In article <30atdp$457@cstatd.cstat.co.za>, vincer@iaccess.za (Vincent Risi) writes:
|>
|> What is the best way to declare variable length classes?  Given the
|> following code snatch, what are the alternatives?  You do not want a static
|> or global instance variable of the class to be declared, it should always be
|> declared as a pointer.  Is there a more elegant (less error prone) mechanism
|> to handle this sort of class structure?
|>
|> typedef class tA* pA;
|> typedef unsigned short ushort;
|>
|> class tA
|> {
|>   ...
|>   ushort Size;
|>   char Data[1];
|>   tA(void):Size(0){}
|> public:
|>   static pA Create(ushort aSize);
|> };
|>
|> pA tA::Create(ushort aSize)
|> {
|>   pA A = pA(new char[aSize+sizeof(tA)-1]);
|>   ...
|>   A->Size = aSize;
|>   return A;
|> }
|>
|>   ...
|>   pA A = tA.Create(200);
|>   ...
|>
|>
|> Vince Risi
|> ==========

I'm not sure what you intend to do with this class (and what you
mean by 'variable length classes') When you know the size that a
tA should have at the point of construction, you can use a
templateclass:

template<ushort Sz> class tA {
 char Data [Sz];
public:
 ta() {};
 ushort Size () { return Sz; }
};

...
tA<200>  ta200;
tA<200>  *pa = new tA<200>;
...



Ulf Schuenemann

--------------------------------------------------------------------
Ulf Sch   nemann
Institut f   r Informatik, Technische Universit   t M   nchen.
email: schuenem@informatik.tu-muenchen.de
WWW:   http://hphalle2/~schuenem  (currently not available from outside)

Devil's advocate

What is the best way to declare variable length classes?  Given the
following code snatch, what are the alternatives?  You do not want a static
or global instance variable of the class to be declared, it should always be
declared as a pointer.  Is there a more elegant (less error prone) mechanism
to handle this sort of class structure?

typedef class tA* pA;
typedef unsigned short ushort;

class tA
{
  ...
  ushort Size;
  char Data[1];
  tA(void):Size(0){}
public:
  static pA Create(ushort aSize);
};

pA tA::Create(ushort aSize)
{
  pA A = pA(new char[aSize+sizeof(tA)-1]);
  ...
  A->Size = aSize;
  return A;
}

  ...
  pA A = tA.Create(200);
  ...


Vince Risi
==========