/* Copyright 2009 10gen Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License, version 3,
* as published by the Free Software Foundation.
*
* 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 Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see .
*
* As a special exception, the copyright holders give permission to link the
* code of portions of this program with the OpenSSL library under certain
* conditions as described in each individual source file and distribute
* linked combinations including the program with the OpenSSL library. You
* must comply with the GNU Affero General Public License in all respects
* for all of the code used other than as permitted herein. If you modify
* file(s) with this exception, you may extend this exception to your
* version of the file(s), but you are not obligated to do so. If you do not
* wish to do so, delete this exception statement from your version. If you
* delete this exception statement from all source files in the program,
* then also delete it in the license file.
*/
#pragma once
#include
#include
#include "mongo/util/concurrency/mutex.h"
namespace mongo {
class TicketHolder {
public:
TicketHolder( int num ) : _mutex("TicketHolder") {
_outof = num;
_num = num;
}
bool tryAcquire() {
scoped_lock lk( _mutex );
return _tryAcquire();
}
void waitForTicket() {
scoped_lock lk( _mutex );
while( ! _tryAcquire() ) {
_newTicket.wait( lk.boost() );
}
}
void release() {
{
scoped_lock lk( _mutex );
_num++;
}
_newTicket.notify_one();
}
void resize( int newSize ) {
{
scoped_lock lk( _mutex );
int used = _outof - _num;
if ( used > newSize ) {
std::cout << "can't resize since we're using (" << used << ") more than newSize(" << newSize << ")" << std::endl;
return;
}
_outof = newSize;
_num = _outof - used;
}
// Potentially wasteful, but easier to see is correct
_newTicket.notify_all();
}
int available() const {
return _num;
}
int used() const {
return _outof - _num;
}
int outof() const { return _outof; }
private:
bool _tryAcquire(){
if ( _num <= 0 ) {
if ( _num < 0 ) {
std::cerr << "DISASTER! in TicketHolder" << std::endl;
}
return false;
}
_num--;
return true;
}
int _outof;
int _num;
mongo::mutex _mutex;
boost::condition_variable_any _newTicket;
};
class ScopedTicket {
public:
ScopedTicket(TicketHolder* holder) : _holder(holder) {
_holder->waitForTicket();
}
~ScopedTicket() {
_holder->release();
}
private:
TicketHolder* _holder;
};
class TicketHolderReleaser {
public:
TicketHolderReleaser( TicketHolder * holder ) {
_holder = holder;
}
~TicketHolderReleaser() {
_holder->release();
}
private:
TicketHolder * _holder;
};
}