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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/objects.h"
      9 #include "src/objects/hash-table.h"
     10 #include "src/objects/ordered-hash-table.h"
     11 
     12 namespace v8 {
     13 namespace internal {
     14 
     15 class JSProxy;
     16 
     17 enum AddKeyConversion { DO_NOT_CONVERT, CONVERT_TO_ARRAY_INDEX };
     18 
     19 // This is a helper class for JSReceiver::GetKeys which collects and sorts keys.
     20 // GetKeys needs to sort keys per prototype level, first showing the integer
     21 // indices from elements then the strings from the properties. However, this
     22 // does not apply to proxies which are in full control of how the keys are
     23 // sorted.
     24 //
     25 // For performance reasons the KeyAccumulator internally separates integer keys
     26 // in |elements_| into sorted lists per prototype level. String keys are
     27 // collected in |string_properties_|, a single OrderedHashSet (similar for
     28 // Symbols in |symbol_properties_|. To separate the keys per level later when
     29 // assembling the final list, |levelLengths_| keeps track of the number of
     30 // String and Symbol keys per level.
     31 //
     32 // Only unique keys are kept by the KeyAccumulator, strings are stored in a
     33 // HashSet for inexpensive lookups. Integer keys are kept in sorted lists which
     34 // are more compact and allow for reasonably fast includes check.
     35 class KeyAccumulator final BASE_EMBEDDED {
     36  public:
     37   KeyAccumulator(Isolate* isolate, KeyCollectionMode mode,
     38                  PropertyFilter filter)
     39       : isolate_(isolate), mode_(mode), filter_(filter) {}
     40   ~KeyAccumulator();
     41 
     42   static MaybeHandle<FixedArray> GetKeys(
     43       Handle<JSReceiver> object, KeyCollectionMode mode, PropertyFilter filter,
     44       GetKeysConversion keys_conversion = GetKeysConversion::kKeepNumbers,
     45       bool is_for_in = false, bool skip_indices = false);
     46 
     47   Handle<FixedArray> GetKeys(
     48       GetKeysConversion convert = GetKeysConversion::kKeepNumbers);
     49   Maybe<bool> CollectKeys(Handle<JSReceiver> receiver,
     50                           Handle<JSReceiver> object);
     51   Maybe<bool> CollectOwnElementIndices(Handle<JSReceiver> receiver,
     52                                        Handle<JSObject> object);
     53   Maybe<bool> CollectOwnPropertyNames(Handle<JSReceiver> receiver,
     54                                       Handle<JSObject> object);
     55   Maybe<bool> CollectAccessCheckInterceptorKeys(
     56       Handle<AccessCheckInfo> access_check_info, Handle<JSReceiver> receiver,
     57       Handle<JSObject> object);
     58 
     59   // Might return directly the object's enum_cache, copy the result before using
     60   // as an elements backing store for a JSObject.
     61   // Does not throw for uninitialized exports in module namespace objects, so
     62   // this has to be checked separately.
     63   static Handle<FixedArray> GetOwnEnumPropertyKeys(Isolate* isolate,
     64                                                    Handle<JSObject> object);
     65 
     66   void AddKey(Object* key, AddKeyConversion convert = DO_NOT_CONVERT);
     67   void AddKey(Handle<Object> key, AddKeyConversion convert = DO_NOT_CONVERT);
     68   void AddKeys(Handle<FixedArray> array, AddKeyConversion convert);
     69   void AddKeys(Handle<JSObject> array_like, AddKeyConversion convert);
     70 
     71   // Jump to the next level, pushing the current |levelLength_| to
     72   // |levelLengths_| and adding a new list to |elements_|.
     73   Isolate* isolate() { return isolate_; }
     74   // Filter keys based on their property descriptors.
     75   PropertyFilter filter() { return filter_; }
     76   // The collection mode defines whether we collect the keys from the prototype
     77   // chain or only look at the receiver.
     78   KeyCollectionMode mode() { return mode_; }
     79   // In case of for-in loops we have to treat JSProxy keys differently and
     80   // deduplicate them. Additionally we convert JSProxy keys back to array
     81   // indices.
     82   void set_is_for_in(bool value) { is_for_in_ = value; }
     83   void set_skip_indices(bool value) { skip_indices_ = value; }
     84   // The last_non_empty_prototype is used to limit the prototypes for which
     85   // we have to keep track of non-enumerable keys that can shadow keys
     86   // repeated on the prototype chain.
