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LSWriteOptimizer.h (4951B)

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