/// <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.Error);
}
if (C != MagicBytes[1])
{
return(VCDiffResult.Error);
}
if (D != MagicBytes[2])
{
return(VCDiffResult.Error);
}
if (version != 0x00 && version != 'S')
{
return(VCDiffResult.Error);
}
//compression not supported
if ((hdr & (int)VCDiffCodeFlags.VCDDECOMPRESS) != 0)
{
return(VCDiffResult.Error);
}
//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.Succes)
{
return(result);
}
}
IsSDHCFormat = version == 'S';
IsStarted = true;
//buffer all the dictionary up front
dict.BufferAll();
return(VCDiffResult.Succes);
}
