1 files changed, 1089 insertions, 0 deletions
diff --git a/dom/localstorage/LSSnapshot.cpp b/dom/localstorage/LSSnapshot.cpp
new file mode 100644
index 0000000000..85920b8b09
--- /dev/null
+++ b/dom/localstorage/LSSnapshot.cpp
@@ -0,0 +1,1089 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/dom/LSSnapshot.h"
+
+// Local includes
+#include "ActorsChild.h"
+#include "LSDatabase.h"
+#include "LSWriteOptimizer.h"
+#include "LSWriteOptimizerImpl.h"
+#include "LocalStorageCommon.h"
+
+// Global includes
+#include <cstdint>
+#include <cstdlib>
+#include <new>
+#include <type_traits>
+#include <utility>
+#include "ErrorList.h"
+#include "mozilla/DebugOnly.h"
+#include "mozilla/MacroForEach.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/Preferences.h"
+#include "mozilla/RefPtr.h"
+#include "mozilla/ScopeExit.h"
+#include "mozilla/StaticPrefs_dom.h"
+#include "mozilla/UniquePtr.h"
+#include "mozilla/dom/BindingDeclarations.h"
+#include "mozilla/dom/LSValue.h"
+#include "mozilla/dom/quota/QuotaCommon.h"
+#include "mozilla/dom/quota/ResultExtensions.h"
+#include "mozilla/dom/quota/ScopedLogExtraInfo.h"
+#include "mozilla/dom/PBackgroundLSDatabase.h"
+#include "mozilla/dom/PBackgroundLSSharedTypes.h"
+#include "mozilla/dom/PBackgroundLSSnapshot.h"
+#include "nsBaseHashtable.h"
+#include "nsCOMPtr.h"
+#include "nsContentUtils.h"
+#include "nsDebug.h"
+#include "nsError.h"
+#include "nsITimer.h"
+#include "nsString.h"
+#include "nsStringFlags.h"
+#include "nsStringFwd.h"
+#include "nsTArray.h"
+#include "nsTStringRepr.h"
+#include "nscore.h"
+
+namespace mozilla::dom {
+
+/**
+ * Coalescing manipulation queue used by `LSSnapshot`.  Used by `LSSnapshot` to
+ * buffer and coalesce manipulations before they are sent to the parent process,
+ * when a Snapshot Checkpoints. (This can only be done when there are no
+ * observers for other content processes.)
+ */
+class SnapshotWriteOptimizer final : public LSWriteOptimizer<LSValue> {
+ public:
+  void Enumerate(nsTArray<LSWriteInfo>& aWriteInfos);
+};
+
+void SnapshotWriteOptimizer::Enumerate(nsTArray<LSWriteInfo>& aWriteInfos) {
+  AssertIsOnOwningThread();
+
+  // The mWriteInfos hash table contains all write infos, but it keeps them in
+  // an arbitrary order, which means write infos need to be sorted before being
+  // processed.
+
+  nsTArray<NotNull<WriteInfo*>> writeInfos;
+  GetSortedWriteInfos(writeInfos);
+
+  for (WriteInfo* writeInfo : writeInfos) {
+    switch (writeInfo->GetType()) {
+      case WriteInfo::InsertItem: {
+        auto insertItemInfo = static_cast<InsertItemInfo*>(writeInfo);
+
+        LSSetItemInfo setItemInfo;
+        setItemInfo.key() = insertItemInfo->GetKey();
+        setItemInfo.value() = insertItemInfo->GetValue();
+
+        aWriteInfos.AppendElement(std::move(setItemInfo));
+
+        break;
+      }
+
+      case WriteInfo::UpdateItem: {
+        auto updateItemInfo = static_cast<UpdateItemInfo*>(writeInfo);
+
+        if (updateItemInfo->UpdateWithMove()) {
+          // See the comment in LSWriteOptimizer::InsertItem for more details
+          // about the UpdateWithMove flag.
