(BinaryValueHandle* obj_handle,
+                 BinaryValueHandle* new_val_handle) -> BinaryValueHandle*;
   auto CallFunction(BinaryValueHandle* func_handle,
                     BinaryValueHandle* this_handle,
                     BinaryValueHandle* argv_handle,

src/v8_py_frontend/exports.cc

@@ -249,6 +249,17 @@ LIB_EXPORT auto mr_splice_array(uint64_t context_id,
                               new_val_handle);
 }
 
+LIB_EXPORT auto mr_array_push(uint64_t context_id,
+                              MiniRacer::BinaryValueHandle* array_handle,
+                              MiniRacer::BinaryValueHandle* new_val_handle)
+    -> MiniRacer::BinaryValueHandle* {
+  auto context = GetContext(context_id);
+  if (!context) {
+    return nullptr;
+  }
+  return context->ArrayPush(array_handle, new_val_handle);
+}
+
 LIB_EXPORT auto mr_call_function(uint64_t context_id,
                                  MiniRacer::BinaryValueHandle* func_handle,
                                  MiniRacer::BinaryValueHandle* this_handle,

src/v8_py_frontend/exports.h

@@ -197,6 +197,16 @@ LIB_EXPORT auto mr_splice_array(uint64_t context_id,
                                 MiniRacer::BinaryValueHandle* new_val_handle)
     -> MiniRacer::BinaryValueHandle*;
 
+/** Call JavaScript `Array.prototype.push(array, new_val)`.
+ *
+ * The result of the operation (passed into the callback) is an exception
+ * in case of failure.
+ **/
+LIB_EXPORT auto mr_array_push(uint64_t context_id,
+                              MiniRacer::BinaryValueHandle* array_handle,
+                              MiniRacer::BinaryValueHandle* new_val_handle)
+    -> MiniRacer::BinaryValueHandle*;
+
 /** Cancel the given asynchronous task.
  *
  * (Such tasks are started by mr_eval, mr_call_function, mr_heap_stats, and

src/v8_py_frontend/object_manipulator.cc

@@ -137,7 +137,7 @@ auto ObjectManipulator::Splice(v8::Isolate* isolate,
   }
 
   if (!splice_val->IsFunction()) {
-    return bv_factory_->New("splice method is not a function",
+    return bv_factory_->New("splice member is not a function",
                             type_execute_exception);
   }
 
@@ -163,6 +163,49 @@ auto ObjectManipulator::Splice(v8::Isolate* isolate,
   return bv_factory_->New(local_context, maybe_value.ToLocalChecked());
 }
 
+auto ObjectManipulator::Push(v8::Isolate* isolate,
+                             BinaryValue* obj_ptr,
+                             BinaryValue* new_val_ptr) -> BinaryValue::Ptr {
+  const v8::Isolate::Scope isolate_scope(isolate);
+  const v8::HandleScope handle_scope(isolate);
+  const v8::Local<v8::Context> local_context = context_->Get()->Get(isolate);
+  const v8::Context::Scope context_scope(local_context);
+
+  const v8::Local<v8::Value> local_obj_val = obj_ptr->ToValue(local_context);
+  const v8::Local<v8::Object> local_obj = local_obj_val.As<v8::Object>();
+
+  // Array.prototype.push doesn't exist in C++ in V8. We have to find the JS
+  // function and call it:
+  const v8::Local<v8::String> push_name =
+      v8::String::NewFromUtf8Literal(isolate, "push");
+
+  v8::Local<v8::Value> push_val;
+  if (!local_obj->Get(local_context, push_name).ToLocal(&push_val)) {
+    return bv_factory_->New("no push method on object", type_execute_exception);
+  }
+
+  if (!push_val->IsFunction()) {
+    return bv_factory_->New("push member is not a function",
+                            type_execute_exception);
+  }
+
+  const v8::Local<v8::Function> push_func = push_val.As<v8::Function>();
+
+  const v8::TryCatch trycatch(isolate);
+
+  std::vector<v8::Local<v8::Value>> argv = {
+      new_val_ptr->ToValue(local_context)};
+
+  v8::MaybeLocal<v8::Value> maybe_value = push_func->Call(
+      local_context, local_obj, static_cast<int>(argv.size()), argv.data());
+  if (maybe_value.IsEmpty()) {
+    return bv_factory_->New(local_context, trycatch.Message(),
+                            trycatch.Exception(), type_execute_exception);
+  }
+
+  return bv_factory_->New(local_context, maybe_value.ToLocalChecked());
+}
+
 auto ObjectManipulator::Call(v8::Isolate* isolate,
                              BinaryValue* func_ptr,
                              BinaryValue* this_ptr,

src/v8_py_frontend/object_manipulator.h

@@ -38,6 +38,9 @@ class ObjectManipulator {
               int32_t start,
               int32_t delete_count,
               BinaryValue* new_val_ptr) -> BinaryValue::Ptr;
+  auto Push(v8::Isolate* isolate,
+            BinaryValue* obj_ptr,
+            BinaryValue* new_val_ptr) -> BinaryValue::Ptr;
   auto Call(v8::Isolate* isolate,
             BinaryValue* func_ptr,
             BinaryValue* this_ptr,