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/* @file value.h
concurrency helpers Atomic<T> and DiagStr
*/
/**
* Copyright (C) 2008 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,b
* 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/>.
*/
#pragma once
namespace mongo {
extern mutex _atomicMutex;
/** atomic wrapper for a value. enters a mutex on each access. must
be copyable.
*/
template<typename T>
class Atomic : boost::noncopyable {
T val;
public:
Atomic<T>() { }
void operator=(const T& a) {
scoped_lock lk(_atomicMutex);
val = a;
}
operator T() const {
scoped_lock lk(_atomicMutex);
return val;
}
/** example:
Atomic<int> q;
...
{
Atomic<int>::tran t(q);
if( q.ref() > 0 )
q.ref()--;
}
*/
class tran : private scoped_lock {
Atomic<T>& _a;
public:
tran(Atomic<T>& a) : scoped_lock(_atomicMutex), _a(a) { }
T& ref() { return _a.val; }
};
};
class DiagStr {
string _s;
static mutex m;
public:
DiagStr(const DiagStr& r) : _s(r.get()) { }
DiagStr() { }
bool empty() const {
mutex::scoped_lock lk(m);
return _s.empty();
}
string get() const {
mutex::scoped_lock lk(m);
return _s;
}
void set(const char *s) {
mutex::scoped_lock lk(m);
_s = s;
}
void set(const string& s) {
mutex::scoped_lock lk(m);
_s = s;
}
operator string() const { return get(); }
void operator=(const string& s) { set(s); }
};
}
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