Set status to Error and wake waiters.
Read a UTF-8 string from the data section, up to length bytes.
Read two null-separated strings from the data section.
Set status to Pending and wake the proxy worker.
Block until status transitions away from Pending.
Write a UTF-8 string into the data section. Returns bytes written.
Write two null-separated strings (for rename: oldPath\0newPath). Returns total bytes written.
Set status to Complete and wake waiters.