public VCDiffResult Decode(IByteBuffer source)
{
VCDiffResult result = VCDiffResult.Succes;
//the custom codetable itself is a VCDiff file but it is required to be encoded with the standard table
//the length should be the first thing after the hdr_indicator if not supporting compression
//at least according to the RFC specs.
int lengthOfCodeTable = VarIntBE.ParseInt32(source);
if (lengthOfCodeTable == 0)
{
return(VCDiffResult.Error);
}
ByteBuffer codeTable = new ByteBuffer(source.ReadBytes(lengthOfCodeTable));
//according to the RFC specifications the next two items will be the size of near and size of same
//they are bytes in the RFC spec, but for some reason Google uses the varint to read which does
//the same thing if it is a single byte
//but I am going to just read in bytes because it is the RFC standard
NearSize = codeTable.ReadByte();
SameSize = codeTable.ReadByte();
if (NearSize == 0 || SameSize == 0 || NearSize > byte.MaxValue || SameSize > byte.MaxValue)
{
return(VCDiffResult.Error);
}
CustomTable = new CodeTable();
//get the original bytes of the default codetable to use as a dictionary
IByteBuffer dictionary = CustomTable.GetBytes();
//Decode the code table VCDiff file itself
//stream the decoded output into a memory stream
using (MemoryStream sout = new MemoryStream())
{
VCDecoder decoder = new VCDecoder(dictionary, codeTable, sout);
result = decoder.Start();
if (result != VCDiffResult.Succes)
{
return(result);
}
long bytesWritten = 0;
result = decoder.Decode(out bytesWritten);
if (result != VCDiffResult.Succes || bytesWritten == 0)
{
return(VCDiffResult.Error);
}
//set the new table data that was decoded
if (!CustomTable.SetBytes(sout.ToArray()))
{
result = VCDiffResult.Error;
}
}
return(result);
}