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/* Copyright 2009 10gen Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#pragma once
#include <boost/thread/condition_variable.hpp>
#include <iostream>
#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;
};
}
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