+
+          LSRemoveItemInfo removeItemInfo;
+          removeItemInfo.key() = updateItemInfo->GetKey();
+
+          aWriteInfos.AppendElement(std::move(removeItemInfo));
+        }
+
+        LSSetItemInfo setItemInfo;
+        setItemInfo.key() = updateItemInfo->GetKey();
+        setItemInfo.value() = updateItemInfo->GetValue();
+
+        aWriteInfos.AppendElement(std::move(setItemInfo));
+
+        break;
+      }
+
+      case WriteInfo::DeleteItem: {
+        auto deleteItemInfo = static_cast<DeleteItemInfo*>(writeInfo);
+
+        LSRemoveItemInfo removeItemInfo;
+        removeItemInfo.key() = deleteItemInfo->GetKey();
+
+        aWriteInfos.AppendElement(std::move(removeItemInfo));
+
+        break;
+      }
+
+      case WriteInfo::Truncate: {
+        LSClearInfo clearInfo;
+
+        aWriteInfos.AppendElement(std::move(clearInfo));
+
+        break;
+      }
+
+      default:
+        MOZ_CRASH("Bad type!");
+    }
+  }
+}
+
+LSSnapshot::LSSnapshot(LSDatabase* aDatabase)
+    : mDatabase(aDatabase),
+      mActor(nullptr),
+      mInitLength(0),
+      mLength(0),
+      mUsage(0),
+      mPeakUsage(0),
+      mLoadState(LoadState::Initial),
+      mHasOtherProcessDatabases(false),
+      mHasOtherProcessObservers(false),
+      mExplicit(false),
+      mHasPendingStableStateCallback(false),
+      mHasPendingIdleTimerCallback(false),
+      mDirty(false)
+#ifdef DEBUG
+      ,
+      mInitialized(false),
+      mSentFinish(false)
+#endif
+{
+  AssertIsOnOwningThread();
+}
+
+LSSnapshot::~LSSnapshot() {
+  AssertIsOnOwningThread();
+  MOZ_ASSERT(mDatabase);
+  MOZ_ASSERT(!mHasPendingStableStateCallback);
+  MOZ_ASSERT(!mHasPendingIdleTimerCallback);
+  MOZ_ASSERT_IF(mInitialized, mSentFinish);
+
+  if (mActor) {
+    mActor->SendDeleteMeInternal();
+    MOZ_ASSERT(!mActor, "SendDeleteMeInternal should have cleared!");
+  }
+}
+
+void LSSnapshot::SetActor(LSSnapshotChild* aActor) {
+  AssertIsOnOwningThread();
+  MOZ_ASSERT(aActor);
+  MOZ_ASSERT(!mActor);
+
+  mActor = aActor;
+}
+
+nsresult LSSnapshot::Init(const nsAString& aKey,
+                          const LSSnapshotInitInfo& aInitInfo, bool aExplicit) {
+  AssertIsOnOwningThread();
+  MOZ_ASSERT(!mSelfRef);
+  MOZ_ASSERT(mActor);
+  MOZ_ASSERT(mLoadState == LoadState::Initial);
+  MOZ_ASSERT(!mInitialized);
+  MOZ_ASSERT(!mSentFinish);
+
+  mSelfRef = this;
+
+  LoadState loadState = aInitInfo.loadState();
+
+  const nsTArray<LSItemInfo>& itemInfos = aInitInfo.itemInfos();
+  for (uint32_t i = 0; i < itemInfos.Length(); i++) {
+    const LSItemInfo& itemInfo = itemInfos[i];
+
+    const LSValue& value = itemInfo.value();
+
+    if (loadState != LoadState::AllOrderedItems && !value.IsVoid()) {
+      mLoadedItems.Insert(itemInfo.key());
+    }
+
+    mValues.InsertOrUpdate(itemInfo.key(), value.AsString());
+  }
+
+  if (loadState == LoadState::Partial) {
+    if (aInitInfo.addKeyToUnknownItems()) {
+      mUnknownItems.Insert(aKey);
+    }
+    mInitLength = aInitInfo.totalLength();
+    mLength = mInitLength;
+  } else if (loadState == LoadState::AllOrderedKeys) {
+    mInitLength = aInitInfo.totalLength();
+  } else {
+    MOZ_ASSERT(loadState == LoadState::AllOrderedItems);
+  }
+
+  mUsage = aInitInfo.usage();
+  mPeakUsage = aInitInfo.peakUsage();
+
+  mLoadState = aInitInfo.loadState();
+
+  mHasOtherProcessDatabases = aInitInfo.hasOtherProcessDatabases();
+  mHasOtherProcessObservers = aInitInfo.hasOtherProcessObservers();
+
+  mExplicit = aExplicit;
+
+#ifdef DEBUG
+  mInitialized = true;
+#endif
+
+  if (mHasOtherProcessObservers) {
+    mWriteAndNotifyInfos = MakeUnique<nsTArray<LSWriteAndNotifyInfo>>();
+  } else {
+    mWriteOptimizer = MakeUnique<SnapshotWriteOptimizer>();
