Import 'regex' package vesion 1.3.6

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Bug: 152884384
Test: make

Change-Id: I455caf7833b6c437c1c133bc7b2f47b83da9cbce
diff --git a/src/re_bytes.rs b/src/re_bytes.rs
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+++ b/src/re_bytes.rs
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+use std::borrow::Cow;
+use std::collections::HashMap;
+use std::fmt;
+use std::ops::{Index, Range};
+use std::str::FromStr;
+use std::sync::Arc;
+
+use find_byte::find_byte;
+
+use error::Error;
+use exec::{Exec, ExecNoSync};
+use expand::expand_bytes;
+use re_builder::bytes::RegexBuilder;
+use re_trait::{self, RegularExpression, SubCapturesPosIter};
+
+/// Match represents a single match of a regex in a haystack.
+///
+/// The lifetime parameter `'t` refers to the lifetime of the matched text.
+#[derive(Copy, Clone, Debug, Eq, PartialEq)]
+pub struct Match<'t> {
+    text: &'t [u8],
+    start: usize,
+    end: usize,
+}
+
+impl<'t> Match<'t> {
+    /// Returns the starting byte offset of the match in the haystack.
+    #[inline]
+    pub fn start(&self) -> usize {
+        self.start
+    }
+
+    /// Returns the ending byte offset of the match in the haystack.
+    #[inline]
+    pub fn end(&self) -> usize {
+        self.end
+    }
+
+    /// Returns the range over the starting and ending byte offsets of the
+    /// match in the haystack.
+    #[inline]
+    pub fn range(&self) -> Range<usize> {
+        self.start..self.end
+    }
+
+    /// Returns the matched text.
+    #[inline]
+    pub fn as_bytes(&self) -> &'t [u8] {
+        &self.text[self.range()]
+    }
+
+    /// Creates a new match from the given haystack and byte offsets.
+    #[inline]
+    fn new(haystack: &'t [u8], start: usize, end: usize) -> Match<'t> {
+        Match { text: haystack, start: start, end: end }
+    }
+}
+
+impl<'t> From<Match<'t>> for Range<usize> {
+    fn from(m: Match<'t>) -> Range<usize> {
+        m.range()
+    }
+}
+
+/// A compiled regular expression for matching arbitrary bytes.
+///
+/// It can be used to search, split or replace text. All searching is done with
+/// an implicit `.*?` at the beginning and end of an expression. To force an
+/// expression to match the whole string (or a prefix or a suffix), you must
+/// use an anchor like `^` or `$` (or `\A` and `\z`).
+///
+/// Like the `Regex` type in the parent module, matches with this regex return
+/// byte offsets into the search text. **Unlike** the parent `Regex` type,
+/// these byte offsets may not correspond to UTF-8 sequence boundaries since
+/// the regexes in this module can match arbitrary bytes.
+#[derive(Clone)]
+pub struct Regex(Exec);
+
+impl fmt::Display for Regex {
+    /// Shows the original regular expression.
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "{}", self.as_str())
+    }
+}
+
+impl fmt::Debug for Regex {
+    /// Shows the original regular expression.
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        fmt::Display::fmt(self, f)
+    }
+}
+
+/// A constructor for Regex from an Exec.
+///
+/// This is hidden because Exec isn't actually part of the public API.
+#[doc(hidden)]
+impl From<Exec> for Regex {
+    fn from(exec: Exec) -> Regex {
+        Regex(exec)
+    }
+}
+
+impl FromStr for Regex {
+    type Err = Error;
+
+    /// Attempts to parse a string into a regular expression
+    fn from_str(s: &str) -> Result<Regex, Error> {
+        Regex::new(s)
+    }
+}
+
+/// Core regular expression methods.
+impl Regex {
+    /// Compiles a regular expression. Once compiled, it can be used repeatedly
+    /// to search, split or replace text in a string.
+    ///
+    /// If an invalid expression is given, then an error is returned.
