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      1 // Copyright 2012 the V8 project authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #ifndef V8_KEYS_H_
      6 #define V8_KEYS_H_
      7 
      8 #include "src/isolate.h"
      9 #include "src/objects.h"
     10 
     11 namespace v8 {
     12 namespace internal {
     13 
     14 enum AddKeyConversion { DO_NOT_CONVERT, CONVERT_TO_ARRAY_INDEX };
     15 
     16 // This is a helper class for JSReceiver::GetKeys which collects and sorts keys.
     17 // GetKeys needs to sort keys per prototype level, first showing the integer
     18 // indices from elements then the strings from the properties. However, this
     19 // does not apply to proxies which are in full control of how the keys are
     20 // sorted.
     21 //
     22 // For performance reasons the KeyAccumulator internally separates integer keys
     23 // in |elements_| into sorted lists per prototype level. String keys are
     24 // collected in |string_properties_|, a single OrderedHashSet (similar for
     25 // Symbols in |symbol_properties_|. To separate the keys per level later when
     26 // assembling the final list, |levelLengths_| keeps track of the number of
     27 // String and Symbol keys per level.
     28 //
     29 // Only unique keys are kept by the KeyAccumulator, strings are stored in a
     30 // HashSet for inexpensive lookups. Integer keys are kept in sorted lists which
     31 // are more compact and allow for reasonably fast includes check.
     32 class KeyAccumulator final BASE_EMBEDDED {
     33  public:
     34   KeyAccumulator(Isolate* isolate, KeyCollectionMode mode,
     35                  PropertyFilter filter)
     36       : isolate_(isolate), mode_(mode), filter_(filter) {}
     37   ~KeyAccumulator();
     38 
     39   static MaybeHandle<FixedArray> GetKeys(
     40       Handle<JSReceiver> object, KeyCollectionMode mode, PropertyFilter filter,
     41       GetKeysConversion keys_conversion = GetKeysConversion::kKeepNumbers,
     42       bool is_for_in = false);
     43 
     44   Handle<FixedArray> GetKeys(
     45       GetKeysConversion convert = GetKeysConversion::kKeepNumbers);
     46   Maybe<bool> CollectKeys(Handle<JSReceiver> receiver,
     47                           Handle<JSReceiver> object);
     48   Maybe<bool> CollectOwnElementIndices(Handle<JSReceiver> receiver,
     49                                        Handle<JSObject> object);
     50   Maybe<bool> CollectOwnPropertyNames(Handle<JSReceiver> receiver,
     51                                       Handle<JSObject> object);
     52   Maybe<bool> CollectAccessCheckInterceptorKeys(
     53       Handle<AccessCheckInfo> access_check_info, Handle<JSReceiver> receiver,
     54       Handle<JSObject> object);
     55 
     56   // Might return directly the object's enum_cache, copy the result before using
     57   // as an elements backing store for a JSObject.
     58   static Handle<FixedArray> GetOwnEnumPropertyKeys(Isolate* isolate,
     59                                                    Handle<JSObject> object);
     60   void AddKey(Object* key, AddKeyConversion convert = DO_NOT_CONVERT);
     61   void AddKey(Handle<Object> key, AddKeyConversion convert = DO_NOT_CONVERT);
     62   void AddKeys(Handle<FixedArray> array, AddKeyConversion convert);
     63   void AddKeys(Handle<JSObject> array_like, AddKeyConversion convert);
     64 
     65   // Jump to the next level, pushing the current |levelLength_| to
     66   // |levelLengths_| and adding a new list to |elements_|.
     67   Isolate* isolate() { return isolate_; }
     68   // Filter keys based on their property descriptors.
     69   PropertyFilter filter() { return filter_; }
     70   // The collection mode defines whether we collect the keys from the prototype
     71   // chain or only look at the receiver.
     72   KeyCollectionMode mode() { return mode_; }
     73   // In case of for-in loops we have to treat JSProxy keys differently and
     74   // deduplicate them. Additionally we convert JSProxy keys back to array
     75   // indices.
     76   void set_is_for_in(bool value) { is_for_in_ = value; }
     77   void set_skip_indices(bool value) { skip_indices_ = value; }
     78   // The last_non_empty_prototype is used to limit the prototypes for which
     79   // we have to keep track of non-enumerable keys that can shadow keys
     80   // repeated on the prototype chain.
