///////////////////////////////////////////////////////////////////
//
// Catches UNIX signals sent to the main application by the operating
// system.
//
// This is a singleton which handles UNIX signals sent by the operating
// system. It must be initialized in the main() function of the program
// by calling SignalHandler::Init(). Then SIGINT (sent by Ctrl-C) will
// be trapped by this handler. All other signals remain connected to the
// default handlers.
//
// When SIGINT is first received, a flag is set and execution
// resumes as normal. The flag can be checked by calling
// SignalHandler::IsTermRequested(). If it returns true, then the
// current operation should be aborted as soon as it is possible without
// losing data. In general, the only objects which need to check this
// flag are subclasses of Producer. If the user really needs to abort
// now, they can hit Ctrl-C again, and the second time SIGINT is
// received, the application terminates immediately with no cleanup.
//
// Note that this class only contains static methods and cannot be
// instantiated.
//
// Author: Stan Seibert <volsung@physics.utexas.edu>
//
///////////////////////////////////////////////////////////////////

#ifndef __RAT_SignalHandler__
#define __RAT_SignalHandler__

#include <signal.h>

namespace RAT {


class SignalHandler {
public:

  /* Initialize signal handler.
   *
   * After this call, this class will catch SIGINT.
   */
  static void Init();

  /* If true, you should stop whatever you are doing after the
     current event. */
  static bool IsTermRequested() { return fSigintPending; }

  /* Send a SIGINT to the handler.
   *
   * In general, this method is only called by the operating system
   * in response to a SIGINT.  You should not call it unless you want to
   * simulate a Ctrl-C.
   *
   * The first time this is received, the termination flag is set.
   * The current SIGINT handler is also changed back to the default
   * OS handler so that the second SIGINT will cause the default
   * behavior (usually immediate termination of the application).
   * Execution resumes without interruption.
   */
  static void SigInt();

private:
  /* This class cannot be instantiated. */
  SignalHandler() { /* Do nothing */ };


  /* Set to true if a SIGINT has been received. */
  static bool fSigintPending;
};


} // namespace RAT

#endif