feat(isolate): expose get/set_data (#911)

Co-authored-by: Bartek Iwańczuk <biwanczuk@gmail.com>

src/isolate.rs

@@ -451,22 +451,25 @@ impl Isolate {
 
   /// Associate embedder-specific data with the isolate. `slot` has to be
   /// between 0 and `Isolate::get_number_of_data_slots()`.
+  ///
+  /// 0-indexed slot is used internally by rusty_v8, so users have 3 slots
+  /// left to use.
   #[inline(always)]
-  unsafe fn set_data(&mut self, slot: u32, ptr: *mut c_void) {
+  pub unsafe fn set_data(&mut self, slot: u32, ptr: *mut c_void) {
+    assert!(slot < 4);
     v8__Isolate__SetData(self, slot + Self::INTERNAL_SLOT_COUNT, ptr)
   }
 
   /// Retrieve embedder-specific data from the isolate.
   /// Returns NULL if SetData has never been called for the given `slot`.
-  #[allow(dead_code)]
+  pub fn get_data(&self, slot: u32) -> *mut c_void {
-  fn get_data(&self, slot: u32) -> *mut c_void {
+    assert!(slot < 4);
     unsafe { v8__Isolate__GetData(self, slot + Self::INTERNAL_SLOT_COUNT) }
   }
 
   /// Returns the maximum number of available embedder data slots. Valid slots
   /// are in the range of 0 - `Isolate::get_number_of_data_slots() - 1`.
-  #[allow(dead_code)]
+  pub fn get_number_of_data_slots(&self) -> u32 {
-  fn get_number_of_data_slots(&self) -> u32 {
     unsafe {
       v8__Isolate__GetNumberOfDataSlots(self) - Self::INTERNAL_SLOT_COUNT
     }

tests/test_api.rs

@@ -7487,6 +7487,60 @@ fn finalizer_on_kept_global() {
   drop(global);
 }
 
+#[test]
+fn isolate_data_fields() {
+  let _setup_guard = setup();
+
+  let mut isolate = v8::Isolate::new(Default::default());
+
+  struct SomeData {
+    foo: &'static str,
+    bar: &'static str,
+    fizz: &'static str,
+  }
+
+  let some_data1 = Box::new(SomeData {
+    foo: "foo",
+    bar: "",
+    fizz: "",
+  });
+  let some_data2 = Box::new(SomeData {
+    foo: "",
+    bar: "bar",
+    fizz: "",
+  });
+  let some_data3 = Box::new(SomeData {
+    foo: "",
+    bar: "",
+    fizz: "fizz",
+  });
+  unsafe {
+    isolate.set_data(1, Box::into_raw(some_data1) as *mut _ as *mut c_void);
+    isolate.set_data(2, Box::into_raw(some_data2) as *mut _ as *mut c_void);
+    isolate.set_data(3, Box::into_raw(some_data3) as *mut _ as *mut c_void);
+  }
+
+  {
+    let data_some_data1 = isolate.get_data(1) as *mut SomeData;
+    let data_some_data1 = unsafe { &mut *data_some_data1 };
+    assert_eq!(data_some_data1.foo, "foo");
+    assert_eq!(data_some_data1.bar, "");
+    assert_eq!(data_some_data1.fizz, "");
+
+    let data_some_data2 = isolate.get_data(2) as *mut SomeData;
+    let data_some_data2 = unsafe { &mut *data_some_data2 };
+    assert_eq!(data_some_data2.foo, "");
+    assert_eq!(data_some_data2.bar, "bar");
+    assert_eq!(data_some_data2.fizz, "");
+
+    let data_some_data3 = isolate.get_data(3) as *mut SomeData;
+    let data_some_data3 = unsafe { &mut *data_some_data3 };
+    assert_eq!(data_some_data3.foo, "");
+    assert_eq!(data_some_data3.bar, "");
+    assert_eq!(data_some_data3.fizz, "fizz");
+  }
+}
+
 #[test]
 fn host_create_shadow_realm_context_callback() {
   let _setup_guard = setup();