Help LLVM remove panicking bounds checks

Author: kornelski

src/kmeans.rs

@@ -124,7 +124,7 @@ impl Kmeans {
 /// This replaces these entries with histogram colors that are currently least-fitting the palette.
 fn replace_unused_colors(palette: &mut PalF, hist: &HistogramInternal) -> Result<(), Error> {
     for pal_idx in 0..palette.len() {
-        let pop = palette.pop_as_slice()[pal_idx];
+        let Some(pop) = palette.pop_as_slice().get(pal_idx) else { break };
         if pop.popularity() == 0. && !pop.is_fixed() {
             let n = Nearest::new(palette)?;
             let mut worst = None;

src/pal.rs

@@ -240,8 +240,14 @@ impl PalF {
     }
 
     pub fn set(&mut self, idx: usize, color: f_pixel, popularity: PalPop) {
-        self.colors[idx] = color;
-        self.pops[idx] = popularity;
+        debug_assert!(idx < self.colors.len() && idx < self.pops.len());
+
+        if let Some(pops_idx) = self.pops.get_mut(idx) {
+            *pops_idx = popularity;
+        }
+        if let Some(colors_idx) = self.colors.get_mut(idx) {
+            *colors_idx = color;
+        }
     }
 
     #[inline(always)]