public override void SaveItemChange(SaveChangeAction saveChangeAction, ItemChange change, SaveChangeContext context)
{
// Extract the data from the change
TransferMechanism data = context.ChangeData as TransferMechanism;
// Item metadata
ItemMetadata item = _sync.GetItemMetaData(saveChangeAction, change, data);
// Now apply the change
if (!(saveChangeAction == SaveChangeAction.UpdateVersionOnly) && ((change.ChangeKind & ChangeKind.Deleted) == 0))
{
// Only copy if destination file name is known
// (May have been lost if loser of name collision)
if (item.Uri != String.Empty)
{
FileInfo fi = new FileInfo(System.IO.Path.Combine(Path, item.Uri));
if (!fi.Directory.Exists)
{
fi.Directory.Create();
}
// Change should have stream data, so copy the file data to the local store
using (FileStream outputStream = new FileStream(System.IO.Path.Combine(Path, item.Uri), FileMode.OpenOrCreate)) {
const int copyBlockSize = 4096;
byte[] buffer = new byte[copyBlockSize];
int bytesRead;
// Simple block-by-block copy
while ((bytesRead = data.DataStream.Read(buffer, 0, copyBlockSize)) > 0)
{
outputStream.Write(buffer, 0, bytesRead);
}
// Truncate if needed
outputStream.SetLength(outputStream.Position);
}
// Update the last write time from the updated file to the metadata entry
item.LastWriteTimeUtc = fi.LastWriteTimeUtc;
}
// Close input stream
data.DataStream.Close();
}
else
{
// Not an update/create, so must be a delete or version only change
// Is it a delete?...
if (item.IsTombstone && item.Uri != String.Empty)
{
// Change is a delete
File.Delete(System.IO.Path.Combine(Path, item.Uri));
}
}
// If we made it here, the change was successfully applied locally
// (or it is a version only change), so we can update our knowledge with the
// learned knowledge from the change
_sync.GetUpdatedKnowledge(context);
}
public object LoadChangeData(LoadChangeContext loadChangeContext)
{
ItemMetadata item;
// Retrieve metadata for the changed item
if (metadataStore.TryGetItem(loadChangeContext.ItemChange.ItemId, out item))
{
// Make sure this isn't a delete
if (item.IsTombstone)
{
throw new InvalidOperationException("Cannot load change data for a deleted item.");
}
// Open the stream for the file we are transferring
Stream dataStream = new FileStream(Path.Combine(FolderPath, item.Uri), FileMode.Open, FileAccess.Read, FileShare.Read);
// Create an instance of our type for transferring change data
TransferMechanism transferMechanism = new TransferMechanism(dataStream, item.Uri);
// Return our data transfer object
return(transferMechanism);
}
return(null);
}
public ItemMetadata GetItemMetaData(SaveChangeAction saveChangeAction, ItemChange change, TransferMechanism data)
{
ItemMetadata item;
// Populate the URI field of the updated item metadata
if (saveChangeAction == SaveChangeAction.UpdateVersionOnly || ((change.ChangeKind & ChangeKind.Deleted) == ChangeKind.Deleted))
{
// Version only changes and deletions will not contain data,
// so we cannot get the item URI from the change data
//
// So, we attempt to look up the item metadata instead (by item id)
// to populate the URI field
if (!metadataStore.TryGetItem(change.ItemId, out item))
{
// Not found, must mean we've never seen this item locally
// Can safely use an empty URI
item = new ItemMetadata();
item.Uri = String.Empty;
}
}
else
{
// Since this isn't a version-only change or a delete, context should contain
// change data
item = new ItemMetadata(); // Used for storing updated item metadata
// Populate the Uri field
item.Uri = data.Uri;
}
// Now copy the rest of the metadata for the item from the change
item.ItemId = change.ItemId;
item.CreationVersion = change.CreationVersion;
item.ChangeVersion = change.ChangeVersion;
// If deletion change, mark it as a tombstone
if ((change.ChangeKind & ChangeKind.Deleted) == ChangeKind.Deleted)
{
item.IsTombstone = true;
}
// Is this a new item?
if (!metadataStore.Has(item.ItemId))
{
ItemMetadata oldItem;
// Not found
// Need to check for duplicates (by URI)
if (metadataStore.TryGetItem(item.Uri, out oldItem))
{
// Duplicate item (same Uri), so we deterministically choose a winner
// by comparing the guid part of the item ids
if (item.ItemId.CompareTo(oldItem.ItemId) > 0)
{
// New item is the winner
// Record old item as a loser
oldItem.IsTombstone = true;
oldItem.Uri = String.Empty;
oldItem.ChangeVersion = new SyncVersion(0, tickCount);
}
else
{
// Old item is the winner
// Record new item as a loser
item.IsTombstone = true;
item.Uri = String.Empty;
item.ChangeVersion = new SyncVersion(0, tickCount);
}
// Record the updated item metadata
metadataStore.SetItemInfo(item);
metadataStore.SetItemInfo(oldItem);
}
}
// Save the updated item metadata
metadataStore.SetItemInfo(item);
return(item);
}
