symlinks

[Olson, Arthur David (NCI)]

Below find a proposed rewrite of the "symbolic link" section of zic.c;
I hope this deals with the problems circulated recently on the time zone
mailing list.

				--ado

#if (HAVE_SYMLINK - 0)
                /*
                ** If hard link fails but from file exists, try a symbolic
link.
                ** We want as relative a link as possible to maximize
chances
                ** of correct behavior when the link is part of an
                ** exported directory.
                */
                if (result != 0 &&
                    access(fromname, F_OK) == 0 &&
                    !itsdir(fromname)) {
                        register char * t = toname;
                        register char * f = fromname;
                        register char * s;
                        register int    n;

                        while ((s = strchr(t, '/')) != NULL &&
                                strncmp(t, f, (n = (s - t) + 1)) == 0) {
                                        t += n;
                                        f += n;
                        }
                        /*
                        ** f            t               desired symlink
value
                        ** /a/b/c       /d/e/f          eliminated just
above
                        ** a/b/c        d/e/f           ../../a/b/c
                        ** a/b          d/e/f           ../../a/b
                        ** a/b/c        d/e             ../a/b/c
                        ** /a/b/c       d/e/f           /a/b/c
                        ** a/b/c        /d/e/f          hard to handle well
                        */
                        if (*f == '/')
                                s = ecpyalloc(f);
                        else {
                                s = NULL;
                                if (*t != '/') {
                                        while (*t != '\0')
                                                if (*t++ == '/')
                                                        s = ecatalloc(s,
"../");
                                        s = ecatalloc(s, f);
                                }
                        }
                        if (s != NULL) {
                                result = symlink(s, toname);
                                ifree(s);
                                if (result == 0)
warning(_("hard link failed, symbolic link used"));
                        }
                }
#endif