public ModelDelta Revert(IDataModel model)
{
var reverse = new ModelDelta {
HasDataChange = HasDataChange
};
foreach (var kvp in oldData)
{
var(index, data) = (kvp.Key, kvp.Value);
reverse.oldData[index] = model.Count > index ? model[index] : (byte)0xFF;
if (model.Count > index)
{
model[index] = data;
}
}
foreach (var kvp in addedRuns)
{
reverse.removedRuns[kvp.Key] = kvp.Value;
}
foreach (var kvp in removedRuns)
{
reverse.addedRuns[kvp.Key] = kvp.Value;
}
foreach (var kvp in addedNames)
{
reverse.removedNames[kvp.Key] = kvp.Value;
}
foreach (var kvp in removedNames)
{
reverse.addedNames[kvp.Key] = kvp.Value;
}
foreach (var kvp in addedLists)
{
reverse.removedLists[kvp.Key] = kvp.Value;
}
foreach (var kvp in removedLists)
{
reverse.addedLists[kvp.Key] = kvp.Value;
}
foreach (var kvp in addedMatchedWords)
{
reverse.removedMatchedWords[kvp.Key] = kvp.Value;
}
foreach (var kvp in removedMatchedWords)
{
reverse.addedMatchedWords[kvp.Key] = kvp.Value;
}
foreach (var kvp in addedOffsetPointers)
{
reverse.removedOffsetPointers[kvp.Key] = kvp.Value;
}
foreach (var kvp in removedOffsetPointers)
{
reverse.addedOffsetPointers[kvp.Key] = kvp.Value;
}
foreach (var kvp in addedUnmappedPointers)
{
reverse.removedUnmappedPointers[kvp.Key] = kvp.Value;
}
foreach (var kvp in removedUnmappedPointers)
{
reverse.addedUnmappedPointers[kvp.Key] = kvp.Value;
}
foreach (var kvp in addedUnmappedConstants)
{
reverse.removedUnmappedConstants[kvp.Key] = kvp.Value;
}
foreach (var kvp in removedUnmappedConstants)
{
reverse.addedUnmappedConstants[kvp.Key] = kvp.Value;
}
if (oldDataLength != -1 || newDataLength != -1)
{
model.ExpandData(reverse, oldDataLength - 1);
model.ContractData(reverse, oldDataLength - 1);
}
model.MassUpdateFromDelta(addedRuns, removedRuns,
addedNames, removedNames,
addedUnmappedPointers, removedUnmappedPointers,
addedMatchedWords, removedMatchedWords,
addedOffsetPointers, removedOffsetPointers,
addedUnmappedConstants, removedUnmappedConstants,
addedLists, removedLists);
return(reverse);
}
// return -1 if the header is wrong (UPS1)
// return -2 if the source file CRC doesn't match
// return -3 if the patch file CRC doesn't match
// return -4 if the source file size doesn't match
// return -5 if the result file CRC doesn't match
// return -6 if the UPS content didn't finish the last chunk with exactly 12 bytes left
// return -7 if trying to write past the end of the destination file
// returns a positive integer, the address of the first change, if everything worked correctly
public static int ApplyUPSPatch(IDataModel model, byte[] patch, Func <ModelDelta> tokenFactory, bool ignoreChecksums, out UpsPatchDirection direction)
{
// 4 byte header: "UPS1"
// variable width source-size
// variable width destination-size
// 12 byte footer: 3 CRC32 checksums. Source file, destination file, patch file (CRC of everything except the last 4 bytes)
direction = UpsPatchDirection.Fail;
// check header
var headerMatches = patch.Take(4).Select(b => (char)b).SequenceEqual("UPS1");
if (!headerMatches)
{
return(-1);
}
// check source CRC
var currentCRC = CalcCRC32(model.RawData);
var patchSourceFileCRC = patch.ReadMultiByteValue(patch.Length - 12, 4);
var patchDestinationFileCRC = patch.ReadMultiByteValue(patch.Length - 8, 4);
if (currentCRC == patchSourceFileCRC)
{
direction = UpsPatchDirection.SourceToDestination;
}
if (currentCRC == patchDestinationFileCRC)
{
direction = UpsPatchDirection.DestinationToSource;
}
if (direction == UpsPatchDirection.Fail && !ignoreChecksums)
{
return(-2);
}
if (direction == UpsPatchDirection.Fail)
{
direction = UpsPatchDirection.SourceToDestination;
}
// check patch CRC
var patchWithoutCRC = new byte[patch.Length - 4];
Array.Copy(patch, patchWithoutCRC, patchWithoutCRC.Length);
var patchCRC = CalcCRC32(patchWithoutCRC);
if (patchCRC != patch.ReadMultiByteValue(patch.Length - 4, 4))
{
return(-3);
}
// resize (bigger)
int readIndex = 4, firstEdit = int.MaxValue;
int sourceSize = ReadVariableWidthInteger(patch, ref readIndex);
int destinationSize = ReadVariableWidthInteger(patch, ref readIndex);
int writeLength = destinationSize;
if (direction == UpsPatchDirection.DestinationToSource)
{
(sourceSize, destinationSize) = (destinationSize, sourceSize);
}
if (sourceSize != model.Count && !ignoreChecksums)
{
return(-4);
}
var token = tokenFactory.Invoke();
model.ExpandData(token, destinationSize - 1);
token.ChangeData(model, sourceSize, new byte[Math.Max(0, destinationSize - sourceSize)]);
token.ChangeData(model, destinationSize, new byte[Math.Max(0, sourceSize - destinationSize)]);
// run algorithm
firstEdit = RunUPSPatchAlgorithm(model, patch, token, writeLength, destinationSize, ref readIndex);
if (firstEdit < 0)
{
return(firstEdit);
}
// resize (smaller)
model.ContractData(token, destinationSize - 1);
// check result CRC
if (!ignoreChecksums)
{
var finalCRC = CalcCRC32(model.RawData);
if (direction == UpsPatchDirection.SourceToDestination && finalCRC != patchDestinationFileCRC)
{
return(-5);
}
if (direction == UpsPatchDirection.DestinationToSource && finalCRC != patchSourceFileCRC)
{
return(-5);
}
}
// check that the chunk ended cleanly
if (direction == UpsPatchDirection.SourceToDestination && readIndex != patch.Length - 12)
{
return(-6);
}
return(firstEdit);
}