News:

MyKidsDiary.in :: Capture your kids magical moment and create your Online Private Diary for your kids

Main Menu

void pointers

Started by sukishan, Jul 10, 2009, 01:16 PM

Previous topic - Next topic

sukishan

void pointers

The void type of pointer is a special type of pointer. In C++, void represents the absence of type, so void pointers are pointers that point to a value that has no type (and thus also an undetermined length and undetermined dereference properties).

This allows void pointers to point to any data type, from an integer value or a float to a string of characters. But in exchange they have a great limitation: the data pointed by them cannot be directly dereferenced (which is logical, since we have no type to dereference to), and for that reason we will always have to cast the address in the void pointer to some other pointer type that points to a concrete data type before dereferencing it.

One of its uses may be to pass generic parameters to a function:

// increaser
#include <iostream>
using namespace std;

void increase (void* data, int psize)
{
  if ( psize == sizeof(char) )
  { char* pchar; pchar=(char*)data; ++(*pchar); }
  else if (psize == sizeof(int) )
  { int* pint; pint=(int*)data; ++(*pint); }
}

int main ()
{
  char a = 'x';
  int b = 1602;
  increase (&a,sizeof(a));
  increase (&b,sizeof(b));
  cout << a << ", " << b << endl;
  return 0;
}
A good beginning makes a good ending

Quick Reply

Warning: this topic has not been posted in for at least 120 days.
Unless you're sure you want to reply, please consider starting a new topic.

Note: this post will not display until it has been approved by a moderator.

Name:
Email:
Verification:
Please leave this box empty:
Type the letters shown in the picture
Listen to the letters / Request another image

Type the letters shown in the picture:

Shortcuts: ALT+S post or ALT+P preview