C++: What is the proper way of resizing a dynamically allocated array?

Question

In C, I would have done it using realloc.

In C++, one would normally consider using the STL vector class.

But how do I properly resize an array in C++ without using any of the above solutions?

Answer 1

There is no good equivalent of realloc in C++. You'll need to manually duplicate the array and copy the old elements over. Fortunately, thanks to the std::copy function in <algorithm>, this isn't too bad:

size_t k =  /* ... */
T* buffer = /* .. get old buffer of size k. .. */

T* newBuffer = new T[newSize];  // Assume newSize >= k
std::copy(buffer, buffer + k, newBuffer);

delete [] buffer;
buffer = newBuffer;

Hope this helps!

EDIT: Reordered the last two lines! Whoops!