/// <summary>
/// Encodes the file
/// </summary>
/// <param name="interleaved">Set this to true to enable SDHC interleaved vcdiff google format</param>
/// <param name="checksum">Set this to true to add checksum for encoded data windows</param>
/// <returns></returns>
public VCDiffResult Encode(bool interleaved = false, bool checksum = false)
{
if (newData.Length == 0 || oldData.Length == 0)
{
return(VCDiffResult.Error);
}
VCDiffResult result = VCDiffResult.Succes;
oldData.Position = 0;
newData.Position = 0;
//file header
//write magic bytes
if (!interleaved && !checksum)
{
sout.writeBytes(MagicBytes);
}
else
{
sout.writeBytes(MagicBytesExtended);
}
//buffer the whole olddata (dictionary)
//otherwise it will be a slow process
//even Google's version reads in the entire dictionary file to memory
//it is just faster that way because of having to move the memory pointer around
//to find all the hash comparisons and stuff.
//It is much slower trying to random access read from file with FileStream class
//however the newData is read in chunks and processed for memory efficiency and speed
oldData.BufferAll();
//read in all the dictionary it is the only thing that needs to be
BlockHash dictionary = new BlockHash(oldData, 0, hasher);
dictionary.AddAllBlocks();
oldData.Position = 0;
ChunkEncoder chunker = new ChunkEncoder(dictionary, oldData, hasher, interleaved, checksum);
while (newData.CanRead)
{
using (ByteBuffer ntarget = new ByteBuffer(newData.ReadBytes(bufferSize)))
{
chunker.EncodeChunk(ntarget, sout);
}
//just in case
// System.GC.Collect();
}
return(result);
}
/// <summary>
/// Call this before calling decode
/// This expects at least the header part of the delta file
/// is available in the stream
/// </summary>
/// <returns></returns>
public VCDiffResult Start()
{
if (!delta.CanRead)
{
return(VCDiffResult.EOD);
}
byte V = delta.ReadByte();
if (!delta.CanRead)
{
return(VCDiffResult.EOD);
}
byte C = delta.ReadByte();
if (!delta.CanRead)
{
return(VCDiffResult.EOD);
}
byte D = delta.ReadByte();
if (!delta.CanRead)
{
return(VCDiffResult.EOD);
}
byte version = delta.ReadByte();
if (!delta.CanRead)
{
return(VCDiffResult.EOD);
}
byte hdr = delta.ReadByte();
if (V != MagicBytes[0])
{
return(VCDiffResult.ERRROR);
}
if (C != MagicBytes[1])
{
return(VCDiffResult.ERRROR);
}
if (D != MagicBytes[2])
{
return(VCDiffResult.ERRROR);
}
if (version != 0x00 && version != 'S')
{
return(VCDiffResult.ERRROR);
}
//compression not supported
if ((hdr & (int)VCDiffCodeFlags.VCDDECOMPRESS) != 0)
{
return(VCDiffResult.ERRROR);
}
//custom code table!
if ((hdr & (int)VCDiffCodeFlags.VCDCODETABLE) != 0)
{
if (!delta.CanRead)
{
return(VCDiffResult.EOD);
}
//try decoding the custom code table
//since we don't support the compress the next line should be the length of the code table
customTable = new CustomCodeTableDecoder();
VCDiffResult result = customTable.Decode(delta);
if (result != VCDiffResult.SUCCESS)
{
return(result);
}
}
googleVersion = version == 'S';
isStarted = true;
//buffer all the dictionary up front
dict.BufferAll();
return(VCDiffResult.SUCCESS);
}
