feat: add ArrayBuffer::was_detached() (#1103)

src/array_buffer.rs

@@ -38,6 +38,7 @@ extern "C" {
   fn v8__ArrayBuffer__Detach(this: *const ArrayBuffer);
   fn v8__ArrayBuffer__Data(this: *const ArrayBuffer) -> *mut c_void;
   fn v8__ArrayBuffer__IsDetachable(this: *const ArrayBuffer) -> bool;
+  fn v8__ArrayBuffer__WasDetached(this: *const ArrayBuffer) -> bool;
   fn v8__ArrayBuffer__ByteLength(this: *const ArrayBuffer) -> usize;
   fn v8__ArrayBuffer__GetBackingStore(
     this: *const ArrayBuffer,
@@ -389,6 +390,15 @@ impl ArrayBuffer {
     unsafe { v8__ArrayBuffer__IsDetachable(self) }
   }
 
+  /// Returns true if this ArrayBuffer was detached.
+  #[inline(always)]
+  pub fn was_detached(&self) -> bool {
+    if self.byte_length() != 0 {
+      return false;
+    }
+    unsafe { v8__ArrayBuffer__WasDetached(self) }
+  }
+
   /// Detaches this ArrayBuffer and all its views (typed arrays).
   /// Detaching sets the byte length of the buffer and all typed arrays to zero,
   /// preventing JavaScript from ever accessing underlying backing store.

src/binding.cc

@@ -828,6 +828,10 @@ bool v8__ArrayBuffer__IsDetachable(const v8::ArrayBuffer& self) {
   return ptr_to_local(&self)->IsDetachable();
 }
 
+bool v8__ArrayBuffer__WasDetached(const v8::ArrayBuffer& self) {
+  return v8::Utils::OpenHandle(&self)->was_detached();
+}
+
 void* v8__BackingStore__Data(const v8::BackingStore& self) {
   return self.Data();
 }

tests/test_api.rs

@@ -573,12 +573,20 @@ fn array_buffer() {
 
     let ab = v8::ArrayBuffer::new(scope, 42);
     assert_eq!(42, ab.byte_length());
-
+    assert!(!ab.was_detached());
     assert!(ab.is_detachable());
+
     ab.detach();
     assert_eq!(0, ab.byte_length());
+    assert!(ab.was_detached());
     ab.detach(); // Calling it twice should be a no-op.
 
+    // detecting if it was detached on a zero-length ArrayBuffer should work
+    let empty_ab = v8::ArrayBuffer::new(scope, 0);
+    assert!(!empty_ab.was_detached());
+    empty_ab.detach();
+    assert!(empty_ab.was_detached());
+
     let bs = v8::ArrayBuffer::new_backing_store(scope, 84);
     assert_eq!(84, bs.byte_length());
     assert!(!bs.is_shared());