src: add ArrayBuffer::Detach() and ::IsDetached()

Refs: nodejs/node#29768
Refs: nodejs/node#30613

PR-URL: #659
Refs: nodejs/node#29768
Refs: nodejs/node#30613
Reviewed-By: Michael Dawson <midawson@redhat.com>
Reviewed-By: Gabriel Schulhof <gabriel.schulhof@intel.com>

Author: tniessen

doc/array_buffer.md

@@ -130,4 +130,20 @@ void* Napi::ArrayBuffer::Data() const;
 
 Returns a pointer the wrapped data.
 
+### Detach
+
+```cpp
+void Napi::ArrayBuffer::Detach();
+```
+
+Invokes the `ArrayBuffer` detach operation on a detachable `ArrayBuffer`.
+
+### IsDetached
+
+```cpp
+bool Napi::ArrayBuffer::IsDetached() const;
+```
+
+Returns `true` if this `ArrayBuffer` has been detached.
+
 [`Napi::Object`]: ./object.md

napi-inl.h

@@ -1530,6 +1530,20 @@ inline size_t ArrayBuffer::ByteLength() {
   return length;
 }
 
+#if NAPI_VERSION >= 7
+inline bool ArrayBuffer::IsDetached() const {
+  bool detached;
+  napi_status status = napi_is_detached_arraybuffer(_env, _value, &detached);
+  NAPI_THROW_IF_FAILED(_env, status, false);
+  return detached;
+}
+
+inline void ArrayBuffer::Detach() {
+  napi_status status = napi_detach_arraybuffer(_env, _value);
+  NAPI_THROW_IF_FAILED_VOID(_env, status);
+}
+#endif  // NAPI_VERSION >= 7
+
 ////////////////////////////////////////////////////////////////////////////////
 // DataView class
 ////////////////////////////////////////////////////////////////////////////////

napi.h

@@ -822,6 +822,11 @@ namespace Napi {
 
     void* Data();        ///< Gets a pointer to the data buffer.
     size_t ByteLength(); ///< Gets the length of the array buffer in bytes.
+
+#if NAPI_VERSION >= 7
+    bool IsDetached() const;
+    void Detach();
+#endif  // NAPI_VERSION >= 7
   };
 
   /// A JavaScript typed-array value with unknown array type.

test/arraybuffer.cc

@@ -157,19 +157,43 @@ void CheckDetachUpdatesData(const CallbackInfo& info) {
     return;
   }
 
-  if (!info[1].IsFunction()) {
-    Error::New(info.Env(), "A function was expected.").ThrowAsJavaScriptException();
-    return;
-  }
-
   ArrayBuffer buffer = info[0].As<ArrayBuffer>();
-  Function detach = info[1].As<Function>();
 
   // This potentially causes the buffer to cache its data pointer and length.
   buffer.Data();
   buffer.ByteLength();
 
-  detach.Call({});
+#if NAPI_VERSION >= 7
+  if (buffer.IsDetached()) {
+    Error::New(info.Env(), "Buffer should not be detached.").ThrowAsJavaScriptException();
+    return;
+  }
+#endif
+
+  if (info.Length() == 2) {
+    // Detach externally (in JavaScript).
+    if (!info[1].IsFunction()) {
+      Error::New(info.Env(), "A function was expected.").ThrowAsJavaScriptException();
+      return;
+    }
+
+    Function detach = info[1].As<Function>();
+    detach.Call({});
+  } else {
+#if NAPI_VERSION >= 7
+    // Detach directly.
+    buffer.Detach();
+#else
+    return;
+#endif
+  }
+
+#if NAPI_VERSION >= 7
+  if (!buffer.IsDetached()) {
+    Error::New(info.Env(), "Buffer should be detached.").ThrowAsJavaScriptException();
+    return;
+  }
+#endif
 
   if (buffer.Data() != nullptr) {
     Error::New(info.Env(), "Incorrect data pointer.").ThrowAsJavaScriptException();

test/arraybuffer.js

@@ -58,8 +58,13 @@ function test(binding) {
 
     'ArrayBuffer updates data pointer and length when detached',
     () => {
+      // Detach the ArrayBuffer in JavaScript.
       const mem = new WebAssembly.Memory({ initial: 1 });
       binding.arraybuffer.checkDetachUpdatesData(mem.buffer, () => mem.grow(1));
+
+      // Let C++ detach the ArrayBuffer.
+      const extBuffer = binding.arraybuffer.createExternalBuffer();
+      binding.arraybuffer.checkDetachUpdatesData(extBuffer);
     },
   ]);
 }