Seeking and Reading a CFile

I am having trouble trying to execute multiple Read calls on a CFile.

I can execute the first Read fine, reading in BUFFER_LENGTH bits...
I then loop through the data, reading and handling different data types (In
my example below, I only showed one case but other types are similar), I
just use one byte to distinquish between different types.
After finding out the type, I check to make sure that the entire structure
made it in the buffer, if not I then try to reposition the file pointer by
dwRead-i, such that the first byte read in is the same type identifier and I
can resume reading the entire type.

I thought this should work, however on the second Read, dwRead = 0, meaning
no bytes were read.

What did I do wrong?

Here is the code:

Cfile file;
file.Open(...);

while((dwRead = file.Read(buffer, BUFFER_LENGTH)) > 0){
    bool refill;
    for(int i = 0 ; i < dwRead;i++)
    {
        //first make sure there was enough room to read next byte (size
byte)
        if(i == (dwRead -1)){
            //the type identifier was the last byte, reposition -1 and get
another chunk
            file.Seek( -(dwRead - i) , CFile::current);
            break;
        }
        refill = false;
        switch(buffer[i])
        {
            case DATAPT:
                if( (i + sizeof(DataPt) ) >= dwRead-1){
                    file.Seek( -(dwRead - i) , CFile::current);
                    refill = true;
                }
                else{
                    handleDataPt((DataPt*) &buffer[i+1]);
                    i += sizeof(DataPt);//advance i past size of DataPt to
next type Identifier
                 }
                break;
          }
           if(refill)
                break;
        }

    if(refill && dwRead != BUFFER_LENGTH)
        break;//requested to refill, however it was end of file...corrupted
data
}
file.Close();

Thanks,

Nick