Current File : //usr/local/include/google/protobuf/map.h
// Protocol Buffers - Google's data interchange format
// Copyright 2008 Google Inc. All rights reserved.
// https://developers.google.com/protocol-buffers/
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
// * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
// This file defines the map container and its helpers to support protobuf maps.
//
// The Map and MapIterator types are provided by this header file.
// Please avoid using other types defined here, unless they are public
// types within Map or MapIterator, such as Map::value_type.
#ifndef GOOGLE_PROTOBUF_MAP_H__
#define GOOGLE_PROTOBUF_MAP_H__
#include <functional>
#include <initializer_list>
#include <iterator>
#include <limits> // To support Visual Studio 2008
#include <map>
#include <string>
#include <type_traits>
#include <utility>
#if defined(__cpp_lib_string_view)
#include <string_view>
#endif // defined(__cpp_lib_string_view)
#include <google/protobuf/stubs/common.h>
#include <google/protobuf/arena.h>
#include <google/protobuf/generated_enum_util.h>
#include <google/protobuf/map_type_handler.h>
#include <google/protobuf/stubs/hash.h>
#ifdef SWIG
#error "You cannot SWIG proto headers"
#endif
#include <google/protobuf/port_def.inc>
namespace google {
namespace protobuf {
template <typename Key, typename T>
class Map;
class MapIterator;
template <typename Enum>
struct is_proto_enum;
namespace internal {
template <typename Derived, typename Key, typename T,
WireFormatLite::FieldType key_wire_type,
WireFormatLite::FieldType value_wire_type>
class MapFieldLite;
template <typename Derived, typename Key, typename T,
WireFormatLite::FieldType key_wire_type,
WireFormatLite::FieldType value_wire_type>
class MapField;
template <typename Key, typename T>
class TypeDefinedMapFieldBase;
class DynamicMapField;
class GeneratedMessageReflection;
// re-implement std::allocator to use arena allocator for memory allocation.
// Used for Map implementation. Users should not use this class
// directly.
template <typename U>
class MapAllocator {
public:
using value_type = U;
using pointer = value_type*;
using const_pointer = const value_type*;
using reference = value_type&;
using const_reference = const value_type&;
using size_type = size_t;
using difference_type = ptrdiff_t;
constexpr MapAllocator() : arena_(nullptr) {}
explicit constexpr MapAllocator(Arena* arena) : arena_(arena) {}
template <typename X>
MapAllocator(const MapAllocator<X>& allocator) // NOLINT(runtime/explicit)
: arena_(allocator.arena()) {}
pointer allocate(size_type n, const void* /* hint */ = nullptr) {
// If arena is not given, malloc needs to be called which doesn't
// construct element object.
if (arena_ == nullptr) {
return static_cast<pointer>(::operator new(n * sizeof(value_type)));
} else {
return reinterpret_cast<pointer>(
Arena::CreateArray<uint8>(arena_, n * sizeof(value_type)));
}
}
void deallocate(pointer p, size_type n) {
if (arena_ == nullptr) {
#if defined(__GXX_DELETE_WITH_SIZE__) || defined(__cpp_sized_deallocation)
::operator delete(p, n * sizeof(value_type));
#else
(void)n;
::operator delete(p);
#endif
}
}
#if !defined(GOOGLE_PROTOBUF_OS_APPLE) && !defined(GOOGLE_PROTOBUF_OS_NACL) && \
!defined(GOOGLE_PROTOBUF_OS_EMSCRIPTEN)
template <class NodeType, class... Args>
void construct(NodeType* p, Args&&... args) {
// Clang 3.6 doesn't compile static casting to void* directly. (Issue
// #1266) According C++ standard 5.2.9/1: "The static_cast operator shall
// not cast away constness". So first the maybe const pointer is casted to
// const void* and after the const void* is const casted.
new (const_cast<void*>(static_cast<const void*>(p)))
NodeType(std::forward<Args>(args)...);
}
template <class NodeType>
void destroy(NodeType* p) {
p->~NodeType();
}
#else
void construct(pointer p, const_reference t) { new (p) value_type(t); }
void destroy(pointer p) { p->~value_type(); }
#endif
template <typename X>
struct rebind {
using other = MapAllocator<X>;
};
template <typename X>
bool operator==(const MapAllocator<X>& other) const {
return arena_ == other.arena_;
}
template <typename X>
bool operator!=(const MapAllocator<X>& other) const {
return arena_ != other.arena_;
}
// To support Visual Studio 2008
size_type max_size() const {
// parentheses around (std::...:max) prevents macro warning of max()
return (std::numeric_limits<size_type>::max)();
}
// To support gcc-4.4, which does not properly
// support templated friend classes
Arena* arena() const { return arena_; }
private:
using DestructorSkippable_ = void;
Arena* arena_;
};
template <typename T>
using KeyForTree =
typename std::conditional<std::is_scalar<T>::value, T,
std::reference_wrapper<const T>>::type;
// Default case: Not transparent.
// We use std::hash<key_type>/std::less<key_type> and all the lookup functions
// only accept `key_type`.
template <typename key_type>
struct TransparentSupport {
using hash = std::hash<key_type>;
using less = std::less<key_type>;
static bool Equals(const key_type& a, const key_type& b) { return a == b; }
template <typename K>
using key_arg = key_type;
};
#if defined(__cpp_lib_string_view)
// If std::string_view is available, we add transparent support for std::string
// keys. We use std::hash<std::string_view> as it supports the input types we
// care about. The lookup functions accept arbitrary `K`. This will include any
// key type that is convertible to std::string_view.
template <>
struct TransparentSupport<std::string> {
static std::string_view ImplicitConvert(std::string_view str) { return str; }
// If the element is not convertible to std::string_view, try to convert to
// std::string first.
