C++ Tutorial/Operator Overloading/overload new operator — различия между версиями
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Версия 14:21, 25 мая 2010
An example of overloading new and delete globally
#include <iostream>
#include <cstdlib>
#include <new>
using namespace std;
class loc {
int longitude, latitude;
public:
loc() {}
loc(int lg, int lt) {
longitude = lg;
latitude = lt;
}
void show() {
cout << longitude << " ";
cout << latitude << "\n";
}
};
// Global new
void *operator new(size_t size)
{
void *p;
p = malloc(size);
if(!p) {
bad_alloc ba;
throw ba;
}
return p;
}
// Global delete
void operator delete(void *p)
{
free(p);
}
int main()
{
loc *p1, *p2;
float *f;
try {
p1 = new loc (10, 20);
} catch (bad_alloc xa) {
cout << "Allocation error for p1.\n";
return 1;;
}
try {
p2 = new loc (-10, -20);
} catch (bad_alloc xa) {
cout << "Allocation error for p2.\n";
return 1;;
}
try {
f = new float; // uses overloaded new, too
} catch (bad_alloc xa) {
cout << "Allocation error for f.\n";
return 1;;
}
*f = 10.10F;
cout << *f << "\n";
p1->show();
p2->show();
delete p1;
delete p2;
delete f;
return 0;
}Overloaded "new" operator relative to Point
#include <iostream>
#include <cstdlib>
#include <new>
using namespace std;
class Point {
int x, y;
public:
Point() {}
Point(int px, int py) {
x = px;
y = py;
}
void show() {
cout << x << " ";
cout << y << "\n";
}
void *operator new(size_t size);
void operator delete(void *p);
};
// new overloaded relative to Point.
void *Point::operator new(size_t size)
{
void *p;
cout << "In overloaded new.\n";
p = malloc(size);
if(!p) {
bad_alloc ba;
throw ba;
}
return p;
}
// delete overloaded relative to Point.
void Point::operator delete(void *p)
{
cout << "In overloaded delete.\n";
free(p);
}
int main()
{
Point *p1, *p2;
try {
p1 = new Point (10, 20);
} catch (bad_alloc xa) {
cout << "Allocation error for p1.\n";
return 1;
}
try {
p2 = new Point (-10, -20);
} catch (bad_alloc xa) {
cout << "Allocation error for p2.\n";
return 1;;
}
p1->show();
p2->show();
delete p1;
delete p2;
return 0;
}In overloaded new. In overloaded new. 10 20 -10 -20 In overloaded delete. In overloaded delete.
Overloading new and delete
#include <iostream>
#include <cstdlib>
#include <new>
using namespace std;
class loc {
int longitude, latitude;
public:
loc() {}
loc(int lg, int lt) {
longitude = lg;
latitude = lt;
}
void show() {
cout << longitude << " ";
cout << latitude << "\n";
}
void *operator new(size_t size);
void operator delete(void *p);
};
// new overloaded relative to loc.
void *loc::operator new(size_t size)
{
void *p;
cout << "In overloaded new.\n";
p = malloc(size);
if(!p) {
bad_alloc ba;
throw ba;
}
return p;
}
// delete overloaded relative to loc.
void loc::operator delete(void *p)
{
cout << "In overloaded delete.\n";
free(p);
}
int main()
{
loc *p1, *p2;
try {
p1 = new loc (10, 20);
} catch (bad_alloc xa) {
cout << "Allocation error for p1.\n";
return 1;
}
try {
p2 = new loc (-10, -20);
} catch (bad_alloc xa) {
cout << "Allocation error for p2.\n";
return 1;;
}
p1->show();
p2->show();
delete p1;
delete p2;
return 0;
}