ArrayBuffer: add binding for IsResizableByUserJavaScript (#1205)

src/array_buffer.rs

@@ -64,6 +64,9 @@ extern "C" {
   fn v8__BackingStore__Data(this: *const BackingStore) -> *mut c_void;
   fn v8__BackingStore__ByteLength(this: *const BackingStore) -> usize;
   fn v8__BackingStore__IsShared(this: *const BackingStore) -> bool;
+  fn v8__BackingStore__IsResizableByUserJavaScript(
+    this: *const BackingStore,
+  ) -> bool;
   fn v8__BackingStore__DELETE(this: *mut BackingStore);
 
   fn std__shared_ptr__v8__BackingStore__COPY(
@@ -304,6 +307,14 @@ impl BackingStore {
   pub fn is_shared(&self) -> bool {
     unsafe { v8__BackingStore__IsShared(self) }
   }
+
+  /// Indicates whether the backing store was created for a resizable ArrayBuffer
+  /// or a growable SharedArrayBuffer, and thus may be resized by user
+  /// JavaScript code.
+  #[inline(always)]
+  pub fn is_resizable_by_user_javascript(&self) -> bool {
+    unsafe { v8__BackingStore__IsResizableByUserJavaScript(self) }
+  }
 }
 
 impl Deref for BackingStore {

src/binding.cc

@@ -846,6 +846,10 @@ two_pointers_t v8__ArrayBuffer__GetBackingStore(const v8::ArrayBuffer& self) {
   return make_pod<two_pointers_t>(ptr_to_local(&self)->GetBackingStore());
 }
 
+bool v8__BackingStore__IsResizableByUserJavaScript(const v8::BackingStore& self) {
+  return ptr_to_local(&self)->IsResizableByUserJavaScript();
+}
+
 void* v8__ArrayBuffer__Data(const v8::ArrayBuffer& self) {
   return ptr_to_local(&self)->Data();
 }

tests/test_api.rs

@@ -7701,6 +7701,28 @@ fn backing_store_data() {
   );
 }
 
+#[test]
+fn backing_store_resizable() {
+  let _setup_guard = setup::parallel_test();
+
+  let v = vec![1, 2, 3, 4, 5];
+  let store_fixed =
+    v8::ArrayBuffer::new_backing_store_from_vec(v).make_shared();
+  assert!(!store_fixed.is_resizable_by_user_javascript());
+
+  let mut isolate = v8::Isolate::new(Default::default());
+  let mut scope = v8::HandleScope::new(&mut isolate);
+  let context = v8::Context::new(&mut scope);
+  let mut scope = v8::ContextScope::new(&mut scope, context);
+
+  let ab_val =
+    eval(&mut scope, "new ArrayBuffer(100, {maxByteLength: 200})").unwrap();
+  assert!(ab_val.is_array_buffer());
+  let ab = v8::Local::<v8::ArrayBuffer>::try_from(ab_val).unwrap();
+  let store_resizable = ab.get_backing_store();
+  assert!(store_resizable.is_resizable_by_user_javascript());
+}
+
 #[test]
 fn current_stack_trace() {
   // Setup isolate