src: add Addon<T> class

* separate out instance-related APIs from `ObjectWrap<T>` into a new
  class `InstanceWrap<T>` which then becomes a base class for
  `ObjectWrap<T>`.
* Add `Addon<T>` class as a subclass of `InstanceWrap<T>`,
  reimplementing `Unwrap()` to retrieve the instance data using
  `GetInstanceData<T>()` of `Napi::Env` instead of `napi_unwrap()`.
* Add macros `NODE_API_ADDON()` and `NODE_API_NAMED_ADDON()` to load an
  add-on from its `Addon<T>` subclass definition.

Bindings created like this perform slightly worse than static ones in
exchange for the benefit of having the context of a class instance as
their C++ `this` object. This way, they avoid having to call
`info.GetInstanceData<ClassName>()` in the bindings, which brings with
it the risk that the wrong `ClassName` will end up in the template
parameter thus resulting in a hard-to-track-down segfault. Static
bindings can still be created and associated with the `exports` object
and they can use `Napi::Env::GetInstanceData()` to retrieve the add-on
instance.

PR-URL: #749
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>

README.md

@@ -77,6 +77,7 @@ The oldest Node.js version supported by the current version of node-addon-api is
 
 The following is the documentation for node-addon-api.
 
+ - [Addon Structure](doc/addon.md)
  - [Basic Types](doc/basic_types.md)
     - [Array](doc/basic_types.md#array)
     - [Symbol](doc/symbol.md)

benchmark/function_args.cc

@@ -78,6 +78,66 @@ static void FourArgFunction(const Napi::CallbackInfo& info) {
   Napi::Value argv3 = info[3]; (void) argv3;
 }
 
+#if NAPI_VERSION > 5
+class FunctionArgsBenchmark : public Napi::Addon<FunctionArgsBenchmark> {
+ public:
+  FunctionArgsBenchmark(Napi::Env env, Napi::Object exports) {
+    DefineAddon(exports, {
+      InstanceValue("addon", DefineProperties(Napi::Object::New(env), {
+        InstanceMethod("noArgFunction", &FunctionArgsBenchmark::NoArgFunction),
+        InstanceMethod("oneArgFunction",
+                       &FunctionArgsBenchmark::OneArgFunction),
+        InstanceMethod("twoArgFunction",
+                       &FunctionArgsBenchmark::TwoArgFunction),
+        InstanceMethod("threeArgFunction",
+                       &FunctionArgsBenchmark::ThreeArgFunction),
+        InstanceMethod("fourArgFunction",
+                       &FunctionArgsBenchmark::FourArgFunction),
+      }), napi_enumerable),
+      InstanceValue("addon_templated",
+        DefineProperties(Napi::Object::New(env), {
+          InstanceMethod<&FunctionArgsBenchmark::NoArgFunction>(
+                                                            "noArgFunction"),
+          InstanceMethod<&FunctionArgsBenchmark::OneArgFunction>(
+                                                            "oneArgFunction"),
+          InstanceMethod<&FunctionArgsBenchmark::TwoArgFunction>(
+                                                            "twoArgFunction"),
+          InstanceMethod<&FunctionArgsBenchmark::ThreeArgFunction>(
+                                                            "threeArgFunction"),
+          InstanceMethod<&FunctionArgsBenchmark::FourArgFunction>(
+                                                            "fourArgFunction"),
+        }), napi_enumerable),
+    });
+  }
+ private:
+  void NoArgFunction(const Napi::CallbackInfo& info) {
+    (void) info;
+  }
+
+  void OneArgFunction(const Napi::CallbackInfo& info) {
+    Napi::Value argv0 = info[0]; (void) argv0;
+  }
+
+  void TwoArgFunction(const Napi::CallbackInfo& info) {
+    Napi::Value argv0 = info[0]; (void) argv0;
+    Napi::Value argv1 = info[1]; (void) argv1;
+  }
+
+  void ThreeArgFunction(const Napi::CallbackInfo& info) {
+    Napi::Value argv0 = info[0]; (void) argv0;
+    Napi::Value argv1 = info[1]; (void) argv1;
+    Napi::Value argv2 = info[2]; (void) argv2;
+  }
+
+  void FourArgFunction(const Napi::CallbackInfo& info) {
+    Napi::Value argv0 = info[0]; (void) argv0;
+    Napi::Value argv1 = info[1]; (void) argv1;
+    Napi::Value argv2 = info[2]; (void) argv2;
+    Napi::Value argv3 = info[3]; (void) argv3;
+  }
+};
+#endif  // NAPI_VERSION > 5
+
 static Napi::Object Init(Napi::Env env, Napi::Object exports) {
   napi_value no_arg_function, one_arg_function, two_arg_function,
       three_arg_function, four_arg_function;
@@ -147,6 +207,10 @@ static Napi::Object Init(Napi::Env env, Napi::Object exports) {
   templated["fourArgFunction"] = Napi::Function::New<FourArgFunction>(env);
   exports["templated"] = templated;
 
+#if NAPI_VERSION > 5
+  FunctionArgsBenchmark::Init(env, exports);
+#endif  // NAPI_VERSION > 5
+
   return exports;
 }
 

benchmark/function_args.js

@@ -4,48 +4,56 @@ const addonName = path.basename(__filename, '.js');
 