+  }
+
+  if (!mExplicit) {
+    mIdleTimer = NS_NewTimer();
+    MOZ_ASSERT(mIdleTimer);
+
+    ScheduleStableStateCallback();
+  }
+
+  return NS_OK;
+}
+
+nsresult LSSnapshot::GetLength(uint32_t* aResult) {
+  AssertIsOnOwningThread();
+  MOZ_ASSERT(mActor);
+  MOZ_ASSERT(mInitialized);
+  MOZ_ASSERT(!mSentFinish);
+
+  MaybeScheduleStableStateCallback();
+
+  if (mLoadState == LoadState::Partial) {
+    *aResult = mLength;
+  } else {
+    *aResult = mValues.Count();
+  }
+
+  return NS_OK;
+}
+
+nsresult LSSnapshot::GetKey(uint32_t aIndex, nsAString& aResult) {
+  AssertIsOnOwningThread();
+  MOZ_ASSERT(mActor);
+  MOZ_ASSERT(mInitialized);
+  MOZ_ASSERT(!mSentFinish);
+
+  MaybeScheduleStableStateCallback();
+
+  nsresult rv = EnsureAllKeys();
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  aResult.SetIsVoid(true);
+  for (auto iter = mValues.ConstIter(); !iter.Done(); iter.Next()) {
+    if (aIndex == 0) {
+      aResult = iter.Key();
+      return NS_OK;
+    }
+    aIndex--;
+  }
+
+  return NS_OK;
+}
+
+nsresult LSSnapshot::GetItem(const nsAString& aKey, nsAString& aResult) {
+  AssertIsOnOwningThread();
+  MOZ_ASSERT(mActor);
+  MOZ_ASSERT(mInitialized);
+  MOZ_ASSERT(!mSentFinish);
+
+  MaybeScheduleStableStateCallback();
+
+  nsString result;
+  nsresult rv = GetItemInternal(aKey, Optional<nsString>(), result);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  aResult = result;
+  return NS_OK;
+}
+
+nsresult LSSnapshot::GetKeys(nsTArray<nsString>& aKeys) {
+  AssertIsOnOwningThread();
+  MOZ_ASSERT(mActor);
+  MOZ_ASSERT(mInitialized);
+  MOZ_ASSERT(!mSentFinish);
+
+  MaybeScheduleStableStateCallback();
+
+  nsresult rv = EnsureAllKeys();
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  AppendToArray(aKeys, mValues.Keys());
+
+  return NS_OK;
+}
+
+nsresult LSSnapshot::SetItem(const nsAString& aKey, const nsAString& aValue,
+                             LSNotifyInfo& aNotifyInfo) {
+  AssertIsOnOwningThread();
+  MOZ_ASSERT(mActor);
+  MOZ_ASSERT(mInitialized);
+  MOZ_ASSERT(!mSentFinish);
+
+  MaybeScheduleStableStateCallback();
+
+  nsString oldValue;
+  nsresult rv =
+      GetItemInternal(aKey, Optional<nsString>(nsString(aValue)), oldValue);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  bool changed;
+  if (oldValue == aValue && oldValue.IsVoid() == aValue.IsVoid()) {
+    changed = false;
+  } else {
+    changed = true;
+
+    auto autoRevertValue = MakeScopeExit([&] {
+      if (oldValue.IsVoid()) {
+        mValues.Remove(aKey);
+      } else {
+        mValues.InsertOrUpdate(aKey, oldValue);
+      }
+    });
+
+    // Anything that can fail must be done early before we start modifying the
+    // state.
+
+    Maybe<LSValue> oldValueFromString;
+    if (mHasOtherProcessObservers) {
+      oldValueFromString.emplace();
+      if (NS_WARN_IF(!oldValueFromString->InitFromString(oldValue))) {
+        return NS_ERROR_FAILURE;
+      }
+    }
+
+    LSValue valueFromString;
+    if (NS_WARN_IF(!valueFromString.InitFromString(aValue))) {
+      return NS_ERROR_FAILURE;
+    }
+
+    int64_t delta = static_cast<int64_t>(aValue.Length()) -
+                    static_cast<int64_t>(oldValue.Length());
+
+    if (oldValue.IsVoid()) {
+      delta += static_cast<int64_t>(aKey.Length());
+    }
+
+    {
+      quota::ScopedLogExtraInfo scope{
+          quota::ScopedLogExtraInfo::kTagContext,
+          "dom::localstorage::LSSnapshot::SetItem::UpdateUsage"_ns};
+      QM_TRY(MOZ_TO_RESULT(UpdateUsage(delta)), QM_PROPAGATE, QM_NO_CLEANUP,
+             ([]() {
+               static uint32_t counter = 0u;
+               const bool result = 0u != (counter & (1u + counter));
+               ++counter;
+               return result;