+    pub fn new(re: &str) -> Result<Regex, Error> {
+        RegexBuilder::new(re).build()
+    }
+
+    /// Returns true if and only if the regex matches the string given.
+    ///
+    /// It is recommended to use this method if all you need to do is test
+    /// a match, since the underlying matching engine may be able to do less
+    /// work.
+    ///
+    /// # Example
+    ///
+    /// Test if some text contains at least one word with exactly 13 ASCII word
+    /// bytes:
+    ///
+    /// ```rust
+    /// # extern crate regex; use regex::bytes::Regex;
+    /// # fn main() {
+    /// let text = b"I categorically deny having triskaidekaphobia.";
+    /// assert!(Regex::new(r"\b\w{13}\b").unwrap().is_match(text));
+    /// # }
+    /// ```
+    pub fn is_match(&self, text: &[u8]) -> bool {
+        self.is_match_at(text, 0)
+    }
+
+    /// Returns the start and end byte range of the leftmost-first match in
+    /// `text`. If no match exists, then `None` is returned.
+    ///
+    /// Note that this should only be used if you want to discover the position
+    /// of the match. Testing the existence of a match is faster if you use
+    /// `is_match`.
+    ///
+    /// # Example
+    ///
+    /// Find the start and end location of the first word with exactly 13
+    /// ASCII word bytes:
+    ///
+    /// ```rust
+    /// # extern crate regex; use regex::bytes::Regex;
+    /// # fn main() {
+    /// let text = b"I categorically deny having triskaidekaphobia.";
+    /// let mat = Regex::new(r"\b\w{13}\b").unwrap().find(text).unwrap();
+    /// assert_eq!((mat.start(), mat.end()), (2, 15));
+    /// # }
+    /// ```
+    pub fn find<'t>(&self, text: &'t [u8]) -> Option<Match<'t>> {
+        self.find_at(text, 0)
+    }
+
+    /// Returns an iterator for each successive non-overlapping match in
+    /// `text`, returning the start and end byte indices with respect to
+    /// `text`.
+    ///
+    /// # Example
+    ///
+    /// Find the start and end location of every word with exactly 13 ASCII
+    /// word bytes:
+    ///
+    /// ```rust
+    /// # extern crate regex; use regex::bytes::Regex;
+    /// # fn main() {
+    /// let text = b"Retroactively relinquishing remunerations is reprehensible.";
+    /// for mat in Regex::new(r"\b\w{13}\b").unwrap().find_iter(text) {
+    ///     println!("{:?}", mat);
+    /// }
+    /// # }
+    /// ```
+    pub fn find_iter<'r, 't>(&'r self, text: &'t [u8]) -> Matches<'r, 't> {
+        Matches(self.0.searcher().find_iter(text))
+    }
+
+    /// Returns the capture groups corresponding to the leftmost-first
+    /// match in `text`. Capture group `0` always corresponds to the entire
+    /// match. If no match is found, then `None` is returned.
+    ///
+    /// You should only use `captures` if you need access to the location of
+    /// capturing group matches. Otherwise, `find` is faster for discovering
+    /// the location of the overall match.
+    ///
+    /// # Examples
+    ///
+    /// Say you have some text with movie names and their release years,
+    /// like "'Citizen Kane' (1941)". It'd be nice if we could search for text
+    /// looking like that, while also extracting the movie name and its release
+    /// year separately.
+    ///
+    /// ```rust
+    /// # extern crate regex; use regex::bytes::Regex;
+    /// # fn main() {
+    /// let re = Regex::new(r"'([^']+)'\s+\((\d{4})\)").unwrap();
+    /// let text = b"Not my favorite movie: 'Citizen Kane' (1941).";
+    /// let caps = re.captures(text).unwrap();
+    /// assert_eq!(caps.get(1).unwrap().as_bytes(), &b"Citizen Kane"[..]);
+    /// assert_eq!(caps.get(2).unwrap().as_bytes(), &b"1941"[..]);
+    /// assert_eq!(caps.get(0).unwrap().as_bytes(), &b"'Citizen Kane' (1941)"[..]);
+    /// // You can also access the groups by index using the Index notation.
