Reading Serial data starting from the header - c++

Question

I am reading continuous serial data which is being sent as 29 byte array
with the first byte which is the header as a value of oxD1.
How can pick the data in the buffer starting from the Header.
This is my code.
int SerialPort::readSerialPortFreedPacket(BYTE *buffer, unsigned int
buf_size)
{
DWORD bytesRead;
int timeout = 500;
OVERLAPPED ovread = { 0 };
ovread.hEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
if (ovread.hEvent == NULL) {
// Error creating overlapped event; abort.
return FALSE;
}
if (!ReadFile( this->handler , (void*)buffer, 29, &bytesRead, &ovread)) {
if (GetLastError() != ERROR_IO_PENDING) {
// Handle error in communications
std::cout << "Error reading data " << std::endl;
}
else {
DWORD ret = WaitForSingleObject(ovread.hEvent, timeout);
switch (ret) {
case WAIT_OBJECT_0:
// HandleASuccessfulRead(buf, bytesRead);
std::cout << buffer << std::endl;
break;
case WAIT_TIMEOUT:
// Handle timeout
break;
case WAIT_FAILED:
// Handle failure
break;
default:
// what else to handle?
break;
}
}
}
else {
// read completed immediately
//HandleASuccessfulRead(buf,bytesRead);
}
return 0;
}