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// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef SYNC_SYNCABLE_SCOPED_INDEX_UPDATER_H_
#define SYNC_SYNCABLE_SCOPED_INDEX_UPDATER_H_
#include "sync/syncable/directory.h"
namespace syncer {
namespace syncable {
class ScopedKernelLock;
// A ScopedIndexUpdater temporarily removes an entry from an index,
// and restores it to the index when the scope exits. This simplifies
// the common pattern where items need to be removed from an index
// before updating the field.
//
// This class is parameterized on the Indexer traits type, which
// must define a Comparator and a static bool ShouldInclude
// function for testing whether the item ought to be included
// in the index.
template<typename Indexer>
class ScopedIndexUpdater {
public:
ScopedIndexUpdater(const ScopedKernelLock& proof_of_lock,
EntryKernel* entry,
typename Index<Indexer>::Set* index)
: entry_(entry),
index_(index) {
// First call to ShouldInclude happens before the field is updated.
if (Indexer::ShouldInclude(entry_)) {
// TODO(lipalani): Replace this CHECK with |SyncAssert| by refactorting
// this class into a function.
CHECK(index_->erase(entry_));
}
}
~ScopedIndexUpdater() {
// Second call to ShouldInclude happens after the field is updated.
if (Indexer::ShouldInclude(entry_)) {
// TODO(lipalani): Replace this CHECK with |SyncAssert| by refactorting
// this class into a function.
CHECK(index_->insert(entry_).second);
}
}
private:
// The entry that was temporarily removed from the index.
EntryKernel* entry_;
// The index which we are updating.
typename Index<Indexer>::Set* const index_;
};
} // namespace syncable
} // namespace syncer
#endif // SYNC_SYNCABLE_SCOPED_INDEX_UPDATER_H_
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