The FEE Server Control Engine of the ALICE-TRD - Westfälische ...

A Using the libTRD
The C++ library libTRD provides comfortable interface classes to control the readout
chamber. Furthermore it provides some general purpose classes like the logging system.
In this appendix an example program is described which illustrates how the libTRD can
be used by stand alone programs. The source code is shown in listing A.1.
In the lines 1 to 14 the necessary header files are included. Apart from iostream and
vector all other header files belongs to libTRD. First the logging system is initialized (lines
20 to 27). In this example two logging output channels are created. One channel writes
all log messages with a log level equal or greater than einfo to standard out (line 21) and
the other channel writes all messages, including debug messages, to a file (line 22). After
the logging system is initialized, a corresponding debug message is printed (lines 29-30).
The message will only show up in the log file but not on the screen because its log level
is smaller than einfo.
Then two SCSN commands are created. In line 32 the array which will hold the commands
is created and filled afterwards (lines 35 to 43). The vector which will hold the
results of the SCSN commands is created in line 46. Next, the SCSN bus is opened, the
two frames are send, the results are stored in the created vector and the bus is closed. In
case of an error, an exception is thrown by the class SCSNBus. To prevent the program
from just quitting in such a case, the exception is caught and printed to tlog (lines 55 to
59). For that output the second highest log-level (eerror) is chosen, because exceptions
thrown by class SCSNBus usually indicate serious problems. The far most common cause
for such an exception are not powered MCMs. If no error occurred, the if-clause in lines
61 to 72 checks if the value was written correctly and prints out a suitable message. Afterwards
the program is finished.
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