// The template makes this overload lose resolution when both have the same
// rank otherwise.
template <typename = void>
static std::string_view ImplicitConvert(const std::string& str) {
return str;
}
struct hash : private std::hash<std::string_view> {
using is_transparent = void;
template <typename T>
size_t operator()(const T& str) const {
return base()(ImplicitConvert(str));
}
private:
const std::hash<std::string_view>& base() const { return *this; }
};
struct less {
using is_transparent = void;
template <typename T, typename U>
bool operator()(const T& t, const U& u) const {
return ImplicitConvert(t) < ImplicitConvert(u);
}
};
template <typename T, typename U>
static bool Equals(const T& t, const U& u) {
return ImplicitConvert(t) == ImplicitConvert(u);
}
template <typename K>
using key_arg = K;
};
#endif // defined(__cpp_lib_string_view)
template <typename Key>
using TreeForMap =
std::map<KeyForTree<Key>, void*, typename TransparentSupport<Key>::less,
MapAllocator<std::pair<const KeyForTree<Key>, void*>>>;
inline bool TableEntryIsEmpty(void* const* table, size_t b) {
return table[b] == nullptr;
}
inline bool TableEntryIsNonEmptyList(void* const* table, size_t b) {
return table[b] != nullptr && table[b] != table[b ^ 1];
}
inline bool TableEntryIsTree(void* const* table, size_t b) {
return !TableEntryIsEmpty(table, b) && !TableEntryIsNonEmptyList(table, b);
}
inline bool TableEntryIsList(void* const* table, size_t b) {
return !TableEntryIsTree(table, b);
}
// This captures all numeric types.
inline size_t MapValueSpaceUsedExcludingSelfLong(bool) { return 0; }
inline size_t MapValueSpaceUsedExcludingSelfLong(const std::string& str) {
return StringSpaceUsedExcludingSelfLong(str);
}
template <typename T,
typename = decltype(std::declval<const T&>().SpaceUsedLong())>
size_t MapValueSpaceUsedExcludingSelfLong(const T& message) {
return message.SpaceUsedLong() - sizeof(T);
}
constexpr size_t kGlobalEmptyTableSize = 1;
PROTOBUF_EXPORT extern void* const kGlobalEmptyTable[kGlobalEmptyTableSize];
// Space used for the table, trees, and nodes.
// Does not include the indirect space used. Eg the data of a std::string.
template <typename Key>
PROTOBUF_NOINLINE size_t SpaceUsedInTable(void** table, size_t num_buckets,
size_t num_elements,
size_t sizeof_node) {
size_t size = 0;
// The size of the table.
size += sizeof(void*) * num_buckets;
// All the nodes.
size += sizeof_node * num_elements;
// For each tree, count the overhead of the those nodes.
// Two buckets at a time because we only care about trees.
for (size_t b = 0; b < num_buckets; b += 2) {
if (internal::TableEntryIsTree(table, b)) {
using Tree = TreeForMap<Key>;
Tree* tree = static_cast<Tree*>(table[b]);
// Estimated cost of the red-black tree nodes, 3 pointers plus a
// bool (plus alignment, so 4 pointers).
size += tree->size() *
(sizeof(typename Tree::value_type) + sizeof(void*) * 4);
}
}
return size;
}
template <typename Map,
typename = typename std::enable_if<
!std::is_scalar<typename Map::key_type>::value ||
!std::is_scalar<typename Map::mapped_type>::value>::type>
size_t SpaceUsedInValues(const Map* map) {
size_t size = 0;
for (const auto& v : *map) {
size += internal::MapValueSpaceUsedExcludingSelfLong(v.first) +
internal::MapValueSpaceUsedExcludingSelfLong(v.second);
}
return size;
}
inline size_t SpaceUsedInValues(const void*) { return 0; }
} // namespace internal
// This is the class for Map's internal value_type. Instead of using
// std::pair as value_type, we use this class which provides us more control of
// its process of construction and destruction.
template <typename Key, typename T>
struct MapPair {
using first_type = const Key;
using second_type = T;
MapPair(const Key& other_first, const T& other_second)
: first(other_first), second(other_second) {}
explicit MapPair(const Key& other_first) : first(other_first), second() {}
explicit MapPair(Key&& other_first)
: first(std::move(other_first)), second() {}
MapPair(const MapPair& other) : first(other.first), second(other.second) {}
~MapPair() {}
// Implicitly convertible to std::pair of compatible types.
template <typename T1, typename T2>
operator std::pair<T1, T2>() const { // NOLINT(runtime/explicit)
return std::pair<T1, T2>(first, second);
}
const Key first;
T second;
private:
friend class Arena;
friend class Map<Key, T>;
};
// Map is an associative container type used to store protobuf map
// fields. Each Map instance may or may not use a different hash function, a
// different iteration order, and so on. E.g., please don't examine
// implementation details to decide if the following would work:
// Map<int, int> m0, m1;
// m0[0] = m1[0] = m0[1] = m1[1] = 0;
// assert(m0.begin()->first == m1.begin()->first); // Bug!