+    /// // Note that this will panic on an invalid index.
+    /// assert_eq!(&caps[1], b"Citizen Kane");
+    /// assert_eq!(&caps[2], b"1941");
+    /// assert_eq!(&caps[0], b"'Citizen Kane' (1941)");
+    /// # }
+    /// ```
+    ///
+    /// Note that the full match is at capture group `0`. Each subsequent
+    /// capture group is indexed by the order of its opening `(`.
+    ///
+    /// We can make this example a bit clearer by using *named* capture groups:
+    ///
+    /// ```rust
+    /// # extern crate regex; use regex::bytes::Regex;
+    /// # fn main() {
+    /// let re = Regex::new(r"'(?P<title>[^']+)'\s+\((?P<year>\d{4})\)")
+    ///                .unwrap();
+    /// let text = b"Not my favorite movie: 'Citizen Kane' (1941).";
+    /// let caps = re.captures(text).unwrap();
+    /// assert_eq!(caps.name("title").unwrap().as_bytes(), b"Citizen Kane");
+    /// assert_eq!(caps.name("year").unwrap().as_bytes(), b"1941");
+    /// assert_eq!(caps.get(0).unwrap().as_bytes(), &b"'Citizen Kane' (1941)"[..]);
+    /// // You can also access the groups by name using the Index notation.
+    /// // Note that this will panic on an invalid group name.
+    /// assert_eq!(&caps["title"], b"Citizen Kane");
+    /// assert_eq!(&caps["year"], b"1941");
+    /// assert_eq!(&caps[0], b"'Citizen Kane' (1941)");
+    ///
+    /// # }
+    /// ```
+    ///
+    /// Here we name the capture groups, which we can access with the `name`
+    /// method or the `Index` notation with a `&str`. Note that the named
+    /// capture groups are still accessible with `get` or the `Index` notation
+    /// with a `usize`.
+    ///
+    /// The `0`th capture group is always unnamed, so it must always be
+    /// accessed with `get(0)` or `[0]`.
+    pub fn captures<'t>(&self, text: &'t [u8]) -> Option<Captures<'t>> {
+        let mut locs = self.capture_locations();
+        self.captures_read_at(&mut locs, text, 0).map(move |_| Captures {
+            text: text,
+            locs: locs.0,
+            named_groups: self.0.capture_name_idx().clone(),
+        })
+    }
+
+    /// Returns an iterator over all the non-overlapping capture groups matched
+    /// in `text`. This is operationally the same as `find_iter`, except it
+    /// yields information about capturing group matches.
+    ///
+    /// # Example
+    ///
+    /// We can use this to find all movie titles and their release years in
+    /// some text, where the movie is formatted like "'Title' (xxxx)":
+    ///
+    /// ```rust
+    /// # extern crate regex; use std::str; use regex::bytes::Regex;
+    /// # fn main() {
+    /// let re = Regex::new(r"'(?P<title>[^']+)'\s+\((?P<year>\d{4})\)")
+    ///                .unwrap();
+    /// let text = b"'Citizen Kane' (1941), 'The Wizard of Oz' (1939), 'M' (1931).";
+    /// for caps in re.captures_iter(text) {
+    ///     let title = str::from_utf8(&caps["title"]).unwrap();
+    ///     let year = str::from_utf8(&caps["year"]).unwrap();
+    ///     println!("Movie: {:?}, Released: {:?}", title, year);
+    /// }
+    /// // Output:
+    /// // Movie: Citizen Kane, Released: 1941
+    /// // Movie: The Wizard of Oz, Released: 1939
+    /// // Movie: M, Released: 1931
+    /// # }
+    /// ```
+    pub fn captures_iter<'r, 't>(
+        &'r self,
+        text: &'t [u8],
+    ) -> CaptureMatches<'r, 't> {
+        CaptureMatches(self.0.searcher().captures_iter(text))
+    }
+
+    /// Returns an iterator of substrings of `text` delimited by a match of the
+    /// regular expression. Namely, each element of the iterator corresponds to
+    /// text that *isn't* matched by the regular expression.
