split / cleanup core utils.

Signed-off-by: Jason Volk <jason@zemos.net>

src/core/utils/html.rs

@@ -0,0 +1,37 @@
+use std::fmt;
+
+/// Wrapper struct which will emit the HTML-escaped version of the contained
+/// string when passed to a format string.
+pub struct Escape<'a>(pub &'a str);
+
+/// Copied from librustdoc:
+/// * <https://github.com/rust-lang/rust/blob/cbaeec14f90b59a91a6b0f17fc046c66fa811892/src/librustdoc/html/escape.rs>
+impl fmt::Display for Escape<'_> {
+	fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+		// Because the internet is always right, turns out there's not that many
+		// characters to escape: http://stackoverflow.com/questions/7381974
+		let Escape(s) = *self;
+		let pile_o_bits = s;
+		let mut last = 0;
+		for (i, ch) in s.char_indices() {
+			let s = match ch {
+				'>' => "&gt;",
+				'<' => "&lt;",
+				'&' => "&amp;",
+				'\'' => "&#39;",
+				'"' => "&quot;",
+				_ => continue,
+			};
+			fmt.write_str(&pile_o_bits[last..i])?;
+			fmt.write_str(s)?;
+			// NOTE: we only expect single byte characters here - which is fine as long as
+			// we only match single byte characters
+			last = i + 1;
+		}
+
+		if last < s.len() {
+			fmt.write_str(&pile_o_bits[last..])?;
+		}
+		Ok(())
+	}
+}