Question

I am able to convert an NSString of (ASCII) text to a NSString of binary numbers, but I am having troubles doing the opposite. For example: “Hi” becomes “01101000 01101001”.

I need: "01101000 01101001" to become "Hi".

I’m looking for the most direct way to implement this. Note the space between every 8 bits of binary numbers.

Answer 1

Considering the format is always like that, this code should work:

NSString *
BinaryToAsciiString (NSString *string)
{
    NSMutableString *result = [NSMutableString string];
    const char *b_str = [string cStringUsingEncoding:NSASCIIStringEncoding];
    char c;
    int i = 0; /* index, used for iterating on the string */
    int p = 7; /* power index, iterating over a byte, 2^p */
    int d = 0; /* the result character */
    while ((c = b_str[i])) { /* get a char */
        if (c == ' ') { /* if it's a space, save the char + reset indexes */
            [result appendFormat:@"%c", d];
            p = 7; d = 0;
        } else { /* else add its value to d and decrement
                  * p for the next iteration */
            if (c == '1') d += pow(2, p);
            --p;
        }
        ++i;
    } [result appendFormat:@"%c", d]; /* this saves the last byte */

    return [NSString stringWithString:result];
}

Tell me if some part of it was unclear.