+/* These are more properly called Xapian fields, but the user facing
+ * docs call them prefixes, so make the error message match */
+static bool
+validate_field_name (const char *str)
+{
+ const char *key;
+
+ if (! g_utf8_validate (str, -1, NULL)) {
+ fprintf (stderr, "Invalid utf8: %s\n", str);
+ return false;
+ }
+
+ key = g_utf8_strrchr (str, -1, '.');
+ if (! key ) {
+ INTERNAL_ERROR ("Impossible code path on input: %s\n", str);
+ }
+
+ key++;
+
+ if (! *key) {
+ fprintf (stderr, "Empty prefix name: %s\n", str);
+ return false;
+ }
+
+ if (! unicode_word_utf8 (key)) {
+ fprintf (stderr, "Non-word character in prefix name: %s\n", key);
+ return false;
+ }
+
+ if (key[0] >= 'a' && key[0] <= 'z') {
+ fprintf (stderr, "Prefix names starting with lower case letters are reserved: %s\n", key);
+ return false;
+ }
+
+ return true;
+}
+