Bug 1789902 - Part 1: Support accessing XPCOM static components from Rust, r=xpcom-reviewers,barret (2d734670) · Commits · Dan Ballard / Mullvad Browser

docs/writing-rust-code/basics.md

+4 −3

Original line number	Diff line number	Diff line
		@@ -52,11 +52,12 @@ reflects `nsresult` codes into Rust.
		- [xpcom](https://searchfox.org/mozilla-central/source/xpcom/rust/xpcom/src)
		provides multiple building blocks for a component's implementation.
		- The `RefPtr` type is for managing reference-counted pointers.
		- XPCOM service getters are generated by
		[xpcom/build/Services.py](https://searchfox.org/mozilla-central/source/xpcom/build/Services.py)
		- XPCOM component getters are generated by
		[xpcom/components/gen_static_components.py](https://searchfox.org/mozilla-central/source/xpcom/components/gen_static_components.py),
		and can be called like this:
		```
		let pref_service = xpcom::services::get_PrefService();
		use xpcom::{interfaces::nsIPrefService, RefPtr};
		let pref_service: RefPtr<nsIPrefService> = xpcom::components::Preferences::service()?;
		```
		- There is also a `get_service` function that works like `do_GetService` in
		C++, as an alternative.

xpcom/components/gen_static_components.py

+78 −0

Original line number	Diff line number	Diff line
		@@ -521,6 +521,57 @@ static inline ::mozilla::xpcom::CreateInstanceHelper Create(nsresult* aRv = null

		return res

		# Generates the rust code for the `xpcom::components::<name>` entry
		# corresponding to this component. This may not be called for modules
		# without an explicit `name` (in which cases, `self.anonymous` will be
		# true).
		def lower_getters_rust(self):
		assert not self.anonymous

		substs = {
		"name": self.name,
		"id": "super::ModuleID::%s" % self.name,
		}

		res = (
		"""
		#[allow(non_snake_case)]
		pub mod %(name)s {
		/// Get the singleton service instance for this component.
		pub fn service<T: crate::XpCom>() -> Result<crate::RefPtr<T>, nserror::nsresult> {
		let mut ga = crate::GetterAddrefs::<T>::new();
		let rv = unsafe { super::Gecko_GetServiceByModuleID(%(id)s, &T::IID, ga.void_ptr()) };
		if rv.failed() {
		return Err(rv);
		}
		ga.refptr().ok_or(nserror::NS_ERROR_NO_INTERFACE)
		}
		"""
		% substs
		)

		if not self.singleton:
		res += (
		"""
		/// Create a new instance of this component.
		pub fn create<T: crate::XpCom>() -> Result<crate::RefPtr<T>, nserror::nsresult> {
		let mut ga = crate::GetterAddrefs::<T>::new();
		let rv = unsafe { super::Gecko_CreateInstanceByModuleID(%(id)s, &T::IID, ga.void_ptr()) };
		if rv.failed() {
		return Err(rv);
		}
		ga.refptr().ok_or(nserror::NS_ERROR_NO_INTERFACE)
		}
		"""
		% substs
		)

		res += """\
		}
		"""

		return res


		# Returns a quoted string literal representing the given raw string, with
		# certain special characters replaced so that it can be used in a C++-style
		@@ -678,6 +729,17 @@ def gen_getters(entries):
		return "".join(entry.lower_getters() for entry in entries if not entry.anonymous)


		# Generates the rust getter code for each named component entry in the
		# `xpcom::components::` module.
		def gen_getters_rust(entries):
		entries = list(entries)
		entries.sort(key=lambda e: e.name)

		return "".join(
		entry.lower_getters_rust() for entry in entries if not entry.anonymous
		)


		def gen_includes(substs, all_headers):
		headers = set()
		absolute_headers = set()
		@@ -843,6 +905,8 @@ def gen_substs(manifests):

		substs["component_getters"] = gen_getters(cid_phf.entries)

		substs["component_getters_rust"] = gen_getters_rust(cid_phf.entries)

		substs["module_cid_table"] = cid_phf.cxx_codegen(
		name="ModuleByCID",
		entry_type="StaticModule",
		@@ -964,6 +1028,20 @@ static constexpr size_t kModuleInitCount = %(init_count)d;
		} // namespace mozilla

		#endif
		"""
		% substs
		)

		with open_output("components.rs") as fh:
		fh.write(
		"""\
		/// Unique IDs for each statically-registered module.
		#[repr(u16)]
		pub enum ModuleID {
		%(module_ids)s
		}

		%(component_getters_rust)s
		"""
		% substs
		)

xpcom/components/moz.build

+1 −0

Original line number	Diff line number	Diff line
		@@ -43,6 +43,7 @@ if CONFIG["COMPILE_ENVIRONMENT"]:
		"StaticComponentData.h",
		"StaticComponents.cpp",
		"services.json",
		"components.rs",
		script="gen_static_components.py",
		inputs=["!manifest-lists.json", "StaticComponents.cpp.in"],
		)

xpcom/components/nsComponentManager.cpp

+19 −0

Original line number	Diff line number	Diff line
		@@ -1557,4 +1557,23 @@ const nsIServiceManager* Gecko_GetServiceManager() {
		const nsIComponentRegistrar* Gecko_GetComponentRegistrar() {
		return nsComponentManagerImpl::gComponentManager;
		}

		// FFI-compatible version of `GetServiceHelper::operator()`.
		nsresult Gecko_GetServiceByModuleID(ModuleID aId, const nsIID* aIID,
		void** aResult) {
		return nsComponentManagerImpl::gComponentManager->GetService(aId, *aIID,
		aResult);
		}

		// FFI-compatible version of `CreateInstanceHelper::operator()`.
		nsresult Gecko_CreateInstanceByModuleID(ModuleID aId, const nsIID* aIID,
		void** aResult) {
		const auto& entry = gStaticModules[size_t(aId)];
		if (!entry.Active()) {
		return NS_ERROR_FACTORY_NOT_REGISTERED;
		}

		nsresult rv = entry.CreateInstance(*aIID, aResult);
		return rv;
		}
		}

xpcom/rust/xpcom/src/components.rs

0 → 100644

+23 −0

Original line number	Diff line number	Diff line
		/* 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/. */

		//! This module contains convenient accessors for static XPCOM components.
		//!
		//! The contents of this file are generated from
		//! `xpcom/components/gen_static_components.py`.

		extern "C" {
		fn Gecko_GetServiceByModuleID(
		id: ModuleID,
		iid: &crate::nsIID,
		result: mut mut libc::c_void,
		) -> nserror::nsresult;
		fn Gecko_CreateInstanceByModuleID(
		id: ModuleID,
		iid: &crate::nsIID,
		result: mut mut libc::c_void,
		) -> nserror::nsresult;
		}

		include!(mozbuild::objdir_path!("xpcom/components/components.rs"));