pr11030.cpp

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////////////////////////////////////////
// File Name: pr11030.cpp
////////////////////////////////////////
#include <iostream>
#include <cstring>
#include <cstddef>
#include <new>

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<elements; ++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;
}