+    ///
+    /// This method will *not* copy the text given.
+    ///
+    /// # Example
+    ///
+    /// To split a string delimited by arbitrary amounts of spaces or tabs:
+    ///
+    /// ```rust
+    /// # extern crate regex; use regex::bytes::Regex;
+    /// # fn main() {
+    /// let re = Regex::new(r"[ \t]+").unwrap();
+    /// let fields: Vec<&[u8]> = re.split(b"a b \t  c\td    e").collect();
+    /// assert_eq!(fields, vec![
+    ///     &b"a"[..], &b"b"[..], &b"c"[..], &b"d"[..], &b"e"[..],
+    /// ]);
+    /// # }
+    /// ```
+    pub fn split<'r, 't>(&'r self, text: &'t [u8]) -> Split<'r, 't> {
+        Split { finder: self.find_iter(text), last: 0 }
+    }
+
+    /// Returns an iterator of at most `limit` substrings of `text` delimited
+    /// by a match of the regular expression. (A `limit` of `0` will return no
+    /// substrings.) Namely, each element of the iterator corresponds to text
+    /// that *isn't* matched by the regular expression. The remainder of the
+    /// string that is not split will be the last element in the iterator.
+    ///
+    /// This method will *not* copy the text given.
+    ///
+    /// # Example
+    ///
+    /// Get the first two words in some text:
+    ///
+    /// ```rust
+    /// # extern crate regex; use regex::bytes::Regex;
+    /// # fn main() {
+    /// let re = Regex::new(r"\W+").unwrap();
+    /// let fields: Vec<&[u8]> = re.splitn(b"Hey! How are you?", 3).collect();
+    /// assert_eq!(fields, vec![&b"Hey"[..], &b"How"[..], &b"are you?"[..]]);
+    /// # }
+    /// ```
+    pub fn splitn<'r, 't>(
+        &'r self,
+        text: &'t [u8],
+        limit: usize,
+    ) -> SplitN<'r, 't> {
+        SplitN { splits: self.split(text), n: limit }
+    }
+
+    /// Replaces the leftmost-first match with the replacement provided. The
+    /// replacement can be a regular byte string (where `$N` and `$name` are
+    /// expanded to match capture groups) or a function that takes the matches'
+    /// `Captures` and returns the replaced byte string.
+    ///
+    /// If no match is found, then a copy of the byte string is returned
+    /// unchanged.
+    ///
+    /// # Replacement string syntax
+    ///
+    /// All instances of `$name` in the replacement text is replaced with the
+    /// corresponding capture group `name`.
+    ///
+    /// `name` may be an integer corresponding to the index of the
+    /// capture group (counted by order of opening parenthesis where `0` is the
+    /// entire match) or it can be a name (consisting of letters, digits or
+    /// underscores) corresponding to a named capture group.
+    ///
+    /// If `name` isn't a valid capture group (whether the name doesn't exist
+    /// or isn't a valid index), then it is replaced with the empty string.
+    ///
+    /// The longest possible name is used. e.g., `$1a` looks up the capture
+    /// group named `1a` and not the capture group at index `1`. To exert more
+    /// precise control over the name, use braces, e.g., `${1}a`.
+    ///
+    /// To write a literal `$` use `$$`.
+    ///
+    /// # Examples
+    ///
+    /// Note that this function is polymorphic with respect to the replacement.
