use std::io; #[crate::bisync::only_async]use crate::transport::client::async_io::ExtendedBufRead;#[crate::bisync::only_sync]use crate::transport::client::blocking_io::ExtendedBufRead;use gix_transport::{Protocol, client::MessageKind}; use crate::fetch::{    Response, response,    response::{Acknowledgement, ShallowUpdate, WantedRef, shallow_update_from_line},}; #[crate::bisync::bisync]async fn parse_v2_section<'a, T>(    line: &mut String,    reader: &mut impl ExtendedBufRead<'a>,    res: &mut Vec<T>,    parse: impl Fn(&str) -> Result<T, response::Error>,) -> Result<bool, response::Error> {    line.clear();    while reader.readline_str(line).await? != 0 {        res.push(parse(line)?);        line.clear();    }    // End of message, or end of section?    Ok(if reader.stopped_at() == Some(MessageKind::Delimiter) {        // try reading more sections        reader.reset(Protocol::V2);        false    } else {        // we are done, there is no pack        true    })} impl Response {    /// Parse a response of the given `version` of the protocol from `reader`.    ///    /// `client_expects_pack` is only relevant for V1 stateful connections, and if `false`, causes us to stop parsing when seeing `NAK`,    /// and if `true` we will keep parsing until we get a pack as the client already signalled to the server that it's done.    /// This way of doing things allows us to exploit knowledge about more recent versions of the protocol, which keeps code easier    /// and more localized without having to support all the cruft that there is.    ///    /// `wants_to_negotiate` should be `false` for clones which is when we don't have sent any haves. The reason for this flag to exist    /// is to predict how to parse V1 output only, and neither `client_expects_pack` nor `wants_to_negotiate` are relevant for V2.    /// This ugliness is in place to avoid having to resort to an [an even more complex ugliness](https://github.com/git/git/blob/9e49351c3060e1fa6e0d2de64505b7becf157f28/fetch-pack.c#L583-L594)    /// that `git` has to use to predict how many acks are supposed to be read. We also genuinely hope that this covers it all….    #[crate::bisync::bisync]    pub async fn from_line_reader<'a>(        version: Protocol,        reader: &mut impl ExtendedBufRead<'a>,        client_expects_pack: bool,        wants_to_negotiate: bool,    ) -> Result<Response, response::Error> {        match version {            Protocol::V0 | Protocol::V1 => {                let mut line = String::new();                let mut acks = Vec::<Acknowledgement>::new();                let mut shallows = Vec::<ShallowUpdate>::new();                let mut saw_ready = false;                let has_pack = 'lines: loop {                    line.clear();                    let peeked_line = match reader.peek_data_line().await {                        Some(Ok(Ok(line))) => String::from_utf8_lossy(line),                        // This special case (hang/block forever) deals with a single NAK being a legitimate EOF sometimes                        // Note that this might block forever in stateful connections as there it's not really clear                        // if something will be following or not by just looking at the response. Instead you have to know                        // [a lot](https://github.com/git/git/blob/9e49351c3060e1fa6e0d2de64505b7becf157f28/fetch-pack.c#L583-L594)                        // to deal with this correctly.                        // For now this is acceptable, as V2 can be used as a workaround, which also is the default.                        Some(Err(err)) if err.kind() == io::ErrorKind::UnexpectedEof => break 'lines false,                        Some(Err(err)) => return Err(err.into()),                        Some(Ok(Err(err))) => return Err(err.into()),                        None => {                            // maybe we saw a shallow flush packet, let's reset and retry                            debug_assert_eq!(                                reader.stopped_at(),                                Some(MessageKind::Flush),                                "If this isn't a flush packet, we don't know what's going on"                            );                            reader.readline_str(&mut line).await?;                            reader.reset(Protocol::V1);                            match reader.peek_data_line().await {                                Some(Ok(Ok(line))) => String::from_utf8_lossy(line),                                Some(Err(err)) => return Err(err.into()),                                Some(Ok(Err(err))) => return Err(err.into()),                                None => break 'lines false, // EOF                            }                        }                    };                     if Response::parse_v1_ack_or_shallow_or_assume_pack(&mut acks, &mut shallows, &peeked_line) {                        break 'lines true;                    }                    assert_ne!(                        reader.readline_str(&mut line).await?,                        0,                        "consuming a peeked line works"                    );                    // When the server sends ready, we know there is going to be a pack so no need to stop early.                    saw_ready |= matches!(acks.last(), Some(Acknowledgement::Ready));                    if let Some(Acknowledgement::Nak) = acks.last().filter(|_| !client_expects_pack || !saw_ready) {                        if !wants_to_negotiate {                            continue;                        }                        break 'lines false;                    }                };                Ok(Response {                    acks,                    shallows,                    wanted_refs: vec![],                    has_pack,                })            }            Protocol::V2 => {                // NOTE: We only read acknowledgements and scrub to the pack file, until we have use for the other features                let mut line = String::new();                reader.reset(Protocol::V2);                let mut acks = Vec::<Acknowledgement>::new();                let mut shallows = Vec::<ShallowUpdate>::new();                let mut wanted_refs = Vec::<WantedRef>::new();                let has_pack = 'section: loop {                    line.clear();                    if reader.readline_str(&mut line).await? == 0 {                        return Err(response::Error::Io(io::Error::new(                            io::ErrorKind::UnexpectedEof,                            "Could not read message headline",                        )));                    }                     match line.trim_end() {                        "acknowledgments" => {                            if parse_v2_section(&mut line, reader, &mut acks, Acknowledgement::from_line).await? {                                break 'section false;                            }                        }                        "shallow-info" => {                            if parse_v2_section(&mut line, reader, &mut shallows, shallow_update_from_line).await? {                                break 'section false;                            }                        }                        "wanted-refs" => {                            if parse_v2_section(&mut line, reader, &mut wanted_refs, WantedRef::from_line).await? {                                break 'section false;                            }                        }                        "packfile" => {                            // what follows is the packfile itself, which can be read with a sideband enabled reader                            break 'section true;                        }                        _ => return Err(response::Error::UnknownSectionHeader { header: line }),                    }                };                Ok(Response {                    acks,                    shallows,                    wanted_refs,                    has_pack,                })            }        }    }}