1 /* 2 * Copyright (c) 2017, 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_VM_OOPS_OOPHANDLE_HPP 26 #define SHARE_VM_OOPS_OOPHANDLE_HPP 27 28 #include "oops/oop.hpp" 29 #include "runtime/atomic.hpp" 30 #include "runtime/orderAccess.hpp" 31 32 class outputStream; 33 34 // Simple class for encapsulating oop pointers stored in metadata. 35 // These are different from Handle. The Handle class stores pointers 36 // to oops on the stack, and manages the allocation from a thread local 37 // area in the constructor. 38 // This assumes that the caller will allocate the handle in the appropriate 39 // area. The reason for the encapsulation is to help with naming and to allow 40 // future uses for read barriers. 41 42 class OopHandle { 43 private: 44 oop* _obj; 45 46 public: 47 OopHandle() : _obj(NULL) {} 48 OopHandle(oop* w) : _obj(w) {} 49 50 oop resolve() const { return (_obj == NULL) ? (oop)NULL : *_obj; } 51 oop* ptr() const { return _obj; } 52 53 // For ModuleEntry the protection_domain field requires memory ordering logic. 54 oop resolve_acquire() const { 55 oop* obj = (oop*)OrderAccess::load_ptr_acquire(&_obj); 56 return (obj == NULL) ? (oop)NULL : *obj; 57 } 58 bool set_atomic(OopHandle value) { 59 return (Atomic::cmpxchg_ptr(value._obj, &_obj, NULL) == NULL); 60 } 61 }; 62 63 #endif // SHARE_VM_OOPS_OOPHANDLE_HPP