join() or implode() in C

Question

One thing I love about Python and PHP is the ability to make a string from array easily:

Python: ', '.join(['a', 'b', 'c'])
PHP: implode(', ', array('a', 'b', 'c'));

However, I was wondering if anybody had an intuitive and clear way to implement this in C. Thanks!

Answer 1

Sure, there are ways - just nothing built-in. Many C utility libraries have functions for this - eg, glib's g_strjoinv. You can also roll your own, for example:

static char *util_cat(char *dest, char *end, const char *str)
{
    while (dest < end && *str)
        *dest++ = *str++;
    return dest;
}

size_t join_str(char *out_string, size_t out_bufsz, const char *delim, char **chararr)
{
    char *ptr = out_string;
    char *strend = out_string + out_bufsz;
    while (ptr < strend && *chararr)
    {
        ptr = util_cat(ptr, strend, *chararr);
        chararr++;
        if (*chararr)
            ptr = util_cat(ptr, strend, delim);
    }
    return ptr - out_string;
}

The main reason it's not built in is because the C standard library is very minimal; they wanted to make it easy to make new implementations of C, so you don't find as many utility functions. There's also the problem that C doesn't give you many guidelines about how to, for example, decide how many elements are in arrays (I used a NULL-array-element terminator convention in the example above).