mirror of https://github.com/OpenTTD/OpenTTD.git
132 lines
4.6 KiB
C++
132 lines
4.6 KiB
C++
/*
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* This file is part of OpenTTD.
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* 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.
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* 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.
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* 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/>.
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*/
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/** @file alloc_func.hpp Functions related to the allocation of memory */
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#ifndef ALLOC_FUNC_HPP
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#define ALLOC_FUNC_HPP
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/*
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* Functions to exit badly with an error message.
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* It has to be linked so the error messages are not
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* duplicated in each object file making the final
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* binary needlessly large.
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*/
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[[noreturn]] void MallocError(size_t size);
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[[noreturn]] void ReallocError(size_t size);
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/**
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* Checks whether allocating memory would overflow size_t.
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*
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* @param element_size Size of the structure to allocate.
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* @param num_elements Number of elements to allocate.
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*/
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inline void CheckAllocationConstraints(size_t element_size, size_t num_elements)
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{
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if (num_elements > SIZE_MAX / element_size) MallocError(SIZE_MAX);
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}
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/**
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* Checks whether allocating memory would overflow size_t.
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*
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* @tparam T Structure to allocate.
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* @param num_elements Number of elements to allocate.
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*/
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template <typename T>
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inline void CheckAllocationConstraints(size_t num_elements)
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{
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CheckAllocationConstraints(sizeof(T), num_elements);
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}
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/**
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* Simplified allocation function that allocates the specified number of
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* elements of the given type. It also explicitly casts it to the requested
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* type.
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* @note throws an error when there is no memory anymore.
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* @note the memory contains garbage data (i.e. possibly non-zero values).
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* @tparam T the type of the variable(s) to allocation.
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* @param num_elements the number of elements to allocate of the given type.
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* @return nullptr when num_elements == 0, non-nullptr otherwise.
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*/
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template <typename T>
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inline T *MallocT(size_t num_elements)
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{
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/*
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* MorphOS cannot handle 0 elements allocations, or rather that always
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* returns nullptr. So we do that for *all* allocations, thus causing it
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* to behave the same on all OSes.
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*/
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if (num_elements == 0) return nullptr;
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/* Ensure the size does not overflow. */
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CheckAllocationConstraints<T>(num_elements);
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T *t_ptr = (T*)malloc(num_elements * sizeof(T));
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if (t_ptr == nullptr) MallocError(num_elements * sizeof(T));
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return t_ptr;
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}
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/**
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* Simplified allocation function that allocates the specified number of
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* elements of the given type. It also explicitly casts it to the requested
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* type.
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* @note throws an error when there is no memory anymore.
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* @note the memory contains all zero values.
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* @tparam T the type of the variable(s) to allocation.
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* @param num_elements the number of elements to allocate of the given type.
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* @return nullptr when num_elements == 0, non-nullptr otherwise.
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*/
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template <typename T>
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inline T *CallocT(size_t num_elements)
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{
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/*
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* MorphOS cannot handle 0 elements allocations, or rather that always
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* returns nullptr. So we do that for *all* allocations, thus causing it
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* to behave the same on all OSes.
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*/
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if (num_elements == 0) return nullptr;
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T *t_ptr = (T*)calloc(num_elements, sizeof(T));
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if (t_ptr == nullptr) MallocError(num_elements * sizeof(T));
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return t_ptr;
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}
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/**
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* Simplified reallocation function that allocates the specified number of
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* elements of the given type. It also explicitly casts it to the requested
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* type. It extends/shrinks the memory allocation given in t_ptr.
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* @note throws an error when there is no memory anymore.
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* @note the pointer to the data may change, but the data will remain valid.
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* @tparam T the type of the variable(s) to allocation.
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* @param t_ptr the previous allocation to extend/shrink.
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* @param num_elements the number of elements to allocate of the given type.
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* @return nullptr when num_elements == 0, non-nullptr otherwise.
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*/
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template <typename T>
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inline T *ReallocT(T *t_ptr, size_t num_elements)
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{
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/*
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* MorphOS cannot handle 0 elements allocations, or rather that always
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* returns nullptr. So we do that for *all* allocations, thus causing it
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* to behave the same on all OSes.
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*/
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if (num_elements == 0) {
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free(t_ptr);
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return nullptr;
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}
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/* Ensure the size does not overflow. */
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CheckAllocationConstraints<T>(num_elements);
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t_ptr = (T*)realloc(static_cast<void *>(t_ptr), num_elements * sizeof(T));
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if (t_ptr == nullptr) ReallocError(num_elements * sizeof(T));
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return t_ptr;
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}
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#endif /* ALLOC_FUNC_HPP */
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