+    /// In typical usage, this can just be a normal byte string:
+    ///
+    /// ```rust
+    /// # extern crate regex; use regex::bytes::Regex;
+    /// # fn main() {
+    /// let re = Regex::new("[^01]+").unwrap();
+    /// assert_eq!(re.replace(b"1078910", &b""[..]), &b"1010"[..]);
+    /// # }
+    /// ```
+    ///
+    /// But anything satisfying the `Replacer` trait will work. For example, a
+    /// closure of type `|&Captures| -> Vec<u8>` provides direct access to the
+    /// captures corresponding to a match. This allows one to access capturing
+    /// group matches easily:
+    ///
+    /// ```rust
+    /// # extern crate regex; use regex::bytes::Regex;
+    /// # use regex::bytes::Captures; fn main() {
+    /// let re = Regex::new(r"([^,\s]+),\s+(\S+)").unwrap();
+    /// let result = re.replace(b"Springsteen, Bruce", |caps: &Captures| {
+    ///     let mut replacement = caps[2].to_owned();
+    ///     replacement.push(b' ');
+    ///     replacement.extend(&caps[1]);
+    ///     replacement
+    /// });
+    /// assert_eq!(result, &b"Bruce Springsteen"[..]);
+    /// # }
+    /// ```
+    ///
+    /// But this is a bit cumbersome to use all the time. Instead, a simple
+    /// syntax is supported that expands `$name` into the corresponding capture
+    /// group. Here's the last example, but using this expansion technique
+    /// with named capture groups:
+    ///
+    /// ```rust
+    /// # extern crate regex; use regex::bytes::Regex;
+    /// # fn main() {
+    /// let re = Regex::new(r"(?P<last>[^,\s]+),\s+(?P<first>\S+)").unwrap();
+    /// let result = re.replace(b"Springsteen, Bruce", &b"$first $last"[..]);
+    /// assert_eq!(result, &b"Bruce Springsteen"[..]);
+    /// # }
+    /// ```
+    ///
+    /// Note that using `$2` instead of `$first` or `$1` instead of `$last`
+    /// would produce the same result. To write a literal `$` use `$$`.
+    ///
+    /// Sometimes the replacement string requires use of curly braces to
+    /// delineate a capture group replacement and surrounding literal text.
+    /// For example, if we wanted to join two words together with an
+    /// underscore:
+    ///
+    /// ```rust
+    /// # extern crate regex; use regex::bytes::Regex;
+    /// # fn main() {
+    /// let re = Regex::new(r"(?P<first>\w+)\s+(?P<second>\w+)").unwrap();
+    /// let result = re.replace(b"deep fried", &b"${first}_$second"[..]);
+    /// assert_eq!(result, &b"deep_fried"[..]);
+    /// # }
+    /// ```
+    ///
+    /// Without the curly braces, the capture group name `first_` would be
+    /// used, and since it doesn't exist, it would be replaced with the empty
+    /// string.
+    ///
+    /// Finally, sometimes you just want to replace a literal string with no
+    /// regard for capturing group expansion. This can be done by wrapping a
+    /// byte string with `NoExpand`:
+    ///
+    /// ```rust
+    /// # extern crate regex; use regex::bytes::Regex;
+    /// # fn main() {
+    /// use regex::bytes::NoExpand;
+    ///
+    /// let re = Regex::new(r"(?P<last>[^,\s]+),\s+(\S+)").unwrap();
+    /// let result = re.replace(b"Springsteen, Bruce", NoExpand(b"$2 $last"));
+    /// assert_eq!(result, &b"$2 $last"[..]);
+    /// # }
+    /// ```
+    pub fn replace<'t, R: Replacer>(
+        &self,
+        text: &'t [u8],
+        rep: R,
+    ) -> Cow<'t, [u8]> {
+        self.replacen(text, 1, rep)
+    }
+
+    /// Replaces all non-overlapping matches in `text` with the replacement
+    /// provided. This is the same as calling `replacen` with `limit` set to
+    /// `0`.
