perf: Slightly improve performance of HTML serialization

CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## [Unreleased]
 
+### Performance
+
+- Slightly improve performance of HTML serialization.
+
 ## [0.14.4] - 2024-12-27
 
 ### Changed

css-inline/src/html/serializer.rs

@@ -171,12 +171,14 @@
                     .expect("Invalid substring")
                     .as_bytes(),
             )?;
-            match part {
-                "&" => self.writer.write_all(b"&")?,
-                "\u{00A0}" => self.writer.write_all(b" ")?,
-                "<" => self.writer.write_all(b"&lt;")?,
-                ">" => self.writer.write_all(b"&gt;")?,
-                _ => unreachable!("Only the variants above are searched"),
+            // This is slightly faster than matching on `char`
+            // Notably, this approach does not work in `write_attributes` below
+            match (part.as_bytes()[0] & 0b0000_1110) >> 1 {
+                1 => self.writer.write_all(b"&nbsp;")?,
+                3 => self.writer.write_all(b"&amp;")?,
+                6 => self.writer.write_all(b"&lt;")?,
+                7 => self.writer.write_all(b"&gt;")?,
+                _ => unreachable!(),
             }
             last_end = start.checked_add(part.len()).expect("Size overflow");
         }