1 files changed, 107 insertions, 0 deletions
diff --git a/third_party/rust/xml-rs/src/util.rs b/third_party/rust/xml-rs/src/util.rs
new file mode 100644
index 0000000000..23fee04eed
--- /dev/null
+++ b/third_party/rust/xml-rs/src/util.rs
@@ -0,0 +1,107 @@
+use std::io::{self, Read};
+use std::str;
+use std::fmt;
+
+#[derive(Debug)]
+pub enum CharReadError {
+    UnexpectedEof,
+    Utf8(str::Utf8Error),
+    Io(io::Error)
+}
+
+impl From<str::Utf8Error> for CharReadError {
+    fn from(e: str::Utf8Error) -> CharReadError {
+        CharReadError::Utf8(e)
+    }
+}
+
+impl From<io::Error> for CharReadError {
+    fn from(e: io::Error) -> CharReadError {
+        CharReadError::Io(e)
+    }
+}
+
+impl fmt::Display for CharReadError {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        use self::CharReadError::*;
+        match *self {
+            UnexpectedEof => write!(f, "unexpected end of stream"),
+            Utf8(ref e) => write!(f, "UTF-8 decoding error: {}", e),
+            Io(ref e) => write!(f, "I/O error: {}", e)
+        }
+    }
+}
+
+pub fn next_char_from<R: Read>(source: &mut R) -> Result<Option<char>, CharReadError> {
+    const MAX_CODEPOINT_LEN: usize = 4;
+
+    let mut bytes = source.bytes();
+    let mut buf = [0u8; MAX_CODEPOINT_LEN];
+    let mut pos = 0;
+
+    loop {
+        let next = match bytes.next() {
+            Some(Ok(b)) => b,
+            Some(Err(e)) => return Err(e.into()),
+            None if pos == 0 => return Ok(None),
+            None => return Err(CharReadError::UnexpectedEof)
+        };
+        buf[pos] = next;
+        pos += 1;
+
+        match str::from_utf8(&buf[..pos]) {
+            Ok(s) => return Ok(s.chars().next()),  // always Some(..)
+            Err(_) if pos < MAX_CODEPOINT_LEN => {},
+            Err(e) => return Err(e.into())
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn test_next_char_from() {
+        use std::io;
+        use std::error::Error;
+
+        let mut bytes: &[u8] = "correct".as_bytes();    // correct ASCII
+        assert_eq!(super::next_char_from(&mut bytes).unwrap(), Some('c'));
+
+        let mut bytes: &[u8] = "правильно".as_bytes();  // correct BMP
+        assert_eq!(super::next_char_from(&mut bytes).unwrap(), Some('п'));
+
+        let mut bytes: &[u8] = "😊".as_bytes();          // correct non-BMP
+        assert_eq!(super::next_char_from(&mut bytes).unwrap(), Some('😊'));
+
+        let mut bytes: &[u8] = b"";                     // empty
+        assert_eq!(super::next_char_from(&mut bytes).unwrap(), None);
+
+        let mut bytes: &[u8] = b"\xf0\x9f\x98";         // incomplete code point
+        match super::next_char_from(&mut bytes).unwrap_err() {
+            super::CharReadError::UnexpectedEof => {},
+            e => panic!("Unexpected result: {:?}", e)
+        };
+
+        let mut bytes: &[u8] = b"\xff\x9f\x98\x32";     // invalid code point
+        match super::next_char_from(&mut bytes).unwrap_err() {
+            super::CharReadError::Utf8(_) => {},
+            e => panic!("Unexpected result: {:?}", e)
+        };
+
+
+        // error during read
+        struct ErrorReader;
+        impl io::Read for ErrorReader {
+            fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
+                Err(io::Error::new(io::ErrorKind::Other, "test error"))
+            }
+        }
+
+        let mut r = ErrorReader;
+        match super::next_char_from(&mut r).unwrap_err() {
+            super::CharReadError::Io(ref e) if e.kind() == io::ErrorKind::Other &&
+                                               e.description() == "test error" => {},
+            e => panic!("Unexpected result: {:?}", e)
+        }
+    }
+}