/*
* Copyright (C) 2008-2014 Max Kellermann <max@duempel.org>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* - Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* - Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the
* distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* FOUNDATION OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
* OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#ifndef MPD_VAR_SIZE_HXX
#define MPD_VAR_SIZE_HXX
#include "Alloc.hxx"
#include "Compiler.h"
#include <type_traits>
#include <utility>
#include <new>
/**
* Allocate and construct a variable-size object. That is useful for
* example when you want to store a variable-length string as the last
* attribute without the overhead of a second allocation.
*
* @param T a struct/class with a variable-size last attribute
* @param declared_tail_size the declared size of the last element in
* #T
* @param real_tail_size the real required size of the last element in
* #T
*/
template<class T, typename... Args>
gcc_malloc
T *
NewVarSize(size_t declared_tail_size, size_t real_tail_size, Args&&... args)
{
static_assert(std::is_standard_layout<T>::value,
"Not standard-layout");
/* determine the total size of this instance */
size_t size = sizeof(T) - declared_tail_size + real_tail_size;
/* allocate memory */
T *instance = (T *)xalloc(size);
/* call the constructor */
new(instance) T(std::forward<Args>(args)...);
return instance;
}
template<typename T>
gcc_nonnull_all
void
DeleteVarSize(T *instance)
{
/* call the destructor */
instance->T::~T();
/* free memory */
free(instance);
}
#endif
