/*
 * Copyright (c) 2017, Google and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 *
 */

#ifndef SHARE_VM_PRIMS_JVMTIHEAPSAMPLING_HPP
#define SHARE_VM_PRIMS_JVMTIHEAPSAMPLING_HPP

// A RAII class that handles transitions from the agent into the VM.
class HeapThreadTransition : StackObj {
 private:
  JavaThreadState _saved_state;
  JavaThread *_jthread;

 public:
  // Transitions this thread from the agent (thread_in_native) to the VM.
  HeapThreadTransition(Thread *thread) {
    if (thread->is_Java_thread()) {
      _jthread = static_cast<JavaThread *>(thread);
      _saved_state = _jthread->thread_state();
      if (_saved_state == _thread_in_native) {
        ThreadStateTransition::transition_from_native(_jthread, _thread_in_vm);
      } else {
        ThreadStateTransition::transition(_jthread,
                                          _saved_state,
                                          _thread_in_vm);
      }
    } else {
      _jthread = NULL;
      _saved_state = _thread_new;
    }
  }

  // Transitions this thread back to the agent from the VM.
  ~HeapThreadTransition() {
    if (_jthread != NULL) {
      ThreadStateTransition::transition(_jthread, _thread_in_vm, _saved_state);
    }
  }
};

#endif // SHARE_VM_PRIMS_JVMTIHEAPSAMPLING_HPP