65 lines
2.3 KiB
C++
65 lines
2.3 KiB
C++
/* Copyright (C) 2005 J.F.Dockes
|
|
* This program is free software; you can redistribute it and/or modify
|
|
* it under the terms of the GNU General Public License as published by
|
|
* the Free Software Foundation; either version 2 of the License, or
|
|
* (at your option) any later version.
|
|
*
|
|
* This program 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 for more details.
|
|
*
|
|
* You should have received a copy of the GNU General Public License
|
|
* along with this program; if not, write to the
|
|
* Free Software Foundation, Inc.,
|
|
* 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
|
|
*/
|
|
#ifndef _CANCELCHECK_H_INCLUDED_
|
|
#define _CANCELCHECK_H_INCLUDED_
|
|
|
|
|
|
/**
|
|
* Common cancel checking mechanism
|
|
*
|
|
* The CancelCheck class is used as a singleton objet (private constructor).
|
|
* The single instance can be accessed as CancelCheck::instance.
|
|
* It is used as follows, in an asynchronous program where there is an
|
|
* interactive (or otherwise controlling) task and a long-working one:
|
|
* - The control task calls setCancel(), usually as a result of user
|
|
* interaction, if the worker takes too long.
|
|
* - The worker task calls checkCancel() at regular intervals, possibly as
|
|
* a side-effect of some other progress-reporting call. If cancellation has
|
|
* been requested, this will raise an exception, to be catched and processed
|
|
* wherever the worker was invoked.
|
|
* The worker side must be exception-clean, but this otherwise avoids
|
|
* having to set-up code to handle a special cancellation error along
|
|
* the whole worker call stack.
|
|
*/
|
|
class CancelExcept {};
|
|
|
|
class CancelCheck {
|
|
public:
|
|
static CancelCheck& instance() {
|
|
static CancelCheck ck;
|
|
return ck;
|
|
}
|
|
void setCancel(bool on = true) {
|
|
cancelRequested = on;
|
|
}
|
|
void checkCancel() {
|
|
if (cancelRequested) {
|
|
cancelRequested = false;
|
|
throw CancelExcept();
|
|
}
|
|
}
|
|
bool cancelState() {return cancelRequested;}
|
|
private:
|
|
bool cancelRequested;
|
|
|
|
CancelCheck() : cancelRequested(false) {}
|
|
CancelCheck& operator=(CancelCheck&);
|
|
CancelCheck(const CancelCheck&);
|
|
};
|
|
|
|
#endif /* _CANCELCHECK_H_INCLUDED_ */
|