1 files changed, 30 insertions, 65 deletions

diff --git a/crates/stdx/src/lib.rs b/crates/stdx/src/lib.rs
index b65875c96..273b0f55b 100644
--- a/crates/stdx/src/lib.rs
+++ b/crates/stdx/src/lib.rs
@@ -1,5 +1,8 @@
 //! Missing batteries for standard libraries.
-use std::{cell::Cell, fmt, time::Instant};
+use std::{
+    sync::atomic::{AtomicUsize, Ordering},
+    time::Instant,
+};
 
 mod macros;
 
@@ -8,69 +11,6 @@ pub fn is_ci() -> bool {
     option_env!("CI").is_some()
 }
 
-pub trait SepBy: Sized {
-    /// Returns an `impl fmt::Display`, which joins elements via a separator.
-    fn sep_by<'a>(self, sep: &'a str) -> SepByBuilder<'a, Self>;
-}
-
-impl<I> SepBy for I
-where
-    I: Iterator,
-    I::Item: fmt::Display,
-{
-    fn sep_by<'a>(self, sep: &'a str) -> SepByBuilder<'a, Self> {
-        SepByBuilder::new(sep, self)
-    }
-}
-
-pub struct SepByBuilder<'a, I> {
-    sep: &'a str,
-    prefix: &'a str,
-    suffix: &'a str,
-    iter: Cell<Option<I>>,
-}
-
-impl<'a, I> SepByBuilder<'a, I> {
-    fn new(sep: &'a str, iter: I) -> SepByBuilder<'a, I> {
-        SepByBuilder { sep, prefix: "", suffix: "", iter: Cell::new(Some(iter)) }
-    }
-
-    pub fn prefix(mut self, prefix: &'a str) -> Self {
-        self.prefix = prefix;
-        self
-    }
-
-    pub fn suffix(mut self, suffix: &'a str) -> Self {
-        self.suffix = suffix;
-        self
-    }
-
-    /// Set both suffix and prefix.
-    pub fn surround_with(self, prefix: &'a str, suffix: &'a str) -> Self {
-        self.prefix(prefix).suffix(suffix)
-    }
-}
-
-impl<I> fmt::Display for SepByBuilder<'_, I>
-where
-    I: Iterator,
-    I::Item: fmt::Display,
-{
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        f.write_str(self.prefix)?;
-        let mut first = true;
-        for item in self.iter.take().unwrap() {
-            if !first {
-                f.write_str(self.sep)?;
-            }
-            first = false;
-            fmt::Display::fmt(&item, f)?;
-        }
-        f.write_str(self.suffix)?;
-        Ok(())
-    }
-}
-
 #[must_use]
 pub fn timeit(label: &'static str) -> impl Drop {
     struct Guard {
@@ -80,7 +20,7 @@ pub fn timeit(label: &'static str) -> impl Drop {
 
     impl Drop for Guard {
         fn drop(&mut self) {
-            eprintln!("{}: {:?}", self.label, self.start.elapsed())
+            eprintln!("{}: {:.2?}", self.label, self.start.elapsed())
         }
     }
 
@@ -197,6 +137,31 @@ where
     left
 }
 
+pub struct RacyFlag(AtomicUsize);
+
+impl RacyFlag {
+    pub const fn new() -> RacyFlag {
+        RacyFlag(AtomicUsize::new(!0))
+    }
+
+    pub fn get(&self, init: impl FnMut() -> bool) -> bool {
+        let mut init = Some(init);
+        self.get_impl(&mut || init.take().map_or(false, |mut f| f()))
+    }
+
+    fn get_impl(&self, init: &mut dyn FnMut() -> bool) -> bool {
+        match self.0.load(Ordering::Relaxed) {
+            0 => false,
+            1 => true,
+            _ => {
+                let res = init();
+                self.0.store(if res { 1 } else { 0 }, Ordering::Relaxed);
+                res
+            }
+        }
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;