Interfaces.C.Strings chars_ptr memory management strategy

[NiGHTS <nights@unku.us>]

I am creating a binding to a C library that requires me to repeat the same function but with a string parameter that changes on each call. I don't want to have to keep creating and destroying string memory for all of these function calls. I would like to create the memory for the string once, allocate enough space so it doesn't need to grow, and reuse that memory for the function call every time I need to pass a new string to it.

The trick here is that whatever strategy I use must be compatible with C, so for instance using a storage pool would not be directly compatible with the C binding.

Here is just a quick and sloppy idea I had on how to tackle my problem.

str : chars_ptr := New_String ("                                     ");
...
Update (Item => str, Offset => 0, Str => "Some Param");
...
Update (Item => str, Offset => 0, Str => "Some Other Param");
...
Free (str);

I find the first line quite ugly. I'm sure there is an easier way to create a large empty string but I can't seem to come up with an elegant way to do it.

As far as the Update commands, will it act like strcpy() in C? If so I'd guess that this is an efficient technique.

Thanks for your help!