+    ///
+    /// See the documentation for `replace` for details on how to access
+    /// capturing group matches in the replacement text.
+    pub fn replace_all<'t, R: Replacer>(
+        &self,
+        text: &'t [u8],
+        rep: R,
+    ) -> Cow<'t, [u8]> {
+        self.replacen(text, 0, rep)
+    }
+
+    /// Replaces at most `limit` non-overlapping matches in `text` with the
+    /// replacement provided. If `limit` is 0, then all non-overlapping matches
+    /// are replaced.
+    ///
+    /// See the documentation for `replace` for details on how to access
+    /// capturing group matches in the replacement text.
+    pub fn replacen<'t, R: Replacer>(
+        &self,
+        text: &'t [u8],
+        limit: usize,
+        mut rep: R,
+    ) -> Cow<'t, [u8]> {
+        if let Some(rep) = rep.no_expansion() {
+            let mut it = self.find_iter(text).enumerate().peekable();
+            if it.peek().is_none() {
+                return Cow::Borrowed(text);
+            }
+            let mut new = Vec::with_capacity(text.len());
+            let mut last_match = 0;
+            for (i, m) in it {
+                if limit > 0 && i >= limit {
+                    break;
+                }
+                new.extend_from_slice(&text[last_match..m.start()]);
+                new.extend_from_slice(&rep);
+                last_match = m.end();
+            }
+            new.extend_from_slice(&text[last_match..]);
+            return Cow::Owned(new);
+        }
+
+        // The slower path, which we use if the replacement needs access to
+        // capture groups.
+        let mut it = self.captures_iter(text).enumerate().peekable();
+        if it.peek().is_none() {
+            return Cow::Borrowed(text);
+        }
+        let mut new = Vec::with_capacity(text.len());
+        let mut last_match = 0;
+        for (i, cap) in it {
+            if limit > 0 && i >= limit {
+                break;
+            }
+            // unwrap on 0 is OK because captures only reports matches
+            let m = cap.get(0).unwrap();
+            new.extend_from_slice(&text[last_match..m.start()]);
+            rep.replace_append(&cap, &mut new);
+            last_match = m.end();
+        }
+        new.extend_from_slice(&text[last_match..]);
+        Cow::Owned(new)
+    }
+}
+
+/// Advanced or "lower level" search methods.
+impl Regex {
+    /// Returns the end location of a match in the text given.
+    ///
+    /// This method may have the same performance characteristics as
+    /// `is_match`, except it provides an end location for a match. In
+    /// particular, the location returned *may be shorter* than the proper end
+    /// of the leftmost-first match.
+    ///
+    /// # Example
+    ///
+    /// Typically, `a+` would match the entire first sequence of `a` in some
+    /// text, but `shortest_match` can give up as soon as it sees the first
+    /// `a`.
+    ///
+    /// ```rust
+    /// # extern crate regex; use regex::bytes::Regex;
+    /// # fn main() {
+    /// let text = b"aaaaa";
+    /// let pos = Regex::new(r"a+").unwrap().shortest_match(text);
+    /// assert_eq!(pos, Some(1));
+    /// # }
+    /// ```
+    pub fn shortest_match(&self, text: &[u8]) -> Option<usize> {
+        self.shortest_match_at(text, 0)
+    }
+
+    /// Returns the same as shortest_match, but starts the search at the given
+    /// offset.
+    ///
+    /// The significance of the starting point is that it takes the surrounding
+    /// context into consideration. For example, the `\A` anchor can only
+    /// match when `start == 0`.
+    pub fn shortest_match_at(
+        &self,
+        text: &[u8],
+        start: usize,
+    ) -> Option<usize> {
+        self.0.searcher().shortest_match_at(text, start)
+    }
+
+    /// Returns the same as is_match, but starts the search at the given
+    /// offset.
