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// Copyright (C) 2006 Douglas Gregor <doug.gregor -at- gmail.com>
// Use, modification and distribution is subject to the Boost Software
// License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)
/** @file allocator.hpp
*
* This header provides an STL-compliant allocator that uses the
* MPI-2 memory allocation facilities.
*/
#ifndef BOOST_MPI_ALLOCATOR_HPP
#define BOOST_MPI_ALLOCATOR_HPP
#include <boost/mpi/config.hpp>
#include <boost/mpi/exception.hpp>
#include <cstddef>
#include <memory>
#include <boost/limits.hpp>
namespace boost { namespace mpi {
#if defined(BOOST_MPI_HAS_MEMORY_ALLOCATION)
template<typename T> class allocator;
/** @brief Allocator specialization for @c void value types.
*
* The @c void specialization of @c allocator is useful only for
* rebinding to another, different value type.
*/
template<>
class BOOST_MPI_DECL allocator<void>
{
public:
typedef void* pointer;
typedef const void* const_pointer;
typedef void value_type;
template <class U>
struct rebind
{
typedef allocator<U> other;
};
};
/** @brief Standard Library-compliant allocator for the MPI-2 memory
* allocation routines.
*
* This allocator provides a standard C++ interface to the @c
* MPI_Alloc_mem and @c MPI_Free_mem routines of MPI-2. It is
* intended to be used with the containers in the Standard Library
* (@c vector, in particular) in cases where the contents of the
* container will be directly transmitted via MPI. This allocator is
* also used internally by the library for character buffers that
* will be used in the transmission of data.
*
* The @c allocator class template only provides MPI memory
* allocation when the underlying MPI implementation is either MPI-2
* compliant or is known to provide @c MPI_Alloc_mem and @c
* MPI_Free_mem as extensions. When the MPI memory allocation
* routines are not available, @c allocator is brought in directly
* from namespace @c std, so that standard allocators are used
* throughout. The macro @c BOOST_MPI_HAS_MEMORY_ALLOCATION will be
* defined when the MPI-2 memory allocation facilities are available.
*/
template<typename T>
class BOOST_MPI_DECL allocator
{
public:
/// Holds the size of objects
typedef std::size_t size_type;
/// Holds the number of elements between two pointers
typedef std::ptrdiff_t difference_type;
/// A pointer to an object of type @c T
typedef T* pointer;
/// A pointer to a constant object of type @c T
typedef const T* const_pointer;
/// A reference to an object of type @c T
typedef T& reference;
/// A reference to a constant object of type @c T
typedef const T& const_reference;
/// The type of memory allocated by this allocator
typedef T value_type;
/** @brief Retrieve the type of an allocator similar to this
* allocator but for a different value type.
*/
template <typename U>
struct rebind
{
typedef allocator<U> other;
};
/** Default-construct an allocator. */
allocator() throw() { }
/** Copy-construct an allocator. */
allocator(const allocator&) throw() { }
/**
* Copy-construct an allocator from another allocator for a
* different value type.
*/
template <typename U>
allocator(const allocator<U>&) throw() { }
/** Destroy an allocator. */
~allocator() throw() { }
/** Returns the address of object @p x. */
pointer address(reference x) const
{
return &x;
}
/** Returns the address of object @p x. */
const_pointer address(const_reference x) const
{
return &x;
}
/**
* Allocate enough memory for @p n elements of type @c T.
*
* @param n The number of elements for which memory should be
* allocated.
*
* @return a pointer to the newly-allocated memory
*/
pointer allocate(size_type n, allocator<void>::const_pointer /*hint*/ = 0)
{
pointer result;
BOOST_MPI_CHECK_RESULT(MPI_Alloc_mem,
(static_cast<MPI_Aint>(n * sizeof(T)),
MPI_INFO_NULL,
&result));
return result;
}
/**
* Deallocate memory referred to by the pointer @c p.
*
* @param p The pointer whose memory should be deallocated. This
* pointer shall have been returned from the @c allocate() function
* and not have already been freed.
*/
void deallocate(pointer p, size_type /*n*/)
{
BOOST_MPI_CHECK_RESULT(MPI_Free_mem, (p));
}
/**
* Returns the maximum number of elements that can be allocated
* with @c allocate().
*/
size_type max_size() const throw()
{
return (std::numeric_limits<std::size_t>::max)() / sizeof(T);
}
/** Construct a copy of @p val at the location referenced by @c p. */
void construct(pointer p, const T& val)
{
new ((void *)p) T(val);
}
/** Destroy the object referenced by @c p. */
void destroy(pointer p)
{
((T*)p)->~T();
}
};
/** @brief Compare two allocators for equality.
*
* Since MPI allocators have no state, all MPI allocators are equal.
*
* @returns @c true
*/
template<typename T1, typename T2>
inline bool operator==(const allocator<T1>&, const allocator<T2>&) throw()
{
return true;
}
/** @brief Compare two allocators for inequality.
*
* Since MPI allocators have no state, all MPI allocators are equal.
*
* @returns @c false
*/
template<typename T1, typename T2>
inline bool operator!=(const allocator<T1>&, const allocator<T2>&) throw()
{
return false;
}
#else
// Bring in the default allocator from namespace std.
using std::allocator;
#endif
} } /// end namespace boost::mpi
#endif // BOOST_MPI_ALLOCATOR_HPP
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