# param.rs.html -- source
Source to the Rust file `src/param.rs`.
Keywords: rust, rustlang, rust-lang

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    use std;
    use std::ops::Index;
    use std::path::PathBuf;
    use std::rc::Rc;
    use std::str::FromStr;

    use http::StatusCode;
    use smallvec::SmallVec;

    use error::{InternalError, ResponseError, UriSegmentError};
    use uri::Url;

    /// A trait to abstract the idea of creating a new instance of a type from a
    /// path parameter.
    pub trait FromParam: Sized {
        /// The associated error which can be returned from parsing.
        type Err: ResponseError;

        /// Parses a string `s` to return a value of this type.
        fn from_param(s: &str) -> Result<Self, Self::Err>;
    }

    #[derive(Debug, Clone)]
    pub(crate) enum ParamItem {
        Static(&'static str),
        UrlSegment(u16, u16),
    }

    /// Route match information
    ///
    /// If resource path contains variable patterns, `Params` stores this variables.
    #[derive(Debug, Clone)]
    pub struct Params {
        url: Url,
        pub(crate) tail: u16,
        pub(crate) segments: SmallVec<[(Rc<String>, ParamItem); 3]>,
    }

    impl Params {
        pub(crate) fn new() -> Params {
            Params {
                url: Url::default(),
                tail: 0,
                segments: SmallVec::new(),
            }
        }

        pub(crate) fn with_url(url: &Url) -> Params {
            Params {
                url: url.clone(),
                tail: 0,
                segments: SmallVec::new(),
            }
        }

        pub(crate) fn clear(&mut self) {
            self.segments.clear();
        }

        pub(crate) fn set_tail(&mut self, tail: u16) {
            self.tail = tail;
        }

        pub(crate) fn set_url(&mut self, url: Url) {
            self.url = url;
        }

        pub(crate) fn add(&mut self, name: Rc<String>, value: ParamItem) {
            self.segments.push((name, value));
        }

        pub(crate) fn add_static(&mut self, name: &str, value: &'static str) {
            self.segments
                .push((Rc::new(name.to_string()), ParamItem::Static(value)));
        }

        /// Check if there are any matched patterns
        pub fn is_empty(&self) -> bool {
            self.segments.is_empty()
        }

        /// Check number of extracted parameters
        pub fn len(&self) -> usize {
            self.segments.len()
        }

        /// Get matched parameter by name without type conversion
        pub fn get(&self, key: &str) -> Option<&str> {
            for item in self.segments.iter() {
                if key == item.0.as_str() {
                    return match item.1 {
                        ParamItem::Static(ref s) => Some(&s),
                        ParamItem::UrlSegment(s, e) => {
                            Some(&self.url.path()[(s as usize)..(e as usize)])
                        }
                    };
                }
            }
            if key == "tail" {
                Some(&self.url.path()[(self.tail as usize)..])
            } else {
                None
            }
        }

        /// Get unprocessed part of path
        pub fn unprocessed(&self) -> &str {
            &self.url.path()[(self.tail as usize)..]
        }

        /// Get matched `FromParam` compatible parameter by name.
        ///
        /// If keyed parameter is not available empty string is used as default
        /// value.
        ///
        /// ```rust
        /// # extern crate actix_web;
        /// # use actix_web::*;
        /// fn index(req: HttpRequest) -> Result<String> {
        ///     let ivalue: isize = req.match_info().query("val")?;
        ///     Ok(format!("isuze value: {:?}", ivalue))
        /// }
        /// # fn main() {}
        /// ```
        pub fn query<T: FromParam>(&self, key: &str) -> Result<T, <T as FromParam>::Err> {
            if let Some(s) = self.get(key) {
                T::from_param(s)
            } else {
                T::from_param("")
            }
        }

        /// Return iterator to items in parameter container
        pub fn iter(&self) -> ParamsIter {
            ParamsIter {
                idx: 0,
                params: self,
            }
        }
    }

    #[derive(Debug)]
    pub struct ParamsIter<'a> {
        idx: usize,
        params: &'a Params,
    }

    impl<'a> Iterator for ParamsIter<'a> {
        type Item = (&'a str, &'a str);

        #[inline]
        fn next(&mut self) -> Option<(&'a str, &'a str)> {
            if self.idx < self.params.len() {
                let idx = self.idx;
                let res = match self.params.segments[idx].1 {
                    ParamItem::Static(ref s) => &s,
                    ParamItem::UrlSegment(s, e) => {
                        &self.params.url.path()[(s as usize)..(e as usize)]
                    }
                };
                self.idx += 1;
                return Some((&self.params.segments[idx].0, res));
            }
            None
        }
    }

    impl<'a> Index<&'a str> for Params {
        type Output = str;

        fn index(&self, name: &'a str) -> &str {
            self.get(name)
                .expect("Value for parameter is not available")
        }
    }

    impl Index<usize> for Params {
        type Output = str;

        fn index(&self, idx: usize) -> &str {
            match self.segments[idx].1 {
                ParamItem::Static(ref s) => &s,
                ParamItem::UrlSegment(s, e) => &self.url.path()[(s as usize)..(e as usize)],
            }
        }
    }