+    ///
+    /// The significance of the starting point is that it takes the surrounding
+    /// context into consideration. For example, the `\A` anchor can only
+    /// match when `start == 0`.
+    pub fn is_match_at(&self, text: &[u8], start: usize) -> bool {
+        self.shortest_match_at(text, start).is_some()
+    }
+
+    /// Returns the same as find, but starts the search at the given
+    /// offset.
+    ///
+    /// The significance of the starting point is that it takes the surrounding
+    /// context into consideration. For example, the `\A` anchor can only
+    /// match when `start == 0`.
+    pub fn find_at<'t>(
+        &self,
+        text: &'t [u8],
+        start: usize,
+    ) -> Option<Match<'t>> {
+        self.0
+            .searcher()
+            .find_at(text, start)
+            .map(|(s, e)| Match::new(text, s, e))
+    }
+
+    /// This is like `captures`, but uses
+    /// [`CaptureLocations`](struct.CaptureLocations.html)
+    /// instead of
+    /// [`Captures`](struct.Captures.html) in order to amortize allocations.
+    ///
+    /// To create a `CaptureLocations` value, use the
+    /// `Regex::capture_locations` method.
+    ///
+    /// This returns the overall match if this was successful, which is always
+    /// equivalence to the `0`th capture group.
+    pub fn captures_read<'t>(
+        &self,
+        locs: &mut CaptureLocations,
+        text: &'t [u8],
+    ) -> Option<Match<'t>> {
+        self.captures_read_at(locs, text, 0)
+    }
+
+    /// Returns the same as `captures_read`, but starts the search at the given
+    /// offset and populates the capture locations given.
+    ///
+    /// The significance of the starting point is that it takes the surrounding
+    /// context into consideration. For example, the `\A` anchor can only
+    /// match when `start == 0`.
+    pub fn captures_read_at<'t>(
+        &self,
+        locs: &mut CaptureLocations,
+        text: &'t [u8],
+        start: usize,
+    ) -> Option<Match<'t>> {
+        self.0
+            .searcher()
+            .captures_read_at(&mut locs.0, text, start)
+            .map(|(s, e)| Match::new(text, s, e))
+    }
+
+    /// An undocumented alias for `captures_read_at`.
+    ///
+    /// The `regex-capi` crate previously used this routine, so to avoid
+    /// breaking that crate, we continue to provide the name as an undocumented
+    /// alias.
+    #[doc(hidden)]
+    pub fn read_captures_at<'t>(
+        &self,
+        locs: &mut CaptureLocations,
+        text: &'t [u8],
+        start: usize,
+    ) -> Option<Match<'t>> {
+        self.captures_read_at(locs, text, start)
+    }
+}
+
+/// Auxiliary methods.
+impl Regex {
+    /// Returns the original string of this regex.
+    pub fn as_str(&self) -> &str {
+        &self.0.regex_strings()[0]
+    }
+
+    /// Returns an iterator over the capture names.
+    pub fn capture_names(&self) -> CaptureNames {
+        CaptureNames(self.0.capture_names().iter())
+    }
+
+    /// Returns the number of captures.
+    pub fn captures_len(&self) -> usize {
+        self.0.capture_names().len()
+    }
+
+    /// Returns an empty set of capture locations that can be reused in
+    /// multiple calls to `captures_read` or `captures_read_at`.
+    pub fn capture_locations(&self) -> CaptureLocations {
+        CaptureLocations(self.0.searcher().locations())
+    }
+
+    /// An alias for `capture_locations` to preserve backward compatibility.
+    ///
+    /// The `regex-capi` crate uses this method, so to avoid breaking that
+    /// crate, we continue to export it as an undocumented API.
+    #[doc(hidden)]
+    pub fn locations(&self) -> CaptureLocations {
+        CaptureLocations(self.0.searcher().locations())
+    }
+}
+
+/// An iterator over all non-overlapping matches for a particular string.
