+/* Calculate the hash of a string. */
+static unsigned
+hash_string_hasher (void const *name, unsigned n_buckets)
+{
+ return hash_string (name, n_buckets);
+}
+
+/* Compare two strings for equality. */
+static bool
+hash_string_compare (void const *name1, void const *name2)
+{
+ return strcmp (name1, name2) == 0;
+}
+
+/* Return zero if TABLE contains a copy of STRING; otherwise, insert a
+ copy of STRING to TABLE and return 1. */
+static bool
+hash_string_insert (Hash_table **table, char const *string)
+{
+ Hash_table *t = *table;
+ char *s = xstrdup (string);
+ char *e;
+
+ if (! ((t
+ || (*table = t = hash_initialize (0, 0, hash_string_hasher,
+ hash_string_compare, 0)))
+ && (e = hash_insert (t, s))))
+ xalloc_die ();
+
+ if (e == s)
+ return 1;
+ else
+ {
+ free (s);
+ return 0;
+ }
+}
+
+/* Return 1 if TABLE contains STRING. */
+static bool
+hash_string_lookup (Hash_table const *table, char const *string)
+{
+ return table && hash_lookup (table, string);
+}
+\f
+/* Names to avoid dumping. */
+static Hash_table *avoided_name_table;
+
+/* Remember to not archive NAME. */
+void
+add_avoided_name (char const *name)
+{
+ hash_string_insert (&avoided_name_table, name);
+}
+
+/* Should NAME be avoided when archiving? */
+bool
+is_avoided_name (char const *name)
+{
+ return hash_string_lookup (avoided_name_table, name);
+}
+
+\f
+static Hash_table *individual_file_table;
+
+static void
+register_individual_file (char const *name)
+{
+ struct stat st;
+
+ if (deref_stat (dereference_option, name, &st) != 0)
+ return; /* Will be complained about later */
+ if (S_ISDIR (st.st_mode))
+ return;
+
+ hash_string_insert (&individual_file_table, name);
+}
+
+bool
+is_individual_file (char const *name)
+{
+ return hash_string_lookup (individual_file_table, name);
+}
+
+\f
+
+static Hash_table *prefix_table[2];
+
+/* Return true if file names of some members in the archive were stripped off
+ their leading components. We could have used
+ return prefix_table[0] || prefix_table[1]
+ but the following seems to be safer: */
+bool
+removed_prefixes_p (void)
+{
+ return (prefix_table[0] && hash_get_n_entries (prefix_table[0]) != 0)
+ || (prefix_table[1] && hash_get_n_entries (prefix_table[1]) != 0);
+}
+
+/* Return a safer suffix of FILE_NAME, or "." if it has no safer
+ suffix. Check for fully specified file names and other atrocities.
+ Warn the user if we do not return NAME. If LINK_TARGET is 1,
+ FILE_NAME is the target of a hard link, not a member name. */