Remove unneccisary multi-`stdout` locking. Added internal buffering.

Fortune for rematch's current commit: Blessing − 吉

src/main.rs

@@ -90,8 +90,8 @@ impl<'a> GroupConfig<'a>
 }
 
 #[inline] 
-fn print_groups<'c, 'a, S: ?Sized, G, T: 'a, I>(to: &mut S, g: G, groups: I, how: GroupConfig<'c>) -> std::io::Result<()>
+fn print_groups<'c, 'a, S: ?Sized, G, T: 'a, I>(to: &mut S, g: G, groups: I, how: impl std::borrow::Borrow<GroupConfig<'c>>) -> std::io::Result<()>
-where S: std::io::Write,
+where S: std::io::Write + 'c, // NOTE: This lifetime bound is not yet used, as it is just `Write`, but if we change this to a context wrapper, then we can copy the `how`'s `'c` references into the context object without direct write/format/cloning.
       G: IntoIterator<Item = &'a Option<T>> + Clone + Copy, // NOTE: Copy bound to ensure we're not accidentally doing deep clones of `g`.
 //G: std::ops::Index<usize>, G::Output: std::borrow::Borrow<Option<T>>,
       T: std::borrow::Borrow<str>,
@@ -101,6 +101,7 @@ where S: std::io::Write,
 	borrow::Borrow,
 	io::Write,
     };
+    let how = how.borrow(); //std::borrow::ToOwned::clone_into(&self, target);
     let mut first = true;
     for group in groups.into_iter() {
 	let group = group.borrow();
@@ -128,7 +129,7 @@ where S: std::io::Write,
 	first = false;
     }
     // If `first == true`, no groups were printed, so we do not print the new-line.
-    if !first && !how.line_delimiter.is_empty() {
+    if !first && how.has_line_delimiter() {
 	to.write_all(how.line_delimiter.as_ref())
     } else {
 	Ok(())
@@ -181,11 +182,11 @@ fn main() -> eyre::Result<()>
 	let mut stdout = std::io::stdout();
 	
 	if &text[..] == "-" {
-	    text::stdin_lines(|text| -> eyre::Result<bool> {
+	    let mut stdout = std::io::BufWriter::new(stdout.lock());
-		let mut stdout = stdout.lock();
+	    text::stdin_lines(move |text| -> eyre::Result<bool> {
 		match re.exec(&text)? {
 		    Some(g) /*if g.len() > group*/ => // NOTE: This check branch has now been moved into `print_groups()`
-			print_groups(&mut stdout, &g, &groups, print_cfg.clone())?, //println!("{}", &g[group]),
+			print_groups(&mut stdout, &g, &groups, &print_cfg)?, //println!("{}", &g[group]),
 		    _ => (),
 		}
 		Ok(true)