//
// Map's interface is similar to std::unordered_map, except that Map is not
// designed to play well with exceptions.
template <typename Key, typename T>
class Map {
public:
using key_type = Key;
using mapped_type = T;
using value_type = MapPair<Key, T>;
using pointer = value_type*;
using const_pointer = const value_type*;
using reference = value_type&;
using const_reference = const value_type&;
using size_type = size_t;
using hasher = typename internal::TransparentSupport<Key>::hash;
constexpr Map() : elements_(nullptr) {}
explicit Map(Arena* arena) : elements_(arena) {}
Map(const Map& other) : Map() { insert(other.begin(), other.end()); }
Map(Map&& other) noexcept : Map() {
if (other.arena() != nullptr) {
*this = other;
} else {
swap(other);
}
}
Map& operator=(Map&& other) noexcept {
if (this != &other) {
if (arena() != other.arena()) {
*this = other;
} else {
swap(other);
}
}
return *this;
}
template <class InputIt>
Map(const InputIt& first, const InputIt& last) : Map() {
insert(first, last);
}
~Map() {}
private:
using Allocator = internal::MapAllocator<void*>;
// InnerMap is a generic hash-based map. It doesn't contain any
// protocol-buffer-specific logic. It is a chaining hash map with the
// additional feature that some buckets can be converted to use an ordered
// container. This ensures O(lg n) bounds on find, insert, and erase, while
// avoiding the overheads of ordered containers most of the time.
//
// The implementation doesn't need the full generality of unordered_map,
// and it doesn't have it. More bells and whistles can be added as needed.
// Some implementation details:
// 1. The hash function has type hasher and the equality function
// equal_to<Key>. We inherit from hasher to save space
// (empty-base-class optimization).
// 2. The number of buckets is a power of two.
// 3. Buckets are converted to trees in pairs: if we convert bucket b then
// buckets b and b^1 will share a tree. Invariant: buckets b and b^1 have
// the same non-null value iff they are sharing a tree. (An alternative
// implementation strategy would be to have a tag bit per bucket.)
// 4. As is typical for hash_map and such, the Keys and Values are always
// stored in linked list nodes. Pointers to elements are never invalidated
// until the element is deleted.
// 5. The trees' payload type is pointer to linked-list node. Tree-converting
// a bucket doesn't copy Key-Value pairs.
// 6. Once we've tree-converted a bucket, it is never converted back. However,
// the items a tree contains may wind up assigned to trees or lists upon a
// rehash.
// 7. The code requires no C++ features from C++14 or later.
// 8. Mutations to a map do not invalidate the map's iterators, pointers to
// elements, or references to elements.
// 9. Except for erase(iterator), any non-const method can reorder iterators.
// 10. InnerMap uses KeyForTree<Key> when using the Tree representation, which
// is either `Key`, if Key is a scalar, or `reference_wrapper<const Key>`
// otherwise. This avoids unnecessary copies of string keys, for example.
class InnerMap : private hasher {
public:
explicit constexpr InnerMap(Arena* arena)
: hasher(),
num_elements_(0),
num_buckets_(internal::kGlobalEmptyTableSize),
seed_(0),
index_of_first_non_null_(internal::kGlobalEmptyTableSize),
table_(const_cast<void**>(internal::kGlobalEmptyTable)),
alloc_(arena) {}
~InnerMap() {
if (alloc_.arena() == nullptr &&
num_buckets_ != internal::kGlobalEmptyTableSize) {
clear();
Dealloc<void*>(table_, num_buckets_);
}
}
private:
enum { kMinTableSize = 8 };
// Linked-list nodes, as one would expect for a chaining hash table.
struct Node {
value_type kv;
Node* next;
};
// Trees. The payload type is a copy of Key, so that we can query the tree
// with Keys that are not in any particular data structure.
// The value is a void* pointing to Node. We use void* instead of Node* to
// avoid code bloat. That way there is only one instantiation of the tree
// class per key type.
using Tree = internal::TreeForMap<Key>;
using TreeIterator = typename Tree::iterator;
static Node* NodeFromTreeIterator(TreeIterator it) {
return static_cast<Node*>(it->second);
}
// iterator and const_iterator are instantiations of iterator_base.
template <typename KeyValueType>
class iterator_base {
public:
using reference = KeyValueType&;
using pointer = KeyValueType*;
// Invariants:
// node_ is always correct. This is handy because the most common
// operations are operator* and operator-> and they only use node_.
// When node_ is set to a non-null value, all the other non-const fields
// are updated to be correct also, but those fields can become stale
// if the underlying map is modified. When those fields are needed they
// are rechecked, and updated if necessary.
iterator_base() : node_(nullptr), m_(nullptr), bucket_index_(0) {}
explicit iterator_base(const InnerMap* m) : m_(m) {
SearchFrom(m->index_of_first_non_null_);
}
// Any iterator_base can convert to any other. This is overkill, and we
// rely on the enclosing class to use it wisely. The standard "iterator
// can convert to const_iterator" is OK but the reverse direction is not.
template <typename U>
explicit iterator_base(const iterator_base<U>& it)
: node_(it.node_), m_(it.m_), bucket_index_(it.bucket_index_) {}
iterator_base(Node* n, const InnerMap* m, size_type index)
: node_(n), m_(m), bucket_index_(index) {}
iterator_base(TreeIterator tree_it, const InnerMap* m, size_type index)
: node_(NodeFromTreeIterator(tree_it)), m_(m), bucket_index_(index) {
// Invariant: iterators that use buckets with trees have an even
// bucket_index_.
GOOGLE_DCHECK_EQ(bucket_index_ % 2, 0u);
}
// Advance through buckets, looking for the first that isn't empty.
