Ldong/IM
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity
IM/include/google/protobuf/map.h

1283 lines
45 KiB
C++
Raw Blame History

// 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 <initializer_list>
#include <iterator>
#include <limits> // To support Visual Studio 2008
#include <set>
#include <type_traits>
#include <utility>
#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, int default_enum_value>
class MapFieldLite;
template <typename Derived, typename Key, typename T,
WireFormatLite::FieldType key_wire_type,
WireFormatLite::FieldType value_wire_type, int default_enum_value>
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;
MapAllocator() : arena_(nullptr) {}
explicit 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 __cplusplus >= 201103L && !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* const arena_;
};
template <typename Key>
struct DerefCompare {
bool operator()(const Key* n0, const Key* n1) const { return *n0 < *n1; }
};
// This class is used to get trivially destructible views of std::string and
// MapKey, which are the only non-trivially destructible allowed key types.
template <typename Key>
class KeyView {
public:
KeyView(const Key& key) : key_(&key) {} // NOLINT(runtime/explicit)
const Key& get() const { return *key_; }
// Allows implicit conversions to `const Key&`, which allows us to use the
// hasher defined for Key.
operator const Key&() const { return get(); } // NOLINT(runtime/explicit)
bool operator==(const KeyView& other) const { return get() == other.get(); }
bool operator==(const Key& other) const { return get() == other; }
bool operator<(const KeyView& other) const { return get() < other.get(); }
bool operator<(const Key& other) const { return get() < other; }
private:
const Key* key_;
};
// Allows the InnerMap type to support skippable destruction.
template <typename Key>
struct GetTrivialKey {
using type =
typename std::conditional<std::is_trivially_destructible<Key>::value, Key,
KeyView<Key>>::type;
};
} // 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() {}
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 = hash<Key>;
Map() : arena_(nullptr), default_enum_value_(0) { Init(); }
explicit Map(Arena* arena) : arena_(arena), default_enum_value_(0) { Init(); }
Map(const Map& other)
: arena_(nullptr), default_enum_value_(other.default_enum_value_) {
Init();
insert(other.begin(), other.end());
}
Map(Map&& other) noexcept : Map() {
if (other.arena_) {
*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)
: arena_(nullptr), default_enum_value_(0) {
Init();
insert(first, last);
}
~Map() {
clear();
if (arena_ == nullptr) {
delete elements_;
}
}
private:
void Init() { elements_ = Arena::CreateMessage<InnerMap>(arena_, 0u); }
// InnerMap's key type is TrivialKey and its value type is value_type*. We
// use a custom class here and for Node, below, to ensure that k_ is at offset
// 0, allowing safe conversion from pointer to Node to pointer to TrivialKey,
// and vice versa when appropriate. We use GetTrivialKey to adapt Key to
// be a trivially destructible view if Key is not already trivially
// destructible. This view points into the Key inside v_ once it's
// initialized.
using TrivialKey = typename internal::GetTrivialKey<Key>::type;
class KeyValuePair {
public:
KeyValuePair(const TrivialKey& k, value_type* v) : k_(k), v_(v) {}
const TrivialKey& key() const { return k_; }
TrivialKey& key() { return k_; }
value_type* value() const { return v_; }
value_type*& value() { return v_; }
private:
TrivialKey k_;
value_type* v_;
};
using Allocator = internal::MapAllocator<KeyValuePair>;
// 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's key is TrivialKey, which is either Key, if Key is trivially
// destructible, or a trivially destructible view of Key otherwise. This
// allows InnerMap's destructor to be skipped when InnerMap is
// arena-allocated.
class InnerMap : private hasher {
public:
using Value = value_type*;
explicit InnerMap(size_type n) : InnerMap(nullptr, n) {}
InnerMap(Arena* arena, size_type n)
: hasher(),
num_elements_(0),
seed_(Seed()),
table_(nullptr),
alloc_(arena) {
n = TableSize(n);
table_ = CreateEmptyTable(n);
num_buckets_ = index_of_first_non_null_ = n;
static_assert(
std::is_trivially_destructible<KeyValuePair>::value,
"We require KeyValuePair to be trivially destructible so that we can "
"skip InnerMap's destructor when it's arena allocated.");
}
~InnerMap() {
if (table_ != nullptr) {
clear();
Dealloc<void*>(table_, num_buckets_);
}
}
private:
enum { kMinTableSize = 8 };
// Linked-list nodes, as one would expect for a chaining hash table.
struct Node {
KeyValuePair kv;
Node* next;
};
// This is safe only if the given pointer is known to point to a Key that is
// part of a Node.
static Node* NodePtrFromKeyPtr(TrivialKey* k) {
return reinterpret_cast<Node*>(k);
}
static TrivialKey* KeyPtrFromNodePtr(Node* node) { return &node->kv.key(); }
// Trees. The payload type is pointer to Key, so that we can query the tree
// with Keys that are not in any particular data structure. When we insert,
// though, the pointer is always pointing to a Key that is inside a Node.
