Disliking omitting braces or really short names is just a matter of taste (however both is classic C coding style), but you can easily find out what they store without comments or a longer name. I personally would have chosen l instead of x, which is a pointer to a character in the current read _l_ine (see L202).
Can you tell me what comments you're expecting? qmail comes with a bunch of man pages (including ones for functions and they're well written). The file is called qmail-pw2u.c and there's qmail-pw2u(8). The function is called dosubuser, so let's look up subuser in it:
> Extra addresses. Each line has the form
> sub:user:pre:
That gives us a pretty good idea about the purpose of the posted code (plus the previous lines).
I agree, a function or macro makes sense (since there are many other equivalent constructs in the same file), but that's "just" giving a bunch of statement a name. Does field_next explain what they do?
static int field_next(int *i, char **x, unsigned *xlen) {
*++i; *x += *i; *xlen -= *i; *i = byte_chr(*x,*xlen,':');
return i == xlen;
}
/ * later */
if (field_next(&i, &x, &xlen)) return;
The rest of the function is writing something. Maybe we should find out the purpose of the program at first? The man page tells us this too:
>qmail-pw2u reads a V7-format passwd file from standard input and prints a qmail-users-format assignment file.