// If nothing non-empty is found then leave node_ == nullptr.
void SearchFrom(size_type start_bucket) {
GOOGLE_DCHECK(m_->index_of_first_non_null_ == m_->num_buckets_ ||
m_->table_[m_->index_of_first_non_null_] != nullptr);
node_ = nullptr;
for (bucket_index_ = start_bucket; bucket_index_ < m_->num_buckets_;
bucket_index_++) {
if (m_->TableEntryIsNonEmptyList(bucket_index_)) {
node_ = static_cast<Node*>(m_->table_[bucket_index_]);
break;
} else if (m_->TableEntryIsTree(bucket_index_)) {
Tree* tree = static_cast<Tree*>(m_->table_[bucket_index_]);
GOOGLE_DCHECK(!tree->empty());
node_ = NodeFromTreeIterator(tree->begin());
break;
}
}
}
reference operator*() const { return node_->kv; }
pointer operator->() const { return &(operator*()); }
friend bool operator==(const iterator_base& a, const iterator_base& b) {
return a.node_ == b.node_;
}
friend bool operator!=(const iterator_base& a, const iterator_base& b) {
return a.node_ != b.node_;
}
iterator_base& operator++() {
if (node_->next == nullptr) {
TreeIterator tree_it;
const bool is_list = revalidate_if_necessary(&tree_it);
if (is_list) {
SearchFrom(bucket_index_ + 1);
} else {
GOOGLE_DCHECK_EQ(bucket_index_ & 1, 0u);
Tree* tree = static_cast<Tree*>(m_->table_[bucket_index_]);
if (++tree_it == tree->end()) {
SearchFrom(bucket_index_ + 2);
} else {
node_ = NodeFromTreeIterator(tree_it);
}
}
} else {
node_ = node_->next;
}
return *this;
}
iterator_base operator++(int /* unused */) {
iterator_base tmp = *this;
++*this;
return tmp;
}
// Assumes node_ and m_ are correct and non-null, but other fields may be
// stale. Fix them as needed. Then return true iff node_ points to a
// Node in a list. If false is returned then *it is modified to be
// a valid iterator for node_.
bool revalidate_if_necessary(TreeIterator* it) {
GOOGLE_DCHECK(node_ != nullptr && m_ != nullptr);
// Force bucket_index_ to be in range.
bucket_index_ &= (m_->num_buckets_ - 1);
// Common case: the bucket we think is relevant points to node_.
if (m_->table_[bucket_index_] == static_cast<void*>(node_)) return true;
// Less common: the bucket is a linked list with node_ somewhere in it,
// but not at the head.
if (m_->TableEntryIsNonEmptyList(bucket_index_)) {
Node* l = static_cast<Node*>(m_->table_[bucket_index_]);
while ((l = l->next) != nullptr) {
if (l == node_) {
return true;
}
}
}
// Well, bucket_index_ still might be correct, but probably
// not. Revalidate just to be sure. This case is rare enough that we
// don't worry about potential optimizations, such as having a custom
// find-like method that compares Node* instead of the key.
iterator_base i(m_->find(node_->kv.first, it));
bucket_index_ = i.bucket_index_;
return m_->TableEntryIsList(bucket_index_);
}
Node* node_;
const InnerMap* m_;
size_type bucket_index_;
};
public:
using iterator = iterator_base<value_type>;
using const_iterator = iterator_base<const value_type>;
Arena* arena() const { return alloc_.arena(); }
void Swap(InnerMap* other) {
std::swap(num_elements_, other->num_elements_);
std::swap(num_buckets_, other->num_buckets_);
std::swap(seed_, other->seed_);
std::swap(index_of_first_non_null_, other->index_of_first_non_null_);
std::swap(table_, other->table_);
std::swap(alloc_, other->alloc_);
}
iterator begin() { return iterator(this); }
iterator end() { return iterator(); }
const_iterator begin() const { return const_iterator(this); }
const_iterator end() const { return const_iterator(); }
void clear() {
for (size_type b = 0; b < num_buckets_; b++) {
if (TableEntryIsNonEmptyList(b)) {
Node* node = static_cast<Node*>(table_[b]);
table_[b] = nullptr;
do {
Node* next = node->next;
DestroyNode(node);
node = next;
} while (node != nullptr);
} else if (TableEntryIsTree(b)) {
Tree* tree = static_cast<Tree*>(table_[b]);
GOOGLE_DCHECK(table_[b] == table_[b + 1] && (b & 1) == 0);
table_[b] = table_[b + 1] = nullptr;
typename Tree::iterator tree_it = tree->begin();
do {
Node* node = NodeFromTreeIterator(tree_it);
typename Tree::iterator next = tree_it;
++next;
tree->erase(tree_it);
DestroyNode(node);
tree_it = next;
} while (tree_it != tree->end());
DestroyTree(tree);
b++;
}
}
num_elements_ = 0;
index_of_first_non_null_ = num_buckets_;
}
const hasher& hash_function() const { return *this; }
static size_type max_size() {
return static_cast<size_type>(1) << (sizeof(void**) >= 8 ? 60 : 28);
}
size_type size() const { return num_elements_; }
bool empty() const { return size() == 0; }
template <typename K>
iterator find(const K& k) {
return iterator(FindHelper(k).first);
}
template <typename K>
const_iterator find(const K& k) const {
return FindHelper(k).first;
}
// Insert the key into the map, if not present. In that case, the value will
// be value initialized.
template <typename K>
std::pair<iterator, bool> insert(K&& k) {
std::pair<const_iterator, size_type> p = FindHelper(k);
// Case 1: key was already present.
