Thread: Implementing space allocated for a character array

I hope the title did a decent job of summarizing my issue. I am trying to extend a two dimensional algorithm to a 3 dimensional solution, and am having some trouble storing my slice files. I have an image object I, which has a member pt that is a pointer to an array of unsigned chars. My code looks like this:

Code:

istream& operator>>(istream& is, Image& I)
{
        if(I.pt) {
                cout << "test\n";
                delete [] I.pt;
                I.width = 0;
                I.height = 0;
        }

        .
        .
        .

        // Now we are ready to read the data
        I.pt = new unsigned char [I.getDataSize()];
        I.pt[1000] = (unsigned char)1;
        cout << I.pt[1000] << endl;
        cout << sizeof(I.pt) / sizeof(unsigned char) << endl;
        cout << I.getDataSize() << endl;
        cout << sizeof(I.pt) << endl;
        cout << sizeof(unsigned char) << endl;

and, my output is:

Code:

8
94633984
8
1

This is some pointless code that I am displaying hoping to resolve a larger issue. I am expecting to see:

Code:

1
94633984
94633984
94633984
1

What am I not understanding about the size of space pointed to by I.pt after the new statement?

cout << sizeof(I.pt) / sizeof(unsigned char) << endl;

Prints the size of a pointer, divided by the size of an unsigned char. Since sizeof(unsigned char) = 1, the answer depends on the pointer size on your system. Commonly 4 or 8. In your case, it seems to be 8, so I'd be guessing you're on a 64-bit system.

cout << I.getDataSize() << endl;

Probably gonna get the size of the array pointed to by pt. Your output seems to corroborate this.

cout << sizeof(I.pt) << endl;

Prints the size of a pointer, thus 8.

cout << sizeof(unsigned char) << endl;

Prints the size of an unsigned char, thus 1.

So, the output you are getting is correct.

You are sending an unsigned char to cout, hence it is interpreted as a printable character and will be printed as such.