libbb: add sketch of tentative 'better' passwd/group API

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

libbb/bb_pwd.c

@@ -110,3 +110,51 @@ unsigned long FAST_FUNC get_ug_id(const char *s,
 		return xname2id(s);
 	return r;
 }
+
+/* Experimental "mallocing" API.
+ * The goal is nice: "we want to support a case when "guests" group is very large"
+ * but the code is butt-ugly.
+ */
+#if 0
+static char *find_latest(char last, char *cp)
+{
+	if (!cp)
+		return last;
+	cp += strlen(cp) + 1;
+	if (last < cp)
+		last = cp;
+	return last;
+}
+
+struct group* FAST_FUNC xmalloc_getgrnam(const char *name)
+{
+	struct {
+		struct group gr;
+		// May still be not enough!
+		char buf[64*1024 - sizeof(struct group) - 16];
+	} *s;
+	struct group *grp;
+	int r;
+	char *last;
+	char **gr_mem;
+
+	s = xmalloc(sizeof(*s));
+	r = getgrnam_r(name, &s->gr, s->buf, sizeof(s->buf), &grp);
+	if (!grp) {
+		free(s);
+		return grp;
+	}
+	last = find_latest(s->buf, grp->gr_name);
+	last = find_latest(last, grp->gr_passwd);
+	gr_mem = grp->gr_mem;
+	while (*gr_mem)
+		last = find_latest(last, *gr_mem++);
+	gr_mem++; /* points past NULL */
+	if (last < (char*)gr_mem)
+		last = (char*)gr_mem;
+//FIXME: what if we get not only truncated, but also moved here?
+// grp->gr_name pointer and friends are invalid now!!!
+	s = xrealloc(s, last - (char*)s);
+	return grp;
+}
+#endif