1 files changed, 93 insertions, 0 deletions
diff --git a/xpcom/base/nsQueryObject.h b/xpcom/base/nsQueryObject.h
new file mode 100644
index 0000000000..7cfbe954ce
--- /dev/null
+++ b/xpcom/base/nsQueryObject.h
@@ -0,0 +1,93 @@
+/* -*- 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 nsQueryObject_h
+#define nsQueryObject_h
+
+#include "mozilla/Attributes.h"
+
+#include "nsCOMPtr.h"
+#include "mozilla/RefPtr.h"
+
+/*****************************************************************************/
+
+template <class T>
+class MOZ_STACK_CLASS nsQueryObject final : public nsCOMPtr_helper {
+ public:
+  explicit nsQueryObject(T* aRawPtr) : mRawPtr(aRawPtr) {}
+
+  virtual nsresult NS_FASTCALL operator()(const nsIID& aIID,
+                                          void** aResult) const override {
+    nsresult status = mRawPtr ? mRawPtr->QueryInterface(aIID, aResult)
+                              : NS_ERROR_NULL_POINTER;
+    return status;
+  }
+
+ private:
+  T* MOZ_NON_OWNING_REF mRawPtr;
+};
+
+template <class T>
+class MOZ_STACK_CLASS nsQueryObjectWithError final : public nsCOMPtr_helper {
+ public:
+  nsQueryObjectWithError(T* aRawPtr, nsresult* aErrorPtr)
+      : mRawPtr(aRawPtr), mErrorPtr(aErrorPtr) {}
+
+  virtual nsresult NS_FASTCALL operator()(const nsIID& aIID,
+                                          void** aResult) const override {
+    nsresult status = mRawPtr ? mRawPtr->QueryInterface(aIID, aResult)
+                              : NS_ERROR_NULL_POINTER;
+    if (mErrorPtr) {
+      *mErrorPtr = status;
+    }
+    return status;
+  }
+
+ private:
+  T* MOZ_NON_OWNING_REF mRawPtr;
+  nsresult* mErrorPtr;
+};
+
+/*****************************************************************************/
+
+/*****************************************************************************/
+
+template <class T>
+inline nsQueryObject<T> do_QueryObject(T* aRawPtr) {
+  return nsQueryObject<T>(aRawPtr);
+}
+
+template <class T>
+inline nsQueryObject<T> do_QueryObject(const nsCOMPtr<T>& aRawPtr) {
+  return nsQueryObject<T>(aRawPtr);
+}
+
+template <class T>
+inline nsQueryObject<T> do_QueryObject(const RefPtr<T>& aRawPtr) {
+  return nsQueryObject<T>(aRawPtr);
+}
+
+template <class T>
+inline nsQueryObjectWithError<T> do_QueryObject(T* aRawPtr,
+                                                nsresult* aErrorPtr) {
+  return nsQueryObjectWithError<T>(aRawPtr, aErrorPtr);
+}
+
+template <class T>
+inline nsQueryObjectWithError<T> do_QueryObject(const nsCOMPtr<T>& aRawPtr,
+                                                nsresult* aErrorPtr) {
+  return nsQueryObjectWithError<T>(aRawPtr, aErrorPtr);
+}
+
+template <class T>
+inline nsQueryObjectWithError<T> do_QueryObject(const RefPtr<T>& aRawPtr,
+                                                nsresult* aErrorPtr) {
+  return nsQueryObjectWithError<T>(aRawPtr, aErrorPtr);
+}
+
+/*****************************************************************************/
+
+#endif  // !defined(nsQueryObject_h)