using KeyPtrAllocator =
typename Allocator::template rebind<TrivialKey*>::other;
using Tree = std::set<TrivialKey*, internal::DerefCompare<TrivialKey>,
KeyPtrAllocator>;
using TreeIterator = typename Tree::iterator;
// 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_(NodePtrFromKeyPtr(*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_ = NodePtrFromKeyPtr(*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_ = NodePtrFromKeyPtr(*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 TrivialKey.
iterator_base i(m_->find(*KeyPtrFromNodePtr(node_), 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<KeyValuePair>;
using const_iterator = iterator_base<const KeyValuePair>;
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 = NodePtrFromKeyPtr(*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; }
iterator find(const TrivialKey& k) { return iterator(FindHelper(k).first); }
const_iterator find(const TrivialKey& k) const { return find(k, nullptr); }
bool contains(const TrivialKey& k) const { return find(k) != end(); }
// In traditional C++ style, this performs "insert if not present."
std::pair<iterator, bool> insert(const KeyValuePair& kv) {
std::pair<const_iterator, size_type> p = FindHelper(kv.key());
// 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(kv.key());
}
const size_type b = p.second; // bucket number
Node* node = Alloc<Node>(1);
alloc_.construct(&node->kv, kv);
iterator result = InsertUnique(b, node);
++num_elements_;
return std::make_pair(result, true);
}
// The same, but if an insertion is necessary then the value portion of the
// inserted key-value pair is left uninitialized.
std::pair<iterator, bool> insert(const TrivialKey& 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 = Alloc<Node>(1);
using KeyAllocator =
typename Allocator::template rebind<TrivialKey>::other;
KeyAllocator(alloc_).construct(&node->kv.key(), k);
iterator result = InsertUnique(b, node);
++num_elements_;
return std::make_pair(result, true);
}
// Returns iterator so that outer map can update the TrivialKey to point to
// the Key inside value_type in case TrivialKey is a view type.
iterator operator[](const TrivialKey& k) {
KeyValuePair kv(k, Value());
return insert(kv).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_;
}
}
}
private:
const_iterator find(const TrivialKey& k, TreeIterator* it) const {
return FindHelper(k, it).first;
}
std::pair<const_iterator, size_type> FindHelper(const TrivialKey& k) const {
return FindHelper(k, nullptr);
}
std::pair<const_iterator, size_type> FindHelper(const TrivialKey& k,
TreeIterator* it) const {
size_type b = BucketNumber(k);
if (TableEntryIsNonEmptyList(b)) {
Node* node = static_cast<Node*>(table_[b]);
do {
if (IsMatch(*KeyPtrFromNodePtr(node), 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]);
TrivialKey* key = const_cast<TrivialKey*>(&k);
typename Tree::iterator tree_it = tree->find(key);
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(*KeyPtrFromNodePtr(node)) == 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;
}
// Helper for InsertUnique. Handles the case where bucket b is a
// not-too-long linked list.
iterator InsertUniqueInList(size_type b, Node* node) {
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(KeyPtrFromNodePtr(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) {
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 (TableEntryIsNonEmptyList(old_table, i)) {
TransferList(old_table, i);
} else if (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(*KeyPtrFromNodePtr(node)), 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 {
Node* node = NodePtrFromKeyPtr(*tree_it);
InsertUnique(BucketNumber(**tree_it), node);
} 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 TableEntryIsEmpty(table_, b);
}
bool TableEntryIsNonEmptyList(size_type b) const {
return TableEntryIsNonEmptyList(table_, b);
}
bool TableEntryIsTree(size_type b) const {
return TableEntryIsTree(table_, b);
}
bool TableEntryIsList(size_type b) const {
return TableEntryIsList(table_, b);
}
static bool TableEntryIsEmpty(void* const* table, size_type b) {
return table[b] == nullptr;
}
static bool TableEntryIsNonEmptyList(void* const* table, size_type b) {
return table[b] != nullptr && table[b] != table[b ^ 1];
}
static bool TableEntryIsTree(void* const* table, size_type b) {
return !TableEntryIsEmpty(table, b) &&
!TableEntryIsNonEmptyList(table, b);
}
static bool TableEntryIsList(void* const* table, size_type b) {
return !TableEntryIsTree(table, b);
}
void TreeConvert(size_type b) {
GOOGLE_DCHECK(!TableEntryIsTree(b) && !TableEntryIsTree(b ^ 1));
typename Allocator::template rebind<Tree>::other tree_allocator(alloc_);
Tree* tree = tree_allocator.allocate(1);
// We want to use the three-arg form of construct, if it exists, but we
// create a temporary and use the two-arg construct that's known to exist.
