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// Copyright (c) 2006-2009 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.
//
// Defines ChangeReorderBuffer, which can be used to sort a list of item
// actions to achieve the ordering constraint required by the SyncObserver
// interface of the SyncAPI.
#ifndef CHROME_BROWSER_SYNC_ENGINE_CHANGE_REORDER_BUFFER_H_
#define CHROME_BROWSER_SYNC_ENGINE_CHANGE_REORDER_BUFFER_H_
#pragma once
#include <map>
#include <vector>
#include "base/linked_ptr.h"
#include "chrome/browser/sync/engine/syncapi.h"
#include "chrome/browser/sync/protocol/sync.pb.h"
namespace sync_api {
// ChangeReorderBuffer is a utility type which accepts an unordered set
// of changes (via its Push methods), and yields a vector of ChangeRecords
// (via the GetAllChangesInTreeOrder method) that are in the order that
// the SyncObserver expects them to be. A buffer is initially empty.
//
// The ordering produced by ChangeReorderBuffer is as follows:
// (a) All Deleted items appear first.
// (b) For Updated and/or Added items, parents appear before their children.
// (c) When there are changes to the sibling order (this means Added items,
// or Updated items with the |position_changed| parameter set to true),
// all siblings under a parent will appear in the output, even if they
// are not explicitly pushed. The sibling order will be preserved in
// the output list -- items will appear before their sibling-order
// successors.
// (d) When there are no changes to the sibling order under a parent node,
// the sibling order is not necessarily preserved in the output for
// its children.
class ChangeReorderBuffer {
public:
typedef SyncManager::ChangeRecord ChangeRecord;
typedef SyncManager::ExtraChangeRecordData ExtraChangeRecordData;
ChangeReorderBuffer();
~ChangeReorderBuffer();
// Insert an item, identified by the metahandle |id|, into the reorder
// buffer. This item will appear in the output list as an ACTION_ADD
// ChangeRecord.
void PushAddedItem(int64 id) {
operations_[id] = OP_ADD;
}
// Insert an item, identified by the metahandle |id|, into the reorder
// buffer. This item will appear in the output list as an ACTION_DELETE
// ChangeRecord.
void PushDeletedItem(int64 id) {
operations_[id] = OP_DELETE;
}
// Insert an item, identified by the metahandle |id|, into the reorder
// buffer. This item will appear in the output list as an ACTION_UPDATE
// ChangeRecord. Also, if |position_changed| is true, all siblings of this
// item will appear in the output list as well; if it wasn't explicitly
// pushed, the siblings will have an ACTION_UPDATE ChangeRecord.
void PushUpdatedItem(int64 id, bool position_changed) {
operations_[id] = position_changed ? OP_UPDATE_POSITION_AND_PROPERTIES :
OP_UPDATE_PROPERTIES_ONLY;
}
void SetExtraDataForId(int64 id, ExtraChangeRecordData* extra) {
extra_data_[id] = make_linked_ptr<ExtraChangeRecordData>(extra);
}
void SetSpecificsForId(int64 id, const sync_pb::EntitySpecifics& specifics) {
specifics_[id] = specifics;
}
// Reset the buffer, forgetting any pushed items, so that it can be used
// again to reorder a new set of changes.
void Clear() {
operations_.clear();
}
bool IsEmpty() const {
return operations_.empty();
}
// Output a reordered list of changes to |changelist| using the items that
// were pushed into the reorder buffer. |sync_trans| is used to determine the
// ordering.
void GetAllChangesInTreeOrder(const BaseTransaction* sync_trans,
std::vector<ChangeRecord>* changelist);
private:
class Traversal;
enum Operation {
OP_ADD, // AddedItem.
OP_DELETE, // DeletedItem.
OP_UPDATE_PROPERTIES_ONLY, // UpdatedItem with position_changed=0.
OP_UPDATE_POSITION_AND_PROPERTIES, // UpdatedItem with position_changed=1.
};
typedef std::map<int64, Operation> OperationMap;
typedef std::map<int64, sync_pb::EntitySpecifics> SpecificsMap;
typedef std::map<int64, linked_ptr<ExtraChangeRecordData> > ExtraDataMap;
// Stores the items that have been pushed into the buffer, and the type of
// operation that was associated with them.
OperationMap operations_;
// Stores entity-specific ChangeRecord data per-ID.
SpecificsMap specifics_;
// Stores type-specific extra data per-ID.
ExtraDataMap extra_data_;
DISALLOW_COPY_AND_ASSIGN(ChangeReorderBuffer);
};
} // namespace sync_api
#endif // CHROME_BROWSER_SYNC_ENGINE_CHANGE_REORDER_BUFFER_H_
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