How to get the memory size of a dynamic array?

Question

In Delphi, you can get the size of a value type with the sizeof() compiler magic function, but calling sizeof() on a reference type will give you the size of a pointer, not of the value it's pointing to.

For objects, you can get the memory size with the InstanceSize method, but what about for dynamic arrays? Due to padding, length(MyArray) * sizeof(element) may not be accurate. So, is there any accurate way to get the memory size of a dynamic array?

Answer 1

Between elements of a dynamic array there is no padding, Length(MyArray)*SizeOf(Element) should be accurate.

Answer 2

In fact, length(MyArray) * sizeof(element) will be accurate for the array content excluding any internal dynamic array or string.

If you want the whole array used memory, including nested reference types content size, you can use our TDynArray wrapper. It is able to serialize into binary any dynamic array, including reference counted members (like dynamic arrays or strings). You have SaveTo / SaveToStream methods for this purpose, and you are able to get the actual size of all content.

Take a look at this blog article, which presents this wrapper. It is open source, and works from Delphi 5 up to XE4, in both Win32 and Win64 platform.