dom/localstorage/LSWriteOptimizer.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 mozilla_dom_localstorage_LSWriteOptimizer_h
   8 #define mozilla_dom_localstorage_LSWriteOptimizer_h
   9
  10 #include <cstdint>
  11 #include <utility>
  12 #include "mozilla/Assertions.h"
  13 #include "mozilla/CheckedInt.h"
  14 #include "mozilla/UniquePtr.h"
  15 #include "nsClassHashtable.h"
  16 #include "nsHashKeys.h"
  17 #include "nsISupports.h"
  18 #include "nsStringFwd.h"
  19 #include "nsTArrayForwardDeclare.h"
  20
  21 namespace mozilla::dom {
  22
  23 /**
  24  * Base class for coalescing manipulation queue.
  25  */
  26 class LSWriteOptimizerBase {
  27   class WriteInfoComparator;
  28
  29  protected:
  30   class WriteInfo;
  31   class DeleteItemInfo;
  32   class TruncateInfo;
  33
  34   UniquePtr<WriteInfo> mTruncateInfo;
  35   nsClassHashtable<nsStringHashKey, WriteInfo> mWriteInfos;
  36   CheckedUint64 mLastSerialNumber;
  37   int64_t mTotalDelta;
  38
  39   NS_DECL_OWNINGTHREAD
  40
  41  public:
  42   LSWriteOptimizerBase() : mLastSerialNumber(0), mTotalDelta(0) {}
  43
  44   LSWriteOptimizerBase(LSWriteOptimizerBase&& aWriteOptimizer)
  45       : mTruncateInfo(std::move(aWriteOptimizer.mTruncateInfo)) {
  46     AssertIsOnOwningThread();
  47     MOZ_ASSERT(&aWriteOptimizer != this);
  48
  49     mWriteInfos.SwapElements(aWriteOptimizer.mWriteInfos);
  50     mTotalDelta = aWriteOptimizer.mTotalDelta;
  51     aWriteOptimizer.mTotalDelta = 0;
  52   }
  53
  54   void AssertIsOnOwningThread() const {
  55     NS_ASSERT_OWNINGTHREAD(LSWriteOptimizerBase);
  56   }
  57
  58   void DeleteItem(const nsAString& aKey, int64_t aDelta = 0);
  59
  60   void Truncate(int64_t aDelta = 0);
  61
  62   bool HasWrites() const {
  63     AssertIsOnOwningThread();
  64
  65     return mTruncateInfo || !mWriteInfos.IsEmpty();
  66   }
  67
  68   void Reset() {
  69     AssertIsOnOwningThread();
  70
  71     mTruncateInfo = nullptr;
  72     mWriteInfos.Clear();
  73   }
  74
  75  protected:
  76   uint64_t NextSerialNumber() {
  77     AssertIsOnOwningThread();
  78
  79     mLastSerialNumber++;
  80
  81     MOZ_ASSERT(mLastSerialNumber.isValid());
  82
  83     return mLastSerialNumber.value();
  84   }
  85
  86   /**
  87    * This method can be used by derived classes to get a sorted list of write
  88    * infos. Write infos are sorted by the serial number.
  89    */
  90   void GetSortedWriteInfos(nsTArray<NotNull<WriteInfo*>>& aWriteInfos);
  91 };
  92
  93 /**
  94  * Base class for specific mutations.
  95  */
  96 class LSWriteOptimizerBase::WriteInfo {
  97   uint64_t mSerialNumber;
  98
  99  public:
 100   WriteInfo(uint64_t aSerialNumber) : mSerialNumber(aSerialNumber) {}
 101
 102   virtual ~WriteInfo() = default;
 103
 104   uint64_t SerialNumber() const { return mSerialNumber; }
 105
 106   enum Type { InsertItem = 0, UpdateItem, DeleteItem, Truncate };
 107
 108   virtual Type GetType() const = 0;
 109 };
 110
 111 class LSWriteOptimizerBase::DeleteItemInfo final : public WriteInfo {
 112   nsString mKey;
 113
 114  public:
 115   DeleteItemInfo(uint64_t aSerialNumber, const nsAString& aKey)
 116       : WriteInfo(aSerialNumber), mKey(aKey) {}
 117
 118   const nsAString& GetKey() const { return mKey; }
 119
 120  private:
 121   Type GetType() const override { return DeleteItem; }
 122 };
 123
 124 /**
 125  * Truncate mutation.
 126  */
 127 class LSWriteOptimizerBase::TruncateInfo final : public WriteInfo {
 128  public:
 129   explicit TruncateInfo(uint64_t aSerialNumber) : WriteInfo(aSerialNumber) {}
 130
 131  private:
 132   Type GetType() const override { return Truncate; }
 133 };
 134
 135 /**
 136  * Coalescing manipulation queue.
 137  */
 138 template <typename T, typename U = T>
 139 class LSWriteOptimizer;
 140
 141 template <typename T, typename U>
 142 class LSWriteOptimizer : public LSWriteOptimizerBase {
 143  protected:
 144   class InsertItemInfo;
 145   class UpdateItemInfo;
 146
 147  public:
 148   void InsertItem(const nsAString& aKey, const T& aValue, int64_t aDelta = 0);
 149
 150   void UpdateItem(const nsAString& aKey, const T& aValue, int64_t aDelta = 0);
 151 };
 152
 153 /**
 154  * Insert mutation (the key did not previously exist).
 155  */
 156 template <typename T, typename U>
 157 class LSWriteOptimizer<T, U>::InsertItemInfo : public WriteInfo {
 158   nsString mKey;
 159   U mValue;
 160
 161  public:
 162   InsertItemInfo(uint64_t aSerialNumber, const nsAString& aKey, const T& aValue)
 163       : WriteInfo(aSerialNumber), mKey(aKey), mValue(aValue) {}
 164
 165   const nsAString& GetKey() const { return mKey; }
 166
 167   const T& GetValue() const { return mValue; }
 168
 169  private:
 170   WriteInfo::Type GetType() const override { return InsertItem; }
 171 };
 172
 173 /**
 174  * Update mutation (the key already existed).
 175  */
 176 template <typename T, typename U>
 177 class LSWriteOptimizer<T, U>::UpdateItemInfo final : public InsertItemInfo {
 178   bool mUpdateWithMove;
 179
 180  public:
 181   UpdateItemInfo(uint64_t aSerialNumber, const nsAString& aKey, const T& aValue,
 182                  bool aUpdateWithMove)
 183       : InsertItemInfo(aSerialNumber, aKey, aValue),
 184         mUpdateWithMove(aUpdateWithMove) {}
 185
 186   bool UpdateWithMove() const { return mUpdateWithMove; }
 187
 188  private:
 189   WriteInfo::Type GetType() const override { return WriteInfo::UpdateItem; }
 190 };
 191
 192 }  // namespace mozilla::dom
 193
 194 #endif  // mozilla_dom_localstorage_LSWriteOptimizer_h