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/**
* Copyright (c) 2011 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.
*/
#pragma once
#include <boost/intrusive_ptr.hpp>
#include <stdlib.h>
#include "mongo/base/disallow_copying.h"
#include "mongo/base/string_data.h"
#include "mongo/platform/atomic_word.h"
#include "mongo/util/allocator.h"
namespace mongo {
/// This is an alternative base class to the above ones (will replace them eventually)
class RefCountable {
MONGO_DISALLOW_COPYING(RefCountable);
public:
/// If false you have exclusive access to this object. This is useful for implementing COW.
bool isShared() const {
// TODO: switch to unfenced read method after SERVER-6973
return reinterpret_cast<unsigned&>(_count) > 1;
}
friend void intrusive_ptr_add_ref(const RefCountable* ptr) {
ptr->_count.addAndFetch(1);
};
friend void intrusive_ptr_release(const RefCountable* ptr) {
if (ptr->_count.subtractAndFetch(1) == 0) {
delete ptr; // uses subclass destructor and operator delete
}
};
protected:
RefCountable() {}
virtual ~RefCountable() {}
private:
mutable AtomicUInt32 _count; // default initialized to 0
};
/// This is an immutable reference-counted string
class RCString : public RefCountable {
public:
const char* c_str() const {
return reinterpret_cast<const char*>(this) + sizeof(RCString);
}
int size() const {
return _size;
}
StringData stringData() const {
return StringData(c_str(), _size);
}
static boost::intrusive_ptr<const RCString> create(StringData s);
// MSVC: C4291: 'declaration' : no matching operator delete found; memory will not be freed if
// initialization throws an exception
// We simply rely on the default global placement delete since a local placement delete would be
// ambiguous for some compilers
#pragma warning(push)
#pragma warning(disable : 4291)
void operator delete(void* ptr) {
free(ptr);
}
#pragma warning(pop)
private:
// these can only be created by calling create()
RCString(){};
void* operator new(size_t objSize, size_t realSize) {
return mongoMalloc(realSize);
}
int _size; // does NOT include trailing NUL byte.
// char[_size+1] array allocated past end of class
};
} // namespace mongo
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