How to print bits in c

Question

I\'m writing a function to print bits in c, I\'m only allowed to use write function. my function doesn\'t work for other numbers.

void    print_bit         


        

Answer 1

Including limits.h for CHAR_BIT, allows you to generalize the funciton to allow passing values of any length but limiting the the output to the number of bytes desired. Passing the file descriptor will allow writing to any open descriptor (or simply passing STDOUT_FILENO to write to stdout.

void writebits (const unsigned long v, int fd)
{
    if (!v)  { putchar ('0'); return; };

    size_t sz = sizeof v * CHAR_BIT;
    unsigned long rem = 0;

    while (sz--)
        if ((rem = v >> sz))
            write (fd, (rem & 1) ? "1" : "0", 1);
}

For example:

#include 
#include 

/* CHAR_BIT */
#ifndef CHAR_BIT
# define CHAR_BIT  8
#endif

void writebits (const unsigned long v, int fd)
{
    if (!v)  { putchar ('0'); return; };

    size_t sz = sizeof v * CHAR_BIT;
    unsigned long rem = 0;

    while (sz--)
        if ((rem = v >> sz))
            write (fd, (rem & 1) ? "1" : "0", 1);
}

int main (void) {

    unsigned v = 0xcafebabe;

    writebits (v, STDOUT_FILENO);
    putchar ('\n');
    writebits ((unsigned char)(v >> 24), STDOUT_FILENO);
    putchar ('\n');

    return 0;
}

Example Output

$ ./bin/writebits
11001010111111101011101010111110
11001010