/*

 * Copyright (c) 2015, 2018, Oracle 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_LOGGING_LOGOUTPUTLIST_HPP

#define SHARE_VM_LOGGING_LOGOUTPUTLIST_HPP

#include "logging/logLevel.hpp"

#include "memory/allocation.hpp"

#include "utilities/globalDefinitions.hpp"

class LogOutput;

// Data structure to keep track of log outputs for a given tagset.

// Essentially a sorted linked list going from error level outputs

// to outputs of finer levels. Keeps an index from each level to

// the first node in the list for the corresponding level.

// This allows a log message on, for example, info level to jump

// straight into the list where the first info level output can

// be found. The log message will then be printed on that output,

// as well as all outputs in nodes that follow in the list (which

// can be additional info level outputs and/or debug and trace outputs).

//

// Each instance keeps track of the number of current readers of the list.

// To remove a node from the list the node must first be unlinked,

// and the memory for that node can be freed whenever the removing

// thread observes an active reader count of 0 (after unlinking it).

class LogOutputList {

 private:

  struct LogOutputNode : public CHeapObj<mtLogging> {

    LogOutput*      _value;

    LogOutputNode*  _next;

    LogLevelType    _level;

  };

  LogOutputNode*  _level_start[LogLevel::Count];

  volatile jint   _active_readers;

  LogOutputNode* find(const LogOutput* output) const;

  void remove_output(LogOutputNode* node);

  void add_output(LogOutput* output, LogLevelType level);

  void update_output_level(LogOutputNode* node, LogLevelType level);

  // Bookkeeping functions to keep track of number of active readers/iterators for the list.

  jint increase_readers();

  jint decrease_readers();

  void wait_until_no_readers() const;

 public:

  LogOutputList() : _active_readers(0) {

    for (size_t i = 0; i < LogLevel::Count; i++) {

      _level_start[i] = NULL;

    }

  }

  // Test if the outputlist has an output for the given level.

  bool is_level(LogLevelType level) const {

    return _level_start[level] != NULL;

  }

  LogLevelType level_for(const LogOutput* output) const {

    LogOutputNode* node = this->find(output);

    if (node == NULL) {

      return LogLevel::Off;

    }

    return node->_level;

  }

  // Set (add/update/remove) the output to the specified level.

  void set_output_level(LogOutput* output, LogLevelType level);

  class Iterator {

    friend class LogOutputList;

   private:

    LogOutputNode*  _current;

    LogOutputList*  _list;

    Iterator(LogOutputList* list, LogOutputNode* start) : _current(start), _list(list) {

    }

   public:

    ~Iterator() {

      _list->decrease_readers();

    }

    LogOutput* operator*() {

      return _current->_value;

    }

    void operator++(int) {

      _current = _current->_next;

    }

    bool operator!=(const LogOutputNode *ref) const {

      return _current != ref;

    }

    LogLevelType level() const {

      return _current->_level;

    }

  };

  Iterator iterator(LogLevelType level = LogLevel::Last) {

    increase_readers();

    return Iterator(this, _level_start[level]);

  }

  LogOutputNode* end() const {

    return NULL;

  }

};

#endif // SHARE_VM_LOGGING_LOGOUTPUTLIST_HPP