func setReadOnly(_ value: Bool)

The function setReadOnly() forces the library to open files in read-only mode. It is useful if you do not want to modify your file accidenatly.
The function isReadOnly() allows you to get current mode.
You have to call setReadOnly before openning a file.

func isReadOnly() -> Bool

    let dbf = cdbfapi()
    if dbf <> nil { return }
    if dbf.openDBFfile("c:\\tmp\\example.dbf")
        // your code