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// Copyright 2015 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "src/base/functional.h"
#include "src/handles/handles.h"
#include "src/objects/heap-object.h"
namespace v8 {
namespace internal {
// Forward declarations.
class Heap;
// Base class of identity maps contains shared code for all template
// instantions.
class V8_EXPORT_PRIVATE IdentityMapBase {
bool empty() const { return size_ == 0; }
int size() const { return size_; }
int capacity() const { return capacity_; }
bool is_iterable() const { return is_iterable_; }
// Allow Tester to access internals, including changing the address of objects
// within the {keys_} array in order to simulate a moving GC.
friend class IdentityMapTester;
using RawEntry = void**;
explicit IdentityMapBase(Heap* heap)
: heap_(heap),
is_iterable_(false) {}
virtual ~IdentityMapBase();
RawEntry GetEntry(Address key);
RawEntry FindEntry(Address key) const;
bool DeleteEntry(Address key, void** deleted_value);
void Clear();
Address KeyAtIndex(int index) const;
RawEntry EntryAtIndex(int index) const;
int NextIndex(int index) const;
void EnableIteration();
void DisableIteration();
virtual void** NewPointerArray(size_t length) = 0;
virtual void DeleteArray(void* array) = 0;
// Internal implementation should not be called directly by subclasses.
int ScanKeysFor(Address address) const;
int InsertKey(Address address);
int Lookup(Address key) const;
int LookupOrInsert(Address key);
bool DeleteIndex(int index, void** deleted_value);
void Rehash();
void Resize(int new_capacity);
int Hash(Address address) const;
base::hash<uintptr_t> hasher_;
Heap* heap_;
int gc_counter_;
int size_;
int capacity_;
int mask_;
Address* keys_;
void** values_;
bool is_iterable_;
// Implements an identity map from object addresses to a given value type {V}.
// The map is robust w.r.t. garbage collection by synchronization with the
// supplied {heap}.
// * Keys are treated as strong roots.
// * The value type {V} must be reinterpret_cast'able to {void*}
// * The value type {V} must not be a heap type.
template <typename V, class AllocationPolicy>
class IdentityMap : public IdentityMapBase {
explicit IdentityMap(Heap* heap,
AllocationPolicy allocator = AllocationPolicy())
: IdentityMapBase(heap), allocator_(allocator) {}
~IdentityMap() override { Clear(); }
// Searches this map for the given key using the object's address
// as the identity, returning:
// found => a pointer to the storage location for the value
// not found => a pointer to a new storage location for the value
V* Get(Handle<Object> key) { return Get(*key); }
V* Get(Object key) { return reinterpret_cast<V*>(GetEntry(key.ptr())); }
// Searches this map for the given key using the object's address
// as the identity, returning:
// found => a pointer to the storage location for the value
// not found => {nullptr}
V* Find(Handle<Object> key) const { return Find(*key); }
V* Find(Object key) const {
return reinterpret_cast<V*>(FindEntry(key.ptr()));
// Set the value for the given key.
void Set(Handle<Object> key, V v) { Set(*key, v); }
void Set(Object key, V v) {
*(reinterpret_cast<V*>(GetEntry(key.ptr()))) = v;
bool Delete(Handle<Object> key, V* deleted_value) {
return Delete(*key, deleted_value);
bool Delete(Object key, V* deleted_value) {
void* v = nullptr;
bool deleted_something = DeleteEntry(key.ptr(), &v);
if (deleted_value != nullptr && deleted_something) {
*deleted_value = *reinterpret_cast<V*>(&v);
return deleted_something;
// Removes all elements from the map.
void Clear() { IdentityMapBase::Clear(); }
// Iterator over IdentityMap. The IteratableScope used to create this Iterator
// must be live for the duration of the iteration.
class Iterator {
Iterator& operator++() {
index_ = map_->NextIndex(index_);
return *this;
Object key() const { return Object(map_->KeyAtIndex(index_)); }
V* entry() const {
return reinterpret_cast<V*>(map_->EntryAtIndex(index_));
V* operator*() { return entry(); }
V* operator->() { return entry(); }
bool operator!=(const Iterator& other) { return index_ != other.index_; }
Iterator(IdentityMap* map, int index) : map_(map), index_(index) {}
IdentityMap* map_;
int index_;
friend class IdentityMap;
class IteratableScope {
explicit IteratableScope(IdentityMap* map) : map_(map) {
~IteratableScope() {
Iterator begin() { return Iterator(map_, map_->NextIndex(-1)); }
Iterator end() { return Iterator(map_, map_->capacity()); }
IdentityMap* map_;
void** NewPointerArray(size_t length) override {
return static_cast<void**>(allocator_.New(sizeof(void*) * length));
void DeleteArray(void* array) override { allocator_.Delete(array); }
AllocationPolicy allocator_;
} // namespace internal
} // namespace v8