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/* -*- 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;
// 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) UniFFIScaffoldingValue;
// 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
UniFFIScaffoldingValue data;
};
// JS handler for a callback interface
//
// These are responsible for invoking callback interface calls. Internally, these map handles to
// objects that implement the callback interface.
//
// Before the JS code returns a callback-interface-implementing object Rust, it first sends the
// object to a UniFFICallbackHandler, which adds an entry in the map. The handle is then what's
// sent to Rust.
//
// When the Rust code wants to invoke a method, it calls into the C++ layer and passes the handle
// along with all arguments. The C++ layer then calls `UniFFICallbackHandler.call()` which then
// looks up the object in the map and invokes the actual method.
//
// Finally, when the Rust code frees the object, it calls into the C++ layer, which then calls
// `UniFFICallbackHandler.release()` to remove the entry in the map.
[Exposed=Window]
callback interface UniFFICallbackHandler {
Promise<UniFFIScaffoldingCallResult> callAsync(UniFFICallbackObjectHandle objectHandle, unsigned long methodIndex, UniFFIScaffoldingValue... args);
UniFFIScaffoldingCallResult callSync(UniFFICallbackObjectHandle objectHandle, unsigned long methodIndex, UniFFIScaffoldingValue... args);
undefined destroy(UniFFICallbackObjectHandle objectHandle);
};
// Functions to facilitate UniFFI scaffolding calls
[ChromeOnly, Exposed=Window]
namespace UniFFIScaffolding {
// Call a sync Rust function
//
// id is a unique identifier for the function, known to both the C++ and JS code
[Throws]
UniFFIScaffoldingCallResult callSync(UniFFIFunctionId id, UniFFIScaffoldingValue... args);
// Call an async Rust function
//
// id is a unique identifier for the function, known to both the C++ and JS code
[Throws]
Promise<UniFFIScaffoldingCallResult> callAsync(UniFFIFunctionId id, UniFFIScaffoldingValue... args);
// Call a sync Rust function, but wrap it to so that it behaves in JS as an async function
//
// id is a unique identifier for the function, known to both the C++ and JS code
[Throws]
Promise<UniFFIScaffoldingCallResult> callAsyncWrapper(UniFFIFunctionId id, UniFFIScaffoldingValue... 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);
};
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