if (p.first.node_ != nullptr)
return std::make_pair(iterator(p.first), false);
// Case 2: insert.
if (ResizeIfLoadIsOutOfRange(num_elements_ + 1)) {
p = FindHelper(k);
}
const size_type b = p.second; // bucket number
Node* node;
// If K is not key_type, make the conversion to key_type explicit.
using TypeToInit = typename std::conditional<
std::is_same<typename std::decay<K>::type, key_type>::value, K&&,
key_type>::type;
if (alloc_.arena() == nullptr) {
node = new Node{value_type(static_cast<TypeToInit>(std::forward<K>(k))),
nullptr};
} else {
node = Alloc<Node>(1);
Arena::CreateInArenaStorage(
const_cast<Key*>(&node->kv.first), alloc_.arena(),
static_cast<TypeToInit>(std::forward<K>(k)));
Arena::CreateInArenaStorage(&node->kv.second, alloc_.arena());
}
iterator result = InsertUnique(b, node);
++num_elements_;
return std::make_pair(result, true);
}
template <typename K>
value_type& operator[](K&& k) {
return *insert(std::forward<K>(k)).first;
}
void erase(iterator it) {
GOOGLE_DCHECK_EQ(it.m_, this);
typename Tree::iterator tree_it;
const bool is_list = it.revalidate_if_necessary(&tree_it);
size_type b = it.bucket_index_;
Node* const item = it.node_;
if (is_list) {
GOOGLE_DCHECK(TableEntryIsNonEmptyList(b));
Node* head = static_cast<Node*>(table_[b]);
head = EraseFromLinkedList(item, head);
table_[b] = static_cast<void*>(head);
} else {
GOOGLE_DCHECK(TableEntryIsTree(b));
Tree* tree = static_cast<Tree*>(table_[b]);
tree->erase(tree_it);
if (tree->empty()) {
// Force b to be the minimum of b and b ^ 1. This is important
// only because we want index_of_first_non_null_ to be correct.
b &= ~static_cast<size_type>(1);
DestroyTree(tree);
table_[b] = table_[b + 1] = nullptr;
}
}
DestroyNode(item);
--num_elements_;
if (PROTOBUF_PREDICT_FALSE(b == index_of_first_non_null_)) {
while (index_of_first_non_null_ < num_buckets_ &&
table_[index_of_first_non_null_] == nullptr) {
++index_of_first_non_null_;
}
}
}
size_t SpaceUsedInternal() const {
return internal::SpaceUsedInTable<Key>(table_, num_buckets_,
num_elements_, sizeof(Node));
}
private:
const_iterator find(const Key& k, TreeIterator* it) const {
return FindHelper(k, it).first;
}
template <typename K>
std::pair<const_iterator, size_type> FindHelper(const K& k) const {
return FindHelper(k, nullptr);
}
template <typename K>
std::pair<const_iterator, size_type> FindHelper(const K& k,
TreeIterator* it) const {
size_type b = BucketNumber(k);
if (TableEntryIsNonEmptyList(b)) {
Node* node = static_cast<Node*>(table_[b]);
do {
if (internal::TransparentSupport<Key>::Equals(node->kv.first, k)) {
return std::make_pair(const_iterator(node, this, b), b);
} else {
node = node->next;
}
} while (node != nullptr);
} else if (TableEntryIsTree(b)) {
GOOGLE_DCHECK_EQ(table_[b], table_[b ^ 1]);
b &= ~static_cast<size_t>(1);
Tree* tree = static_cast<Tree*>(table_[b]);
auto tree_it = tree->find(k);
if (tree_it != tree->end()) {
if (it != nullptr) *it = tree_it;
return std::make_pair(const_iterator(tree_it, this, b), b);
}
}
return std::make_pair(end(), b);
}
// Insert the given Node in bucket b. If that would make bucket b too big,
// and bucket b is not a tree, create a tree for buckets b and b^1 to share.
// Requires count(*KeyPtrFromNodePtr(node)) == 0 and that b is the correct
// bucket. num_elements_ is not modified.
iterator InsertUnique(size_type b, Node* node) {
GOOGLE_DCHECK(index_of_first_non_null_ == num_buckets_ ||
table_[index_of_first_non_null_] != nullptr);
// In practice, the code that led to this point may have already
// determined whether we are inserting into an empty list, a short list,
// or whatever. But it's probably cheap enough to recompute that here;
// it's likely that we're inserting into an empty or short list.
iterator result;
GOOGLE_DCHECK(find(node->kv.first) == end());
if (TableEntryIsEmpty(b)) {
result = InsertUniqueInList(b, node);
} else if (TableEntryIsNonEmptyList(b)) {
if (PROTOBUF_PREDICT_FALSE(TableEntryIsTooLong(b))) {
TreeConvert(b);
result = InsertUniqueInTree(b, node);
GOOGLE_DCHECK_EQ(result.bucket_index_, b & ~static_cast<size_type>(1));
} else {
// Insert into a pre-existing list. This case cannot modify
// index_of_first_non_null_, so we skip the code to update it.
return InsertUniqueInList(b, node);
}
} else {
// Insert into a pre-existing tree. This case cannot modify
// index_of_first_non_null_, so we skip the code to update it.
return InsertUniqueInTree(b, node);
}
// parentheses around (std::min) prevents macro expansion of min(...)
