1 /* 2 * Copyright (c) 2017, 2024, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #ifndef SHARE_OOPS_OOPHANDLE_HPP 26 #define SHARE_OOPS_OOPHANDLE_HPP 27 28 #include "metaprogramming/primitiveConversions.hpp" 29 #include "oops/oopsHierarchy.hpp" 30 31 #include <type_traits> 32 33 class OopStorage; 34 35 // Simple classes for wrapping oop and atomically accessed oop pointers 36 // stored in OopStorage, or stored in the ClassLoaderData handles area. 37 // These classes help with allocation, release, and NativeAccess loads and 38 // stores with the appropriate barriers. 39 40 class OopHandle { 41 friend class VMStructs; 42 private: 43 oop* _obj; 44 45 public: 46 OopHandle() : _obj(nullptr) {} 47 explicit OopHandle(oop* w) : _obj(w) {} 48 OopHandle(OopStorage* storage, oop obj); 49 50 OopHandle(const OopHandle& copy) : _obj(copy._obj) {} 51 52 OopHandle& operator=(const OopHandle& copy) { 53 // Allow "this" to be junk if copy is empty; needed by initialization of 54 // raw memory in hashtables. 55 assert(is_empty() || copy.is_empty(), "can only copy if empty"); 56 _obj = copy._obj; 57 return *this; 58 } 59 60 void swap(OopHandle& copy) { 61 ::swap(_obj, copy._obj); 62 } 63 64 inline oop resolve() const; 65 inline oop peek() const; 66 67 bool is_empty() const { return _obj == nullptr; } 68 69 inline void release(OopStorage* storage); 70 71 inline void replace(oop obj); 72 73 inline oop xchg(oop new_value); 74 75 oop* ptr_raw() const { return _obj; } 76 }; 77 78 #endif // SHARE_OOPS_OOPHANDLE_HPP