Add simpler shell parser

This obsoletes `shlex`. The quoting turned out unnecessary, and the
splitting supported a lot more than we need. It also forced
unncessary allocations: The splitting doesn't add any characters and
keeps UTF-8 intact, so returning slices from the input is perfectly
possible.
Though this particular implementation will only come to use in the
future, as `CmdLine` still requires that the slices are cloned.

Still, the custom implementation performs about 3x faster.

crates/dtmt/Cargo.toml

@@ -33,7 +33,10 @@ path-slash = "0.2.1"
 async-recursion = "1.0.2"
 notify = "5.1.0"
 luajit2-sys = { path = "../../lib/luajit2-sys", version = "*" }
-shlex = "1.2.0"
+shlex = { version = "1.2.0", optional = true }
 
 [dev-dependencies]
 tempfile = "3.3.0"
+
+[features]
+shlex-bench = ["dep:shlex"]

crates/dtmt/src/cmd/bundle/extract.rs

@@ -3,7 +3,7 @@ use std::path::{Path, PathBuf};
 use std::sync::Arc;
 
 use clap::{value_parser, Arg, ArgAction, ArgMatches, Command};
-use color_eyre::eyre::{self, Context, Result};
+use color_eyre::eyre::{self, bail, Context, Result};
 use color_eyre::{Help, Report};
 use futures::future::try_join_all;
 use futures::StreamExt;
@@ -12,7 +12,9 @@ use sdk::{Bundle, BundleFile, CmdLine};
 use tokio::fs;
 
 use crate::cmd::util::resolve_bundle_paths;
+use crate::shell_parse::ShellParser;
 
+#[inline]
 fn parse_glob_pattern(s: &str) -> Result<Pattern, String> {
     match Pattern::new(s) {
         Ok(p) => Ok(p),
@@ -20,6 +22,7 @@ fn parse_glob_pattern(s: &str) -> Result<Pattern, String> {
     }
 }
 
+#[inline]
 fn flatten_name(s: &str) -> String {
     s.replace('/', "_")
 }
@@ -131,26 +134,29 @@ async fn parse_command_line_template(tmpl: &String) -> Result<CmdLine> {
     let mut cmd = if matches!(fs::try_exists(tmpl).await, Ok(true)) {
         let path = PathBuf::from(tmpl);
         if path.file_name() == Some(OsStr::new("main.py")) {
-            let arg = path.display().to_string();
             let mut cmd = CmdLine::new("python");
-            cmd.arg(shlex::quote(&arg).to_string());
+            cmd.arg(path);
             cmd
         } else {
             CmdLine::new(path)
         }
     } else {
-        let Some(args) = shlex::split(tmpl) else {
-            eyre::bail!("Invalid shell syntax");
-        };
+        let mut parsed = ShellParser::new(tmpl.as_bytes());
+        // Safety: The initial `tmpl` was a `&String` (i.e. valid UTF-8), and `shlex` does not
+        // insert or remove characters, nor does it split UTF-8 characters.
+        // So the resulting byte stream is still valid UTF-8.
+        let mut cmd = CmdLine::new(unsafe {
+            let bytes = parsed.next().expect("Template is not empty");
+            String::from_utf8_unchecked(bytes.to_vec())
+        });
 
-        // We already checked that the template is not empty
-        let mut cmd = CmdLine::new(args[0].clone());
-        let mut it = args.iter();
-        // Skip the first one, that's the command name
-        it.next();
+        while let Some(arg) = parsed.next() {
+            // Safety: See above.
+            cmd.arg(unsafe { String::from_utf8_unchecked(arg.to_vec()) });
+        }
 
-        for arg in it {
-            cmd.arg(arg);
+        if parsed.errored {
+            bail!("Invalid command line template");
         }
 
         cmd

crates/dtmt/src/main.rs

@@ -1,6 +1,7 @@
 #![feature(io_error_more)]
 #![feature(let_chains)]
 #![feature(result_flattening)]
+#![feature(test)]
 #![windows_subsystem = "console"]
 
 use std::path::PathBuf;
@@ -27,6 +28,7 @@ mod cmd {
     mod util;
     pub mod watch;
 }
+mod shell_parse;
 
