1 files changed, 126 insertions, 0 deletions
diff --git a/third_party/rust/xml-rs/src/escape.rs b/third_party/rust/xml-rs/src/escape.rs
new file mode 100644
index 0000000000..18298b9be1
--- /dev/null
+++ b/third_party/rust/xml-rs/src/escape.rs
@@ -0,0 +1,126 @@
+//! Contains functions for performing XML special characters escaping.
+
+use std::borrow::Cow;
+
+enum Value {
+    Char(char),
+    Str(&'static str)
+}
+
+impl Value {
+    fn dispatch_for_attribute(c: char) -> Value {
+        match c {
+            '<'  => Value::Str("&lt;"),
+            '>'  => Value::Str("&gt;"),
+            '"'  => Value::Str("&quot;"),
+            '\'' => Value::Str("&apos;"),
+            '&'  => Value::Str("&amp;"),
+            '\n' => Value::Str("&#xA;"),
+            '\r' => Value::Str("&#xD;"),
+            _    => Value::Char(c)
+        }
+    }
+
+    fn dispatch_for_pcdata(c: char) -> Value {
+        match c {
+            '<'  => Value::Str("&lt;"),
+            '&'  => Value::Str("&amp;"),
+            _    => Value::Char(c)
+        }
+    }
+}
+
+enum Process<'a> {
+    Borrowed(&'a str),
+    Owned(String)
+}
+
+impl<'a> Process<'a> {
+    fn process(&mut self, (i, next): (usize, Value)) {
+        match next {
+            Value::Str(s) => match *self {
+                Process::Owned(ref mut o) => o.push_str(s),
+                Process::Borrowed(b) => {
+                    let mut r = String::with_capacity(b.len() + s.len());
+                    r.push_str(&b[..i]);
+                    r.push_str(s);
+                    *self = Process::Owned(r);
+                }
+            },
+            Value::Char(c) => match *self {
+                Process::Borrowed(_) => {}
+                Process::Owned(ref mut o) => o.push(c)
+            }
+        }
+    }
+
+    fn into_result(self) -> Cow<'a, str> {
+        match self {
+            Process::Borrowed(b) => Cow::Borrowed(b),
+            Process::Owned(o) => Cow::Owned(o)
+        }
+    }
+}
+
+impl<'a> Extend<(usize, Value)> for Process<'a> {
+    fn extend<I: IntoIterator<Item=(usize, Value)>>(&mut self, it: I) {
+        for v in it.into_iter() {
+            self.process(v);
+        }
+    }
+}
+
+fn escape_str(s: &str, dispatch: fn(char) -> Value) -> Cow<str> {
+    let mut p = Process::Borrowed(s);
+    p.extend(s.char_indices().map(|(ind, c)| (ind, dispatch(c))));
+    p.into_result()
+}
+
+/// Performs escaping of common XML characters inside an attribute value.
+///
+/// This function replaces several important markup characters with their
+/// entity equivalents:
+///
+/// * `<` → `&lt;`
+/// * `>` → `&gt;`
+/// * `"` → `&quot;`
+/// * `'` → `&apos;`
+/// * `&` → `&amp;`
+///
+/// The resulting string is safe to use inside XML attribute values or in PCDATA sections.
+///
+/// Does not perform allocations if the given string does not contain escapable characters.
+#[inline]
+pub fn escape_str_attribute(s: &str) -> Cow<str> {
+    escape_str(s, Value::dispatch_for_attribute)
+}
+
+/// Performs escaping of common XML characters inside PCDATA.
+///
+/// This function replaces several important markup characters with their
+/// entity equivalents:
+///
+/// * `<` → `&lt;`
+/// * `&` → `&amp;`
+///
+/// The resulting string is safe to use inside PCDATA sections but NOT inside attribute values.
+///
+/// Does not perform allocations if the given string does not contain escapable characters.
+#[inline]
+pub fn escape_str_pcdata(s: &str) -> Cow<str> {
+    escape_str(s, Value::dispatch_for_pcdata)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::{escape_str_pcdata, escape_str_attribute};
+
+    // TODO: add more tests
+
+    #[test]
+    fn test_escape_multibyte_code_points() {
+        assert_eq!(escape_str_attribute("☃<"), "☃&lt;");
+        assert_eq!(escape_str_pcdata("☃<"), "☃&lt;");
+    }
+}
+