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/// Application instance class header
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/**
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 * \file appinst.h
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 *
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 * Copyright (C) 2007 Lukas Jelinek, <lukas@aiken.cz>
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 *
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 * This program is free software; you can redistribute it and/or
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 * modify it under the terms of one of the following licenses:
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 *
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 * \li 1. X11-style license (see LICENSE-X11)
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 * \li 2. GNU Lesser General Public License, version 2.1 (see LICENSE-LGPL)
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 * \li 3. GNU General Public License, version 2  (see LICENSE-GPL)
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 *
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 * If you want to help with choosing the best license for you,
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 * please visit http://www.gnu.org/licenses/license-list.html.
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 *
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 */
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#ifndef APPINST_H_
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#define APPINST_H_
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#include <string>
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#define APPLOCK_BASEDIR "/var/run"
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/// Exception class.
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/**
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 * This class provides information about occurred errors.
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 */
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class AppInstException
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{
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public:
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  /// Constructor.
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  /**
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   * \param[in] iErr error number
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   */
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  AppInstException(int iErr) : m_iErr(iErr) {}
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  /// Returns the error number.
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  /**
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   * \return error number
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   */
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  inline int GetErrorNumber() const
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  {
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    return m_iErr;
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  }
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private:
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  int m_iErr; ///< error number
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};
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/// Application instance management class.
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/**
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 * This class is intended for application which require to
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 * be running only once (one instance only). It provides some
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 * methods for simple locking, signaling etc.
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 */
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class AppInstance
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{
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public:
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  /// Constructor.
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  /**
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   * \param[in] rName application name
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   * \param[in] rBase lockfile base directory
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   *
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   * \attention If an empty base directory is given it is replaced by
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   *            the default value.
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   */
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  AppInstance(const std::string& rName, const std::string& rBase = APPLOCK_BASEDIR);
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  /// Destructor.
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  ~AppInstance();
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  /// Attempts to lock the instance.
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  /**
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   * This method attempts to create a lockfile. If the file
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   * already exists it checks whether its owner is still living.
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   * If it does this method fails. Otherwise it unlinks this file
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   * and re-attempts to create it.
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   *
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   * \return true = instance locked, false = otherwise
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   */
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  bool Lock();
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  /// Unlocks the instance.
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  /**
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   * This method removes (unlinks) the appropriate lockfile.
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   * If the instance hasn't been locked this method has no
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   * effect.
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   */
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  void Unlock();
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  /// Checks whether an instance of this application exists.
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  /**
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   * If this instance has acquired the lockfile the call will
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   * be successful. Otherwise it checks for existence of
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   * another running instance.
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   *
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   * \return true = instance exists, false = otherwise
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   */
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  bool Exists() const;
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  /// Sends a signal to an instance of this application.
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  /**
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   * This method doesn't signal the current instance.
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   *
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   * \param[in] iSigNo signal number
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   * \return true = success, false = otherwise
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   */
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  bool SendSignal(int iSigNo) const;
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  /// Terminates an instance of this application.
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  /**
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   * This method doesn't terminate the current instance.
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   *
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   * \return true = success, false = otherwise
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   */
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  inline bool Terminate() const
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  {
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    return SendSignal(SIGTERM);
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  }
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protected:
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  bool DoLock();
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private:
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  std::string m_path; ///< lock path
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  bool m_fLocked;     ///< locked yes/no
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};
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#endif /*APPINST_H_*/