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/*
* This file is part of OpenTTD.
* OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
* OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
* See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
*/
/** @file alloc_func.hpp Functions related to the allocation of memory */
#ifndef ALLOC_FUNC_HPP
#define ALLOC_FUNC_HPP
/*
* Functions to exit badly with an error message.
* It has to be linked so the error messages are not
* duplicated in each object file making the final
* binary needlessly large.
*/
void NORETURN MallocError(size_t size);
void NORETURN ReallocError(size_t size);
/**
* Checks whether allocating memory would overflow size_t.
*
* @param element_size Size of the structure to allocate.
* @param num_elements Number of elements to allocate.
*/
static inline void CheckAllocationConstraints(size_t element_size, size_t num_elements)
{
if (num_elements > SIZE_MAX / element_size) MallocError(SIZE_MAX);
}
/**
* Checks whether allocating memory would overflow size_t.
*
* @tparam T Structure to allocate.
* @param num_elements Number of elements to allocate.
*/
template <typename T>
static inline void CheckAllocationConstraints(size_t num_elements)
{
CheckAllocationConstraints(sizeof(T), num_elements);
}
/**
* Simplified allocation function that allocates the specified number of
* elements of the given type. It also explicitly casts it to the requested
* type.
* @note throws an error when there is no memory anymore.
* @note the memory contains garbage data (i.e. possibly non-zero values).
* @tparam T the type of the variable(s) to allocation.
* @param num_elements the number of elements to allocate of the given type.
* @return nullptr when num_elements == 0, non-nullptr otherwise.
*/
template <typename T>
static inline T *MallocT(size_t num_elements)
{
/*
* MorphOS cannot handle 0 elements allocations, or rather that always
* returns nullptr. So we do that for *all* allocations, thus causing it
* to behave the same on all OSes.
*/
if (num_elements == 0) return nullptr;
/* Ensure the size does not overflow. */
CheckAllocationConstraints<T>(num_elements);
T *t_ptr = (T*)malloc(num_elements * sizeof(T));
if (t_ptr == nullptr) MallocError(num_elements * sizeof(T));
return t_ptr;
}
/**
* Simplified allocation function that allocates the specified number of
* elements of the given type. It also explicitly casts it to the requested
* type.
* @note throws an error when there is no memory anymore.
* @note the memory contains all zero values.
* @tparam T the type of the variable(s) to allocation.
* @param num_elements the number of elements to allocate of the given type.
* @return nullptr when num_elements == 0, non-nullptr otherwise.
*/
template <typename T>
static inline T *CallocT(size_t num_elements)
{
/*
* MorphOS cannot handle 0 elements allocations, or rather that always
* returns nullptr. So we do that for *all* allocations, thus causing it
* to behave the same on all OSes.
*/
if (num_elements == 0) return nullptr;
T *t_ptr = (T*)calloc(num_elements, sizeof(T));
if (t_ptr == nullptr) MallocError(num_elements * sizeof(T));
return t_ptr;
}
/**
* Simplified reallocation function that allocates the specified number of
* elements of the given type. It also explicitly casts it to the requested
* type. It extends/shrinks the memory allocation given in t_ptr.
* @note throws an error when there is no memory anymore.
* @note the pointer to the data may change, but the data will remain valid.
* @tparam T the type of the variable(s) to allocation.
* @param t_ptr the previous allocation to extend/shrink.
* @param num_elements the number of elements to allocate of the given type.
* @return nullptr when num_elements == 0, non-nullptr otherwise.
*/
template <typename T>
static inline T *ReallocT(T *t_ptr, size_t num_elements)
{
/*
* MorphOS cannot handle 0 elements allocations, or rather that always
* returns nullptr. So we do that for *all* allocations, thus causing it
* to behave the same on all OSes.
*/
if (num_elements == 0) {
free(t_ptr);
return nullptr;
}
/* Ensure the size does not overflow. */
CheckAllocationConstraints<T>(num_elements);
t_ptr = (T*)realloc(static_cast<void *>(t_ptr), num_elements * sizeof(T));
if (t_ptr == nullptr) ReallocError(num_elements * sizeof(T));
return t_ptr;
}
/** alloca() has to be called in the parent function, so define AllocaM() as a macro */
#define AllocaM(T, num_elements) \
(CheckAllocationConstraints<T>(num_elements), \
(T*)alloca((num_elements) * sizeof(T)))
#endif /* ALLOC_FUNC_HPP */
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