1 files changed, 62 insertions, 0 deletions
diff --git a/xpcom/rust/xpcom/src/promise.rs b/xpcom/rust/xpcom/src/promise.rs
new file mode 100644
index 0000000000..0fdab9b6aa
--- /dev/null
+++ b/xpcom/rust/xpcom/src/promise.rs
@@ -0,0 +1,62 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+use crate::{
+    create_instance,
+    interfaces::{nsIVariant, nsIWritableVariant},
+    RefCounted,
+};
+
+use cstr::*;
+
+mod ffi {
+    use super::*;
+
+    extern "C" {
+        // These are implemented in dom/promise/Promise.cpp
+        pub fn DomPromise_AddRef(promise: *const Promise);
+        pub fn DomPromise_Release(promise: *const Promise);
+        pub fn DomPromise_RejectWithVariant(promise: *const Promise, variant: *const nsIVariant);
+        pub fn DomPromise_ResolveWithVariant(promise: *const Promise, variant: *const nsIVariant);
+    }
+}
+
+#[repr(C)]
+pub struct Promise {
+    private: [u8; 0],
+
+    /// This field is a phantomdata to ensure that the Promise type and any
+    /// struct containing it is not safe to send across threads, as DOM is
+    /// generally not threadsafe.
+    __nosync: ::std::marker::PhantomData<::std::rc::Rc<u8>>,
+}
+
+impl Promise {
+    pub fn reject_with_undefined(&self) {
+        let variant = create_instance::<nsIWritableVariant>(cstr!("@mozilla.org/variant;1"))
+            .expect("Failed to create writable variant");
+        unsafe {
+            variant.SetAsVoid();
+        }
+        self.reject_with_variant(&variant);
+    }
+
+    pub fn reject_with_variant(&self, variant: &nsIVariant) {
+        unsafe { ffi::DomPromise_RejectWithVariant(self, variant) }
+    }
+
+    pub fn resolve_with_variant(&self, variant: &nsIVariant) {
+        unsafe { ffi::DomPromise_ResolveWithVariant(self, variant) }
+    }
+}
+
+unsafe impl RefCounted for Promise {
+    unsafe fn addref(&self) {
+        ffi::DomPromise_AddRef(self)
+    }
+
+    unsafe fn release(&self) {
+        ffi::DomPromise_Release(self)
+    }
+}