napi: implement napi_is_detached_arraybuffer

doc/api/n-api.md

@@ -3258,6 +3258,29 @@ that is, created with [`napi_create_external_arraybuffer`][].
 This API represents the invocation of the `ArrayBuffer` detach operation as
 defined in [Section 24.1.1.3][] of the ECMAScript Language Specification.
 
+### napi_is_detached_arraybuffer
+<!-- YAML
+added: REPLACEME
+-->
+
+```C
+napi_status napi_is_detached_arraybuffer(napi_env env,
+                                         napi_value arraybuffer,
+                                         bool* result)
+```
+
+* `[in] env`: The environment that the API is invoked under.
+* `[in] arraybuffer`: The JavaScript `ArrayBuffer` to be checked.
+* `[out] result`: Whether the `arraybuffer` is detached.
+
+Returns `napi_ok` if the API succeeded.
+
+The `ArrayBuffer` is considered detached if its internal data is `null`.
+
+This API represents the invocation of the `ArrayBuffer` `IsDetachedBuffer`
+operation as defined in [Section 24.1.1.2][] of the ECMAScript Language
+Specification.
+
 ## Working with JavaScript Properties
 
 N-API exposes a set of APIs to get and set properties on JavaScript
@@ -5259,6 +5282,7 @@ This API may only be called from the main thread.
 [Section 7]: https://tc39.github.io/ecma262/#sec-abstract-operations
 [Section 8.7]: https://tc39.es/ecma262/#sec-agents
 [Section 9.1.6]: https://tc39.github.io/ecma262/#sec-ordinary-object-internal-methods-and-internal-slots-defineownproperty-p-desc
+[Section 24.1.1.2]: https://tc39.es/ecma262/#sec-isdetachedbuffer
 [Travis CI]: https://travis-ci.org
 [Visual Studio]: https://visualstudio.microsoft.com
 [Working with JavaScript Properties]: #n_api_working_with_javascript_properties

src/js_native_api.h

@@ -518,6 +518,10 @@ NAPI_EXTERN napi_status napi_get_instance_data(napi_env env,
 // ArrayBuffer detaching
 NAPI_EXTERN napi_status napi_detach_arraybuffer(napi_env env,
                                                 napi_value arraybuffer);
+
+NAPI_EXTERN napi_status napi_is_detached_arraybuffer(napi_env env,
+                                                     napi_value value,
+                                                     bool* result);
 #endif  // NAPI_EXPERIMENTAL
 
 EXTERN_C_END

src/js_native_api_v8.cc

@@ -3039,3 +3039,17 @@ napi_status napi_detach_arraybuffer(napi_env env, napi_value arraybuffer) {
 
   return napi_clear_last_error(env);
 }
+
+napi_status napi_is_detached_arraybuffer(napi_env env,
+                                         napi_value arraybuffer,
+                                         bool* result) {
+  CHECK_ENV(env);
+  CHECK_ARG(env, arraybuffer);
+
+  v8::Local<v8::Value> value = v8impl::V8LocalValueFromJsValue(arraybuffer);
+
+  *result = value->IsArrayBuffer() &&
+            value.As<v8::ArrayBuffer>()->GetBackingStore()->Data() == nullptr;
+
+  return napi_clear_last_error(env);
+}

test/js-native-api/test_typedarray/test.js

@@ -87,8 +87,21 @@ arrayTypes.forEach((currentType) => {
   assert.ok(externalResult instanceof Int8Array);
   assert.strictEqual(externalResult.length, 3);
   assert.strictEqual(externalResult.byteLength, 3);
+  assert.ok(!test_typedarray.IsDetached(buffer.buffer));
   test_typedarray.Detach(buffer);
+  assert.ok(test_typedarray.IsDetached(buffer.buffer));
   assert.ok(externalResult instanceof Int8Array);
   assert.strictEqual(buffer.length, 0);
   assert.strictEqual(buffer.byteLength, 0);
 }
+
+{
+  const buffer = new ArrayBuffer(128);
+  assert.ok(!test_typedarray.IsDetached(buffer));
+}
+
+{
+  const buffer = test_typedarray.NullArrayBuffer();
+  assert.ok(buffer instanceof ArrayBuffer);
+  assert.ok(test_typedarray.IsDetached(buffer));
+}

test/js-native-api/test_typedarray/test_typedarray.c

@@ -97,6 +97,15 @@ static napi_value External(napi_env env, napi_callback_info info) {
   return output_array;
 }
 
+
+static napi_value NullArrayBuffer(napi_env env, napi_callback_info info) {
+  static void* data = NULL;
+  napi_value arraybuffer;
+  NAPI_CALL(env,
+      napi_create_external_arraybuffer(env, data, 0, NULL, NULL, &arraybuffer));
+  return arraybuffer;
+}
+
 static napi_value CreateTypedArray(napi_env env, napi_callback_info info) {
   size_t argc = 4;
   napi_value args[4];
@@ -183,13 +192,36 @@ static napi_value Detach(napi_env env, napi_callback_info info) {
   return NULL;
 }
 
+static napi_value IsDetached(napi_env env, napi_callback_info info) {
+  size_t argc = 1;
+  napi_value args[1];
+  NAPI_CALL(env, napi_get_cb_info(env, info, &argc, args, NULL, NULL));
+  NAPI_ASSERT(env, argc == 1, "Wrong number of arguments.");
+
+  napi_value array_buffer = args[0];
+  bool is_arraybuffer;
+  NAPI_CALL(env, napi_is_arraybuffer(env, array_buffer, &is_arraybuffer));
+  NAPI_ASSERT(env, is_arraybuffer,
+      "Wrong type of arguments. Expects an array buffer as first argument.");
+
+  bool is_detached;
+  NAPI_CALL(env, napi_is_detached_arraybuffer(env, array_buffer, &is_detached));
+
+  napi_value result;
+  NAPI_CALL(env, napi_get_boolean(env, is_detached, &result));
+
+  return result;
+}
+
 EXTERN_C_START
 napi_value Init(napi_env env, napi_value exports) {
   napi_property_descriptor descriptors[] = {
     DECLARE_NAPI_PROPERTY("Multiply", Multiply),
     DECLARE_NAPI_PROPERTY("External", External),
+    DECLARE_NAPI_PROPERTY("NullArrayBuffer", NullArrayBuffer),
     DECLARE_NAPI_PROPERTY("CreateTypedArray", CreateTypedArray),
     DECLARE_NAPI_PROPERTY("Detach", Detach),
+    DECLARE_NAPI_PROPERTY("IsDetached", IsDetached),
   };
 
   NAPI_CALL(env, napi_define_properties(