+             }));
+    }
+
+    if (oldValue.IsVoid() && mLoadState == LoadState::Partial) {
+      mLength++;
+    }
+
+    if (mHasOtherProcessObservers) {
+      MOZ_ASSERT(mWriteAndNotifyInfos);
+      MOZ_ASSERT(oldValueFromString.isSome());
+
+      LSSetItemAndNotifyInfo setItemAndNotifyInfo;
+      setItemAndNotifyInfo.key() = aKey;
+      setItemAndNotifyInfo.oldValue() = oldValueFromString.value();
+      setItemAndNotifyInfo.value() = valueFromString;
+
+      mWriteAndNotifyInfos->AppendElement(std::move(setItemAndNotifyInfo));
+    } else {
+      MOZ_ASSERT(mWriteOptimizer);
+
+      if (oldValue.IsVoid()) {
+        mWriteOptimizer->InsertItem(aKey, valueFromString);
+      } else {
+        mWriteOptimizer->UpdateItem(aKey, valueFromString);
+      }
+    }
+
+    autoRevertValue.release();
+  }
+
+  aNotifyInfo.changed() = changed;
+  aNotifyInfo.oldValue() = oldValue;
+
+  return NS_OK;
+}
+
+nsresult LSSnapshot::RemoveItem(const nsAString& aKey,
+                                LSNotifyInfo& aNotifyInfo) {
+  AssertIsOnOwningThread();
+  MOZ_ASSERT(mActor);
+  MOZ_ASSERT(mInitialized);
+  MOZ_ASSERT(!mSentFinish);
+
+  MaybeScheduleStableStateCallback();
+
+  nsString oldValue;
+  nsresult rv =
+      GetItemInternal(aKey, Optional<nsString>(VoidString()), oldValue);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  bool changed;
+  if (oldValue.IsVoid()) {
+    changed = false;
+  } else {
+    changed = true;
+
+    auto autoRevertValue = MakeScopeExit([&] {
+      MOZ_ASSERT(!oldValue.IsVoid());
+      mValues.InsertOrUpdate(aKey, oldValue);
+    });
+
+    // Anything that can fail must be done early before we start modifying the
+    // state.
+
+    Maybe<LSValue> oldValueFromString;
+    if (mHasOtherProcessObservers) {
+      oldValueFromString.emplace();
+      if (NS_WARN_IF(!oldValueFromString->InitFromString(oldValue))) {
+        return NS_ERROR_FAILURE;
+      }
+    }
+
+    int64_t delta = -(static_cast<int64_t>(aKey.Length()) +
+                      static_cast<int64_t>(oldValue.Length()));
+
+    DebugOnly<nsresult> rv = UpdateUsage(delta);
+    MOZ_ASSERT(NS_SUCCEEDED(rv));
+
+    if (mLoadState == LoadState::Partial) {
+      mLength--;
+    }
+
+    if (mHasOtherProcessObservers) {
+      MOZ_ASSERT(mWriteAndNotifyInfos);
+      MOZ_ASSERT(oldValueFromString.isSome());
+
+      LSRemoveItemAndNotifyInfo removeItemAndNotifyInfo;
+      removeItemAndNotifyInfo.key() = aKey;
+      removeItemAndNotifyInfo.oldValue() = oldValueFromString.value();
+
+      mWriteAndNotifyInfos->AppendElement(std::move(removeItemAndNotifyInfo));
+    } else {
+      MOZ_ASSERT(mWriteOptimizer);
+
+      mWriteOptimizer->DeleteItem(aKey);
+    }
+
+    autoRevertValue.release();
+  }
+
+  aNotifyInfo.changed() = changed;
+  aNotifyInfo.oldValue() = oldValue;
+
+  return NS_OK;
+}
+
+nsresult LSSnapshot::Clear(LSNotifyInfo& aNotifyInfo) {
+  AssertIsOnOwningThread();
+  MOZ_ASSERT(mActor);
+  MOZ_ASSERT(mInitialized);
+  MOZ_ASSERT(!mSentFinish);
+
+  MaybeScheduleStableStateCallback();
+
+  uint32_t length;
+  if (mLoadState == LoadState::Partial) {
+    length = mLength;
+    MOZ_ASSERT(length);
+
+    MOZ_ALWAYS_TRUE(mActor->SendLoaded());
+
+    mLoadedItems.Clear();
+    mUnknownItems.Clear();
+    mLength = 0;
+    mLoadState = LoadState::AllOrderedItems;
+  } else {
+    length = mValues.Count();
+  }
+
+  bool changed;
+  if (!length) {
+    changed = false;
+  } else {
+    changed = true;
+
+    int64_t delta = 0;
+    for (const auto& entry : mValues) {
+      const nsAString& key = entry.GetKey();
+      const nsString& value = entry.GetData();
+
+      delta += -static_cast<int64_t>(key.Length()) -
