1 files changed, 113 insertions, 0 deletions
diff --git a/js/xpconnect/loader/nsImportModule.h b/js/xpconnect/loader/nsImportModule.h
new file mode 100644
index 0000000000..b1105278d3
--- /dev/null
+++ b/js/xpconnect/loader/nsImportModule.h
@@ -0,0 +1,113 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* 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/. */
+
+#ifndef nsImportModule_h
+#define nsImportModule_h
+
+#include "mozilla/Attributes.h"
+
+#include "nsCOMPtr.h"
+#include "mozilla/RefPtr.h"
+
+namespace mozilla {
+namespace loader {
+
+nsresult ImportModule(const char* aURI, const char* aExportName,
+                      const nsIID& aIID, void** aResult);
+
+}  // namespace loader
+}  // namespace mozilla
+
+class MOZ_STACK_CLASS nsImportModule final : public nsCOMPtr_helper {
+ public:
+  nsImportModule(const char* aURI, const char* aExportName, nsresult* aErrorPtr)
+      : mURI(aURI), mExportName(aExportName), mErrorPtr(aErrorPtr) {}
+
+  virtual nsresult NS_FASTCALL operator()(const nsIID& aIID,
+                                          void** aResult) const override {
+    nsresult rv =
+        ::mozilla::loader::ImportModule(mURI, mExportName, aIID, aResult);
+    if (mErrorPtr) {
+      *mErrorPtr = rv;
+    }
+    return rv;
+  }
+
+ private:
+  const char* mURI;
+  const char* mExportName;
+  nsresult* mErrorPtr;
+};
+
+/**
+ * These helpers make it considerably easier for C++ code to import a JS module
+ * and wrap it in an appropriately-defined XPIDL interface for its exports.
+ * Typical usage is something like:
+ *
+ * Foo.jsm:
+ *
+ *   var EXPORTED_SYMBOLS = ["foo"];
+ *
+ *   function foo(bar) {
+ *     return bar.toString();
+ *   }
+ *
+ * mozIFoo.idl:
+ *
+ *   interface mozIFoo : nsISupports {
+ *     AString foo(double meh);
+ *   }
+ *
+ * Thing.cpp:
+ *
+ *   nsCOMPtr<mozIFoo> foo = do_ImportModule(
+ *     "resource://meh/Foo.jsm");
+ *
+ *   MOZ_TRY(foo->Foo(42));
+ *
+ * For JS modules which export all fields within a single named object, a second
+ * argument can be passed naming that object.
+ *
+ * Foo.jsm:
+ *
+ *   var EXPORTED_SYMBOLS = ["Foo"];
+ *
+ *   var Foo = {
+ *     function foo(bar) {
+ *       return bar.toString();
+ *     }
+ *   };
+ *
+ * Thing.cpp:
+ *
+ *   nsCOMPtr<mozIFoo> foo = do_ImportModule(
+ *       "resource:://meh/Foo.jsm", "Foo");
+ */
+
+template <size_t N>
+inline nsImportModule do_ImportModule(const char (&aURI)[N]) {
+  return {aURI, nullptr, nullptr};
+}
+
+template <size_t N>
+inline nsImportModule do_ImportModule(const char (&aURI)[N], nsresult* aRv) {
+  return {aURI, nullptr, aRv};
+}
+
+template <size_t N, size_t N2>
+inline nsImportModule do_ImportModule(const char (&aURI)[N],
+                                      const char (&aExportName)[N2]) {
+  return {aURI, aExportName, nullptr};
+}
+
+template <size_t N, size_t N2>
+inline nsImportModule do_ImportModule(const char (&aURI)[N],
+                                      const char (&aExportName)[N2],
+                                      nsresult* aRv) {
+  return {aURI, aExportName, aRv};
+}
+
+#endif  // defined nsImportModule_h