Zero-copy to/from streaming about lolraft HOT 3 CLOSED

#[derive(Clone, PartialEq, ::prost::Message)]
pub struct AppendStreamEntry {
    #[prost(uint64, tag = "1")]
    pub term: u64,
    #[prost(uint64, tag = "2")]
    pub index: u64,
    #[prost(bytes = "vec", tag = "3")]
    pub command: ::prost::alloc::vec::Vec<u8>,
}
#[derive(Clone, PartialEq, ::prost::Message)]
pub struct AppendEntryReq {
    #[prost(oneof = "append_entry_req::Elem", tags = "1, 2")]
    pub elem: ::core::option::Option<append_entry_req::Elem>,
}

struct LogStreamElem {
    term: Term,
    index: Index,
    command: Bytes,
}

fn into_out_stream(
    x: LogStream
) -> impl futures::stream::Stream<Item = crate::proto_compiled::AppendEntryReq> {
    use crate::proto_compiled::{append_entry_req::Elem, AppendStreamHeader, AppendStreamEntry};
    let header_stream = vec![Elem::Header(AppendStreamHeader {
        sender_id: x.sender_id,
        prev_log_index: x.prev_log_index,
        prev_log_term: x.prev_log_term,
    })];
    let header_stream = futures::stream::iter(header_stream);
    let chunk_stream = x.entries.map(|e| {
        Elem::Entry(AppendStreamEntry {
            term: e.term,
            index: e.index,
            command: e.command.as_ref().into(), // HERE
        })
    });
    header_stream.chain(chunk_stream).map(|e| crate::proto_compiled::AppendEntryReq {
        elem: Some(e)
    })
}