Merge branch 'cpp-11' into save_ext
Jonathan G Rennison
7 years ago
commit
48bbe0325d
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/* $Id$ */
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/*
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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 dyn_arena_alloc.hpp Dynamic chunk-size arena allocator. */
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#ifndef DYN_ARENA_ALLOC_HPP
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#define DYN_ARENA_ALLOC_HPP
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#include <vector>
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/**
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* Custom arena allocator for uniform-size allocations of a variable size.
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* The allocation and chunk sizes may only be changed when the arena is empty.
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*/
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class DynUniformArenaAllocator {
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std::vector<void *> used_blocks;
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void *current_block = nullptr;
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void *last_freed = nullptr;
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size_t next_position = 0;
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size_t item_size = 0;
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size_t items_per_chunk = 0;
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void NewBlock()
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{
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current_block = malloc(item_size * items_per_chunk);
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assert(current_block != nullptr);
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next_position = 0;
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used_blocks.push_back(current_block);
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}
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public:
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DynUniformArenaAllocator() = default;
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DynUniformArenaAllocator(const DynUniformArenaAllocator &other) = delete;
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DynUniformArenaAllocator& operator=(const DynUniformArenaAllocator &other) = delete;
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~DynUniformArenaAllocator()
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{
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EmptyArena();
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}
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void EmptyArena()
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{
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current_block = nullptr;
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last_freed = nullptr;
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next_position = 0;
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for (void *block : used_blocks) {
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free(block);
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}
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used_blocks.clear();
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}
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void ResetArena()
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{
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EmptyArena();
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item_size = 0;
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items_per_chunk = 0;
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}
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void *Allocate() {
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assert(item_size != 0);
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if (last_freed) {
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void *ptr = last_freed;
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last_freed = *reinterpret_cast<void**>(ptr);
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return ptr;
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} else {
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if (current_block == nullptr || next_position == items_per_chunk) {
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NewBlock();
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}
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void *out = reinterpret_cast<char *>(current_block) + (item_size * next_position);
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next_position++;
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return out;
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}
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}
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void Free(void *ptr) {
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if (!ptr) return;
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assert(current_block != nullptr);
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*reinterpret_cast<void**>(ptr) = last_freed;
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last_freed = ptr;
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}
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void SetParameters(size_t item_size, size_t items_per_chunk)
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{
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if (item_size < sizeof(void *)) item_size = sizeof(void *);
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if (this->item_size == item_size && this->items_per_chunk == items_per_chunk) return;
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assert(current_block == nullptr);
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this->item_size = item_size;
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this->items_per_chunk = items_per_chunk;
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}
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};
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#endif /* DYN_ARENA_ALLOC_HPP */
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