11.2 �ӿ�Ƕ�׽ӿ�

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��ӿ� File �� ReadWrite �� Lock ��з��һ�� Close() ��

type ReadWrite interface {
    Read(b Buffer) bool
    Write(b Buffer) bool
}

type Lock interface {
    Lock()
    Unlock()
}

type File interface {
    ReadWrite
    Lock
    Close()
}