The Tor Browser: mobile/android/base/sync/repositories/StoreTracker.java@fc2d59ddac77

     1 /* This Source Code Form is subject to the terms of the Mozilla Public

     2  * License, v. 2.0. If a copy of the MPL was not distributed with this

     3  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

     5 package org.mozilla.gecko.sync.repositories;

     7 import java.util.Iterator;

     9 /**

    10  * Our hacky version of transactional semantics. The goal is to prevent

    11  * the following situation:

    12  *

    13  * * AAA is not modified locally.

    14  * * A modified AAA is downloaded during the storing phase. Its local

    15  *   timestamp is advanced.

    16  * * The direction of syncing changes, and AAA is now uploaded to the server.

    17  *

    18  * The following situation should still be supported:

    19  *

    20  * * AAA is not modified locally.

    21  * * A modified AAA is downloaded and merged with the local AAA.

    22  * * The merged AAA is uploaded to the server.

    23  *

    24  * As should:

    25  *

    26  * * AAA is modified locally.

    27  * * A modified AAA is downloaded, and discarded or merged.

    28  * * The current version of AAA is uploaded to the server.

    29  *

    30  * We achieve this by tracking GUIDs during the storing phase. If we

    31  * apply a record such that the local copy is substantially the same

    32  * as the record we just downloaded, we add it to a list of records

    33  * to avoid uploading. The definition of "substantially the same"

    34  * depends on the particular repository. The only consideration is "do we

    35  * want to upload this record in this sync?".

    36  *

    37  * Note that items are removed from this list when a fetch that

    38  * considers them for upload completes successfully. The entire list

    39  * is discarded when the session is completed.

    40  *

    41  * This interface exposes methods to:

    42  *

    43  * * During a store, recording that a record has been stored, and should

    44  *   thus not be returned in subsequent fetches;

    45  * * During a fetch, checking whether a record should be returned.

    46  *

    47  * In the future this might also grow self-persistence.

    48  *

    49  * See also RepositorySession.trackRecord.

    50  *

    51  * @author rnewman

    52  *

    53  */

    54 public interface StoreTracker {

    56   /**

    57    * @param guid

    58    *        The GUID of the item to track.

    59    * @return

    60    *        Whether the GUID was a newly tracked value.

    61    */

    62   public boolean trackRecordForExclusion(String guid);

    64   /**

    65    * @param guid

    66    *        The GUID of the item to check.

    67    * @return

    68    *        true if the item is already tracked.

    69    */

    70   public boolean isTrackedForExclusion(String guid);

    72   /**

    73   *

    74   * @param guid

    75   * @return true if the specified GUID was removed from the tracked set.

    76   */

    77   public boolean untrackStoredForExclusion(String guid);

    79   public RecordFilter getFilter();

    81   public Iterator<String> recordsTrackedForExclusion();

    82 }

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