Fix empdump not to grow game state files with fixed size

empdump -i now complains about extra rows instead of silently growing
the file to a size the server will reject.  Affects tables sector,
nation, realms, game.

Bonus fix: better error message on I/O error or insufficient memory.

include/file.h

@@ -219,6 +219,7 @@ extern int ef_write(int, int, void *);
 extern void ef_set_uid(int, void *, int);
 extern int ef_extend(int, int);
 extern int ef_ensure_space(int, int, int);
+extern int ef_id_limit(int);
 extern int ef_truncate(int, int);
 extern int ef_nelem(int);
 extern int ef_flags(int);

src/lib/common/file.c

@@ -36,6 +36,7 @@
 
 #include <errno.h>
 #include <fcntl.h>
+#include <limits.h>
 #include <sys/stat.h>
 #include <sys/types.h>
 #include <unistd.h>
@@ -931,3 +932,24 @@ ef_ensure_space(int type, int id, int count)
     }
     return 1;
 }
+
+/*
+ * Return maximum ID acceptable for table TYPE.
+ * Assuming infinite memory and disk space.
+ */
+int
+ef_id_limit(int type)
+{
+    struct empfile *ep;
+
+    if (ef_check(type) < 0)
+	return -1;
+    ep = &empfile[type];
+    if (ep->nent >= 0)
+	return ep->nent - 1;
+    if (ep->flags & EFF_MEM) {
+	if (ep->flags & EFF_STATIC)
+	    return ep->csize - 1 - ((ep->flags & EFF_SENTINEL) != 0);
+    }
+    return INT_MAX;
+}

src/lib/common/xundump.c

@@ -487,16 +487,20 @@ static void *
 getobj(void)
 {
     struct empfile *ep = &empfile[cur_type];
+    int max_id;
 
     if (!cur_obj) {
 	cur_obj_is_blank = cur_id >= ep->fids;
 	if (cur_obj_is_blank) {
-	    if (ef_ensure_space(cur_type, cur_id, 1))
+	    max_id = ef_id_limit(cur_type);
+	    if (cur_id > max_id)
+		gripe("Can't put ID %d into table %s, it holds only 0..%d",
+		      cur_id, ep->name, max_id);
+	    else if (!ef_ensure_space(cur_type, cur_id, 1))
+		gripe("Can't put ID %d into table %s",
+		      cur_id, ep->name);
+	    else
 		cur_obj = ef_ptr(cur_type, cur_id);
-	    /* FIXME diagnose out of dynamic memory vs. static table full */
-	    if (!cur_obj)
-		gripe("Can't put ID %d into table %s, it holds only 0..%d.",
-		      cur_id, ep->name, ep->fids - 1);
 	} else
 	    cur_obj = ef_ptr(cur_type, cur_id);
     }