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// -*- c++ -*-
/******************************************************************************
* arenaalloc.h
*
* Arena allocator based on the example logic provided by Nicolai Josuttis
* and available at http://www.josuttis.com/libbook/examples.html.
* This enhanced work is provided under the terms of the MIT license.
*
*****************************************************************************/
#ifndef _ARENA_ALLOC_H
#define _ARENA_ALLOC_H
#include <limits>
#include <memory>
#if __cplusplus >= 201103L
#include <type_traits>
#include <utility>
#endif
// Define macro ARENA_ALLOC_DEBUG to enable some tracing of the allocator
#include "arenaallocimpl.h"
namespace ArenaAlloc
{
struct _newAllocatorImpl
{
// these two functions should be supported by a specialized
// allocator for shared memory or another source of specialized
// memory such as device mapped memory.
void* allocate( size_t numBytes ) { return new char[ numBytes ]; }
void deallocate( void* ptr ) { delete[]( (char*)ptr ); }
};
template <class T,
class AllocatorImpl = _newAllocatorImpl,
class MemblockImpl = _memblockimpl<AllocatorImpl> >
class Alloc {
private:
MemblockImpl* m_impl;
public:
// type definitions
typedef T value_type;
typedef T* pointer;
typedef const T* const_pointer;
typedef T& reference;
typedef const T& const_reference;
typedef std::size_t size_type;
typedef std::ptrdiff_t difference_type;
#if __cplusplus >= 201103L
// when containers are swapped, (i.e. vector.swap)
// swap the allocators also. This was not specified in c++98
// thus users of this code not using c++11 must
// exercise caution when using the swap algorithm or
// specialized swap member function. Specifically,
// don't swap containers not sharing the same
// allocator internal implementation in c++98. This is ok
// in c++11.
typedef std::true_type propagate_on_container_swap;
// container moves should move the allocator also.
typedef std::true_type propagate_on_container_move_assignment;
#endif
// rebind allocator to type U
template <class U>
struct rebind {
typedef Alloc<U,AllocatorImpl,MemblockImpl> other;
};
// return address of values
pointer address (reference value) const {
return &value;
}
const_pointer address (const_reference value) const {
return &value;
}
Alloc( std::size_t defaultSize = 32768, AllocatorImpl allocImpl = AllocatorImpl() ) throw():
m_impl( MemblockImpl::create( defaultSize, allocImpl ) )
{
}
Alloc(const Alloc& src) throw():
m_impl( src.m_impl )
{
m_impl->incrementRefCount();
}
template <class U>
Alloc (const Alloc<U,AllocatorImpl,MemblockImpl>& src) throw():
m_impl( 0 )
{
MemblockImpl::assign( src, m_impl );
m_impl->incrementRefCount();
}
~Alloc() throw()
{
m_impl->decrementRefCount();
}
// return maximum number of elements that can be allocated
size_type max_size () const throw()
{
return std::numeric_limits<std::size_t>::max() / sizeof(T);
}
// allocate but don't initialize num elements of type T
pointer allocate (size_type num, const void* = 0)
{
return reinterpret_cast<pointer>( m_impl->allocate(num*sizeof(T)) );
}
// initialize elements of allocated storage p with value value
#if __cplusplus >= 201103L
// use c++11 style forwarding to construct the object
template< typename P, typename... Args>
void construct( P* obj, Args&&... args )
{
::new((void*) obj ) P( std::forward<Args>( args )... );
}
template< typename P >
void destroy( P* obj ) { obj->~P(); }
#else
void construct (pointer p, const T& value)
{
new((void*)p)T(value);
}
void destroy (pointer p) { p->~T(); }
#endif
// deallocate storage p of deleted elements
void deallocate (pointer p, size_type num)
{
m_impl->deallocate( p );
}
bool equals( const MemblockImpl * impl ) const
{
return impl == m_impl;
}
bool operator == ( const Alloc& t2 ) const
{
return m_impl == t2.m_impl;
}
friend MemblockImpl;
template< typename Other >
bool operator == ( const Alloc< Other, AllocatorImpl, MemblockImpl >& t2 )
{
return t2.equals( m_impl );
}
template< typename Other >
bool operator != ( const Alloc< Other, AllocatorImpl, MemblockImpl >& t2 )
{
return !t2.equals( m_impl );
}
// These are extension functions not required for an stl allocator
size_t getNumAllocations() { return m_impl->getNumAllocations(); }
size_t getNumDeallocations() { return m_impl->getNumDeallocations(); }
size_t getNumBytesAllocated() { return m_impl->getNumBytesAllocated(); }
};
template<typename A>
template<typename T>
void _memblockimpl<A>::assign( const Alloc<T,A, _memblockimpl<A> >& src, _memblockimpl<A> *& dest )
{
dest = const_cast<_memblockimpl<A>* >(src.m_impl);
}
}
#endif
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