 [ addonName, addonName + '_noexcept' ]
   .forEach((addonName) => {
-    const rootAddon = require(`./build/Release/${addonName}`);
+    const rootAddon = require('bindings')({
+      bindings: addonName,
+      module_root: __dirname
+    });
+    delete rootAddon.path;
     const implems = Object.keys(rootAddon);
+    const maxNameLength =
+      implems.reduce((soFar, value) => Math.max(soFar, value.length), 0);
     const anObject = {};
 
-    console.log(`${addonName}: `);
+    console.log(`\n${addonName}: `);
 
     console.log('no arguments:');
     implems.reduce((suite, implem) => {
       const fn = rootAddon[implem].noArgFunction;
-      return suite.add(implem, () => fn());
+      return suite.add(implem.padStart(maxNameLength, ' '), () => fn());
     }, new Benchmark.Suite)
       .on('cycle', (event) => console.log(String(event.target)))
       .run();
 
     console.log('one argument:');
     implems.reduce((suite, implem) => {
       const fn = rootAddon[implem].oneArgFunction;
-      return suite.add(implem, () => fn('x'));
+      return suite.add(implem.padStart(maxNameLength, ' '), () => fn('x'));
     }, new Benchmark.Suite)
       .on('cycle', (event) => console.log(String(event.target)))
       .run();
 
     console.log('two arguments:');
     implems.reduce((suite, implem) => {
       const fn = rootAddon[implem].twoArgFunction;
-      return suite.add(implem, () => fn('x', 12));
+      return suite.add(implem.padStart(maxNameLength, ' '), () => fn('x', 12));
     }, new Benchmark.Suite)
       .on('cycle', (event) => console.log(String(event.target)))
       .run();
 
     console.log('three arguments:');
     implems.reduce((suite, implem) => {
       const fn = rootAddon[implem].threeArgFunction;
-      return suite.add(implem, () => fn('x', 12, true));
+      return suite.add(implem.padStart(maxNameLength, ' '),
+        () => fn('x', 12, true));
     }, new Benchmark.Suite)
       .on('cycle', (event) => console.log(String(event.target)))
       .run();
 
     console.log('four arguments:');
     implems.reduce((suite, implem) => {
       const fn = rootAddon[implem].fourArgFunction;
-      return suite.add(implem, () => fn('x', 12, true, anObject));
+      return suite.add(implem.padStart(maxNameLength, ' '),
+        () => fn('x', 12, true, anObject));
     }, new Benchmark.Suite)
       .on('cycle', (event) => console.log(String(event.target)))
       .run();

benchmark/property_descriptor.cc

@@ -26,6 +26,33 @@ static void Setter(const Napi::CallbackInfo& info) {
   (void) info[0];
 }
 
+#if NAPI_VERSION > 5
+class PropDescBenchmark : public Napi::Addon<PropDescBenchmark> {
+ public:
+  PropDescBenchmark(Napi::Env, Napi::Object exports) {
+    DefineAddon(exports, {
+      InstanceAccessor("addon",
+                       &PropDescBenchmark::Getter,
+                       &PropDescBenchmark::Setter,
+                       napi_enumerable),
+      InstanceAccessor<&PropDescBenchmark::Getter,
+                       &PropDescBenchmark::Setter>("addon_templated",
+                                                   napi_enumerable),
+    });
+  }
+
+ private:
+  Napi::Value Getter(const Napi::CallbackInfo& info) {
+    return Napi::Number::New(info.Env(), 42);
+  }
+
+  void Setter(const Napi::CallbackInfo& info, const Napi::Value& val) {
+    (void) info[0];
+    (void) val;
+  }
+};
+#endif  // NAPI_VERSION > 5
+
 static Napi::Object Init(Napi::Env env, Napi::Object exports) {
   napi_status status;
   napi_property_descriptor core_prop = {
@@ -54,6 +81,10 @@ static Napi::Object Init(Napi::Env env, Napi::Object exports) {
       Napi::PropertyDescriptor::Accessor<Getter, Setter>("templated",
                                                          napi_enumerable));
 
+#if NAPI_VERSION > 5
+  PropDescBenchmark::Init(env, exports);
+#endif  // NAPI_VERSION > 5
+
   return exports;
 }
 

benchmark/property_descriptor.js

@@ -4,17 +4,23 @@ const addonName = path.basename(__filename, '.js');
 
 [ addonName, addonName + '_noexcept' ]
   .forEach((addonName) => {
-    const rootAddon = require(`./build/Release/${addonName}`);
+    const rootAddon = require('bindings')({
+      bindings: addonName,
+      module_root: __dirname
+    });
+    delete rootAddon.path;
     const getters = new Benchmark.Suite;
     const setters = new Benchmark.Suite;
+    const maxNameLength = Object.keys(rootAddon)
+      .reduce((soFar, value) => Math.max(soFar, value.length), 0);
 
-    console.log(`${addonName}: `);
+    console.log(`\n${addonName}: `);
 
     Object.keys(rootAddon).forEach((key) => {
-      getters.add(`${key} getter`, () => {
+      getters.add(`${key} getter`.padStart(maxNameLength + 7), () => {
         const x = rootAddon[key];
       });
-      setters.add(`${key} setter`, () => {
+      setters.add(`${key} setter`.padStart(maxNameLength + 7), () => {
         rootAddon[key] = 5;
       })
     });
@@ -23,6 +29,8 @@ const addonName = path.basename(__filename, '.js');
       .on('cycle', (event) => console.log(String(event.target)))
       .run();
 
+    console.log('');
+
     setters
       .on('cycle', (event) => console.log(String(event.target)))
       .run();