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    use std::str;

    use actix_web::web::BytesMut;

    enum State {
        YieldStr,
        YieldQuote,
    }

    struct Quoted<'a> {
        inner: ::std::iter::Peekable<str::Split<'a, char>>,
        state: State,
    }

    impl<'a> Quoted<'a> {
        pub fn new(s: &'a str) -> Quoted<'_> {
            Quoted {
                inner: s.split('"').peekable(),
                state: State::YieldStr,
            }
        }
    }

    impl<'a> Iterator for Quoted<'a> {
        type Item = &'a str;

        fn next(&mut self) -> Option<Self::Item> {
            match self.state {
                State::YieldStr => match self.inner.next() {
                    Some(val) => {
                        self.state = State::YieldQuote;
                        Some(val)
                    }
                    None => None,
                },

                State::YieldQuote => match self.inner.peek() {
                    Some(_) => {
                        self.state = State::YieldStr;
                        Some("\\\"")
                    }
                    None => None,
                },
            }
        }
    }

    /// Escapes the quotes in `val`.
    pub fn put_quoted(buf: &mut BytesMut, val: &str) {
        for part in Quoted::new(val) {
            buf.extend_from_slice(part.as_bytes());
        }
    }

    #[cfg(test)]
    mod tests {
        use std::str;

        use actix_web::web::BytesMut;

        use super::put_quoted;

        #[test]
        fn test_quote_str() {
            let input = "a \"quoted\" string";
            let mut output = BytesMut::new();
            put_quoted(&mut output, input);
            let result = str::from_utf8(&output).unwrap();

            assert_eq!(result, "a \\\"quoted\\\" string");
        }

        #[test]
        fn test_without_quotes() {
            let input = "non-quoted string";
            let mut output = BytesMut::new();
            put_quoted(&mut output, input);
            let result = str::from_utf8(&output).unwrap();

            assert_eq!(result, "non-quoted string");
        }

        #[test]
        fn test_starts_with_quote() {
            let input = "\"first-quoted string";
            let mut output = BytesMut::new();
            put_quoted(&mut output, input);
            let result = str::from_utf8(&output).unwrap();

            assert_eq!(result, "\\\"first-quoted string");
        }

        #[test]
        fn test_ends_with_quote() {
            let input = "last-quoted string\"";
            let mut output = BytesMut::new();
            put_quoted(&mut output, input);
            let result = str::from_utf8(&output).unwrap();

            assert_eq!(result, "last-quoted string\\\"");
        }

        #[test]
        fn test_double_quote() {
            let input = "quote\"\"string";
            let mut output = BytesMut::new();
            put_quoted(&mut output, input);
            let result = str::from_utf8(&output).unwrap();

            assert_eq!(result, "quote\\\"\\\"string");
        }
    }