index_of_first_non_null_ =
(std::min)(index_of_first_non_null_, result.bucket_index_);
return result;
}
// Returns whether we should insert after the head of the list. For
// non-optimized builds, we randomly decide whether to insert right at the
// head of the list or just after the head. This helps add a little bit of
// non-determinism to the map ordering.
bool ShouldInsertAfterHead(void* node) {
#ifdef NDEBUG
(void)node;
return false;
#else
// Doing modulo with a prime mixes the bits more.
return (reinterpret_cast<uintptr_t>(node) ^ seed_) % 13 > 6;
#endif
}
// Helper for InsertUnique. Handles the case where bucket b is a
// not-too-long linked list.
iterator InsertUniqueInList(size_type b, Node* node) {
if (table_[b] != nullptr && ShouldInsertAfterHead(node)) {
Node* first = static_cast<Node*>(table_[b]);
node->next = first->next;
first->next = node;
return iterator(node, this, b);
}
node->next = static_cast<Node*>(table_[b]);
table_[b] = static_cast<void*>(node);
return iterator(node, this, b);
}
// Helper for InsertUnique. Handles the case where bucket b points to a
// Tree.
iterator InsertUniqueInTree(size_type b, Node* node) {
GOOGLE_DCHECK_EQ(table_[b], table_[b ^ 1]);
// Maintain the invariant that node->next is null for all Nodes in Trees.
node->next = nullptr;
return iterator(
static_cast<Tree*>(table_[b])->insert({node->kv.first, node}).first,
this, b & ~static_cast<size_t>(1));
}
// Returns whether it did resize. Currently this is only used when
// num_elements_ increases, though it could be used in other situations.
// It checks for load too low as well as load too high: because any number
// of erases can occur between inserts, the load could be as low as 0 here.
// Resizing to a lower size is not always helpful, but failing to do so can
// destroy the expected big-O bounds for some operations. By having the
// policy that sometimes we resize down as well as up, clients can easily
// keep O(size()) = O(number of buckets) if they want that.
bool ResizeIfLoadIsOutOfRange(size_type new_size) {
const size_type kMaxMapLoadTimes16 = 12; // controls RAM vs CPU tradeoff
const size_type hi_cutoff = num_buckets_ * kMaxMapLoadTimes16 / 16;
const size_type lo_cutoff = hi_cutoff / 4;
// We don't care how many elements are in trees. If a lot are,
// we may resize even though there are many empty buckets. In
// practice, this seems fine.
if (PROTOBUF_PREDICT_FALSE(new_size >= hi_cutoff)) {
if (num_buckets_ <= max_size() / 2) {
Resize(num_buckets_ * 2);
return true;
}
} else if (PROTOBUF_PREDICT_FALSE(new_size <= lo_cutoff &&
num_buckets_ > kMinTableSize)) {
size_type lg2_of_size_reduction_factor = 1;
// It's possible we want to shrink a lot here... size() could even be 0.
// So, estimate how much to shrink by making sure we don't shrink so
// much that we would need to grow the table after a few inserts.
const size_type hypothetical_size = new_size * 5 / 4 + 1;
while ((hypothetical_size << lg2_of_size_reduction_factor) <
hi_cutoff) {
++lg2_of_size_reduction_factor;
}
size_type new_num_buckets = std::max<size_type>(
kMinTableSize, num_buckets_ >> lg2_of_size_reduction_factor);
if (new_num_buckets != num_buckets_) {
Resize(new_num_buckets);
return true;
}
}
return false;
}
// Resize to the given number of buckets.
void Resize(size_t new_num_buckets) {
if (num_buckets_ == internal::kGlobalEmptyTableSize) {
// This is the global empty array.
// Just overwrite with a new one. No need to transfer or free anything.
num_buckets_ = index_of_first_non_null_ = kMinTableSize;
table_ = CreateEmptyTable(num_buckets_);
seed_ = Seed();
return;
}
GOOGLE_DCHECK_GE(new_num_buckets, kMinTableSize);
void** const old_table = table_;
const size_type old_table_size = num_buckets_;
num_buckets_ = new_num_buckets;
table_ = CreateEmptyTable(num_buckets_);
const size_type start = index_of_first_non_null_;
index_of_first_non_null_ = num_buckets_;
for (size_type i = start; i < old_table_size; i++) {
if (internal::TableEntryIsNonEmptyList(old_table, i)) {
TransferList(old_table, i);
} else if (internal::TableEntryIsTree(old_table, i)) {
TransferTree(old_table, i++);
}
}
Dealloc<void*>(old_table, old_table_size);
}
void TransferList(void* const* table, size_type index) {
Node* node = static_cast<Node*>(table[index]);
do {
Node* next = node->next;
InsertUnique(BucketNumber(node->kv.first), node);
node = next;
} while (node != nullptr);
}
void TransferTree(void* const* table, size_type index) {
Tree* tree = static_cast<Tree*>(table[index]);
typename Tree::iterator tree_it = tree->begin();
do {
InsertUnique(BucketNumber(std::cref(tree_it->first).get()),
NodeFromTreeIterator(tree_it));
} while (++tree_it != tree->end());
DestroyTree(tree);
}
Node* EraseFromLinkedList(Node* item, Node* head) {
if (head == item) {
return head->next;
} else {
head->next = EraseFromLinkedList(item, head->next);
return head;
}
}
bool TableEntryIsEmpty(size_type b) const {
return internal::TableEntryIsEmpty(table_, b);
}
bool TableEntryIsNonEmptyList(size_type b) const {
return internal::TableEntryIsNonEmptyList(table_, b);
}
bool TableEntryIsTree(size_type b) const {
return internal::TableEntryIsTree(table_, b);
}
bool TableEntryIsList(size_type b) const {
return internal::TableEntryIsList(table_, b);
}
void TreeConvert(size_type b) {
GOOGLE_DCHECK(!TableEntryIsTree(b) && !TableEntryIsTree(b ^ 1));
Tree* tree =
Arena::Create<Tree>(alloc_.arena(), typename Tree::key_compare(),
typename Tree::allocator_type(alloc_));
size_type count = CopyListToTree(b, tree) + CopyListToTree(b ^ 1, tree);
GOOGLE_DCHECK_EQ(count, tree->size());
table_[b] = table_[b ^ 1] = static_cast<void*>(tree);
}
// Copy a linked list in the given bucket to a tree.
