C++ - Inserting and Extracting Characters from an Integer Array

Question

For example:

char mem[100000];

int reg[8];

mem[36] = 'p';         // add char p to our 36th index of our char array

reg[3] = (int)mem[36]; // store value of mem[36] into reg[3]

Now I want to print the char value at index 3 of that int array.
So far my thought process has lead me to code such as this:

char *c = (char*)reg[3];

cout << *c << endl;

But I am still getting weird values and characters when trying to print it out.

From my understanding, an integer is equal to 4 characters. Since a character is technically a byte and an integer is 4 bytes.

So I am storing a character into my integer array as 4 bytes, but when I pull it out, there is garbage data since the character I inserted is only one byte compared to the index being 4 bytes in size.

Yes, and instead of the char 'p' being printed, a long integer is printed. This is due to garbage data in my index, since a character is technically only 1 byte, and an integer is 4 bytes. — kabuzashi
– kabuzashi, Commented Oct 7, 2017 at 2:14

CAMD_3441 · Accepted Answer · 2017-10-07 02:59:06Z

1

Have you tried this:

char mem[100000];
int reg[8];
mem[36] = 'p';         // add char p to our 36th index of our char array
reg[3] = (int)mem[36]; // store value of mem[36] into reg[3]
char txt[16];
sprintf(txt, "%c", reg[3]);  // assigns the value as a char to txt array
cout<<txt<<endl;

This prints out the value 'p'

answered Oct 7, 2017 at 2:59

CAMD_3441

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Comments

frslm · Accepted Answer · 2017-10-07 02:19:57Z

0

You shouldn't be using pointers here; it's sufficient to work with chars:

char c = reg[3];
cout << c << endl;

Note, however, that you could lose information when trying to stuff an int into a char variable.

answered Oct 7, 2017 at 2:19

frslm

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5 Comments

kabuzashi Over a year ago

Your solution is correct. But my problem is that I am not directly adding a character to my array. I was trying to show a simplified example. In reality I am adding a character from a separate char array into this int array. So I am getting an error that says "char* cannot be assigned to int." So the only way to make it work, is to cast it to an integer, which gives it a different representation in the array. And because of this casting, I am having troubles grabbing the character back out of the array.

frslm Over a year ago

Show us how you're adding the character from that other char array. You might be trying to assign the whole array to a single index in the int array.

frslm Over a year ago

Your "char* cannot be assigned to int" issue is solved if you use chars instead of char *s as given in the solution. Even with your additional code, using a char seems to solve your issue. Is there something I might be misunderstanding here?

kabuzashi Over a year ago

The "char*" in my error is referring to my char array. I am taking an element from my char array (char*) and inserting it into my int array. That is why I am getting the "char* cannot be assigned to an int" error. So the only way I can insert something from my character array into my integer array is to cast the value into an integer.

kabuzashi Over a year ago

(continued...) Now if I want to print out what I just inserted into my integer array, it gives me a weird representation. And that is because I am storing a 1-byte character into an index that is 4-bytes long (since it is an integer array). So I just can not figure out how to print out the character representation of what I just inserted.

Artemy Vysotsky · Accepted Answer · 2017-10-07 05:19:52Z

0

I do not see what is your problem. You store the char into int var. You want to print it back - just cast the value to char and print it

#include <iostream>

int main()
{
    char mem[100];

    int reg[8];

    mem[36] = 'p';         // add char p to our 36th index of our char array

    // store value of mem[36] into reg[3]
    reg[3] = mem[36]; 

    // store value of mem[36] into reg[4] with cast
    reg[4] = static_cast<int>(mem[36]); 

    std::cout << static_cast<char>(reg[3]) << '\n';
    std::cout << static_cast<char>(reg[4]) << '\n';

}

/****************
 * Output
$ ./test
p
p
*/

answered Oct 7, 2017 at 5:19

Artemy Vysotsky

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