Example of New operator overloading in c++

Posted Date: 24 Aug 2009	Resource Type: Code Snippets	Category: General
Author: Santosh Kumar Singh	Member Level: Gold
Rating:	Points: 3

////////////////////////////////////////
#include
#include
#include
#include

const int maxnames = 5;

////////////////////////////////////////
// The Names class.
////////////////////////////////////////
class Names
{
char name[25];
static char Names::pool[];
static short int Names::inuse[maxnames];

public:
Names(char* s = 0)
{
if (s)
strncpy(name, s, sizeof(name));
}
void* operator new[](size_t) throw(std::bad_alloc);
void operator delete[](void*) throw();
void display() const
{ std::cout << name << std::endl; }
};

// Simple memory pool to handle fixed number of Names.
char Names::pool[maxnames * sizeof(Names)];
short int Names::inuse[maxnames];

// Overloaded new[] operator for the Names class.
void* Names::operator new[](size_t size) throw(std::bad_alloc)
{
int elements = size / sizeof(Names);

// Find the first empty element (if any).
int p = -1;
int i = 0;
while ((i < maxnames) && (p == -1))
{
if (!inuse[i])
p = i;
++i;
}

// Not enough room.
if ((p == -1) || ((maxnames - p) < elements))
throw std::bad_alloc();

// Mark the elements as used.
for (int x=0; x inuse[p+x] = elements;

// Return pointer to memory.
return pool+p*sizeof(Names);
}

// Overloaded delete[] operator for the Names class.
void Names::operator delete[](void* b) throw()
{
if (b != 0)
{
int p = ((char*)b - pool) / sizeof(Names);
int elements = inuse[p];
for (int i = 0; i < elements; i++)
inuse[p + i] = 0;
}
}

////////////////////////////////////////
// The main() function.
////////////////////////////////////////
int main()
{
Names* np = new Names[maxnames];

int i;
for (i = 0; i < maxnames; i++)
{
std::cout << std::endl << "Enter name # "
<< i+1 << ": ";
char name[25];
std::cin >> name;
*(np + i) = name;
}

for (i = 0; i < maxnames; i++)
(np + i)->display();

delete [] np;

return 0;
}

Responses

Author: Miss Meetu Choudhary 27 Aug 2009

Member Level: Diamond Points : 2

Must add description to your code.

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