2014-01-07 22:04:19 +01:00
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/*
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* Copyright (C) 2008-2014 Max Kellermann <max@duempel.org>
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* - Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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*
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* - Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the
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* distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* FOUNDATION OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
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* OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#ifndef MPD_VAR_SIZE_HXX
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#define MPD_VAR_SIZE_HXX
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2014-01-07 23:33:46 +01:00
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#include "Alloc.hxx"
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2014-01-07 22:04:19 +01:00
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#include "Compiler.h"
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#include <type_traits>
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#include <utility>
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#include <new>
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/**
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* Allocate and construct a variable-size object. That is useful for
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* example when you want to store a variable-length string as the last
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* attribute without the overhead of a second allocation.
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*
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* @param T a struct/class with a variable-size last attribute
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* @param declared_tail_size the declared size of the last element in
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* #T
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* @param real_tail_size the real required size of the last element in
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* #T
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*/
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template<class T, typename... Args>
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gcc_malloc
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T *
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NewVarSize(size_t declared_tail_size, size_t real_tail_size, Args&&... args)
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{
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static_assert(std::is_standard_layout<T>::value,
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"Not standard-layout");
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/* determine the total size of this instance */
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size_t size = sizeof(T) - declared_tail_size + real_tail_size;
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/* allocate memory */
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2014-01-07 23:33:46 +01:00
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T *instance = (T *)xalloc(size);
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2014-01-07 22:04:19 +01:00
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/* call the constructor */
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new(instance) T(std::forward<Args>(args)...);
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return instance;
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}
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template<typename T>
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gcc_nonnull_all
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void
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DeleteVarSize(T *instance)
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{
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/* call the destructor */
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instance->T::~T();
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/* free memory */
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2014-01-07 23:33:46 +01:00
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free(instance);
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2014-01-07 22:04:19 +01:00
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}
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#endif
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