Thread: Quick Fill "struct"s

Hullo

Let's say I Initialise a struct with:

Code:

struct MyStruct
{
FLOAT A, B, C;
};

Now, when I initialise a variable, I can do:

Code:

MyStruct MyVariable[]=
{
{1, 2, 3}
{2, 6, 2}
//And so forth
};

What if though, I want to add another data set to the array? Right now MyVariable[0] and MyVariable[1] have info, but MyVariable[2] does not.
Do I have to do each component seperately?
I.e.

Code:

MyVariable[2].A = 4;
MyVariable[2].B = 1;
MyVariable[2].C = 0;

I've tried:

Code:

MyVariable[2]=
{
{4, 1, 0}
};
//Which gives me many errors about the {} brackets.

//I also tried:
MyVariable[2] = (4, 1, 0);
//Which tells me that the Binary "=" sign can't assign the floats (or something to that effect)

//I've also tried other combinations, but none have worked

So, I guess my question is, do I have to settle for that first one? Doing each element of the structure individually?

Either you do it individually, or..

Code:

MyStruct blah = { 0, 1, 2 } ;

memcpy(&MyVariable[2],&blah,sizeof(MyStruct)) ;

Along the same lines, would I be able to use the memcpy method to copy over an array of "MyStruct"s INTO another array?

I.e. Given:

Code:

MyStruct Temp[3];
MyStruct All[];

I'm looking for a faster way to accomplish:

Code:

memcpy(&All[1],&Temp[0],sizeof(MyStruct));
memcpy(&All[2],&Temp[1],sizeof(MyStruct));
memcpy(&All[3],&Temp[2],sizeof(MyStruct));

Is there some way I could choose a starting point in the "All" variable and bring over the entire "Temp" variable at once to fill in a chunk of the "All" variable?

Thanks a ton for the help so far

try:

Code:

memcpy(&All[1], &Temp[0], sizeof(MyStruct) * number_of_items);

where number_of_items equals the number of elements that you want to copy.

I can't?........damn.

The thing is, I don't know how big I want it to be yet, so I was just planning on adding to it during runtime. And I don't know how much I'll be adding...should I just make it one very massive variable? Cause that seems like a waste of resources....and there's always the problem that, what if I need more than initialised?

I would use

Code:

MyStruct * myvariable = (MyStruct *) malloc(sizeof(MyStruct) * numberofelements) ;

instead of your calloc example. malloc doesn't waste cycles setting everything to 0.

You can't do if (Structures[3] == NULL)
since it isn't a pointer.

The only way to do it is to add a variable telling if Structures[X] is initalized or using an array of pointers to MyStructs