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#ifndef QPID_INLINEALLOCATOR_H
#define QPID_INLINEALLOCATOR_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 <memory>
#include <assert.h>
#include <boost/type_traits/type_with_alignment.hpp>
#include <boost/type_traits/alignment_of.hpp>
namespace qpid {
template <typename RequestedType, typename InlineType, typename BaseAllocator, size_t Max>
struct InlineRebind;
/**
* An allocator that has inline storage for up to Max objects
* of type BaseAllocator::value_type.
*/
template <class BaseAllocator, size_t Max>
class InlineAllocator : public BaseAllocator {
public:
typedef typename BaseAllocator::pointer pointer;
typedef typename BaseAllocator::size_type size_type;
typedef typename BaseAllocator::value_type value_type;
InlineAllocator() : allocated(false) {}
InlineAllocator(const InlineAllocator& x) : BaseAllocator(x), allocated(false) {}
pointer allocate(size_type n) {
if (n <= Max && !allocated) {
allocated=true;
return reinterpret_cast<value_type*>(address());
}
else
return BaseAllocator::allocate(n, 0);
}
void deallocate(pointer p, size_type n) {
if (p == address()) {
assert(allocated);
allocated=false;
}
else
BaseAllocator::deallocate(p, n);
}
template<typename T1>
struct rebind {
typedef typename InlineRebind<T1, value_type, BaseAllocator, Max>::other other;
};
private:
// POD object with alignment and size to hold Max value_types.
static const size_t ALIGNMENT=boost::alignment_of<value_type>::value;
typedef typename boost::type_with_alignment<ALIGNMENT>::type Aligner;
union Store {
Aligner aligner_;
char sizer_[sizeof(value_type)*Max];
} store;
value_type* address() { return reinterpret_cast<value_type*>(&store); }
bool allocated;
};
// Rebind: if RequestedType == InlineType, use the InlineAllocator,
// otherwise, use the BaseAllocator without any inlining.
template <typename RequestedType, typename InlineType, typename BaseAllocator, size_t Max>
struct InlineRebind {
typedef typename BaseAllocator::template rebind<RequestedType>::other other;
};
template <typename T, typename BaseAllocator, size_t Max>
struct InlineRebind<T, T, BaseAllocator, Max> {
typedef typename qpid::InlineAllocator<BaseAllocator, Max> other;
};
} // namespace qpid
#endif /*!QPID_INLINEALLOCATOR_H*/
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