xmpp: rewrite xml element parsers using coroutines

crates/proto-xmpp/src/roster.rs

@@ -1,47 +1,30 @@
 use quick_xml::events::{BytesStart, Event};
 
 use crate::xml::*;
-use anyhow::{anyhow as ffail, Result};
+use anyhow::{anyhow, Result};
+use quick_xml::name::ResolveResult;
 
 pub const XMLNS: &'static str = "jabber:iq:roster";
 
 #[derive(PartialEq, Eq, Debug)]
 pub struct RosterQuery;
 
-pub struct QueryParser(QueryParserInner);
-
-enum QueryParserInner {
-    Initial,
-    InQuery,
-}
-
-impl Parser for QueryParser {
-    type Output = Result<RosterQuery>;
-
-    fn consume<'a>(
-        self: Self,
-        namespace: quick_xml::name::ResolveResult,
-        event: &quick_xml::events::Event<'a>,
-    ) -> Continuation<Self, Self::Output> {
-        match self.0 {
-            QueryParserInner::Initial => match event {
-                Event::Start(_) => Continuation::Continue(QueryParser(QueryParserInner::InQuery)),
-                Event::Empty(_) => Continuation::Final(Ok(RosterQuery)),
-                _ => Continuation::Final(Err(ffail!("Unexpected XML event: {event:?}"))),
-            },
-            QueryParserInner::InQuery => match event {
-                Event::End(_) => Continuation::Final(Ok(RosterQuery)),
-                _ => Continuation::Final(Err(ffail!("Unexpected XML event: {event:?}"))),
-            },
-        }
-    }
-}
-
 impl FromXml for RosterQuery {
-    type P = QueryParser;
+    type P = impl Parser<Output = Result<Self>>;
 
     fn parse() -> Self::P {
-        QueryParser(QueryParserInner::Initial)
+        |(mut namespace, mut event): (ResolveResult<'static>, &'static Event<'static>)| -> Result<Self> {
+            match event {
+                Event::Start(_) => (),
+                Event::Empty(_) => return Ok(RosterQuery),
+                _ => return Err(anyhow!("Unexpected XML event: {event:?}")),
+            }
+            (namespace, event) = yield;
+            match event {
+                Event::End(_) => return Ok(RosterQuery),
+                _ => return Err(anyhow!("Unexpected XML event: {event:?}")),
+            }
+        }
     }
 }
 

crates/proto-xmpp/src/session.rs

@@ -2,46 +2,29 @@ use quick_xml::events::{BytesStart, Event};
 
 use crate::xml::*;
 use anyhow::{anyhow, Result};
+use quick_xml::name::ResolveResult;
 
 pub const XMLNS: &'static str = "urn:ietf:params:xml:ns:xmpp-session";
 
 #[derive(PartialEq, Eq, Debug)]
 pub struct Session;
 
-pub struct SessionParser(SessionParserInner);
-
-enum SessionParserInner {
-    Initial,
-    InSession,
-}
-
-impl Parser for SessionParser {
-    type Output = Result<Session>;
-
-    fn consume<'a>(
-        self: Self,
-        namespace: quick_xml::name::ResolveResult,
-        event: &quick_xml::events::Event<'a>,
-    ) -> Continuation<Self, Self::Output> {
-        match self.0 {
-            SessionParserInner::Initial => match event {
-                Event::Start(_) => Continuation::Continue(SessionParser(SessionParserInner::InSession)),
-                Event::Empty(_) => Continuation::Final(Ok(Session)),
-                _ => Continuation::Final(Err(anyhow!("Unexpected XML event: {event:?}"))),
-            },
-            SessionParserInner::InSession => match event {
-                Event::End(_) => Continuation::Final(Ok(Session)),
-                _ => Continuation::Final(Err(anyhow!("Unexpected XML event: {event:?}"))),
-            },
-        }
-    }
-}
-
 impl FromXml for Session {
-    type P = SessionParser;
+    type P = impl Parser<Output = Result<Self>>;
 
     fn parse() -> Self::P {
-        SessionParser(SessionParserInner::Initial)
+        |(mut namespace, mut event): (ResolveResult<'static>, &'static Event<'static>)| -> Result<Self> {
+            match event {
+                Event::Start(_) => (),
+                Event::Empty(_) => return Ok(Session),
+                _ => return Err(anyhow!("Unexpected XML event: {event:?}")),
+            }
+            (namespace, event) = yield;
+            match event {
+                Event::End(_) => return Ok(Session),
+                _ => return Err(anyhow!("Unexpected XML event: {event:?}")),
+            }
+        }
     }
 }
 

crates/proto-xmpp/src/xml/ignore.rs

@@ -1,49 +1,35 @@
 use super::*;
-use derive_more::From;
 
 #[derive(Default, Debug, PartialEq, Eq)]
 pub struct Ignore;
 
-#[derive(From)]
-pub struct IgnoreParser(IgnoreParserInner);
-
-enum IgnoreParserInner {
-    Initial,
-    InTag { name: Vec<u8>, depth: u8 },
-}
-
-impl Parser for IgnoreParser {
-    type Output = Result<Ignore>;
-
-    fn consume<'a>(self: Self, _: ResolveResult, event: &Event<'a>) -> Continuation<Self, Self::Output> {
-        match self.0 {
-            IgnoreParserInner::Initial => match event {
-                Event::Start(bytes) => {
-                    let name = bytes.name().0.to_owned();
-                    Continuation::Continue(IgnoreParserInner::InTag { name, depth: 0 }.into())
-                }
-                Event::Empty(_) => Continuation::Final(Ok(Ignore)),
-                _ => Continuation::Final(Ok(Ignore)),
-            },
-            IgnoreParserInner::InTag { name, depth } => match event {
-                Event::End(bytes) if name == bytes.name().0 => {
-                    if depth == 0 {
-                        Continuation::Final(Ok(Ignore))
-                    } else {
-                        Continuation::Continue(IgnoreParserInner::InTag { name, depth: depth - 1 }.into())
-                    }
-                }
-                _ => Continuation::Continue(IgnoreParserInner::InTag { name, depth }.into()),
-            },
-        }
-    }
-}
-
 impl FromXml for Ignore {
-    type P = IgnoreParser;
+    type P = impl Parser<Output = Result<Self>>;
 
     fn parse() -> Self::P {
-        IgnoreParserInner::Initial.into()
+        |(mut namespace, mut event): (ResolveResult<'static>, &'static Event<'static>)| -> Result<Self> {
+            let mut depth = match event {
+                Event::Start(bytes) => 0,
+                Event::Empty(_) => return Ok(Ignore),
+                _ => return Ok(Ignore),
+            };
+            loop {
+                (namespace, event) = yield;
+                match event {
+                    Event::End(_) => {
+                        if depth == 0 {
+                            return Ok(Ignore);
+                        } else {
+                            depth -= 1;
+                        }
+                    }
+                    Event::Start(_) => {
+                        depth += 1;
+                    }
+                    _ => (),
+                }
+            }
+        }
     }
 }