// Returns the number of things it copied.
size_type CopyListToTree(size_type b, Tree* tree) {
size_type count = 0;
Node* node = static_cast<Node*>(table_[b]);
while (node != nullptr) {
tree->insert({node->kv.first, node});
++count;
Node* next = node->next;
node->next = nullptr;
node = next;
}
return count;
}
// Return whether table_[b] is a linked list that seems awfully long.
// Requires table_[b] to point to a non-empty linked list.
bool TableEntryIsTooLong(size_type b) {
const size_type kMaxLength = 8;
size_type count = 0;
Node* node = static_cast<Node*>(table_[b]);
do {
++count;
node = node->next;
} while (node != nullptr);
// Invariant: no linked list ever is more than kMaxLength in length.
GOOGLE_DCHECK_LE(count, kMaxLength);
return count >= kMaxLength;
}
template <typename K>
size_type BucketNumber(const K& k) const {
// We xor the hash value against the random seed so that we effectively
// have a random hash function.
uint64 h = hash_function()(k) ^ seed_;
// We use the multiplication method to determine the bucket number from
// the hash value. The constant kPhi (suggested by Knuth) is roughly
// (sqrt(5) - 1) / 2 * 2^64.
constexpr uint64 kPhi = uint64{0x9e3779b97f4a7c15};
return ((kPhi * h) >> 32) & (num_buckets_ - 1);
}
// Return a power of two no less than max(kMinTableSize, n).
// Assumes either n < kMinTableSize or n is a power of two.
size_type TableSize(size_type n) {
return n < static_cast<size_type>(kMinTableSize)
? static_cast<size_type>(kMinTableSize)
: n;
}
// Use alloc_ to allocate an array of n objects of type U.
template <typename U>
U* Alloc(size_type n) {
using alloc_type = typename Allocator::template rebind<U>::other;
return alloc_type(alloc_).allocate(n);
}
// Use alloc_ to deallocate an array of n objects of type U.
template <typename U>
void Dealloc(U* t, size_type n) {
using alloc_type = typename Allocator::template rebind<U>::other;
alloc_type(alloc_).deallocate(t, n);
}
void DestroyNode(Node* node) {
if (alloc_.arena() == nullptr) {
delete node;
}
}
void DestroyTree(Tree* tree) {
if (alloc_.arena() == nullptr) {
delete tree;
}
}
void** CreateEmptyTable(size_type n) {
GOOGLE_DCHECK(n >= kMinTableSize);
GOOGLE_DCHECK_EQ(n & (n - 1), 0);
void** result = Alloc<void*>(n);
memset(result, 0, n * sizeof(result[0]));
return result;
}
// Return a randomish value.
size_type Seed() const {
// We get a little bit of randomness from the address of the map. The
// lower bits are not very random, due to alignment, so we discard them
// and shift the higher bits into their place.
size_type s = reinterpret_cast<uintptr_t>(this) >> 12;
#if defined(__x86_64__) && defined(__GNUC__) && \
!defined(GOOGLE_PROTOBUF_NO_RDTSC)
uint32 hi, lo;
asm volatile("rdtsc" : "=a"(lo), "=d"(hi));
s += ((static_cast<uint64>(hi) << 32) | lo);
#endif
return s;
}
friend class Arena;
using InternalArenaConstructable_ = void;
using DestructorSkippable_ = void;
size_type num_elements_;
size_type num_buckets_;
size_type seed_;
size_type index_of_first_non_null_;
void** table_; // an array with num_buckets_ entries
Allocator alloc_;
GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(InnerMap);
}; // end of class InnerMap
template <typename LookupKey>
using key_arg = typename internal::TransparentSupport<
key_type>::template key_arg<LookupKey>;
public:
// Iterators
class const_iterator {
using InnerIt = typename InnerMap::const_iterator;
public:
using iterator_category = std::forward_iterator_tag;
using value_type = typename Map::value_type;
using difference_type = ptrdiff_t;
using pointer = const value_type*;
using reference = const value_type&;
const_iterator() {}
explicit const_iterator(const InnerIt& it) : it_(it) {}
const_reference operator*() const { return *it_; }
const_pointer operator->() const { return &(operator*()); }
const_iterator& operator++() {
++it_;
return *this;
}
const_iterator operator++(int) { return const_iterator(it_++); }
friend bool operator==(const const_iterator& a, const const_iterator& b) {
return a.it_ == b.it_;
}
friend bool operator!=(const const_iterator& a, const const_iterator& b) {
return !(a == b);
}
private:
InnerIt it_;
};
class iterator {
using InnerIt = typename InnerMap::iterator;
public:
using iterator_category = std::forward_iterator_tag;
using value_type = typename Map::value_type;
using difference_type = ptrdiff_t;
using pointer = value_type*;
using reference = value_type&;
iterator() {}
explicit iterator(const InnerIt& it) : it_(it) {}
reference operator*() const { return *it_; }
pointer operator->() const { return &(operator*()); }
iterator& operator++() {
++it_;
return *this;
}
iterator operator++(int) { return iterator(it_++); }
// Allow implicit conversion to const_iterator.