+               static_cast<int64_t>(value.Length());
+    }
+
+    DebugOnly<nsresult> rv = UpdateUsage(delta);
+    MOZ_ASSERT(NS_SUCCEEDED(rv));
+
+    mValues.Clear();
+
+    if (mHasOtherProcessObservers) {
+      MOZ_ASSERT(mWriteAndNotifyInfos);
+
+      LSClearInfo clearInfo;
+
+      mWriteAndNotifyInfos->AppendElement(std::move(clearInfo));
+    } else {
+      MOZ_ASSERT(mWriteOptimizer);
+
+      mWriteOptimizer->Truncate();
+    }
+  }
+
+  aNotifyInfo.changed() = changed;
+
+  return NS_OK;
+}
+
+void LSSnapshot::MarkDirty() {
+  AssertIsOnOwningThread();
+  MOZ_ASSERT(mActor);
+  MOZ_ASSERT(mInitialized);
+  MOZ_ASSERT(!mSentFinish);
+
+  if (mDirty) {
+    return;
+  }
+
+  mDirty = true;
+
+  if (!mExplicit && !mHasPendingStableStateCallback) {
+    CancelIdleTimer();
+
+    MOZ_ALWAYS_SUCCEEDS(Checkpoint());
+
+    MOZ_ALWAYS_SUCCEEDS(Finish());
+  } else {
+    MOZ_ASSERT(!mHasPendingIdleTimerCallback);
+  }
+}
+
+nsresult LSSnapshot::ExplicitCheckpoint() {
+  AssertIsOnOwningThread();
+  MOZ_ASSERT(mActor);
+  MOZ_ASSERT(mExplicit);
+  MOZ_ASSERT(!mHasPendingStableStateCallback);
+  MOZ_ASSERT(!mHasPendingIdleTimerCallback);
+  MOZ_ASSERT(mInitialized);
+  MOZ_ASSERT(!mSentFinish);
+
+  nsresult rv = Checkpoint(/* aSync */ true);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  return NS_OK;
+}
+
+nsresult LSSnapshot::ExplicitEnd() {
+  AssertIsOnOwningThread();
+  MOZ_ASSERT(mActor);
+  MOZ_ASSERT(mExplicit);
+  MOZ_ASSERT(!mHasPendingStableStateCallback);
+  MOZ_ASSERT(!mHasPendingIdleTimerCallback);
+  MOZ_ASSERT(mInitialized);
+  MOZ_ASSERT(!mSentFinish);
+
+  nsresult rv = Checkpoint();
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  RefPtr<LSSnapshot> kungFuDeathGrip = this;
+
+  rv = Finish(/* aSync */ true);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  return NS_OK;
+}
+
+int64_t LSSnapshot::GetUsage() const {
+  AssertIsOnOwningThread();
+  MOZ_ASSERT(mActor);
+  MOZ_ASSERT(mInitialized);
+  MOZ_ASSERT(!mSentFinish);
+
+  return mUsage;
+}
+
+void LSSnapshot::ScheduleStableStateCallback() {
+  AssertIsOnOwningThread();
+  MOZ_ASSERT(mIdleTimer);
+  MOZ_ASSERT(!mExplicit);
+  MOZ_ASSERT(!mHasPendingStableStateCallback);
+
+  CancelIdleTimer();
+
+  nsCOMPtr<nsIRunnable> runnable = this;
+  nsContentUtils::RunInStableState(runnable.forget());
+
+  mHasPendingStableStateCallback = true;
+}
+
+void LSSnapshot::MaybeScheduleStableStateCallback() {
+  AssertIsOnOwningThread();
+
+  if (!mExplicit && !mHasPendingStableStateCallback) {
+    ScheduleStableStateCallback();
+  } else {
+    MOZ_ASSERT(!mHasPendingIdleTimerCallback);
+  }
+}
+
+nsresult LSSnapshot::GetItemInternal(const nsAString& aKey,
+                                     const Optional<nsString>& aValue,
+                                     nsAString& aResult) {
+  AssertIsOnOwningThread();
+  MOZ_ASSERT(mActor);
+  MOZ_ASSERT(mInitialized);
+  MOZ_ASSERT(!mSentFinish);
+
+  nsString result;
+
+  switch (mLoadState) {
+    case LoadState::Partial: {
+      if (mValues.Get(aKey, &result)) {
+        MOZ_ASSERT(!result.IsVoid());
+      } else if (mLoadedItems.Contains(aKey) || mUnknownItems.Contains(aKey)) {
+        result.SetIsVoid(true);
+      } else {
+        LSValue value;
+        nsTArray<LSItemInfo> itemInfos;
+        if (NS_WARN_IF(!mActor->SendLoadValueAndMoreItems(
+                nsString(aKey), &value, &itemInfos))) {
+          return NS_ERROR_FAILURE;
+        }
+
+        result = value.AsString();
+
+        if (result.IsVoid()) {
+          mUnknownItems.Insert(aKey);
+        } else {
+          mLoadedItems.Insert(aKey);
+          mValues.InsertOrUpdate(aKey, result);
+
+          // mLoadedItems.Count()==mInitLength is checked below.
