js/src/gc/WeakMapPtr.cpp

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
   2  * vim: set ts=8 sts=2 et sw=2 tw=80:
   3  * This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #include "js/WeakMapPtr.h"
   8
   9 #include "gc/WeakMap-inl.h"
  10
  11 //
  12 // Machinery for the externally-linkable JS::WeakMapPtr, which wraps js::WeakMap
  13 // for a few public data types.
  14 //
  15
  16 using namespace js;
  17
  18 namespace WeakMapDetails {
  19
  20 template <typename T>
  21 struct DataType {};
  22
  23 template <>
  24 struct DataType<JSObject*> {
  25   using BarrieredType = HeapPtr<JSObject*>;
  26   using HasherType = StableCellHasher<BarrieredType>;
  27   static JSObject* NullValue() { return nullptr; }
  28 };
  29
  30 template <>
  31 struct DataType<JS::Value> {
  32   using BarrieredType = HeapPtr<Value>;
  33   static JS::Value NullValue() { return JS::UndefinedValue(); }
  34 };
  35
  36 template <typename K, typename V>
  37 struct Utils {
  38   using KeyType = typename DataType<K>::BarrieredType;
  39   using ValueType = typename DataType<V>::BarrieredType;
  40   using Type = WeakMap<KeyType, ValueType>;
  41   using PtrType = Type*;
  42   static PtrType cast(void* ptr) { return static_cast<PtrType>(ptr); }
  43 };
  44
  45 }  // namespace WeakMapDetails
  46
  47 template <typename K, typename V>
  48 void JS::WeakMapPtr<K, V>::destroy() {
  49   MOZ_ASSERT(initialized());
  50   js_delete(WeakMapDetails::Utils<K, V>::cast(ptr));
  51   ptr = nullptr;
  52 }
  53
  54 template <typename K, typename V>
  55 bool JS::WeakMapPtr<K, V>::init(JSContext* cx) {
  56   MOZ_ASSERT(!initialized());
  57   typename WeakMapDetails::Utils<K, V>::PtrType map =
  58       cx->new_<typename WeakMapDetails::Utils<K, V>::Type>(cx);
  59   if (!map) {
  60     return false;
  61   }
  62   ptr = map;
  63   return true;
  64 }
  65
  66 template <typename K, typename V>
  67 void JS::WeakMapPtr<K, V>::trace(JSTracer* trc) {
  68   MOZ_ASSERT(initialized());
  69   return WeakMapDetails::Utils<K, V>::cast(ptr)->trace(trc);
  70 }
  71
  72 template <typename K, typename V>
  73 V JS::WeakMapPtr<K, V>::lookup(const K& key) {
  74   MOZ_ASSERT(initialized());
  75   typename WeakMapDetails::Utils<K, V>::Type::Ptr result =
  76       WeakMapDetails::Utils<K, V>::cast(ptr)->lookup(key);
  77   if (!result) {
  78     return WeakMapDetails::DataType<V>::NullValue();
  79   }
  80   return result->value();
  81 }
  82
  83 template <typename K, typename V>
  84 bool JS::WeakMapPtr<K, V>::put(JSContext* cx, const K& key, const V& value) {
  85   MOZ_ASSERT(initialized());
  86   return WeakMapDetails::Utils<K, V>::cast(ptr)->put(key, value);
  87 }
  88
  89 template <typename K, typename V>
  90 V JS::WeakMapPtr<K, V>::removeValue(const K& key) {
  91   using Map = typename WeakMapDetails::Utils<K, V>::Type;
  92   using Ptr = typename Map::Ptr;
  93
  94   MOZ_ASSERT(initialized());
  95
  96   Map* map = WeakMapDetails::Utils<K, V>::cast(ptr);
  97   if (Ptr result = map->lookup(key)) {
  98     V value = result->value();
  99     map->remove(result);
 100     return value;
 101   }
 102   return WeakMapDetails::DataType<V>::NullValue();
 103 }
 104
 105 //
 106 // Supported specializations of JS::WeakMap:
 107 //
 108
 109 template class JS_PUBLIC_API JS::WeakMapPtr<JSObject*, JSObject*>;
 110
 111 #ifdef DEBUG
 112 // Nobody's using this at the moment, but we want to make sure it compiles.
 113 template class JS_PUBLIC_API JS::WeakMapPtr<JSObject*, JS::Value>;
 114 #endif