xpcom/ds/nsClassHashtable.h

   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 #ifndef nsClassHashtable_h__
   8 #define nsClassHashtable_h__
   9
  10 #include <utility>
  11
  12 #include "mozilla/UniquePtr.h"
  13 #include "nsBaseHashtable.h"
  14 #include "nsHashKeys.h"
  15
  16 /**
  17  * Helper class that provides methods to wrap and unwrap the UserDataType.
  18  */
  19 template <class T>
  20 class nsUniquePtrConverter {
  21  public:
  22   using UserDataType = T*;
  23   using DataType = mozilla::UniquePtr<T>;
  24
  25   static UserDataType Unwrap(DataType& src) { return src.get(); }
  26   static DataType Wrap(UserDataType&& src) { return DataType(std::move(src)); }
  27   static DataType Wrap(const UserDataType& src) { return DataType(src); }
  28 };
  29
  30 /**
  31  * templated hashtable class maps keys to C++ object pointers.
  32  * See nsBaseHashtable for complete declaration.
  33  * @param KeyClass a wrapper-class for the hashtable key, see nsHashKeys.h
  34  *   for a complete specification.
  35  * @param Class the class-type being wrapped
  36  * @see nsInterfaceHashtable, nsClassHashtable
  37  */
  38 template <class KeyClass, class T>
  39 class nsClassHashtable : public nsBaseHashtable<KeyClass, mozilla::UniquePtr<T>,
  40                                                 T*, nsUniquePtrConverter<T>> {
  41  public:
  42   typedef typename KeyClass::KeyType KeyType;
  43   typedef T* UserDataType;
  44   typedef nsBaseHashtable<KeyClass, mozilla::UniquePtr<T>, T*,
  45                           nsUniquePtrConverter<T>>
  46       base_type;
  47
  48   using base_type::IsEmpty;
  49   using base_type::Remove;
  50
  51   nsClassHashtable() = default;
  52   explicit nsClassHashtable(uint32_t aInitLength) : base_type(aInitLength) {}
  53
  54   /**
  55    * @copydoc nsBaseHashtable::Get
  56    * @param aData if the key doesn't exist, pData will be set to nullptr.
  57    */
  58   bool Get(KeyType aKey, UserDataType* aData) const;
  59
  60   /**
  61    * @copydoc nsBaseHashtable::Get
  62    * @returns nullptr if the key is not present.
  63    */
  64   [[nodiscard]] UserDataType Get(KeyType aKey) const;
  65 };
  66
  67 template <typename K, typename T>
  68 inline void ImplCycleCollectionUnlink(nsClassHashtable<K, T>& aField) {
  69   aField.Clear();
  70 }
  71
  72 template <typename K, typename T>
  73 inline void ImplCycleCollectionTraverse(
  74     nsCycleCollectionTraversalCallback& aCallback,
  75     const nsClassHashtable<K, T>& aField, const char* aName,
  76     uint32_t aFlags = 0) {
  77   for (auto iter = aField.ConstIter(); !iter.Done(); iter.Next()) {
  78     ImplCycleCollectionTraverse(aCallback, *iter.UserData(), aName, aFlags);
  79   }
  80 }
  81
  82 //
  83 // nsClassHashtable definitions
  84 //
  85
  86 template <class KeyClass, class T>
  87 bool nsClassHashtable<KeyClass, T>::Get(KeyType aKey, T** aRetVal) const {
  88   typename base_type::EntryType* ent = this->GetEntry(aKey);
  89
  90   if (ent) {
  91     if (aRetVal) {
  92       *aRetVal = ent->GetData().get();
  93     }
  94
  95     return true;
  96   }
  97
  98   if (aRetVal) {
  99     *aRetVal = nullptr;
 100   }
 101
 102   return false;
 103 }
 104
 105 template <class KeyClass, class T>
 106 T* nsClassHashtable<KeyClass, T>::Get(KeyType aKey) const {
 107   typename base_type::EntryType* ent = this->GetEntry(aKey);
 108   if (!ent) {
 109     return nullptr;
 110   }
 111
 112   return ent->GetData().get();
 113 }
 114
 115 #endif  // nsClassHashtable_h__