std::strings's capacity(), reserve() & resize() functions

Question

I wan to use std::string simply to create a dynamic buffer and than iterate through it using an index. Is resize() the only function to actually allocate the buffer?

Answer 1

No -- the point of reserve is to prevent re-allocation. resize sets the usable size, reserve does not -- it just sets an amount of space that's reserved, but not yet directly usable.

Here's one example -- we're going to create a 1000-character random string:

static const int size = 1000;
std::string x;
x.reserve(size);
for (int i=0; i

reserve is primarily an optimization tool though -- most code that works with reserve should also work (just, possibly, a little more slowly) without calling reserve. The one exception to that is that reserve can ensure that iterators remain valid, when they wouldn't without the call to reserve.