improve docs

actix-http/src/header/shared/quality.rs

@@ -78,14 +78,21 @@ impl fmt::Display for Quality {
 
                 // This implementation avoids string allocation for removing trailing zeroes.
                 // In benchmarks it is twice as fast as approach using something like
-                // `format!("{}").trim_end_matches('0')` for non-fast path quality values.
+                // `format!("{}").trim_end_matches('0')` for non-fast-path quality values.
 
                 if x < 10 {
+                    // x in is range 1–9
+
                     f.write_str("00")?;
-                    // 0 is handled so it's not possible to have a trailing 0, we can just return
+
+                    // 0 is already handled so it's not possible to have a trailing 0 in this range
+                    // we can just write the integer
                     itoa::fmt(f, x)
                 } else if x < 100 {
+                    // x in is range 10–99
+
                     f.write_str("0")?;
+
                     if x % 10 == 0 {
                         // trailing 0, divide by 10 and write
                         itoa::fmt(f, x / 10)
@@ -93,7 +100,7 @@ impl fmt::Display for Quality {
                         itoa::fmt(f, x)
                     }
                 } else {
-                    // x is in range 101–999
+                    // x is in range 100–999
 
                     if x % 100 == 0 {
                         // two trailing 0s, divide by 100 and write
@@ -179,6 +186,12 @@ mod tests {
         assert_eq!(q(0.22).to_string(), "0.22");
         assert_eq!(q(0.123).to_string(), "0.123");
         assert_eq!(q(0.999).to_string(), "0.999");
+
+        for x in 0..=1000 {
+            // if trailing zeroes are handled correctly, we would not expect the serialized length
+            // to ever exceed "0." + 3 decimal places = 5 in length
+            assert!(q(x as f32 / 1000.0).to_string().len() <= 5);
+        }
     }
 
     #[test]

actix-http/src/header/shared/quality_item.rs

@@ -48,12 +48,12 @@ impl<T> QualityItem<T> {
         QualityItem { item, quality }
     }
 
-    /// Constructs a new `QualityItem` with from an item, using the maximum q-value.
+    /// Constructs a new `QualityItem` from an item, using the maximum q-value.
     pub fn max(item: T) -> Self {
         Self::new(item, Quality::MAX)
     }
 
-    /// Constructs a new `QualityItem` with from an item, using the minimum q-value.
+    /// Constructs a new `QualityItem` from an item, using the minimum q-value.
     pub fn min(item: T) -> Self {
         Self::new(item, Quality::MIN)
     }
@@ -74,7 +74,6 @@ impl<T: fmt::Display> fmt::Display for QualityItem<T> {
             Quality::MAX => Ok(()),
 
             Quality::MIN => f.write_str("; q=0"),
-
             q => write!(f, "; q={}", q),
         }
     }
@@ -88,7 +87,7 @@ impl<T: str::FromStr> str::FromStr for QualityItem<T> {
             return Err(ParseError::Header);
         }
 
-        // set defaults used if quality-item parsing fails, i.e., item has no q-factor
+        // set defaults used if quality-item parsing fails, i.e., item has no q attribute
         let mut raw_item = q_item_str;
         let mut quality = Quality::MAX;