// It's clunky, but the compiler should be able to generate more-or-less
// the same code.
tree_allocator.construct(
tree, Tree(typename Tree::key_compare(), KeyPtrAllocator(alloc_)));
// Now the tree is ready to use.
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(KeyPtrFromNodePtr(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;
}
size_type BucketNumber(const TrivialKey& k) const {
size_type h = hash_function()(k);
return (h + seed_) & (num_buckets_ - 1);
}
bool IsMatch(const TrivialKey& k0, const TrivialKey& k1) const {
return k0 == k1;
}
// 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) {
alloc_.destroy(&node->kv);
Dealloc<Node>(node, 1);
}
void DestroyTree(Tree* tree) {
typename Allocator::template rebind<Tree>::other tree_allocator(alloc_);
tree_allocator.destroy(tree);
tree_allocator.deallocate(tree, 1);
}
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 {
size_type s = static_cast<size_type>(reinterpret_cast<uintptr_t>(this));
#if defined(__x86_64__) && defined(__GNUC__) && \
!defined(GOOGLE_PROTOBUF_NO_RDTSC)
uint32 hi, lo;
asm("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
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_->value(); }
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_->value(); }
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(iterator(elements_->begin()));
}
const_iterator end() const {
return const_iterator(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
T& operator[](const key_type& key) {
typename InnerMap::iterator it = (*elements_)[key];
value_type** value = &it->value();
if (*value == nullptr) {
*value = CreateValueTypeInternal(key);
// We need to update the key in case it's a view type.
it->key() = (*value)->first;
internal::MapValueInitializer<is_proto_enum<T>::value, T>::Initialize(
(*value)->second, default_enum_value_);
}
return (*value)->second;
}
const T& at(const key_type& key) const {
const_iterator it = find(key);
GOOGLE_CHECK(it != end()) << "key not found: " << key;
return it->second;
}
T& at(const key_type& key) {
iterator it = find(key);
GOOGLE_CHECK(it != end()) << "key not found: " << key;
return it->second;
}
// Lookup
size_type count(const key_type& key) const {
const_iterator it = find(key);
GOOGLE_DCHECK(it == end() || key == it->first);
return it == end() ? 0 : 1;
}
const_iterator find(const key_type& key) const {
return const_iterator(iterator(elements_->find(key)));
}
iterator find(const key_type& key) { return iterator(elements_->find(key)); }
bool contains(const Key& key) const { return elements_->contains(key); }
std::pair<const_iterator, const_iterator> equal_range(
const key_type& 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);
}
}
std::pair<iterator, iterator> equal_range(const key_type& 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->value() = CreateValueTypeInternal(value);
// We need to update the key in case it's a view type.
p.first->key() = p.first->value()->first;
}
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
size_type erase(const key_type& key) {
iterator it = find(key);
if (it == end()) {
return 0;
} else {
erase(it);
return 1;
}
}
iterator erase(iterator pos) {
value_type* value = pos.operator->();
iterator i = pos++;
elements_->erase(i.it_);
// Note: we need to delete the value after erasing from the inner map
// because the inner map's key may be a view of the value's key.
if (arena_ == nullptr) delete value;
return pos;
}
void erase(iterator first, iterator last) {
while (first != last) {
first = erase(first);
}
}
void clear() { erase(begin(), end()); }
// 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_) {
std::swap(default_enum_value_, other.default_enum_value_);
std::swap(elements_, other.elements_);
} 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;
}
}
// 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(); }
private:
// Set default enum value only for proto2 map field whose value is enum type.
void SetDefaultEnumValue(int default_enum_value) {
default_enum_value_ = default_enum_value;
}
value_type* CreateValueTypeInternal(const Key& key) {
if (arena_ == nullptr) {
return new value_type(key);
} else {
value_type* value = reinterpret_cast<value_type*>(
Arena::CreateArray<uint8>(arena_, sizeof(value_type)));
Arena::CreateInArenaStorage(const_cast<Key*>(&value->first), arena_, key);
Arena::CreateInArenaStorage(&value->second, arena_);
return value;
}
}
value_type* CreateValueTypeInternal(const value_type& value) {
if (arena_ == nullptr) {
return new value_type(value);
} else {
value_type* p = reinterpret_cast<value_type*>(
Arena::CreateArray<uint8>(arena_, sizeof(value_type)));
Arena::CreateInArenaStorage(const_cast<Key*>(&p->first), arena_,
value.first);
Arena::CreateInArenaStorage(&p->second, arena_);
p->second = value.second;
return p;
}
}
Arena* arena_;
int default_enum_value_;
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,
int default_enum_value>
friend class internal::MapFieldLite;
};
} // namespace protobuf
} // namespace google
#include <google/protobuf/port_undef.inc>
#endif // GOOGLE_PROTOBUF_MAP_H__
Reference in New Issue View Git Blame Copy Permalink