Don't copy file contents just to remove the BOM

Author: bugadani

src/librustdoc/html/highlight.rs

@@ -17,7 +17,7 @@ use rustc_span::with_default_session_globals;
 
 /// Highlights `src`, returning the HTML output.
 crate fn render_with_highlighting(
-    src: String,
+    src: &str,
     class: Option<&str>,
     playground_button: Option<&str>,
     tooltip: Option<(Option<Edition>, &str)>,

src/librustdoc/html/markdown.rs

@@ -299,7 +299,7 @@ impl<'a, I: Iterator<Item = Event<'a>>> Iterator for CodeBlocks<'_, 'a, I> {
         };
 
         s.push_str(&highlight::render_with_highlighting(
-            text,
+            &text,
             Some(&format!(
                 "rust-example-rendered{}",
                 if let Some((_, class)) = tooltip { format!(" {}", class) } else { String::new() }

src/librustdoc/html/render/mod.rs

@@ -4785,7 +4785,7 @@ fn sidebar_foreign_type(cx: &Context<'_>, buf: &mut Buffer, it: &clean::Item) {
 fn item_macro(w: &mut Buffer, cx: &Context<'_>, it: &clean::Item, t: &clean::Macro) {
     wrap_into_docblock(w, |w| {
         w.write_str(&highlight::render_with_highlighting(
-            t.source.clone(),
+            &t.source,
             Some("macro"),
             None,
             None,

src/librustdoc/html/sources.rs

@@ -86,17 +86,16 @@ impl SourceCollector<'_, '_> {
             return Ok(());
         }
 
-        let mut contents = match fs::read_to_string(&p) {
+        let contents = match fs::read_to_string(&p) {
             Ok(contents) => contents,
             Err(e) => {
                 return Err(Error::new(e, &p));
             }
         };
 
         // Remove the utf-8 BOM if any
-        if contents.starts_with('\u{feff}') {
-            contents.drain(..3);
-        }
+        let contents =
+            if contents.starts_with('\u{feff}') { &contents[3..] } else { &contents[..] };
 
         // Create the intermediate directories
         let mut cur = self.dst.clone();
@@ -171,7 +170,7 @@ where
 
 /// Wrapper struct to render the source code of a file. This will do things like
 /// adding line numbers to the left-hand side.
-fn print_src(buf: &mut Buffer, s: String, edition: Edition) {
+fn print_src(buf: &mut Buffer, s: &str, edition: Edition) {
     let lines = s.lines().count();
     let mut cols = 0;
     let mut tmp = lines;