Extract CSE

Author: DrPeaboss

src/sinc.rs

@@ -143,11 +143,10 @@ impl Converter {
             left = iter_count - 1;
             right = iter_count;
         }
+        let coef = coef + self.half_order;
         for _ in 0..iter_count {
-            let idx1 = left as f64 - self.half_order;
-            let idx2 = right as f64 - self.half_order;
-            let pos1 = (coef - idx1).abs() * self.quan;
-            let pos2 = (coef - idx2).abs() * self.quan;
+            let pos1 = (coef - left as f64).abs() * self.quan;
+            let pos2 = (coef - right as f64).abs() * self.quan;
             let pos1u = pos1 as usize;
             let pos2u = pos2 as usize;
             if pos1u < pos_max {