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#pragma once
/**
* Copyright (C) 2012 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 <http://www.gnu.org/licenses/>.
*
* 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.
*/
#include "mongo/platform/unordered_map.h"
namespace mongo {
/** Thread safe map.
Be careful not to use this too much or it could make things slow;
if not a hot code path no problem.
Examples:
mapsf< std::map<int,int>, int, int > mp;
int x = mp.get();
std::map< std::map<int,int>, int, int > two;
mp.swap(two);
{
mapsf< std::map<int,int>, int, int >::ref r(mp);
r[9] = 1;
std::map<int,int>::iterator i = r.r.begin();
}
*/
template< class M >
struct mapsf {
MONGO_DISALLOW_COPYING(mapsf);
SimpleMutex m;
M val;
friend struct ref;
public:
typedef typename M::const_iterator const_iterator;
typedef typename M::key_type key_type;
typedef typename M::mapped_type mapped_type;
mapsf() : m("mapsf") { }
void swap(M& rhs) {
SimpleMutex::scoped_lock lk(m);
val.swap(rhs);
}
bool empty() {
SimpleMutex::scoped_lock lk(m);
return val.empty();
}
// safe as we pass by value:
mapped_type get(key_type k) {
SimpleMutex::scoped_lock lk(m);
const_iterator i = val.find(k);
if( i == val.end() )
return mapped_type();
return i->second;
}
// think about deadlocks when using ref. the other methods
// above will always be safe as they are "leaf" operations.
struct ref {
SimpleMutex::scoped_lock lk;
public:
M &r;
ref(mapsf &m) : lk(m.m), r(m.val) { }
mapped_type& operator[](const key_type& k) { return r[k]; }
};
};
}
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