    /// Creates a `PathBuf` from a path parameter. The returned `PathBuf` is
    /// percent-decoded. If a segment is equal to "..", the previous segment (if
    /// any) is skipped.
    ///
    /// For security purposes, if a segment meets any of the following conditions,
    /// an `Err` is returned indicating the condition met:
    ///
    ///   * Decoded segment starts with any of: `.` (except `..`), `*`
    ///   * Decoded segment ends with any of: `:`, `>`, `<`
    ///   * Decoded segment contains any of: `/`
    ///   * On Windows, decoded segment contains any of: '\'
    ///   * Percent-encoding results in invalid UTF8.
    ///
    /// As a result of these conditions, a `PathBuf` parsed from request path
    /// parameter is safe to interpolate within, or use as a suffix of, a path
    /// without additional checks.
    impl FromParam for PathBuf {
        type Err = UriSegmentError;

        fn from_param(val: &str) -> Result<PathBuf, UriSegmentError> {
            let mut buf = PathBuf::new();
            for segment in val.split('/') {
                if segment == ".." {
                    buf.pop();
                } else if segment.starts_with('.') {
                    return Err(UriSegmentError::BadStart('.'));
                } else if segment.starts_with('*') {
                    return Err(UriSegmentError::BadStart('*'));
                } else if segment.ends_with(':') {
                    return Err(UriSegmentError::BadEnd(':'));
                } else if segment.ends_with('>') {
                    return Err(UriSegmentError::BadEnd('>'));
                } else if segment.ends_with('<') {
                    return Err(UriSegmentError::BadEnd('<'));
                } else if segment.is_empty() {
                    continue;
                } else if cfg!(windows) && segment.contains('\\') {
                    return Err(UriSegmentError::BadChar('\\'));
                } else {
                    buf.push(segment)
                }
            }

            Ok(buf)
        }
    }

    macro_rules! FROM_STR {
        ($type:ty) => {
            impl FromParam for $type {
                type Err = InternalError<<$type as FromStr>::Err>;
                fn from_param(val: &str) -> Result<Self, Self::Err> {
                    <$type as FromStr>::from_str(val)
                        .map_err(|e| InternalError::new(e, StatusCode::BAD_REQUEST))
                }
            }
        };
    }

    FROM_STR!(u8);
    FROM_STR!(u16);
    FROM_STR!(u32);
    FROM_STR!(u64);
    FROM_STR!(usize);
    FROM_STR!(i8);
    FROM_STR!(i16);
    FROM_STR!(i32);
    FROM_STR!(i64);
    FROM_STR!(isize);
    FROM_STR!(f32);
    FROM_STR!(f64);
    FROM_STR!(String);
    FROM_STR!(std::net::IpAddr);
    FROM_STR!(std::net::Ipv4Addr);
    FROM_STR!(std::net::Ipv6Addr);
    FROM_STR!(std::net::SocketAddr);
    FROM_STR!(std::net::SocketAddrV4);
    FROM_STR!(std::net::SocketAddrV6);

    #[cfg(test)]
    mod tests {
        use super::*;
        use std::iter::FromIterator;

        #[test]
        fn test_path_buf() {
            assert_eq!(
                PathBuf::from_param("/test/.tt"),
                Err(UriSegmentError::BadStart('.'))
            );
            assert_eq!(
                PathBuf::from_param("/test/*tt"),
                Err(UriSegmentError::BadStart('*'))
            );
            assert_eq!(
                PathBuf::from_param("/test/tt:"),
                Err(UriSegmentError::BadEnd(':'))
            );
            assert_eq!(
                PathBuf::from_param("/test/tt<"),
                Err(UriSegmentError::BadEnd('<'))
            );
            assert_eq!(
                PathBuf::from_param("/test/tt>"),
                Err(UriSegmentError::BadEnd('>'))
            );
            assert_eq!(
                PathBuf::from_param("/seg1/seg2/"),
                Ok(PathBuf::from_iter(vec!["seg1", "seg2"]))
            );
            assert_eq!(
                PathBuf::from_param("/seg1/../seg2/"),
                Ok(PathBuf::from_iter(vec!["seg2"]))
            );
        }
    }

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