how to write a structure in a shared mem segment.

[nass]

cool i found the answer as to why this is
basically a void* can not be dereferenced because it has no type...
so trying to offest a void* the compiler didn't know the base unit of offset (ie for a char the offseting is 1byte, for int its 4bytes, for double 64bytes).. so basically i cast the void* to char* in order to do the offset (since i know the offset i need in single byte units), then recast it to myStruct*...
lets see it its gonna save though..

[nass]

ok i have created a shared memory segment and can save data into it.. i can check because the segment is directly connected to a file in the disk. so yes i have verified data (bytes really) is written into the memory. the problem is reading...
basically just like in saving i create the same exact structure:
struct manualStruct {
Q_UINT8 mC1St;
Q_UINT8 mC2St;
Q_UINT8 mC3St;
};
and then
struct manualStruct *manualVar=(manualStruct*)((char*)file_memory + 0xC5);
basically file_memory is a void* pointer to the shared memory segment, so i cast it, add an offset to the exact location where data is written and then i simply assingn manualVar.
next i should be able to just:
MANUAL_cap1State=manualVar->mC1St;
MANUAL_cap2State=manualVar->mC2St;
MANUAL_cap3State=manualVar->mC3St;
where MANUAL_* variables are int.
then i just test with cout to see if the values have been copies and well they haven't...
any ideas why?
nass

[wysota]

Did you check that the shared segment got updated? For example by printf()ing the data directly from within the shared segment.

[nass]

isnt it sufficient looking directly at the associated file on the disk?
cause as soon as i save, i can see changes on the file... so i figure i save in the shared memory and directly the file on the disk is updated. causei surely dont write to the file.. i just 'save' to a location pointed to by the file_memory pointer (+ the offset)
nass

[wysota]

isnt it sufficient looking directly at the associated file on the disk?

If it seems that the segment is not updated, then it's better to check that out. There is no reason why the assignment should fail, so if it fails, there is a reason to suspect that the segment wasn't updated.