Re: [Mingw-users] Resizing arrays in C++

[Phil <ph...@fl...>]

Thanks very much! I've rewritten the function, taking the recommendations
into account. It now looks like this:

template <class T> void resize_array(T *&array, int old_size, int new_size)
{
 cerr << "resize_array called: old_size: " << old_size << " new_size: " <<
new_size << "\n";

 if (old_size = 0)
  array =  new T[new_size];

 if (new_size == old_size)
  return;

 int items_to_copy = (new_size > old_size)?old_size:new_size;

 T *new_array = new T[new_size];

 memcpy(new_array, array, sizeof(array[0]) * items_to_copy);

 delete []array;
 array = new_array;
}

template void resize_array(KeyboardEventHandler *&array, int old_size, int
new_size);
template void resize_array(MouseMotionEventHandler *&array, int old_size,
int new_size);
template void resize_array(MouseButtonEventHandler *&array, int old_size,
int new_size);

There's only one problem: now I'm getting errors that look like this:
client_api.cpp:53: no matching function for call to `resize_array
(KeyboardEventHandler *&, int &, int &)'

I assume this has something to do with my use of templates, but I'm not
experienced enough with them to say for sure.

Thanks, Philip Bock

----- Original Message -----
From: "Stephen M.Webb" <ste...@cr...>
To: "Phil" <ph...@fl...>
Sent: Thursday, April 25, 2002 1:38 PM
Subject: Re: [Mingw-users] Resizing arrays in C++


> On April 25, 2002 02:02 pm, you wrote:
> > Thanks. I have an old reference book that came with Turbo C++ 3.0
> > which says sizeof(array) returns the number of bytes allocated, which
> > is the reason I was using that. I guess I should stop using that
> > book.
>
> Well, the book may be right.
>
>   int array[10]; // statically bound to 10 ints
>   assert(sizeof(array) == 10));
>
> is not the same as
>
>   int* arrayPtr = array; // dynamically bound to the same memory
>   assert(sizeof(arrayPtr) == sizeof(int*));
>
> > As for this delete[], it's the first I've heard about it. How
> > would that statement look? I suppose something like this:
> >
> > delete array[];
> >
> > Or do I have to include the number of elements to delete in the
> > square brackets?
>
>   int bufsize = 10;
>   char* buff = new char[bufSize];
>   ....
>   delete[] buf;
>
> the important thing is to pair the new[] operator with the delete[]
> operator, because between the two of them the number of elements of the
> array are tracked.
>
> Note that you can overload the new and delete operators and their array
> cousins for a class.  Looks weird but lets you perform custom memory
> allocation.
>
>   class C
>   {
>     static void* operator new[](size_t size);
>     static void  operator delete[](void* p, size_t);
>   };
>
>   C* cptr = new C[csize]; // calls C::operator new[](csize)
>   ...
>   delete[] cptr; // calls C::operator delete[](cptr, csize)
>
> --
> Stephen M. Webb
>