     81   void set_last_non_empty_prototype(Handle<JSReceiver> object) {
     82     last_non_empty_prototype_ = object;
     83   }
     84   // Shadowing keys are used to filter keys. This happens when non-enumerable
     85   // keys appear again on the prototype chain.
     86   void AddShadowingKey(Object* key);
     87   void AddShadowingKey(Handle<Object> key);
     88 
     89  private:
     90   Maybe<bool> CollectOwnKeys(Handle<JSReceiver> receiver,
     91                              Handle<JSObject> object);
     92   Maybe<bool> CollectOwnJSProxyKeys(Handle<JSReceiver> receiver,
     93                                     Handle<JSProxy> proxy);
     94   Maybe<bool> CollectOwnJSProxyTargetKeys(Handle<JSProxy> proxy,
     95                                           Handle<JSReceiver> target);
     96   Maybe<bool> AddKeysFromJSProxy(Handle<JSProxy> proxy,
     97                                  Handle<FixedArray> keys);
     98   bool IsShadowed(Handle<Object> key);
     99   bool HasShadowingKeys();
    100   Handle<OrderedHashSet> keys() { return Handle<OrderedHashSet>::cast(keys_); }
    101 
    102   Isolate* isolate_;
    103   // keys_ is either an Handle<OrderedHashSet> or in the case of own JSProxy
    104   // keys a Handle<FixedArray>. The OrderedHashSet is in-place converted to the
    105   // result list, a FixedArray containing all collected keys.
    106   Handle<FixedArray> keys_;
    107   Handle<JSReceiver> last_non_empty_prototype_;
    108   Handle<ObjectHashSet> shadowing_keys_;
    109   KeyCollectionMode mode_;
    110   PropertyFilter filter_;
    111   bool is_for_in_ = false;
    112   bool skip_indices_ = false;
    113   // For all the keys on the first receiver adding a shadowing key we can skip
    114   // the shadow check.
    115   bool skip_shadow_check_ = true;
    116 
    117   DISALLOW_COPY_AND_ASSIGN(KeyAccumulator);
    118 };
    119 
    120 // The FastKeyAccumulator handles the cases where there are no elements on the
    121 // prototype chain and forwords the complex/slow cases to the normal
    122 // KeyAccumulator. This significantly speeds up the cases where the OWN_ONLY
    123 // case where we do not have to walk the prototype chain.
    124 class FastKeyAccumulator {
    125  public:
    126   FastKeyAccumulator(Isolate* isolate, Handle<JSReceiver> receiver,
    127                      KeyCollectionMode mode, PropertyFilter filter)
    128       : isolate_(isolate), receiver_(receiver), mode_(mode), filter_(filter) {
    129     Prepare();
    130   }
    131 
    132   bool is_receiver_simple_enum() { return is_receiver_simple_enum_; }
    133   bool has_empty_prototype() { return has_empty_prototype_; }
    134   void set_is_for_in(bool value) { is_for_in_ = value; }
    135 
    136   MaybeHandle<FixedArray> GetKeys(
    137       GetKeysConversion convert = GetKeysConversion::kKeepNumbers);
    138 
    139  private:
    140   void Prepare();
    141   MaybeHandle<FixedArray> GetKeysFast(GetKeysConversion convert);
    142   MaybeHandle<FixedArray> GetKeysSlow(GetKeysConversion convert);
    143 
    144   MaybeHandle<FixedArray> GetOwnKeysWithUninitializedEnumCache();
    145 
    146   Isolate* isolate_;
    147   Handle<JSReceiver> receiver_;
    148   Handle<JSReceiver> last_non_empty_prototype_;
    149   KeyCollectionMode mode_;
    150   PropertyFilter filter_;
    151   bool is_for_in_ = false;
    152   bool is_receiver_simple_enum_ = false;
    153   bool has_empty_prototype_ = false;
    154 
    155   DISALLOW_COPY_AND_ASSIGN(FastKeyAccumulator);
    156 };
    157 
    158 }  // namespace internal
    159 }  // namespace v8
    160 
    161 #endif  // V8_KEYS_H_
    162