Bug 1293362 - Part 7: Expose the nsComponentManager static interfaces to rust code, r=froydnj

MozReview-Commit-ID: D4kvNFgmIpH

xpcom/components/nsComponentManager.cpp

@@ -2001,3 +2001,27 @@ XRE_AddJarManifestLocation(NSLocationType aType, nsIFile* aLocation)
   return NS_OK;
 }
 
+// Expose some important global interfaces to rust for the rust xpcom API. These
+// methods return a non-owning reference to the component manager, which should
+// live for the lifetime of XPCOM.
+extern "C" {
+
+const nsIComponentManager*
+Gecko_GetComponentManager()
+{
+  return nsComponentManagerImpl::gComponentManager;
+}
+
+const nsIServiceManager*
+Gecko_GetServiceManager()
+{
+  return nsComponentManagerImpl::gComponentManager;
+}
+
+const nsIComponentRegistrar*
+Gecko_GetComponentRegistrar()
+{
+  return nsComponentManagerImpl::gComponentManager;
+}
+
+}

xpcom/rust/xpcom/src/lib.rs

@@ -29,6 +29,9 @@ pub use base::*;
 mod refptr;
 pub use refptr::*;
 
+mod statics;
+pub use statics::*;
+
 // XPCOM interface definitions.
 pub mod interfaces;
 

xpcom/rust/xpcom/src/statics.rs

@@ -0,0 +1,104 @@
+/* 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/. */
+
+use std::ffi::CStr;
+use std::ptr;
+use nserror::NsresultExt;
+use {
+    RefPtr,
+    GetterAddrefs,
+    XpCom,
+};
+
+use interfaces::{
+    nsIComponentManager,
+    nsIServiceManager,
+    nsIComponentRegistrar,
+};
+
+macro_rules! try_opt {
+    ($e: expr) => {
+        match $e {
+            Some(x) => x,
+            None => return None,
+        }
+    }
+}
+
+/// Get a reference to the global `nsIComponentManager`.
+///
+/// Can return `None` during shutdown.
+#[inline]
+pub fn component_manager() -> Option<RefPtr<nsIComponentManager>> {
+    unsafe {
+        RefPtr::from_raw(Gecko_GetComponentManager())
+    }
+}
+
+/// Get a reference to the global `nsIServiceManager`.
+///
+/// Can return `None` during shutdown.
+#[inline]
+pub fn service_manager() -> Option<RefPtr<nsIServiceManager>> {
+    unsafe {
+        RefPtr::from_raw(Gecko_GetServiceManager())
+    }
+}
+
+/// Get a reference to the global `nsIComponentRegistrar`
+///
+/// Can return `None` during shutdown.
+#[inline]
+pub fn component_registrar() -> Option<RefPtr<nsIComponentRegistrar>> {
+    unsafe {
+        RefPtr::from_raw(Gecko_GetComponentRegistrar())
+    }
+}
+
+/// Helper for calling `nsIComponentManager::CreateInstanceByContractID` on the
+/// global `nsIComponentRegistrar`.
+///
+/// This method is similar to `do_CreateInstance` in C++.
+#[inline]
+pub fn create_instance<T: XpCom>(id: &CStr) -> Option<RefPtr<T>> {
+    unsafe {
+        let mut ga = GetterAddrefs::<T>::new();
+        if try_opt!(component_manager()).CreateInstanceByContractID(
+            id.as_ptr(),
+            ptr::null(),
+            &T::IID,
+            ga.void_ptr(),
+        ).succeeded() {
+            ga.refptr()
+        } else {
+            None
+        }
+    }
+}
+
+/// Helper for calling `nsIServiceManager::GetServiceByContractID` on the global
+/// `nsIServiceManager`.
+///
+/// This method is similar to `do_GetService` in C++.
+#[inline]
+pub fn get_service<T: XpCom>(id: &CStr) -> Option<RefPtr<T>> {
+    unsafe {
+        let mut ga = GetterAddrefs::<T>::new();
+        if try_opt!(service_manager()).GetServiceByContractID(
+            id.as_ptr(),
+            &T::IID,
+            ga.void_ptr()
+        ).succeeded() {
+            ga.refptr()
+        } else {
+            None
+        }
+    }
+}
+
+extern "C" {
+    fn Gecko_GetComponentManager() -> *const nsIComponentManager;
+    fn Gecko_GetServiceManager() -> *const nsIServiceManager;
+    fn Gecko_GetComponentRegistrar() -> *const nsIComponentRegistrar;
+}