operator const_iterator() const { // NOLINT(runtime/explicit)
return const_iterator(typename InnerMap::const_iterator(it_));
}
friend bool operator==(const iterator& a, const iterator& b) {
return a.it_ == b.it_;
}
friend bool operator!=(const iterator& a, const iterator& b) {
return !(a == b);
}
private:
friend class Map;
InnerIt it_;
};
iterator begin() { return iterator(elements_.begin()); }
iterator end() { return iterator(elements_.end()); }
const_iterator begin() const { return const_iterator(elements_.begin()); }
const_iterator end() const { return const_iterator(elements_.end()); }
const_iterator cbegin() const { return begin(); }
const_iterator cend() const { return end(); }
// Capacity
size_type size() const { return elements_.size(); }
bool empty() const { return size() == 0; }
// Element access
template <typename K = key_type>
T& operator[](const key_arg<K>& key) {
return elements_[key].second;
}
template <
typename K = key_type,
// Disable for integral types to reduce code bloat.
typename = typename std::enable_if<!std::is_integral<K>::value>::type>
T& operator[](key_arg<K>&& key) {
return elements_[std::forward<K>(key)].second;
}
template <typename K = key_type>
const T& at(const key_arg<K>& key) const {
const_iterator it = find(key);
GOOGLE_CHECK(it != end()) << "key not found: " << static_cast<Key>(key);
return it->second;
}
template <typename K = key_type>
T& at(const key_arg<K>& key) {
iterator it = find(key);
GOOGLE_CHECK(it != end()) << "key not found: " << static_cast<Key>(key);
return it->second;
}
// Lookup
template <typename K = key_type>
size_type count(const key_arg<K>& key) const {
return find(key) == end() ? 0 : 1;
}
template <typename K = key_type>
const_iterator find(const key_arg<K>& key) const {
return const_iterator(elements_.find(key));
}
template <typename K = key_type>
iterator find(const key_arg<K>& key) {
return iterator(elements_.find(key));
}
template <typename K = key_type>
bool contains(const key_arg<K>& key) const {
return find(key) != end();
}
template <typename K = key_type>
std::pair<const_iterator, const_iterator> equal_range(
const key_arg<K>& key) const {
const_iterator it = find(key);
if (it == end()) {
return std::pair<const_iterator, const_iterator>(it, it);
} else {
const_iterator begin = it++;
return std::pair<const_iterator, const_iterator>(begin, it);
}
}
template <typename K = key_type>
std::pair<iterator, iterator> equal_range(const key_arg<K>& key) {
iterator it = find(key);
if (it == end()) {
return std::pair<iterator, iterator>(it, it);
} else {
iterator begin = it++;
return std::pair<iterator, iterator>(begin, it);
}
}
// insert
std::pair<iterator, bool> insert(const value_type& value) {
std::pair<typename InnerMap::iterator, bool> p =
elements_.insert(value.first);
if (p.second) {
p.first->second = value.second;
}
return std::pair<iterator, bool>(iterator(p.first), p.second);
}
template <class InputIt>
void insert(InputIt first, InputIt last) {
for (InputIt it = first; it != last; ++it) {
iterator exist_it = find(it->first);
if (exist_it == end()) {
operator[](it->first) = it->second;
}
}
}
void insert(std::initializer_list<value_type> values) {
insert(values.begin(), values.end());
}
// Erase and clear
template <typename K = key_type>
size_type erase(const key_arg<K>& key) {
iterator it = find(key);
if (it == end()) {
return 0;
} else {
erase(it);
return 1;
}
}
iterator erase(iterator pos) {
iterator i = pos++;
elements_.erase(i.it_);
return pos;
}
void erase(iterator first, iterator last) {
while (first != last) {
first = erase(first);
}
}
void clear() { elements_.clear(); }
// Assign
Map& operator=(const Map& other) {
if (this != &other) {
clear();
insert(other.begin(), other.end());
}
return *this;
}
void swap(Map& other) {
if (arena() == other.arena()) {
InternalSwap(other);
} else {
// TODO(zuguang): optimize this. The temporary copy can be allocated
// in the same arena as the other message, and the "other = copy" can
// be replaced with the fast-path swap above.
Map copy = *this;
*this = other;
other = copy;
}
}
void InternalSwap(Map& other) { elements_.Swap(&other.elements_); }
// Access to hasher. Currently this returns a copy, but it may
// be modified to return a const reference in the future.
hasher hash_function() const { return elements_.hash_function(); }
size_t SpaceUsedExcludingSelfLong() const {
if (empty()) return 0;
return elements_.SpaceUsedInternal() + internal::SpaceUsedInValues(this);
}
private:
Arena* arena() const { return elements_.arena(); }
InnerMap elements_;
friend class Arena;
using InternalArenaConstructable_ = void;
using DestructorSkippable_ = void;
template <typename Derived, typename K, typename V,
internal::WireFormatLite::FieldType key_wire_type,
internal::WireFormatLite::FieldType value_wire_type>
friend class internal::MapFieldLite;
};
} // namespace protobuf
} // namespace google
#include <google/protobuf/port_undef.inc>
#endif // GOOGLE_PROTOBUF_MAP_H__
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