Shifting values within an array

[Steven Schveighoffer]

On Tue, 10 Aug 2010 09:01:28 -0400, Chris Williams <aahz at seanet.com> wrote:

> I would like to be able to do something like this:
>
> class A {
> 	int i;
> }
>
> int main() {
> 	A[] list;
>
> 	for (uint L = 0; L < 3; L++) {
> 		for (uint L2 = 0; L2 < 3; L2++) {
> 			uint index = L + L2;
>
> 			uint copyAmount = list.length - index;
> 			list.length = list.length + 1;
> 			if (copyAmount > 0) {  // Move data after index one slot later to  
> make room
> 				A[] sliceFrom = list[index .. (index + copyAmount)];
> 				A[] sliceTo = list[(index + 1) .. (index + 1 + copyAmount)];
> 				sliceTo[] = sliceFrom[];
> 			}
> 			list[index] = new A();
> 			list[index].i = index;
> 		}
> 	}
>
> 	return 0;
> }
>
> I have a running implementation which uses C's memmove(), but I gather  
> that this isn't a safe means to do it as the garbage collector
> might run while the references to the object are being manipulated. Is  
> there a way to do this outside of a loop?

I think memmove should be fine.  All thread stacks are scanned during GC  
cycles, so there is no danger of having one element get collected.  I  
think memmove will not copy half a reference anyways.

-Steve