/// <summary>
/// Decode normally
/// </summary>
/// <returns></returns>
public VCDiffResult Decode()
{
ByteBuffer instructionBuffer = new ByteBuffer(window.InstructionsAndSizesData);
ByteBuffer addressBuffer = new ByteBuffer(window.AddressesForCopyData);
ByteBuffer addRunBuffer = new ByteBuffer(window.AddRunData);
InstructionDecoder instrDecoder = new InstructionDecoder(instructionBuffer, this.customTable);
VCDiffResult result = VCDiffResult.SUCCESS;
while (decodedOnly < window.DecodedDeltaLength && instructionBuffer.CanRead)
{
int decodedSize = 0;
byte mode = 0;
VCDiffInstructionType instruction = instrDecoder.Next(out decodedSize, out mode);
switch (instruction)
{
case VCDiffInstructionType.EOD:
targetData.Clear();
return(VCDiffResult.EOD);
case VCDiffInstructionType.ERROR:
targetData.Clear();
return(VCDiffResult.ERRROR);
default:
break;
}
switch (instruction)
{
case VCDiffInstructionType.ADD:
result = DecodeAdd(decodedSize, addRunBuffer);
break;
case VCDiffInstructionType.RUN:
result = DecodeRun(decodedSize, addRunBuffer);
break;
case VCDiffInstructionType.COPY:
result = DecodeCopy(decodedSize, mode, addressBuffer);
break;
default:
targetData.Clear();
return(VCDiffResult.ERRROR);
}
}
if (window.HasChecksum)
{
uint adler = Checksum.ComputeAdler32(targetData.ToArray());
if (adler != window.Checksum)
{
result = VCDiffResult.ERRROR;
}
}
targetData.Clear();
return(result);
}
/// <summary>
/// Decode if as expecting interleave
/// </summary>
/// <returns></returns>
public VCDiffResult DecodeInterleave()
{
VCDiffResult result = VCDiffResult.SUCCESS;
//since interleave expected then the last point that was most likely decoded was the lengths section
//so following is all data for the add run copy etc
long interleaveLength = window.InstructionAndSizesLength;
List <byte> previous = new List <byte>();
bool didBreakBeforeComplete = false;
int lastDecodedSize = 0;
VCDiffInstructionType lastDecodedInstruction = VCDiffInstructionType.NOOP;
while (interleaveLength > 0)
{
if (target.CanRead)
{
//read in
didBreakBeforeComplete = false;
//try to read in all interleaved bytes
//if not then it will buffer for next time
previous.AddRange(target.ReadBytes((int)interleaveLength));
ByteBuffer incoming = new ByteBuffer(previous.ToArray());
previous.Clear();
long initialLength = incoming.Length;
InstructionDecoder instrDecoder = new InstructionDecoder(incoming, this.customTable);
while (incoming.CanRead && decodedOnly < window.DecodedDeltaLength)
{
int decodedSize = 0;
byte mode = 0;
VCDiffInstructionType instruction = VCDiffInstructionType.NOOP;
if (lastDecodedSize > 0 && lastDecodedInstruction != VCDiffInstructionType.NOOP)
{
decodedSize = lastDecodedSize;
instruction = lastDecodedInstruction;
}
else
{
instruction = instrDecoder.Next(out decodedSize, out mode);
switch (instruction)
{
case VCDiffInstructionType.EOD:
didBreakBeforeComplete = true;
break;
case VCDiffInstructionType.ERROR:
targetData.Clear();
return(VCDiffResult.ERRROR);
default:
break;
}
}
//if instruction is EOD then decodedSize will be 0 as well
//the last part of the buffer containing the instruction will be
//buffered for the next loop
lastDecodedInstruction = instruction;
lastDecodedSize = decodedSize;
if (didBreakBeforeComplete)
{
//we don't have all the data so store this pointer into a temporary list to resolve next loop
didBreakBeforeComplete = true;