 #[derive(Default, Deserialize, Serialize)]
 struct GlobalConfig {

crates/dtmt/src/shell_parse.rs

@@ -0,0 +1,189 @@
+#[derive(Copy, Clone, PartialEq, Eq, Debug)]
+enum ParserState {
+    Start,
+    Word,
+    SingleQuote,
+    DoubleQuote,
+}
+
+pub struct ShellParser<'a> {
+    bytes: &'a [u8],
+    offset: usize,
+    pub errored: bool,
+}
+
+impl<'a> ShellParser<'a> {
+    pub fn new(bytes: &'a [u8]) -> Self {
+        Self {
+            bytes,
+            offset: 0,
+            errored: false,
+        }
+    }
+
+    fn parse_word(&mut self) -> Option<&'a [u8]> {
+        // The start of the current word. Certain leading characters should be ignored,
+        // so this might change.
+        let mut start = self.offset;
+        let mut state = ParserState::Start;
+
+        while self.offset < self.bytes.len() {
+            let c = self.bytes[self.offset];
+            self.offset += 1;
+
+            match state {
+                ParserState::Start => match c {
+                    // Ignore leading whitespace
+                    b' ' | b'\t' | b'\n' => start += 1,
+                    b'\'' => {
+                        state = ParserState::SingleQuote;
+                        start += 1;
+                    }
+                    b'"' => {
+                        state = ParserState::DoubleQuote;
+                        start += 1;
+                    }
+                    _ => {
+                        state = ParserState::Word;
+                    }
+                },
+                ParserState::Word => match c {
+                    // Unquoted whitespace ends the current word
+                    b' ' | b'\t' | b'\n' => {
+                        return Some(&self.bytes[start..self.offset - 1]);
+                    }
+                    _ => {}
+                },
+                ParserState::SingleQuote => match c {
+                    b'\'' => {
+                        return Some(&self.bytes[start..(self.offset - 1)]);
+                    }
+                    _ => {}
+                },
+                ParserState::DoubleQuote => match c {
+                    b'"' => {
+                        return Some(&self.bytes[start..(self.offset - 1)]);
+                    }
+                    _ => {}
+                },
+            }
+        }
+
+        match state {
+            ParserState::Start => None,
+            ParserState::Word => Some(&self.bytes[start..self.offset]),
+            ParserState::SingleQuote | ParserState::DoubleQuote => {
+                self.errored = true;
+                None
+            }
+        }
+    }
+}
+
+impl<'a> Iterator for ShellParser<'a> {
+    type Item = &'a [u8];
+
+    fn next(&mut self) -> Option<Self::Item> {
+        self.parse_word()
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn test_one_word() {
+        let mut it = ShellParser::new(b"hello");
+        assert_eq!(it.next(), Some("hello".as_bytes()));
+        assert_eq!(it.next(), None);
+    }
+
+    #[test]
+    fn test_one_single() {
+        let mut it = ShellParser::new(b"'hello'");
+        assert_eq!(it.next(), Some("hello".as_bytes()));
+        assert_eq!(it.next(), None);
+    }
+
+    #[test]
+    fn test_open_quote() {
+        let mut it = ShellParser::new(b"'hello");
+        assert_eq!(it.next(), None);
+        assert!(it.errored)
+    }
+
+    #[test]
+    fn test_ww2ogg() {
+        let mut it = ShellParser::new(
+            b"ww2ogg.exe --pcb \"/usr/share/ww2ogg/packed_cookbook_aoTuV_603.bin\"",
+        );
+        assert_eq!(it.next(), Some("ww2ogg.exe".as_bytes()));
+        assert_eq!(it.next(), Some("--pcb".as_bytes()));
+        assert_eq!(
+            it.next(),
+            Some("/usr/share/ww2ogg/packed_cookbook_aoTuV_603.bin".as_bytes())
+        );
+        assert_eq!(it.next(), None);
+    }
+}
+
+#[cfg(test)]
+mod bench {
+    extern crate test;
+
+    use super::*;
+    #[cfg(feature = "shlex-bench")]
+    use shlex::bytes::Shlex;
+    use test::Bencher;
+
+    mod ww2ogg {
+        use super::*;
+
+        #[bench]
+        fn custom(b: &mut Bencher) {
+            let val = test::black_box(
+                b"ww2ogg.exe --pcb \"/usr/share/ww2ogg/packed_cookbook_aoTuV_603.bin\"",
+            );
+            b.iter(|| {
+                let it = ShellParser::new(val);
+                let _: Vec<_> = test::black_box(it.collect());
+            })
+        }
+
+        #[cfg(feature = "shlex-bench")]
+        #[bench]
+        fn shlex(b: &mut Bencher) {
+            let val = test::black_box(
+                b"ww2ogg.exe --pcb \"/usr/share/ww2ogg/packed_cookbook_aoTuV_603.bin\"",
+            );
+            b.iter(|| {
+                let it = Shlex::new(val);
+                let _: Vec<_> = test::black_box(it.collect());
+            })
+        }
+    }
+
+    mod one_single {
+        use super::*;
+
+        #[bench]
+        fn custom(b: &mut Bencher) {
+            let val = test::black_box(b"'hello'");
+            b.iter(|| {
+                let it = ShellParser::new(val);
+                let _: Vec<_> = test::black_box(it.collect());
+            })
+        }
+
+        #[cfg(feature = "shlex-bench")]
+        #[bench]
+        fn shlex(b: &mut Bencher) {
+            let val = test::black_box(b"'hello'");
+            b.iter(|| {
+                let it = Shlex::new(val);
+                let _: Vec<_> = test::black_box(it.collect());
+            })
+        }
+    }
+}