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#ifndef QPID_SYS_COPYONWRITEARRAY_H
#define QPID_SYS_COPYONWRITEARRAY_H
/*
*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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.
*
*/
#include "qpid/sys/Mutex.h"
#include <algorithm>
#include <vector>
#include <boost/shared_ptr.hpp>
namespace qpid {
namespace sys {
/**
* An array that copies on adding/removing element allowing lock-free
* iteration.
*/
template <class T>
class CopyOnWriteArray
{
public:
typedef boost::shared_ptr<const std::vector<T> > ConstPtr;
CopyOnWriteArray() {}
CopyOnWriteArray(const CopyOnWriteArray& c) : array(c.array) {}
void add(T& t)
{
Mutex::ScopedLock l(lock);
ArrayPtr copy(array ? new std::vector<T>(*array) : new std::vector<T>());
copy->push_back(t);
array = copy;
}
bool remove(T& t)
{
Mutex::ScopedLock l(lock);
if (array && std::find(array->begin(), array->end(), t) != array->end()) {
ArrayPtr copy(new std::vector<T>(*array));
copy->erase(std::find(copy->begin(), copy->end(), t));
array = copy;
return true;
} else {
return false;
}
}
bool clear()
{
Mutex::ScopedLock l(lock);
if (array && !array->empty()) {
ArrayPtr copy;
array = copy;
return true;
} else {
return false;
}
}
template <class F>
bool add_unless(T& t, F f)
{
Mutex::ScopedLock l(lock);
if (array && std::find_if(array->begin(), array->end(), f) != array->end()) {
return false;
} else {
ArrayPtr copy(array ? new std::vector<T>(*array) : new std::vector<T>());
copy->push_back(t);
array = copy;
return true;
}
}
template <class F>
bool remove_if(F f)
{
Mutex::ScopedLock l(lock);
if (array && std::find_if(array->begin(), array->end(), f) != array->end()) {
ArrayPtr copy(new std::vector<T>(*array));
copy->erase(std::remove_if(copy->begin(), copy->end(), f), copy->end());
array = copy;
return true;
}
return false;
}
template <class TestFn, class ModifierFn>
bool modify_if(TestFn f, ModifierFn & m)
{
if (!array)
return false;
{
Mutex::ScopedLock l(lock);
if (std::find_if(array->begin(), array->end(), f) != array->end())
{
ArrayPtr copy(new std::vector<T>(*array));
m(*std::find_if(copy->begin(), copy->end(), f));
array = copy;
return true;
}
}
return false;
}
template <class F>
F for_each(F f)
{
ArrayPtr a;
{
Mutex::ScopedLock l(lock);
a = array;
}
if (!a) return f;
return std::for_each(a->begin(), a->end(), f);
}
ConstPtr snapshot()
{
ConstPtr a;
{
Mutex::ScopedLock l(lock);
a = array;
}
return a;
}
private:
typedef boost::shared_ptr< std::vector<T> > ArrayPtr;
Mutex lock;
ArrayPtr array;
};
}}
#endif /*!QPID_SYS_COPYONWRITEARRAY_H*/
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