--- /dev/null
+#ifndef INDEX_MAILBOX_SIZE_H
+#define INDEX_MAILBOX_SIZE_H
+
+struct mailbox;
+
+struct mailbox_vsize_update *
+index_mailbox_vsize_update_init(struct mailbox *box);
+void index_mailbox_vsize_update_deinit(struct mailbox_vsize_update **update);
+
+void index_mailbox_vsize_hdr_expunge(struct mailbox_vsize_update *update,
+ uint32_t uid, uoff_t vsize);
+
+bool index_mailbox_vsize_update_try_lock(struct mailbox_vsize_update *update);
+bool index_mailbox_vsize_update_wait_lock(struct mailbox_vsize_update *update);
+/* Returns TRUE if expunges & appends should be updating the header. */
+bool index_mailbox_vsize_want_updates(struct mailbox_vsize_update *update);
+
+void index_mailbox_vsize_update_appends(struct mailbox *box);
+
+#endif