how to test for bits in a structure

[MikeW]

I am trying to test bits in a structure, can anyone help ?


this fails with " element is not a member".

how do I do a bit test to get a true/false ?

code --------------------


if (!current_data.Sequential_Shutter_Active_flag) // not active
{
// do something 'cos the bit is 0 not 1
}


structure definition ------------

struct data
{
long magicnumber;
signed level;
signed gain;
signed long ref_os;
int ext_ref_freq;
int address;
signed ref_state;
short NTSC_60Hz_flag;
short Sequential_Shutter_Active_flag;
short rs485;
short extref;
short rs422;
short rs232;
short ref_int;
short ref_ext;
short ref_auto;
short dummy1; //not used for anything, allows us to have an even amount of memory.
short dummy2; //not used for anything, allows us to have an even amount of memory.
short dummy3; //not used for anything, allows us to have an even amount of memory.
short dummy4; //not used for anything, allows us to have an even amount of memory.
short dummy5; //not used for anything, allows us to have an even amount of memory.
short dummy6; //not used for anything, allows us to have an even amount of memory.
short dummy7; //not used for anything, allows us to have an even amount of memory.
int chksum; //data checksum - equal to everything in the struct except this number
// mod 255.
};

struct data current_data;

[libor]

you can only use this syntax for bit fields: (There is an issue with byte boundaries, I think, you can't cross a byte with a bit field. Using 1 bit fields this does not concerns your code.)

[MikeW]

libor, sorry you are wrong.


the error is caused by the naming

reducing current_data.Sequential_Shutter_Active_flag to
current_data.Seq_Shutter_Active_flag



if (current_data.Seq_Shutter_Active_flag==OFF) // not active


it now compiles

[libor]

OK. thanks for the info, so you just reached the variable name length limit. ..and I have been avoiding using shorts in structs in vain.