speed up for reading and writing ply files

wu_xinjun

2022-04-02 b7a9cf522716f3236d4077c75d7ed147a67200b4

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HAND_SHAKE_MAGIC = b"\x01\x09\x08\x09\x01\x00\x02\x02" 
HEADER_MAGIC = b"\x02\x01\x04\x03\x06\x05\x08\x07"