public static Snapshot UnpackDelta(Snapshot from, int[] inputData,
int inputOffset, int inputSize)
{
var snapshotBuilder = new SnapshotBuilder();
var endIndex = inputOffset + inputSize;
var numDeletedItems = inputData[inputOffset++];
var numUpdatedItems = inputData[inputOffset++];
var numTempItems = inputData[inputOffset++];
var deletedOffset = inputOffset;
inputOffset += numDeletedItems;
if (inputOffset > endIndex)
{
return(null);
}
snapshotBuilder.StartBuild();
for (var i = 0; i < from.ItemsCount; i++)
{
var item = from[i];
var keep = true;
for (var d = 0; d < numDeletedItems; d++)
{
if (inputData[deletedOffset + d] == item.Key)
{
keep = false;
break;
}
}
if (keep)
{
snapshotBuilder.AddItem(item.Object.MakeCopy(), item.Id);
}
}
for (var i = 0; i < numUpdatedItems; i++)
{
if (inputOffset + 2 > endIndex)
{
return(null);
}
var type = (SnapObject)inputData[inputOffset++];
var id = inputData[inputOffset++];
int itemSize; // in bytes
if (SnapObjectsInfo.GetSizeByType(type) != 0)
{
itemSize = SnapObjectsInfo.GetSizeByType(type);
}
else
{
if (inputOffset + 1 > endIndex)
{
return(null);
}
itemSize = inputData[inputOffset++] * sizeof(int);
}
if (itemSize < 0 || !RangeCheck(endIndex, inputOffset, itemSize / sizeof(int)))
{
return(null);
}
var key = ((int)type << 16) | id;
var newItem = snapshotBuilder.FindItem(key)?.Object;
if (newItem == null)
{
var item = SnapObjectsInfo.GetInstanceByType(type);
if (snapshotBuilder.AddItem(item, id))
{
newItem = item;
}
}
if (newItem == null)
{
return(null);
}
var fromItem = from.FindItem(key);
if (fromItem != null)
{
UndiffItem(fromItem.Object, inputData, inputOffset, newItem);
}
else
{
newItem.Deserialize(inputData, inputOffset);
}
inputOffset += itemSize / sizeof(int);
}
return(snapshotBuilder.EndBuild());
}
public static int CreateDelta(Snapshot from, Snapshot to, int[] outputData)
{
var numDeletedItems = 0;
var numUpdatedItems = 0;
var numTempItems = 0;
var outputOffset = 3;
var hashItems = new HashItem[HASHLIST_SIZE];
for (var i = 0; i < hashItems.Length; i++)
{
hashItems[i] = new HashItem();
}
GenerateHash(hashItems, to);
// pack deleted stuff
for (var i = 0; i < from.ItemsCount; i++)
{
var fromItem = from[i];
if (GetItemIndexHashed(fromItem.Key, hashItems) == -1)
{
// deleted
numDeletedItems++;
outputData[outputOffset++] = fromItem.Key;
}
}
GenerateHash(hashItems, from);
var pastIndecies = new int[SnapshotBuilder.MAX_SNAPSHOT_ITEMS];
// fetch previous indices
// we do this as a separate pass because it helps the cache
for (var i = 0; i < to.ItemsCount; i++)
{
pastIndecies[i] = GetItemIndexHashed(to[i].Key, hashItems);
}
for (var i = 0; i < to.ItemsCount; i++)
{
var currentItem = to[i];
var pastIndex = pastIndecies[i];
if (pastIndex != -1)
{
var pastItem = from[pastIndex];
var offset = outputOffset + 3;
if (SnapObjectsInfo.GetSizeByType(currentItem.Type) != 0)
{
offset = outputOffset + 2;
}
if (DiffItem(pastItem.Object, currentItem.Object,
outputData, offset) != 0)
{
outputData[outputOffset++] = (int)currentItem.Type;
outputData[outputOffset++] = currentItem.Id;
if (SnapObjectsInfo.GetSizeByType(currentItem.Type) == 0)
{
outputData[outputOffset++] = currentItem.Object.SerializeLength;
}
outputOffset += currentItem.Object.SerializeLength; // count item int fields
numUpdatedItems++;
}
}
else
{
outputData[outputOffset++] = (int)currentItem.Type;
outputData[outputOffset++] = currentItem.Id;
if (SnapObjectsInfo.GetSizeByType(currentItem.Type) == 0)
{
outputData[outputOffset++] = currentItem.Object.SerializeLength;
}
var data = currentItem.Object.Serialize();
Array.Copy(data, 0, outputData, outputOffset, data.Length);
outputOffset += data.Length;
numUpdatedItems++;
}
}
if (numDeletedItems == 0 && numUpdatedItems == 0 && numTempItems == 0)
{
return(0);
}
outputData[0] = numDeletedItems;
outputData[1] = numUpdatedItems;
outputData[2] = numTempItems;
return(outputOffset);
}