     87   void set_last_non_empty_prototype(Handle<JSReceiver> object) {
     88     last_non_empty_prototype_ = object;
     89   }
     90   // Shadowing keys are used to filter keys. This happens when non-enumerable
     91   // keys appear again on the prototype chain.
     92   void AddShadowingKey(Object* key);
     93   void AddShadowingKey(Handle<Object> key);
     94 
     95  private:
     96   Maybe<bool> CollectOwnKeys(Handle<JSReceiver> receiver,
     97                              Handle<JSObject> object);
     98   Maybe<bool> CollectOwnJSProxyKeys(Handle<JSReceiver> receiver,
     99                                     Handle<JSProxy> proxy);
    100   Maybe<bool> CollectOwnJSProxyTargetKeys(Handle<JSProxy> proxy,
    101                                           Handle<JSReceiver> target);
    102   Maybe<bool> AddKeysFromJSProxy(Handle<JSProxy> proxy,
    103                                  Handle<FixedArray> keys);
    104   bool IsShadowed(Handle<Object> key);
    105   bool HasShadowingKeys();
    106   Handle<OrderedHashSet> keys();
    107 
    108   Isolate* isolate_;
    109   // keys_ is either an Handle<OrderedHashSet> or in the case of own JSProxy
    110   // keys a Handle<FixedArray>. The OrderedHashSet is in-place converted to the
    111   // result list, a FixedArray containing all collected keys.
    112   Handle<FixedArray> keys_;
    113   Handle<JSReceiver> last_non_empty_prototype_;
    114   Handle<ObjectHashSet> shadowing_keys_;
    115   KeyCollectionMode mode_;
    116   PropertyFilter filter_;
    117   bool is_for_in_ = false;
    118   bool skip_indices_ = false;
    119   // For all the keys on the first receiver adding a shadowing key we can skip
    120   // the shadow check.
    121   bool skip_shadow_check_ = true;
    122 
    123   DISALLOW_COPY_AND_ASSIGN(KeyAccumulator);
    124 };
    125 
    126 // The FastKeyAccumulator handles the cases where there are no elements on the
    127 // prototype chain and forwords the complex/slow cases to the normal
    128 // KeyAccumulator. This significantly speeds up the cases where the OWN_ONLY
    129 // case where we do not have to walk the prototype chain.
    130 class FastKeyAccumulator {
    131  public:
    132   FastKeyAccumulator(Isolate* isolate, Handle<JSReceiver> receiver,
    133                      KeyCollectionMode mode, PropertyFilter filter,
    134                      bool is_for_in = false, bool skip_indices = false)
    135       : isolate_(isolate),
    136         receiver_(receiver),
    137         mode_(mode),
    138         filter_(filter),
    139         is_for_in_(is_for_in),
    140         skip_indices_(skip_indices) {
    141     Prepare();
    142   }
    143 
    144   bool is_receiver_simple_enum() { return is_receiver_simple_enum_; }
    145   bool has_empty_prototype() { return has_empty_prototype_; }
    146 
    147   MaybeHandle<FixedArray> GetKeys(
    148       GetKeysConversion convert = GetKeysConversion::kKeepNumbers);
    149 
    150  private:
    151   void Prepare();
    152   MaybeHandle<FixedArray> GetKeysFast(GetKeysConversion convert);
    153   MaybeHandle<FixedArray> GetKeysSlow(GetKeysConversion convert);
    154 
    155   MaybeHandle<FixedArray> GetOwnKeysWithUninitializedEnumCache();
    156 
    157   Isolate* isolate_;
    158   Handle<JSReceiver> receiver_;
    159   Handle<JSReceiver> last_non_empty_prototype_;
    160   KeyCollectionMode mode_;
    161   PropertyFilter filter_;
    162   bool is_for_in_ = false;
    163   bool skip_indices_ = false;
    164   bool is_receiver_simple_enum_ = false;
    165   bool has_empty_prototype_ = false;
    166 
    167   DISALLOW_COPY_AND_ASSIGN(FastKeyAccumulator);
    168 };
    169 
    170 }  // namespace internal
    171 }  // namespace v8
    172 
    173 #endif  // V8_KEYS_H_
    174