Is there a method to print a n-bit (like 256-bit) integer in c without using an external library?

Question

I Have found a way to make a n-bit integer and do arithmetic on the integers, But I don't know how to print those integers, My method to make a n-bit integer is just to make an array of, lets say char's, and make the array (size of array elements) / n elements long. Does anyone know how to print these?

• I had an idea to store the powers of 2 ^ x as strings but I realized that would not work.

Answer 1

You can't use standard library functions to convert to string or print in base != 2, 4, 8, 16 (generally 2^n).

If you want to print using those bases you can easily write your own function (example one assuming little endian)

void printInteger(const void *buff, size_t size, int base)
{
    const char digits[] = "0123456789ABCDEF";
    const unsigned char *uc = buff + size - 1;
    unsigned nbits;
    unsigned mask;

    switch(base)
    {
        case 2:
            nbits = 1;
            break;
        case 4:
            nbits = 2;
            break;
        case 8:
            nbits = 3;
            break;
        case 16:
            nbits = 4;
            break;
        default: 
            return;
    }
    mask =  (1U << nbits) - 1;
    while(size--)
    {
        for(int nb = CHAR_BIT / nbits - 1; nb >= 0; nb--)
        {
            printf("%c", digits[(*uc >> (nb * nbits)) & mask]);
        }
        uc--;
    }
}

int main(void)
{
    unsigned test = 0x12345678;

    printInteger(&test, sizeof(test), 16);
    printf("\n");
    printInteger(&test, sizeof(test), 8);
    printf("\n");
    printInteger(&test, sizeof(test), 4);
    printf("\n");
    printInteger(&test, sizeof(test), 2);
    printf("\n");
}