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2010-05-25T14:21:17Z

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==Allocate an array==

<source lang="cpp">#include <iostream>
#include <new>
using namespace std;

int main()
{
int *p, i;

try {
p = new int [10]; // allocate 10 integer array
} catch (bad_alloc xa) {
cout << "Allocation Failure\n";
return 1;
}

for(i=0; i<10; i++ )
p[i] = i;

for(i=0; i<10; i++)
cout << p[i] << " ";

delete [] p; // release the array

return 0;
}</source>
<pre class=codeResult>0 1 2 3 4 5 6 7 8 9</pre>

==Allocate an array of objects by overloading new and delete operators==

<source lang="cpp">#include <iostream>
#include <cstdlib>
#include <new>
using namespace std;
class Point {
int x, y;
public:
Point() {x = y = 0;}
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);
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);
}
// new overloaded for Point arrays.
void *Point::operator new[](size_t size)
{
void *p;
cout << "Using overload new[].\n";
p = malloc(size);
if(!p) {
bad_alloc ba;
throw ba;
}
return p;
}
// delete overloaded for Point arrays.
void Point::operator delete[](void *p)
{
cout << "Freeing array using overloaded delete[]\n";
free(p);
}
int main()
{
Point *p1, *p2;
int i;
try {
p1 = new Point (10, 20); // allocate an object
} catch (bad_alloc xa) {
cout << "Allocation error for p1.\n";
return 1;;
}
try {
p2 = new Point [10]; // allocate an array
} catch (bad_alloc xa) {
cout << "Allocation error for p2.\n";
return 1;;
}
p1->show();
for(i=0; i<10; i++)
p2[i].show();
delete p1; // free an object
delete [] p2; // free an array
return 0;
}</source>
<pre class=codeResult>In overloaded new.
Using overload new[].
10 20
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
0 0
In overloaded delete.
Freeing array using overloaded delete[]</pre>

==Allocate an object==

<source lang="cpp">#include <iostream>
#include <new>
using namespace std;

class Rectangle {
int width;
int height;
public:
Rectangle(int w, int h) {
width = w;
height = h;
cout << "Constructing " << width << " by " << height << " rectangle.\n";
}

~Rectangle() {
cout << "Destructing " << width << " by " << height << " rectangle.\n";
}

int area() {
return width * height;
}
};

int main()
{
Rectangle *p;

try {
p = new Rectangle(10, 8);
} catch (bad_alloc xa) {
cout << "Allocation Failure\n";
return 1;
}

cout << "Area is " << p->area();

delete p;

return 0;
}</source>
<pre class=codeResult>Constructing 10 by 8 rectangle.
Area is 80Destructing 10 by 8 rectangle.</pre>

==Allocate memory for an object==

<source lang="cpp">#include <iostream>
#include <new>
using namespace std;

class Rectangle {
int width;
int height;
public:
Rectangle(int w, int h) {
width = w;
height = h;
cout << "Constructing " << width << " by " << height << " rectangle.\n";
}

~Rectangle() {
cout << "Destructing " << width << " by " << height << " rectangle.\n";
}

int area() {
return width * height;
}
};

int main()
{
Rectangle *p;

try {
p = new Rectangle(10, 8);
} catch (bad_alloc xa) {
cout << "Allocation Failure\n";
return 1;
}

cout << "Area is " << p->area();

delete p;

return 0;
}</source>
<pre class=codeResult>Constructing 10 by 8 rectangle.
Area is 80Destructing 10 by 8 rectangle.</pre>

==Catch "new" memory allocation exception==

<source lang="cpp">#include <iostream>
#include <new>
using namespace std;

class Rectangle {
int width;
int height;
public:
Rectangle(int w, int h) {
width = w;
height = h;
cout << "Constructing " << width << " by " << height << " rectangle.\n";
}

~Rectangle() {
cout << "Destructing " << width << " by " << height << " rectangle.\n";
}

int area() {
return width * height;
}
};

int main()
{
Rectangle *p;

try {
p = new Rectangle(10, 8);
} catch (bad_alloc xa) {
cout << "Allocation Failure\n";
return 1;
}

cout << "Area is " << p->area();

delete p;

return 0;
}</source>
<pre class=codeResult>Constructing 10 by 8 rectangle.
Area is 80Destructing 10 by 8 rectangle.</pre>

==dynamically allocated objects may have constructors and destructors==

<source lang="cpp">#include <iostream>
#include <new>
#include <cstring>
using namespace std;

class balance {
double cur_bal;
char name[80];
public:
balance(double n, char *s) {
cur_bal = n;
strcpy(name, s);
}
~balance() {
cout << "Destructing ";
cout << name << "\n";
}
void get_bal(double &n, char *s) {
n = cur_bal;
strcpy(s, name);
}
};

int main()
{
balance *p;
char s[80];
double n;
// this version uses an initializer
try {
p = new balance (1.1, "A");
} catch (bad_alloc xa) {
cout << "Allocation Failure\n";
return 1;
}

p->get_bal(n, s);

cout << s << ""s balance is: " << n;
cout << "\n";

delete p;

return 0;
}</source>

==Global new==

<source lang="cpp">#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";
}
};
// 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()
{
Point *p1, *p2;
float *f;
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;;
}
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;
}</source>
<pre class=codeResult>10.1
10 20
-10 -20</pre>

==Initialize memory==

<source lang="cpp">#include <iostream>
#include <new>
using namespace std;

int main()
{
int *p;

try {
p = new int (87); // initialize to 87
} catch (bad_alloc xa) {
cout << "Allocation Failure\n";
return 1;
}

cout << "At " << p << " is the value " << *p << "\n";

delete p;

return 0;
}</source>
<pre class=codeResult>At 0x3d2448 is the value 87</pre>

==Use new and delete==

<source lang="cpp">#include <iostream>
#include <new>
using namespace std;

int main()
{
int *p;

try {
p = new int; // allocate space for an int
} catch (bad_alloc xa) {
cout << "Allocation Failure\n";
return 1;
}

*p = 100;

cout << "At " << p << " is the value " << *p << "\n";

delete p;

return 0;
}</source>
<pre class=codeResult>At 0x3d2448 is the value 100</pre>

==using new to get memory for strings==

<source lang="cpp">#include <iostream>
#include <cstring>
using namespace std;
class String {
private:
char* str;
public:
String(char* s){
int length = strlen(s);
str = new char[length+1];
strcpy(str, s);
}
~String() {
delete[] str;
}
void display(){
cout << str << endl;
}
};
int main()
{
String s1 = "this is a test";

cout << "s1=";
s1.display();
return 0;
}</source>

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