/usr/include/mongo/util/concurrency/value.h is in mongodb-dev 1:2.4.9-1ubuntu2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 | /* @file value.h
concurrency helpers DiagStr, Guarded
*/
/**
* 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
#include "spin_lock.h"
namespace mongo {
/** declare that a variable that is "guarded" by a mutex.
The decl documents the rule. For example "counta and countb are guarded by xyzMutex":
Guarded<int, xyzMutex> counta;
Guarded<int, xyzMutex> countb;
Upon use, specify the scoped_lock object. This makes it hard for someone
later to forget to be in the lock. Check is made that it is the right lock in _DEBUG
builds at runtime.
*/
template <typename T, SimpleMutex& BY>
class Guarded {
T _val;
public:
T& ref(const SimpleMutex::scoped_lock& lk) {
dassert( &lk.m() == &BY );
return _val;
}
};
// todo: rename this to ThreadSafeString or something
/** there is now one mutex per DiagStr. If you have hundreds or millions of
DiagStrs you'll need to do something different.
*/
class DiagStr {
mutable SpinLock m;
string _s;
public:
DiagStr(const DiagStr& r) : _s(r.get()) { }
DiagStr(const string& r) : _s(r) { }
DiagStr() { }
bool empty() const {
scoped_spinlock lk(m);
return _s.empty();
}
string get() const {
scoped_spinlock lk(m);
return _s;
}
void set(const char *s) {
scoped_spinlock lk(m);
_s = s;
}
void set(const string& s) {
scoped_spinlock lk(m);
_s = s;
}
operator string() const { return get(); }
void operator=(const string& s) { set(s); }
void operator=(const DiagStr& rhs) {
set( rhs.get() );
}
// == is not defined. use get() == ... instead. done this way so one thinks about if composing multiple operations
bool operator==(const string& s) const;
};
}
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