Binary to string

Hello everyone,

I am having a bit of trouble. I am trying to read a string and convert it to binary. I finished the code, and it works, but I can't figure out how to convert binary back to string.

Here is what I have so far:

Code:

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#include <stdlib.h>
#include <string.h>

int power(int, int);
char* stob(char *);        // string to binary

int main() {
        char str[1024];

        printf("Enter some text: ");
        scanf("%s", str);

        printf("Binary value: %s\n", stob(str));

        return 0;
}

int power(int base, int exponent) {
        int p;

        for (p = 1; exponent > 0; --exponent)
                p = p * base;

        return p;
}

char* stob(char *str) {
        int i, j, len;
        static char temp[8192];
        char *buffer = &temp[0];

        buffer[0] = '\0';
        len = (strlen(str) > 1024) ? 1024 : strlen(str);

        for (i = 0; i < len; i++) {
                for (j = 7; j >= 0; j--) {
                        if (str[i] >= power(2, j)) {
                                strcat(buffer, "1");
                                str[i] -= power(2, j);
                        }else {
                                strcat(buffer, "0");
                        }
                }
                strcat(buffer, " ");
        }

        return buffer;
}

---

I just don't know how I'd write to convert that binary value back to a string. I have some ideas, but they don't seem to be right. Can anyone assist me in this?

Also, sry I didn't feel like using pow() from math.h so I wrote my own, doh.


- Stack Overflow

Use strtol()

char *bin = "1100";
int number;

number = strtol(bin, (bin + sizeof(bin), 2);

Oh, it didnt compile.

I also tried making it like:

number = strtol(bin, (bin + sizeof(bin)), 2);

then I got an error: 'strtol' : cannot convert parameter 2 from 'char *' to 'char ** '

Dunno, it might just be me.

- Stack Overflow

>number = strtol(bin, (bin + sizeof(bin)), 2);

That second parameter is a pointer to where it stopped translating. You either have to declare an endptr, or make it NULL if you don't need to know where it stopped.

number = strtol( bin, NULL, 2 );

Code:

---

#include <limits.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

/* You aren't supposed to understand this */
int btod ( const char *b )
{
  return *b ? btod ( b + 1 ) + ( *b - '0' << strlen ( b ) - 1 ) : 0;
}

/* Nor are you supposed to take it seriously */
long double dtob ( int d )
{
  return d ? dtob ( d >> 1 ) * 10 + ( d & 1 ) : 0;
}

char *stob ( char *str )
{
  char buf[CHAR_BIT + 1];
  char *bin = malloc ( strlen ( str ) * ( CHAR_BIT - 1 ) + 1 );

  bin[0] = '\0';
  while ( *str != '\0' ) {
    sprintf ( buf, "%.0Lf", dtob ( *str++ ) );
    strcat ( bin, buf );
  }

  return bin;
}

char *btos ( char *bin )
{
  char buf[CHAR_BIT - 1 + 1];
  char *str = malloc ( strlen ( bin ) / ( CHAR_BIT - 1 ) + 1 );
  int i = 0;

  while ( *bin != '\0' ) {
    buf[0] = '\0';
    strncat ( buf, bin, CHAR_BIT - 1 );
    str[i++] = (char)btod ( buf );
    bin += CHAR_BIT - 1;
  }
  str[i] = '\0';

  return str;
}

int main ( void )
{
  char *bin = stob ( "abc" );
  char *str;

  puts ( bin );
  str = btos ( bin );
  puts ( str );
  free ( str );
  free ( bin );

  return 0;
}

---

;)

Ah :),

Thanks alot Prelude, and everyone!

- Stack Overflow

Given your user name, it is somewhat appropriate that your code includes:

Code:

---

        scanf("%s", str);

---

Quote:

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Originally Posted by anonytmouse

Given your user name, it is somewhat appropriate that your code includes:

Code:

---

        scanf("%s", str);

---

---

It is rather ironic, isn't it? But I see a steady progression in most C programmers:

Code:

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/* Newbie */
scanf ( "%s", string );

---

becomes

Code:

---

/* Warned about buffer overflow */
scanf ( "%1023s", string );

---

becomes

Code:

---

/* Really neat trick! */
sprintf ( fmt, "%%%ds", sizeof string - 1 );
scanf ( fmt, string );

---

becomes

Code:

---

/* Never use scanf */
fgets ( string, sizeof string, stdin );

---

becomes

Code:

---

/* Too lazy to do it right */
scanf ( "%s", string );

---

becomes

Code:

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/* Got burned with scanf */
fgets ( string, sizeof string, stdin );

---

Some even go so far as to say that fgetc is the only "right" way to do it because it gives you the most control, but not many actually practice what they preach. ;)