From bcd03dd04d52f8d51199426d61e8512d9e41df3b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tobias=20Nie=C3=9Fen?= <tniessen@tnie.de>
Date: Sun, 26 Jan 2020 00:30:38 -0400
Subject: [PATCH] Add ArrayBuffer::Detach() and ::IsDetached()

Refs: https://github.com/nodejs/node/pull/29768
Refs: https://github.com/nodejs/node/pull/30613
---
 napi-inl.h          | 14 ++++++++++++++
 napi.h              |  5 +++++
 test/arraybuffer.cc | 31 ++++++++++++++++++++++++-------
 test/arraybuffer.js |  5 +++++
 4 files changed, 48 insertions(+), 7 deletions(-)

diff --git a/napi-inl.h b/napi-inl.h
index 2855e80ef..476edf8cc 100644
--- a/napi-inl.h
+++ b/napi-inl.h
@@ -1415,6 +1415,20 @@ inline size_t ArrayBuffer::ByteLength() {
   return length;
 }
 
+#ifdef NAPI_EXPERIMENTAL
+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_EXPERIMENTAL
+
 ////////////////////////////////////////////////////////////////////////////////
 // DataView class
 ////////////////////////////////////////////////////////////////////////////////
diff --git a/napi.h b/napi.h
index 49435d59b..8c5197536 100644
--- a/napi.h
+++ b/napi.h
@@ -813,6 +813,11 @@ namespace Napi {
 
     void* Data();        ///< Gets a pointer to the data buffer.
     size_t ByteLength(); ///< Gets the length of the array buffer in bytes.
+
+#ifdef NAPI_EXPERIMENTAL
+    bool IsDetached() const;
+    void Detach();
+#endif  // NAPI_EXPERIMENTAL
   };
 
   /// A JavaScript typed-array value with unknown array type.
diff --git a/test/arraybuffer.cc b/test/arraybuffer.cc
index cc4f1f51c..142f12c84 100644
--- a/test/arraybuffer.cc
+++ b/test/arraybuffer.cc
@@ -1,3 +1,4 @@
+#define NAPI_EXPERIMENTAL
 #include "napi.h"
 
 using namespace Napi;
@@ -157,19 +158,35 @@ 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 (buffer.IsDetached()) {
+    Error::New(info.Env(), "Buffer should not be detached.").ThrowAsJavaScriptException();
+    return;
+  }
+
+  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 {
+    // Detach directly.
+    buffer.Detach();
+  }
+
+  if (!buffer.IsDetached()) {
+    Error::New(info.Env(), "Buffer should be detached.").ThrowAsJavaScriptException();
+    return;
+  }
 
   if (buffer.Data() != nullptr) {
     Error::New(info.Env(), "Incorrect data pointer.").ThrowAsJavaScriptException();
diff --git a/test/arraybuffer.js b/test/arraybuffer.js
index 30136980b..7f222446c 100644
--- a/test/arraybuffer.js
+++ b/test/arraybuffer.js
@@ -64,8 +64,13 @@ 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);
     },
   ]);
 }