RootedOwningNonNull.h (2066B)
1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ 2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */ 3 /* This Source Code Form is subject to the terms of the Mozilla Public 4 * License, v. 2.0. If a copy of the MPL was not distributed with this file, 5 * You can obtain one at http://mozilla.org/MPL/2.0/. */ 6 7 /** 8 * An implementation of Rooted for OwningNonNull<T>. This works by assuming 9 * that T has a Trace() method defined on it which will trace whatever things 10 * inside the T instance need tracing. 11 * 12 * This implementation has one serious drawback: operator= doesn't work right 13 * because it's declared on Rooted directly and expects the type Rooted is 14 * templated over. 15 */ 16 17 #ifndef mozilla_RootedOwningNonNull_h__ 18 #define mozilla_RootedOwningNonNull_h__ 19 20 #include "js/GCPolicyAPI.h" 21 #include "js/TypeDecls.h" 22 #include "mozilla/OwningNonNull.h" 23 24 namespace JS { 25 template <typename T> 26 struct GCPolicy<mozilla::OwningNonNull<T>> { 27 typedef mozilla::OwningNonNull<T> SmartPtrType; 28 29 static SmartPtrType initial() { return SmartPtrType(); } 30 31 static void trace(JSTracer* trc, SmartPtrType* tp, const char* name) { 32 // We have to be very careful here. Normally, OwningNonNull can't be null. 33 // But binding code can end up in a situation where it sets up a 34 // Rooted<OwningNonNull> and then before it gets a chance to assign to it 35 // (e.g. from the constructor of the thing being assigned) a GC happens. So 36 // we can land here when *tp stores a null pointer because it's not 37 // initialized. 38 // 39 // So we need to check for that before jumping. 40 if ((*tp).isInitialized()) { 41 (*tp)->Trace(trc); 42 } 43 } 44 45 static bool isValid(const SmartPtrType& v) { 46 return !v.isInitialized() || GCPolicy<T>::isValid(v); 47 } 48 }; 49 } // namespace JS 50 51 namespace js { 52 template <typename T, typename Wrapper> 53 struct WrappedPtrOperations<mozilla::OwningNonNull<T>, Wrapper> { 54 operator T&() const { return static_cast<const Wrapper*>(this)->get(); } 55 }; 56 } // namespace js 57 58 #endif /* mozilla_RootedOwningNonNull_h__ */