Function i64_array 

pub fn i64_array<T, S>(array: T, serializer: S) -> Result<S::Ok, S::Error>
where
    T: IntoIterator,
    <T as IntoIterator>::Item: Borrow<i64>,
    S: Serializer,

This function provides serde serialization support for NBT type LongArray.

It should be used in conjunction with serde’s field annotation serialize_with. In the following example int_data will be serialized as a LongArray instead of a List of Ints:

extern crate serde;
use nbt::to_writer;
use serde::Serialize;

let mut serialized = Vec::new();

// Declare your struct
#[derive(Serialize)]
struct Enderman {
    #[serde(serialize_with="nbt::i64_array")]
    long_data: Vec<i64>,
}

// Serialize to NBT!
to_writer(
    &mut serialized,
    &Enderman {
        long_data: vec![0x1848ccd2157df10e, 0x64c5efff28280e9a],
    },
    None
).unwrap();

print!("Serialized: {:?}", serialized);