97 lines
2.9 KiB
C++
97 lines
2.9 KiB
C++
/*
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* Copyright (c) Facebook, Inc. and its affiliates.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef FOLLY_ARENA_H_
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#error This file may only be included from Arena.h
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#endif
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// Implementation of Arena.h functions
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namespace folly {
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template <class Alloc>
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std::pair<typename Arena<Alloc>::Block*, size_t>
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Arena<Alloc>::Block::allocate(Alloc& alloc, size_t size, bool allowSlack) {
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size_t allocSize = sizeof(Block) + size;
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if (allowSlack) {
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allocSize = ArenaAllocatorTraits<Alloc>::goodSize(alloc, allocSize);
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}
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void* mem = std::allocator_traits<Alloc>::allocate(alloc, allocSize);
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return std::make_pair(new (mem) Block(), allocSize - sizeof(Block));
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}
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template <class Alloc>
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void Arena<Alloc>::Block::deallocate(Alloc& alloc) {
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this->~Block();
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std::allocator_traits<Alloc>::deallocate(alloc, this, 1);
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}
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template <class Alloc>
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void* Arena<Alloc>::allocateSlow(size_t size) {
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std::pair<Block*, size_t> p;
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char* start;
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size_t allocSize;
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if (!checked_add(&allocSize, std::max(size, minBlockSize()), sizeof(Block))) {
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throw_exception<std::bad_alloc>();
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}
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if (sizeLimit_ != kNoSizeLimit &&
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allocSize > sizeLimit_ - totalAllocatedSize_) {
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throw_exception(std::bad_alloc());
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}
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if (size > minBlockSize()) {
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// Allocate a large block for this chunk only, put it at the back of the
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// list so it doesn't get used for small allocations; don't change ptr_
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// and end_, let them point into a normal block (or none, if they're
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// null)
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p = Block::allocate(alloc(), size, false);
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start = p.first->start();
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blocks_.push_back(*p.first);
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} else {
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// Allocate a normal sized block and carve out size bytes from it
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p = Block::allocate(alloc(), minBlockSize(), true);
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start = p.first->start();
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blocks_.push_front(*p.first);
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ptr_ = start + size;
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end_ = start + p.second;
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}
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assert(p.second >= size);
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totalAllocatedSize_ += p.second + sizeof(Block);
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return start;
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}
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template <class Alloc>
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void Arena<Alloc>::merge(Arena<Alloc>&& other) {
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blocks_.splice_after(blocks_.before_begin(), other.blocks_);
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other.blocks_.clear();
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other.ptr_ = other.end_ = nullptr;
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totalAllocatedSize_ += other.totalAllocatedSize_;
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other.totalAllocatedSize_ = 0;
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}
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template <class Alloc>
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Arena<Alloc>::~Arena() {
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auto disposer = [this](Block* b) { b->deallocate(this->alloc()); };
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while (!blocks_.empty()) {
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blocks_.pop_front_and_dispose(disposer);
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}
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}
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} // namespace folly
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