1/*
2 * Copyright 2012-present Facebook, Inc.
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#ifndef FOLLY_ARENA_H_
18#error This file may only be included from Arena.h
19#endif
20
21// Implementation of Arena.h functions
22
23namespace folly {
24
25template <class Alloc>
26std::pair<typename Arena<Alloc>::Block*, size_t>
27Arena<Alloc>::Block::allocate(Alloc& alloc, size_t size, bool allowSlack) {
28 size_t allocSize = sizeof(Block) + size;
29 if (allowSlack) {
30 allocSize = ArenaAllocatorTraits<Alloc>::goodSize(alloc, allocSize);
31 }
32
33 void* mem = std::allocator_traits<Alloc>::allocate(alloc, allocSize);
34 return std::make_pair(new (mem) Block(), allocSize - sizeof(Block));
35}
36
37template <class Alloc>
38void Arena<Alloc>::Block::deallocate(Alloc& alloc) {
39 this->~Block();
40 std::allocator_traits<Alloc>::deallocate(alloc, this, 1);
41}
42
43template <class Alloc>
44void* Arena<Alloc>::allocateSlow(size_t size) {
45 std::pair<Block*, size_t> p;
46 char* start;
47
48 size_t allocSize = std::max(size, minBlockSize()) + sizeof(Block);
49 if (sizeLimit_ != kNoSizeLimit &&
50 allocSize > sizeLimit_ - totalAllocatedSize_) {
51 throw_exception(std::bad_alloc());
52 }
53
54 if (size > minBlockSize()) {
55 // Allocate a large block for this chunk only, put it at the back of the
56 // list so it doesn't get used for small allocations; don't change ptr_
57 // and end_, let them point into a normal block (or none, if they're
58 // null)
59 p = Block::allocate(alloc(), size, false);
60 start = p.first->start();
61 blocks_.push_back(*p.first);
62 } else {
63 // Allocate a normal sized block and carve out size bytes from it
64 p = Block::allocate(alloc(), minBlockSize(), true);
65 start = p.first->start();
66 blocks_.push_front(*p.first);
67 ptr_ = start + size;
68 end_ = start + p.second;
69 }
70
71 assert(p.second >= size);
72 totalAllocatedSize_ += p.second + sizeof(Block);
73 return start;
74}
75
76template <class Alloc>
77void Arena<Alloc>::merge(Arena<Alloc>&& other) {
78 blocks_.splice_after(blocks_.before_begin(), other.blocks_);
79 other.blocks_.clear();
80 other.ptr_ = other.end_ = nullptr;
81 totalAllocatedSize_ += other.totalAllocatedSize_;
82 other.totalAllocatedSize_ = 0;
83}
84
85template <class Alloc>
86Arena<Alloc>::~Arena() {
87 auto disposer = [this](Block* b) { b->deallocate(this->alloc()); };
88 while (!blocks_.empty()) {
89 blocks_.pop_front_and_dispose(disposer);
90 }
91}
92
93} // namespace folly
94