+        }
+
+        for (uint32_t i = 0; i < itemInfos.Length(); i++) {
+          const LSItemInfo& itemInfo = itemInfos[i];
+
+          mLoadedItems.Insert(itemInfo.key());
+          mValues.InsertOrUpdate(itemInfo.key(), itemInfo.value().AsString());
+        }
+
+        if (mLoadedItems.Count() == mInitLength) {
+          mLoadedItems.Clear();
+          mUnknownItems.Clear();
+          mLength = 0;
+          mLoadState = LoadState::AllUnorderedItems;
+        }
+      }
+
+      if (aValue.WasPassed()) {
+        const nsString& value = aValue.Value();
+        if (!value.IsVoid()) {
+          mValues.InsertOrUpdate(aKey, value);
+        } else if (!result.IsVoid()) {
+          mValues.Remove(aKey);
+        }
+      }
+
+      break;
+    }
+
+    case LoadState::AllOrderedKeys: {
+      if (mValues.Get(aKey, &result)) {
+        if (result.IsVoid()) {
+          LSValue value;
+          nsTArray<LSItemInfo> itemInfos;
+          if (NS_WARN_IF(!mActor->SendLoadValueAndMoreItems(
+                  nsString(aKey), &value, &itemInfos))) {
+            return NS_ERROR_FAILURE;
+          }
+
+          result = value.AsString();
+
+          MOZ_ASSERT(!result.IsVoid());
+
+          mLoadedItems.Insert(aKey);
+          mValues.InsertOrUpdate(aKey, result);
+
+          // mLoadedItems.Count()==mInitLength is checked below.
+
+          for (uint32_t i = 0; i < itemInfos.Length(); i++) {
+            const LSItemInfo& itemInfo = itemInfos[i];
+
+            mLoadedItems.Insert(itemInfo.key());
+            mValues.InsertOrUpdate(itemInfo.key(), itemInfo.value().AsString());
+          }
+
+          if (mLoadedItems.Count() == mInitLength) {
+            mLoadedItems.Clear();
+            MOZ_ASSERT(mLength == 0);
+            mLoadState = LoadState::AllOrderedItems;
+          }
+        }
+      } else {
+        result.SetIsVoid(true);
+      }
+
+      if (aValue.WasPassed()) {
+        const nsString& value = aValue.Value();
+        if (!value.IsVoid()) {
+          mValues.InsertOrUpdate(aKey, value);
+        } else if (!result.IsVoid()) {
+          mValues.Remove(aKey);
+        }
+      }
+
+      break;
+    }
+
+    case LoadState::AllUnorderedItems:
+    case LoadState::AllOrderedItems: {
+      if (aValue.WasPassed()) {
+        const nsString& value = aValue.Value();
+        if (!value.IsVoid()) {
+          mValues.WithEntryHandle(aKey, [&](auto&& entry) {
+            if (entry) {
+              result = std::exchange(entry.Data(), value);
+            } else {
+              result.SetIsVoid(true);
+              entry.Insert(value);
+            }
+          });
+        } else {
+          if (auto entry = mValues.Lookup(aKey)) {
+            result = entry.Data();
+            MOZ_ASSERT(!result.IsVoid());
+            entry.Remove();
+          } else {
+            result.SetIsVoid(true);
+          }
+        }
+      } else {
+        if (mValues.Get(aKey, &result)) {
+          MOZ_ASSERT(!result.IsVoid());
+        } else {
+          result.SetIsVoid(true);
+        }
+      }
+
+      break;
+    }
+
+    default:
+      MOZ_CRASH("Bad state!");
+  }
+
+  aResult = result;
+  return NS_OK;
+}
+
+nsresult LSSnapshot::EnsureAllKeys() {
+  AssertIsOnOwningThread();
+  MOZ_ASSERT(mActor);
+  MOZ_ASSERT(mInitialized);
+  MOZ_ASSERT(!mSentFinish);
+  MOZ_ASSERT(mLoadState != LoadState::Initial);
+
+  if (mLoadState == LoadState::AllOrderedKeys ||
+      mLoadState == LoadState::AllOrderedItems) {
+    return NS_OK;
+  }
+
+  nsTArray<nsString> keys;
+  if (NS_WARN_IF(!mActor->SendLoadKeys(&keys))) {
+    return NS_ERROR_FAILURE;
+  }
+
+  nsTHashMap<nsStringHashKey, nsString> newValues;
+
+  for (auto key : keys) {
+    newValues.InsertOrUpdate(key, VoidString());
+  }
+
+  if (mHasOtherProcessObservers) {
+    MOZ_ASSERT(mWriteAndNotifyInfos);
+
+    if (!mWriteAndNotifyInfos->IsEmpty()) {
+      for (uint32_t index = 0; index < mWriteAndNotifyInfos->Length();
+           index++) {
+        const LSWriteAndNotifyInfo& writeAndNotifyInfo =
+            mWriteAndNotifyInfos->ElementAt(index);
+
+        switch (writeAndNotifyInfo.type()) {
+          case LSWriteAndNotifyInfo::TLSSetItemAndNotifyInfo: {
+            newValues.InsertOrUpdate(
+                writeAndNotifyInfo.get_LSSetItemAndNotifyInfo().key(),
