optimize checkArgs

this makes the lineTo benchmark (lineTo executes a very small
number of operations, so it mostly measures the js<->C++ barrier)
run about 50% faster

src/CanvasRenderingContext2d.cc

@@ -45,12 +45,29 @@ constexpr double twoPi = M_PI * 2.;
  pango_context_get_language(pango_layout_get_context(LAYOUT)))
 
 inline static bool checkArgs(const Napi::CallbackInfo&info, double *args, int argsNum, int offset = 0){
- Napi::Number zero = Napi::Number::New(info.Env(), 0);
- int argsEnd = offset + argsNum;
+ Napi::Env env = info.Env();
+ int argsEnd = std::min(9, offset + argsNum);
  bool areArgsValid = true;
 
+ napi_value argv[9];
+ size_t argc = 9;
+ napi_get_cb_info(env, static_cast<napi_callback_info>(info), &argc, argv, nullptr, nullptr);
+
  for (int i = offset; i < argsEnd; i++) {
- double val = info[i].ToNumber().UnwrapOr(zero).DoubleValue();
+ napi_valuetype type;
+ double val = 0;
+
+ napi_typeof(env, argv[i], &type);
+ if (type == napi_number) {
+ // fast path
+ napi_get_value_double(env, argv[i], &val);
+ } else {
+ napi_value num;
+ napi_create_double(env, 0, &num);
+ if (napi_coerce_to_number(env, argv[i], &num) == napi_ok) {
+ napi_get_value_double(env, num, &val);
+ }
+ }
 
  if (areArgsValid) {
  if (!std::isfinite(val)) {