1 files changed, 107 insertions, 0 deletions
diff --git a/dom/chrome-webidl/UniFFI.webidl b/dom/chrome-webidl/UniFFI.webidl
new file mode 100644
index 0000000000..7a3f68fbbd
--- /dev/null
+++ b/dom/chrome-webidl/UniFFI.webidl
@@ -0,0 +1,107 @@
+/* -*- Mode: IDL; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* 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 http://mozilla.org/MPL/2.0/. */
+
+// Interface for making UniFFI scaffolding calls
+//
+// Gecko uses UniFFI to generate privileged JS bindings for Rust components.
+// UniFFI defines a C-ABI FFI layer for calling into Rust, called the
+// scaffolding. This interface is a bridge that allows the JS code to make
+// scaffolding calls
+//
+// See https://mozilla.github.io/uniffi-rs/ for details.
+
+// Define some ID types to identify various parts of the UDL interfaces.  Using
+// these IDs, allow this .webidl file to remain static, but support new
+// interfaces.  Using IDs is that the C++ and JS code need to agree on their
+// meaning, which is handled by
+// toolkit/components/uniffi-bindgen-gecko-js/src/ci_list.rs.
+
+// Identifies a scaffolding function.
+typedef unsigned long long UniFFIFunctionId;
+
+// Identifies a pointer type
+typedef unsigned long long UniFFIPointerId;
+
+// Identifies a callback interface
+typedef unsigned long UniFFICallbackInterfaceId;
+
+// Identifies a method of a callback interface
+typedef unsigned long UniFFICallbackMethodId;
+
+// Handle for a callback interface instance
+typedef unsigned long long UniFFICallbackObjectHandle;
+
+// Opaque type used to represent a pointer from Rust
+[ChromeOnly, Exposed=Window]
+interface UniFFIPointer {};
+
+// Types that can be passed or returned from scaffolding functions
+//
+// - double is used for all numeric types and types which the JS code coerces
+//   to an int including Boolean and CallbackInterface.
+// - ArrayBuffer is used for RustBuffer
+// - UniFFIPointer is used for Arc pointers
+typedef (double or ArrayBuffer or UniFFIPointer) UniFFIScaffoldingType;
+
+// The result of a call into UniFFI scaffolding call
+enum UniFFIScaffoldingCallCode {
+   "success",         // Successful return
+   "error",           // Rust Err return
+   "internal-error",  // Internal/unexpected error
+};
+
+dictionary UniFFIScaffoldingCallResult {
+    required UniFFIScaffoldingCallCode code;
+    // For success, this will be the return value for non-void returns
+    // For error, this will be an ArrayBuffer storing the serialized error value
+    UniFFIScaffoldingType data;
+    // For internal-error, this will be a utf-8 string describing the error
+    ByteString internalErrorMessage;
+};
+
+// JS handler for calling a CallbackInterface method.
+// The arguments and return value are always packed into an ArrayBuffer
+callback UniFFICallbackHandler = undefined (UniFFICallbackObjectHandle objectId, UniFFICallbackMethodId methodId, ArrayBuffer aArgs);
+
+// Functions to facilitate UniFFI scaffolding calls
+[ChromeOnly, Exposed=Window]
+namespace UniFFIScaffolding {
+  // Call a scaffolding function on the worker thread.
+  //
+  // id is a unique identifier for the function, known to both the C++ and JS code
+  [Throws]
+  Promise<UniFFIScaffoldingCallResult> callAsync(UniFFIFunctionId id, UniFFIScaffoldingType... args);
+
+  // Call a scaffolding function on the main thread
+  //
+  // id is a unique identifier for the function, known to both the C++ and JS code
+  [Throws]
+  UniFFIScaffoldingCallResult callSync(UniFFIFunctionId id, UniFFIScaffoldingType... args);
+
+  // Read a UniFFIPointer from an ArrayBuffer
+  //
+  // id is a unique identifier for the pointer type, known to both the C++ and JS code
+  [Throws]
+  UniFFIPointer readPointer(UniFFIPointerId id, ArrayBuffer buff, long position);
+
+  // Write a UniFFIPointer to an ArrayBuffer
+  //
+  // id is a unique identifier for the pointer type, known to both the C++ and JS code
+  [Throws]
+  undefined writePointer(UniFFIPointerId id, UniFFIPointer ptr, ArrayBuffer buff, long position);
+
+  // Register the global calblack handler
+  //
+  // This will be used to invoke all calls for a CallbackInterface.
+  // interfaceId is a unique identifier for the callback interface, known to both the C++ and JS code
+  [Throws]
+  undefined registerCallbackHandler(UniFFICallbackInterfaceId interfaceId, UniFFICallbackHandler handler);
+
+  // Deregister the global calblack handler
+  //
+  // This is called at shutdown to clear out the reference to the JS function.
+  [Throws]
+  undefined deregisterCallbackHandler(UniFFICallbackInterfaceId interfaceId);
+};