Access to raw v8::Context slots (#1092)

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

src/context.rs

@@ -52,6 +52,7 @@ extern "C" {
 
 impl Context {
   const ANNEX_SLOT: c_int = 1;
+  const INTERNAL_SLOT_COUNT: c_int = 1;
 
   /// Creates a new context.
   #[inline(always)]
@@ -307,6 +308,32 @@ impl Context {
     }
   }
 
+  #[inline(always)]
+  pub unsafe fn set_aligned_pointer_in_embedder_data(
+    &self,
+    slot: i32,
+    data: *mut c_void,
+  ) {
+    v8__Context__SetAlignedPointerInEmbedderData(
+      self,
+      slot + Self::INTERNAL_SLOT_COUNT,
+      data,
+    )
+  }
+
+  #[inline(always)]
+  pub fn get_aligned_pointer_from_embedder_data(
+    &self,
+    slot: i32,
+  ) -> *mut c_void {
+    unsafe {
+      v8__Context__GetAlignedPointerFromEmbedderData(
+        self,
+        slot + Self::INTERNAL_SLOT_COUNT,
+      )
+    }
+  }
+
   /// Create a new context from a (non-default) context snapshot. There
   /// is no way to provide a global object template since we do not create
   /// a new global object from template, but we can reuse a global object.

tests/test_api.rs

@@ -7674,6 +7674,46 @@ fn isolate_data_slots() {
   assert_eq!(actual1, expected1);
 }
 
+#[test]
+fn context_embedder_data() {
+  let _setup_guard = setup();
+  let isolate = &mut v8::Isolate::new(Default::default());
+  let global_context;
+
+  let expected0 = "Bla";
+  let expected1 = 123.456f64;
+  {
+    let scope = &mut v8::HandleScope::new(isolate);
+    let context = v8::Context::new(scope);
+
+    unsafe {
+      context.set_aligned_pointer_in_embedder_data(
+        0,
+        &expected0 as *const _ as *mut &str as *mut c_void,
+      );
+      context.set_aligned_pointer_in_embedder_data(
+        1,
+        &expected1 as *const _ as *mut f64 as *mut c_void,
+      );
+    }
+
+    global_context = v8::Global::new(scope, context);
+  }
+
+  {
+    let scope = &mut v8::HandleScope::new(isolate);
+    let context = global_context.open(scope);
+    let actual0 =
+      context.get_aligned_pointer_from_embedder_data(0) as *mut &str;
+    let actual0 = unsafe { *actual0 };
+    assert_eq!(actual0, expected0);
+
+    let actual1 = context.get_aligned_pointer_from_embedder_data(1) as *mut f64;
+    let actual1 = unsafe { *actual1 };
+    assert_eq!(actual1, expected1);
+  }
+}
+
 #[test]
 fn host_create_shadow_realm_context_callback() {
   let _setup_guard = setup();