interleaveLength -= incoming.Position;
if (initialLength - incoming.Position > 0)
{
previous.AddRange(incoming.ReadBytes((int)(initialLength - incoming.Position)));
}
break;
}
switch (instruction)
{
case VCDiffInstructionType.ADD:
result = DecodeAdd(decodedSize, incoming);
break;
case VCDiffInstructionType.RUN:
result = DecodeRun(decodedSize, incoming);
break;
case VCDiffInstructionType.COPY:
result = DecodeCopy(decodedSize, mode, incoming);
break;
default:
targetData.Clear();
return(VCDiffResult.ERRROR);
}
if (result == VCDiffResult.EOD)
{
//we don't have all the data so store this pointer into a temporary list to resolve next loop
didBreakBeforeComplete = true;
interleaveLength -= incoming.Position;
if (initialLength - incoming.Position > 0)
{
previous.AddRange(incoming.ReadBytes((int)(initialLength - incoming.Position)));
}
break;
}
//reset these as we have successfully used them
lastDecodedInstruction = VCDiffInstructionType.NOOP;
lastDecodedSize = 0;
}
if (!didBreakBeforeComplete)
{
interleaveLength -= initialLength;
}
}
}
if (window.HasChecksum)
{
uint adler = Checksum.ComputeAdler32(targetData.ToArray());
if (adler != window.Checksum)
{
result = VCDiffResult.ERRROR;
}
}
targetData.Clear();
return(result);
}
/// <summary>
/// Encodes the data using the settings from initialization
/// </summary>
/// <param name="newData">the target data</param>
/// <param name="sout">the out stream</param>
public void EncodeChunk(IByteBuffer newData, ByteStreamWriter sout)
{
uint checksum = 0;
///If checksum needed
///Generate Adler32 checksum for the incoming bytes
if (hasChecksum)
{
newData.Position = 0;
byte[] bytes = newData.ReadBytes((int)newData.Length);
checksum = Checksum.ComputeAdler32(bytes);
bytes = null;
}
windowEncoder = new WindowEncoder(oldData.Length, checksum, interleaved, hasChecksum);
oldData.Position = 0;
newData.Position = 0;
this.newData = newData;
long nextEncode = newData.Position;
long targetEnd = newData.Length;
long startOfLastBlock = targetEnd - BlockHash.BlockSize;
long candidatePos = nextEncode;
//create the first hash
ulong hash = hasher.Hash(newData.PeekBytes(BlockHash.BlockSize));
while (true)
{
//if less than block size exit and then write as an ADD
if (newData.Length - nextEncode < BlockHash.BlockSize)
{
break;
}
//try and encode the copy and add instructions that best match
long bytesEncoded = EncodeCopyForBestMatch(hash, candidatePos, nextEncode, targetEnd);
if (bytesEncoded > 0)
{
nextEncode += bytesEncoded;
candidatePos = nextEncode;
if (candidatePos > startOfLastBlock)
{
break;
}
newData.Position = candidatePos;
//cannot use rolling hash since we skipped so many
hash = hasher.Hash(newData.ReadBytes(BlockHash.BlockSize));
}
else
{
if (candidatePos + 1 > startOfLastBlock)
{
break;
}
//update hash requires the first byte of the last hash as well as the byte that is first byte pos + blockSize
//in order to properly calculate the rolling hash
newData.Position = candidatePos;
byte peek0 = newData.ReadByte();
newData.Position = candidatePos + BlockHash.BlockSize;
byte peek1 = newData.ReadByte();
hash = hasher.UpdateHash(hash, peek0, peek1);
candidatePos++;
}
}
//Add the rest of the data that was not encoded
if (nextEncode < newData.Length)
{
int len = (int)(newData.Length - nextEncode);
newData.Position = nextEncode;
windowEncoder.Add(newData.ReadBytes(len));
}
//output the final window
windowEncoder.Output(sout);
}