+                VoidString());
+            break;
+          }
+          case LSWriteAndNotifyInfo::TLSRemoveItemAndNotifyInfo: {
+            newValues.Remove(
+                writeAndNotifyInfo.get_LSRemoveItemAndNotifyInfo().key());
+            break;
+          }
+          case LSWriteAndNotifyInfo::TLSClearInfo: {
+            newValues.Clear();
+            break;
+          }
+
+          default:
+            MOZ_CRASH("Should never get here!");
+        }
+      }
+    }
+  } else {
+    MOZ_ASSERT(mWriteOptimizer);
+
+    if (mWriteOptimizer->HasWrites()) {
+      nsTArray<LSWriteInfo> writeInfos;
+      mWriteOptimizer->Enumerate(writeInfos);
+
+      MOZ_ASSERT(!writeInfos.IsEmpty());
+
+      for (uint32_t index = 0; index < writeInfos.Length(); index++) {
+        const LSWriteInfo& writeInfo = writeInfos[index];
+
+        switch (writeInfo.type()) {
+          case LSWriteInfo::TLSSetItemInfo: {
+            newValues.InsertOrUpdate(writeInfo.get_LSSetItemInfo().key(),
+                                     VoidString());
+            break;
+          }
+          case LSWriteInfo::TLSRemoveItemInfo: {
+            newValues.Remove(writeInfo.get_LSRemoveItemInfo().key());
+            break;
+          }
+          case LSWriteInfo::TLSClearInfo: {
+            newValues.Clear();
+            break;
+          }
+
+          default:
+            MOZ_CRASH("Should never get here!");
+        }
+      }
+    }
+  }
+
+  MOZ_ASSERT_IF(mLoadState == LoadState::AllUnorderedItems,
+                newValues.Count() == mValues.Count());
+
+  for (auto iter = newValues.Iter(); !iter.Done(); iter.Next()) {
+    nsString value;
+    if (mValues.Get(iter.Key(), &value)) {
+      iter.Data() = value;
+    }
+  }
+
+  mValues.SwapElements(newValues);
+
+  if (mLoadState == LoadState::Partial) {
+    mUnknownItems.Clear();
+    mLength = 0;
+    mLoadState = LoadState::AllOrderedKeys;
+  } else {
+    MOZ_ASSERT(mLoadState == LoadState::AllUnorderedItems);
+
+    MOZ_ASSERT(mUnknownItems.Count() == 0);
+    MOZ_ASSERT(mLength == 0);
+    mLoadState = LoadState::AllOrderedItems;
+  }
+
+  return NS_OK;
+}
+
+nsresult LSSnapshot::UpdateUsage(int64_t aDelta) {
+  AssertIsOnOwningThread();
+  MOZ_ASSERT(mDatabase);
+  MOZ_ASSERT(mActor);
+  MOZ_ASSERT(mPeakUsage >= mUsage);
+  MOZ_ASSERT(mInitialized);
+  MOZ_ASSERT(!mSentFinish);
+
+  int64_t newUsage = mUsage + aDelta;
+  if (newUsage > mPeakUsage) {
+    const int64_t minSize = newUsage - mPeakUsage;
+
+    int64_t size;
+    if (NS_WARN_IF(!mActor->SendIncreasePeakUsage(minSize, &size))) {
+      return NS_ERROR_FAILURE;
+    }
+
+    MOZ_ASSERT(size >= 0);
+
+    if (size == 0) {
+      return NS_ERROR_FILE_NO_DEVICE_SPACE;
+    }
+
+    mPeakUsage += size;
+  }
+
+  mUsage = newUsage;
+  return NS_OK;
+}
+
+nsresult LSSnapshot::Checkpoint(bool aSync) {
+  AssertIsOnOwningThread();
+  MOZ_ASSERT(mActor);
+  MOZ_ASSERT(mInitialized);
+  MOZ_ASSERT(!mSentFinish);
+
+  if (mHasOtherProcessObservers) {
+    MOZ_ASSERT(mWriteAndNotifyInfos);
+
+    if (!mWriteAndNotifyInfos->IsEmpty()) {
+      if (aSync) {
+        MOZ_ALWAYS_TRUE(
+            mActor->SendSyncCheckpointAndNotify(*mWriteAndNotifyInfos));
+      } else {
+        MOZ_ALWAYS_TRUE(
+            mActor->SendAsyncCheckpointAndNotify(*mWriteAndNotifyInfos));
+      }
+
+      mWriteAndNotifyInfos->Clear();
+    }
+  } else {
+    MOZ_ASSERT(mWriteOptimizer);
+
+    if (mWriteOptimizer->HasWrites()) {
+      nsTArray<LSWriteInfo> writeInfos;
+      mWriteOptimizer->Enumerate(writeInfos);
+
+      MOZ_ASSERT(!writeInfos.IsEmpty());
+
+      if (aSync) {
+        MOZ_ALWAYS_TRUE(mActor->SendSyncCheckpoint(writeInfos));
+      } else {
+        MOZ_ALWAYS_TRUE(mActor->SendAsyncCheckpoint(writeInfos));
+      }
+
+      mWriteOptimizer->Reset();
+    }
+  }
+
+  return NS_OK;
+}
+
+nsresult LSSnapshot::Finish(bool aSync) {
+  AssertIsOnOwningThread();
+  MOZ_ASSERT(mDatabase);
+  MOZ_ASSERT(mActor);
+  MOZ_ASSERT(mInitialized);
+  MOZ_ASSERT(!mSentFinish);
+
+  if (aSync) {
+    MOZ_ALWAYS_TRUE(mActor->SendSyncFinish());
+  } else {
+    MOZ_ALWAYS_TRUE(mActor->SendAsyncFinish());
+  }
+
+  mDatabase->NoteFinishedSnapshot(this);
+
+#ifdef DEBUG
+  mSentFinish = true;
+#endif
+
+  // Clear the self reference added in Init method.
