int to char

Is it possible to convert an int to a char?

I have a source code where that is done but it makes no sense to me. I can see how 2 or 9 could be converted to a char, but not how 345 can be.

Code:

unsigned char *buffer[100];
int value = 4333;

*buffer[0] = value;

I try to do the same in my code, it compiles, but I get a windows error when I run the program.

So, what happens here really?

thanks

Originally Posted by h3ro

Is it possible to convert an int to a char?

I have a source code where that is done but it makes no sense to me. I can see how 2 or 9 could be converted to a char, but not how 345 can be.

It can't. The compiler bit-slices the larger value to fit into the smaller one. It loses data.

Code:

unsigned char *buffer[100];
int value = 4333;

*buffer[0] = value;

I try to do the same in my code, it compiles, but I get a windows error when I run the program.

I doubt that very much. EDIT: the problem is that buffer is an array of 100 pointers to char. This array is uninitialized. You take the first pointer (buffer[0]) and dereference it. This causes a crash. The problem has nothing to do with the conversion.

Have you heard of a static_cast?

Code:

 int num; // user input
   
   std::cout << "Enter a number: ";
   std::cin >> num;
   
   // output the character using a static cast
   std::cout << "\ncharacter equivalent: " << static_cast<char>( num );

Code:

unsigned char *buffer[100];
int value = 4333;

*buffer[0] = value;

this allocates an array of 100 pointers to unsigned chars. But doeasnt allocate any space for the chars . buffer[0] points to a random location. dereferencing it -> boom.

BTW to assigne an int to a char no cast is needed.

Kurt

EDIT: just noticed that brewbuck has alredy mentioned that. sorry

Originally Posted by swgh

Have you heard of a static_cast?

Did you actually try it to make sure it did anything useful?

I'm sorry, but I dont really inderstand what the problem is. I am still having truble with pointers and are not sure on how they work.

Code:

unsigned char  *colorBuffer[300 * 400 * 3];
unsigned int r = 0, g = 0, b = 0;

 // GetR,G,B returns an int between 0 and 255
 r = currentMaterial.getR();
 g = currentMaterial.getG();
 b = currentMaterial.getB();
                                        
 *colorBuffer[arrayTracer + 0] = r;
 *colorBuffer[arrayTracer + 1] = g;
 *colorBuffer[arrayTracer + 2] = b;

Its the *colorBuffers that couse the problem. I feel kind of clueless right now.

I would think that you don't want an arry of pointers to char but an arry of chars
like this

Code:

unsigned char  colorBuffer[300 * 400 * 3];
unsigned int r = 0, g = 0, b = 0;

 // GetR,G,B returns an int between 0 and 255
 r = currentMaterial.getR();
 g = currentMaterial.getG();
 b = currentMaterial.getB();
                                        
 colorBuffer[arrayTracer + 0] = r;
 colorBuffer[arrayTracer + 1] = g;
 colorBuffer[arrayTracer + 2] = b;

Kurt

edit: If you really want it to be an arry of pointers to char you would have to allocate space for the chars but that is most unusual ( and a wast of space ).
like this

Code:

unsigned char * colorBuffer[300 * 400 * 3];
unsigned int r = 0, g = 0, b = 0;
int i;
for ( i = 0; i < 300 * 400 * 3; ++i )
    colorBuffer[i] = malloc(1);

 // GetR,G,B returns an int between 0 and 255
 r = currentMaterial.getR();
 g = currentMaterial.getG();
 b = currentMaterial.getB();
                                        
* colorBuffer[arrayTracer + 0] = r;
* colorBuffer[arrayTracer + 1] = g;
* colorBuffer[arrayTracer + 2] = b;

Think of pointers as the 'Shortcuts' you can create in Windows to files - only C++ pointers point to units of memory. You create a pointer like this: type it will point to* It's name.
Then, to extract the information it points to, you write *it's name. That * can mean two things! So what is happening here:

Code:

*colorBuffer[arrayTracer + 0] = r;

is that someone is using pointer called colourbuffer, and extracting (dereferencing) the information from the thing it points to (a variable, most likely). Hope it explained it a bit, I'm not much of an explainer.

EDIT: I'm assuming that you didn't write this code yourself? Because you sounded unsure.

Thank you