Get tcp.ack and tcp.seq in C

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Hello. I have a question when writing a dissector in C. Is it Possible in a custom Protocol over tcp to obtain the values of seq and ack. I know in Lua i can use

tcp_ack_f = Field.new("tcp.ack")

tcp_seq_f = Field.new("tcp.seq")

local ack = tcp_ack_f()

local seq = tcp_seq_f()

But how i can get it in C?