+  MOZ_ASSERT(mSelfRef);
+  mSelfRef = nullptr;
+
+  return NS_OK;
+}
+
+void LSSnapshot::CancelIdleTimer() {
+  AssertIsOnOwningThread();
+  MOZ_ASSERT(mIdleTimer);
+
+  if (mHasPendingIdleTimerCallback) {
+    MOZ_ALWAYS_SUCCEEDS(mIdleTimer->Cancel());
+    mHasPendingIdleTimerCallback = false;
+  }
+}
+
+// static
+void LSSnapshot::IdleTimerCallback(nsITimer* aTimer, void* aClosure) {
+  MOZ_ASSERT(aTimer);
+
+  auto* self = static_cast<LSSnapshot*>(aClosure);
+  MOZ_ASSERT(self);
+  MOZ_ASSERT(self->mIdleTimer);
+  MOZ_ASSERT(SameCOMIdentity(self->mIdleTimer, aTimer));
+  MOZ_ASSERT(!self->mHasPendingStableStateCallback);
+  MOZ_ASSERT(self->mHasPendingIdleTimerCallback);
+
+  self->mHasPendingIdleTimerCallback = false;
+
+  MOZ_ALWAYS_SUCCEEDS(self->Finish());
+}
+
+NS_IMPL_ISUPPORTS(LSSnapshot, nsIRunnable)
+
+NS_IMETHODIMP
+LSSnapshot::Run() {
+  AssertIsOnOwningThread();
+  MOZ_ASSERT(!mExplicit);
+  MOZ_ASSERT(mHasPendingStableStateCallback);
+  MOZ_ASSERT(!mHasPendingIdleTimerCallback);
+
+  mHasPendingStableStateCallback = false;
+
+  MOZ_ALWAYS_SUCCEEDS(Checkpoint());
+
+  // 1. The unused pre-incremented snapshot peak usage can't be undone when
+  //    there are other snapshots for the same database. We only add a pending
+  //    usage delta when a snapshot finishes and usage deltas are then applied
+  //    when the last database becomes inactive.
+  // 2. If there's a snapshot with pre-incremented peak usage, the next
+  //    snapshot will use that as a base for its usage.
+  // 3. When a task for given snapshot finishes, we try to reuse the snapshot
+  //    by only checkpointing the snapshot and delaying the finish by a timer.
+  // 4. If two or more tabs for the same origin use localStorage periodically
+  //    at the same time the usage gradually grows until it hits the quota
+  //    limit.
+  // 5. We prevent that from happening by finishing the snapshot immediatelly
+  //    if there are databases in other processess.
+
+  if (mDirty || mHasOtherProcessDatabases ||
+      !Preferences::GetBool("dom.storage.snapshot_reusing")) {
+    MOZ_ALWAYS_SUCCEEDS(Finish());
+  } else {
+    MOZ_ASSERT(mIdleTimer);
+
+    MOZ_ALWAYS_SUCCEEDS(mIdleTimer->InitWithNamedFuncCallback(
+        IdleTimerCallback, this,
+        StaticPrefs::dom_storage_snapshot_idle_timeout_ms(),
+        nsITimer::TYPE_ONE_SHOT, "LSSnapshot::IdleTimerCallback"));
+
+    mHasPendingIdleTimerCallback = true;
+  }
+
+  return NS_OK;
+}
+
+}  // namespace mozilla::dom