+++ /dev/null
-/*
- * Copyright 2017 Facebook, Inc.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-#pragma once
-#define FOLLY_ARENA_H_
-
-#include <cassert>
-#include <limits>
-#include <stdexcept>
-#include <utility>
-
-#include <boost/intrusive/slist.hpp>
-
-#include <folly/Conv.h>
-#include <folly/Likely.h>
-#include <folly/Malloc.h>
-#include <folly/Memory.h>
-
-namespace folly {
-
-/**
- * Simple arena: allocate memory which gets freed when the arena gets
- * destroyed.
- *
- * The arena itself allocates memory using a custom allocator which provides
- * the following interface (same as required by StlAllocator in StlAllocator.h)
- *
- * void* allocate(size_t size);
- * Allocate a block of size bytes, properly aligned to the maximum
- * alignment required on your system; throw std::bad_alloc if the
- * allocation can't be satisfied.
- *
- * void deallocate(void* ptr);
- * Deallocate a previously allocated block.
- *
- * You may also specialize ArenaAllocatorTraits for your allocator type to
- * provide:
- *
- * size_t goodSize(const Allocator& alloc, size_t size) const;
- * Return a size (>= the provided size) that is considered "good" for your
- * allocator (for example, if your allocator allocates memory in 4MB
- * chunks, size should be rounded up to 4MB). The provided value is
- * guaranteed to be rounded up to a multiple of the maximum alignment
- * required on your system; the returned value must be also.
- *
- * An implementation that uses malloc() / free() is defined below, see SysArena.
- */
-template <class Alloc> struct ArenaAllocatorTraits;
-template <class Alloc>
-class Arena {
- public:
- explicit Arena(const Alloc& alloc,
- size_t minBlockSize = kDefaultMinBlockSize,
- size_t sizeLimit = kNoSizeLimit,
- size_t maxAlign = kDefaultMaxAlign)
- : allocAndSize_(alloc, minBlockSize)
- , ptr_(nullptr)
- , end_(nullptr)
- , totalAllocatedSize_(0)
- , bytesUsed_(0)
- , sizeLimit_(sizeLimit)
- , maxAlign_(maxAlign) {
- if ((maxAlign_ & (maxAlign_ - 1)) || maxAlign_ > alignof(Block)) {
- throw std::invalid_argument(
- folly::to<std::string>("Invalid maxAlign: ", maxAlign_));
- }
- }
-
- ~Arena();
-
- void* allocate(size_t size) {
- size = roundUp(size);
- bytesUsed_ += size;
-
- assert(ptr_ <= end_);
- if (LIKELY((size_t)(end_ - ptr_) >= size)) {
- // Fast path: there's enough room in the current block
- char* r = ptr_;
- ptr_ += size;
- assert(isAligned(r));
- return r;
- }
-
- // Not enough room in the current block
- void* r = allocateSlow(size);
- assert(isAligned(r));
- return r;
- }
-
- void deallocate(void* /* p */) {
- // Deallocate? Never!
- }
-
- // Transfer ownership of all memory allocated from "other" to "this".
- void merge(Arena&& other);
-
- // Gets the total memory used by the arena
- size_t totalSize() const {
- return totalAllocatedSize_ + sizeof(Arena);
- }
-
- // Gets the total number of "used" bytes, i.e. bytes that the arena users
- // allocated via the calls to `allocate`. Doesn't include fragmentation, e.g.
- // if block size is 4KB and you allocate 2 objects of 3KB in size,
- // `bytesUsed()` will be 6KB, while `totalSize()` will be 8KB+.
- size_t bytesUsed() const {
- return bytesUsed_;
- }
-
- // not copyable
- Arena(const Arena&) = delete;
- Arena& operator=(const Arena&) = delete;
-
- // movable
- Arena(Arena&&) = default;
- Arena& operator=(Arena&&) = default;
-
- private:
- struct Block;
- typedef boost::intrusive::slist_member_hook<
- boost::intrusive::tag<Arena>> BlockLink;
-
- struct FOLLY_ALIGNED_MAX Block {
- BlockLink link;
-
- // Allocate a block with at least size bytes of storage.
- // If allowSlack is true, allocate more than size bytes if convenient
- // (via ArenaAllocatorTraits::goodSize()) as we'll try to pack small
- // allocations in this block.
- static std::pair<Block*, size_t> allocate(
- Alloc& alloc, size_t size, bool allowSlack);
- void deallocate(Alloc& alloc);
-
- char* start() {
- return reinterpret_cast<char*>(this + 1);
- }
-
- private:
- Block() = default;
- ~Block() = default;
- };
-
- public:
- static constexpr size_t kDefaultMinBlockSize = 4096 - sizeof(Block);
- static constexpr size_t kNoSizeLimit = 0;
- static constexpr size_t kDefaultMaxAlign = alignof(Block);
- static constexpr size_t kBlockOverhead = sizeof(Block);
-
- private:
- bool isAligned(uintptr_t address) const {
- return (address & (maxAlign_ - 1)) == 0;
- }
- bool isAligned(void* p) const {
- return isAligned(reinterpret_cast<uintptr_t>(p));
- }
-
- // Round up size so it's properly aligned
- size_t roundUp(size_t size) const {
- return (size + maxAlign_ - 1) & ~(maxAlign_ - 1);
- }
-
- // cache_last<true> makes the list keep a pointer to the last element, so we
- // have push_back() and constant time splice_after()
- typedef boost::intrusive::slist<
- Block,
- boost::intrusive::member_hook<Block, BlockLink, &Block::link>,
- boost::intrusive::constant_time_size<false>,
- boost::intrusive::cache_last<true>> BlockList;
-
- void* allocateSlow(size_t size);
-
- // Empty member optimization: package Alloc with a non-empty member
- // in case Alloc is empty (as it is in the case of SysAlloc).
- struct AllocAndSize : public Alloc {
- explicit AllocAndSize(const Alloc& a, size_t s)
- : Alloc(a), minBlockSize(s) {
- }
-
- size_t minBlockSize;
- };
-
- size_t minBlockSize() const {
- return allocAndSize_.minBlockSize;
- }
- Alloc& alloc() { return allocAndSize_; }
- const Alloc& alloc() const { return allocAndSize_; }
-
- AllocAndSize allocAndSize_;
- BlockList blocks_;
- char* ptr_;
- char* end_;
- size_t totalAllocatedSize_;
- size_t bytesUsed_;
- const size_t sizeLimit_;
- const size_t maxAlign_;
-};
-
-template <class Alloc>
-struct IsArenaAllocator<Arena<Alloc>> : std::true_type { };
-
-/**
- * By default, don't pad the given size.
- */
-template <class Alloc>
-struct ArenaAllocatorTraits {
- static size_t goodSize(const Alloc& /* alloc */, size_t size) { return size; }
-};
-
-template <>
-struct ArenaAllocatorTraits<SysAlloc> {
- static size_t goodSize(const SysAlloc& /* alloc */, size_t size) {
- return goodMallocSize(size);
- }
-};
-
-/**
- * Arena that uses the system allocator (malloc / free)
- */
-class SysArena : public Arena<SysAlloc> {
- public:
- explicit SysArena(size_t minBlockSize = kDefaultMinBlockSize,
- size_t sizeLimit = kNoSizeLimit,
- size_t maxAlign = kDefaultMaxAlign)
- : Arena<SysAlloc>(SysAlloc(), minBlockSize, sizeLimit, maxAlign) {
- }
-};
-
-template <>
-struct IsArenaAllocator<SysArena> : std::true_type { };
-
-} // namespace folly
-
-#include <folly/Arena-inl.h>
projects / folly.git / blobdiff