Minor refactorings for 'data-' attribute logic.

components/script/dom/htmlelement.rs

@@ -32,7 +32,6 @@ use dom::virtualmethods::VirtualMethods;
 use dom_struct::dom_struct;
 use html5ever::{LocalName, Prefix};
 use std::ascii::AsciiExt;
-use std::borrow::ToOwned;
 use std::default::Default;
 use std::rc::Rc;
 use style::attr::AttrValue;
@@ -374,11 +373,15 @@ impl HTMLElementMethods for HTMLElement {
 
 // https://html.spec.whatwg.org/multipage/#attr-data-*
 
+static DATA_PREFIX: &str = "data-";
+static DATA_HYPHEN_SEPARATOR: char = '\x2d';
+
 fn to_snake_case(name: DOMString) -> DOMString {
-    let mut attr_name = "data-".to_owned();
+    let mut attr_name = String::with_capacity(name.len() + DATA_PREFIX.len());
+    attr_name.push_str(DATA_PREFIX);
     for ch in name.chars() {
         if ch.is_ascii_uppercase() {
-            attr_name.push('\x2d');
+            attr_name.push(DATA_HYPHEN_SEPARATOR);
             attr_name.push(ch.to_ascii_lowercase());
         } else {
             attr_name.push(ch);
@@ -394,19 +397,19 @@ fn to_snake_case(name: DOMString) -> DOMString {
 // without the data prefix.
 
 fn to_camel_case(name: &str) -> Option<DOMString> {
-    if !name.starts_with("data-") {
+    if !name.starts_with(DATA_PREFIX) {
         return None;
     }
     let name = &name[5..];
     let has_uppercase = name.chars().any(|curr_char| curr_char.is_ascii_uppercase());
     if has_uppercase {
         return None;
     }
-    let mut result = "".to_owned();
+    let mut result = String::with_capacity(name.len().saturating_sub(DATA_PREFIX.len()));
     let mut name_chars = name.chars();
     while let Some(curr_char) = name_chars.next() {
         //check for hyphen followed by character
-        if curr_char == '\x2d' {
+        if curr_char == DATA_HYPHEN_SEPARATOR {
             if let Some(next_char) = name_chars.next() {
                 if next_char.is_ascii_lowercase() {
                     result.push(next_char.to_ascii_uppercase());