perf: Avoid hashing in some cases

Author: Stranger6667

CHANGELOG.md

@@ -5,6 +5,7 @@
 ### Performance
 
 - Use a simpler way for HTML tree traversal.
+- Avoid hashing in some cases.
 
 ## [0.10.0] - 2023-06-16
 

bindings/python/CHANGELOG.md

@@ -5,6 +5,7 @@
 ### Performance
 
 - Use a simpler way for HTML tree traversal.
+- Avoid hashing in some cases.
 
 ## [0.10.0] - 2023-06-16
 

bindings/ruby/CHANGELOG.md

@@ -5,6 +5,7 @@
 ### Performance
 
 - Use a simpler way for HTML tree traversal.
+- Avoid hashing in some cases.
 
 ## 0.10.0 - 2023-06-17
 

bindings/wasm/CHANGELOG.md

@@ -5,6 +5,7 @@
 ### Performance
 
 - Use a simpler way for HTML tree traversal.
+- Avoid hashing in some cases.
 
 ## [0.10.0] - 2023-06-16
 

css-inline/src/hasher.rs

@@ -0,0 +1,86 @@
+use core::hash::{BuildHasherDefault, Hasher};
+
+pub(crate) type BuildNoHashHasher = BuildHasherDefault<NoHashHasher>;
+
+#[derive(Default)]
+pub(crate) struct NoHashHasher(u64);
+
+impl Hasher for NoHashHasher {
+    fn finish(&self) -> u64 {
+        self.0
+    }
+
+    fn write(&mut self, _: &[u8]) {
+        panic!("Should not happen")
+    }
+    fn write_u8(&mut self, n: u8) {
+        self.0 = u64::from(n)
+    }
+    fn write_u16(&mut self, n: u16) {
+        self.0 = u64::from(n)
+    }
+    fn write_u32(&mut self, n: u32) {
+        self.0 = u64::from(n)
+    }
+    fn write_u64(&mut self, n: u64) {
+        self.0 = n
+    }
+
+    fn write_usize(&mut self, n: usize) {
+        self.0 = n as u64
+    }
+    fn write_i8(&mut self, n: i8) {
+        self.0 = n as u64
+    }
+    fn write_i16(&mut self, n: i16) {
+        self.0 = n as u64
+    }
+    fn write_i32(&mut self, n: i32) {
+        self.0 = n as u64
+    }
+    fn write_i64(&mut self, n: i64) {
+        self.0 = n as u64
+    }
+
+    fn write_isize(&mut self, n: isize) {
+        self.0 = n as u64
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::NoHashHasher;
+    use std::hash::Hasher;
+
+    #[test]
+    fn hasher() {
+        let mut hasher = NoHashHasher::default();
+        hasher.write_u8(42);
+        assert_eq!(hasher.0, 42);
+        hasher.write_u16(42);
+        assert_eq!(hasher.0, 42);
+        hasher.write_u32(42);
+        assert_eq!(hasher.0, 42);
+        hasher.write_u64(42);
+        assert_eq!(hasher.0, 42);
+        hasher.write_usize(42);
+        assert_eq!(hasher.0, 42);
+        hasher.write_i8(42);
+        assert_eq!(hasher.0, 42);
+        hasher.write_i16(42);
+        assert_eq!(hasher.0, 42);
+        hasher.write_i32(42);
+        assert_eq!(hasher.0, 42);
+        hasher.write_i64(42);
+        assert_eq!(hasher.0, 42);
+        hasher.write_isize(42);
+        assert_eq!(hasher.0, 42);
+    }
+
+    #[test]
+    #[should_panic]
+    fn test_panic() {
+        let mut hasher = NoHashHasher::default();
+        hasher.write(b"a");
+    }
+}

css-inline/src/lib.rs

@@ -26,6 +26,7 @@
 )]
 
 pub mod error;
+mod hasher;
 mod html;
 mod parser;
 
@@ -39,7 +40,8 @@ use std::{
     io::{ErrorKind, Write},
 };
 
-use crate::html::{Document, NodeId, Specificity};
+use hasher::BuildNoHashHasher;
+use html::{Document, NodeId, Specificity};
 pub use url::{ParseError, Url};
 
 /// Replace double quotes in property values.
@@ -232,7 +234,7 @@ impl<'a> CSSInliner<'a> {
         //      selector's specificity. When two rules overlap on the same declaration, then
         //      the one with higher specificity replaces another.
         //   2. Resulting styles are merged into existing "style" tags.
-        let mut styles = IndexMap::with_capacity(128);
+        let mut styles = IndexMap::with_capacity_and_hasher(128, BuildNoHashHasher::default());
         for style in document.styles() {
             process_css(&document, style, &mut styles);
         }
@@ -338,7 +340,7 @@ fn load_external(location: &str) -> Result<String> {
 fn process_css(
     document: &Document,
     css: &str,
-    styles: &mut IndexMap<NodeId, IndexMap<String, (Specificity, String)>>,
+    styles: &mut IndexMap<NodeId, IndexMap<String, (Specificity, String)>, BuildNoHashHasher>,
 ) {
     let mut parse_input = cssparser::ParserInput::new(css);
     let mut parser = cssparser::Parser::new(&mut parse_input);