+///
+/// The iterator yields a tuple of integers corresponding to the start and end
+/// of the match. The indices are byte offsets. The iterator stops when no more
+/// matches can be found.
+///
+/// `'r` is the lifetime of the compiled regular expression and `'t` is the
+/// lifetime of the matched byte string.
+pub struct Matches<'r, 't>(re_trait::Matches<'t, ExecNoSync<'r>>);
+
+impl<'r, 't> Iterator for Matches<'r, 't> {
+    type Item = Match<'t>;
+
+    fn next(&mut self) -> Option<Match<'t>> {
+        let text = self.0.text();
+        self.0.next().map(|(s, e)| Match::new(text, s, e))
+    }
+}
+
+/// An iterator that yields all non-overlapping capture groups matching a
+/// particular regular expression.
+///
+/// The iterator stops when no more matches can be found.
+///
+/// `'r` is the lifetime of the compiled regular expression and `'t` is the
+/// lifetime of the matched byte string.
+pub struct CaptureMatches<'r, 't>(
+    re_trait::CaptureMatches<'t, ExecNoSync<'r>>,
+);
+
+impl<'r, 't> Iterator for CaptureMatches<'r, 't> {
+    type Item = Captures<'t>;
+
+    fn next(&mut self) -> Option<Captures<'t>> {
+        self.0.next().map(|locs| Captures {
+            text: self.0.text(),
+            locs: locs,
+            named_groups: self.0.regex().capture_name_idx().clone(),
+        })
+    }
+}
+
+/// Yields all substrings delimited by a regular expression match.
+///
+/// `'r` is the lifetime of the compiled regular expression and `'t` is the
+/// lifetime of the byte string being split.
+pub struct Split<'r, 't> {
+    finder: Matches<'r, 't>,
+    last: usize,
+}
+
+impl<'r, 't> Iterator for Split<'r, 't> {
+    type Item = &'t [u8];
+
+    fn next(&mut self) -> Option<&'t [u8]> {
+        let text = self.finder.0.text();
+        match self.finder.next() {
+            None => {
+                if self.last > text.len() {
+                    None
+                } else {
+                    let s = &text[self.last..];
+                    self.last = text.len() + 1; // Next call will return None
+                    Some(s)
+                }
+            }
+            Some(m) => {
+                let matched = &text[self.last..m.start()];
+                self.last = m.end();
+                Some(matched)
+            }
+        }
+    }
+}
+
+/// Yields at most `N` substrings delimited by a regular expression match.
+///
+/// The last substring will be whatever remains after splitting.
+///
+/// `'r` is the lifetime of the compiled regular expression and `'t` is the
+/// lifetime of the byte string being split.
+pub struct SplitN<'r, 't> {
+    splits: Split<'r, 't>,
+    n: usize,
+}
+
+impl<'r, 't> Iterator for SplitN<'r, 't> {
+    type Item = &'t [u8];
+
+    fn next(&mut self) -> Option<&'t [u8]> {
+        if self.n == 0 {
+            return None;
+        }
+
+        self.n -= 1;
+        if self.n > 0 {
+            return self.splits.next();
+        }
+
+        let text = self.splits.finder.0.text();
+        if self.splits.last > text.len() {
+            // We've already returned all substrings.
+            None
+        } else {
+            // self.n == 0, so future calls will return None immediately
+            Some(&text[self.splits.last..])
+        }
+    }
+}
+
+/// An iterator over the names of all possible captures.
+///
+/// `None` indicates an unnamed capture; the first element (capture 0, the
+/// whole matched region) is always unnamed.
+///
+/// `'r` is the lifetime of the compiled regular expression.
+pub struct CaptureNames<'r>(::std::slice::Iter<'r, Option<String>>);
+
+impl<'r> Iterator for CaptureNames<'r> {
+    type Item = Option<&'r str>;
+
+    fn next(&mut self) -> Option<Option<&'r str>> {
+        self.0
+            .next()
+            .as_ref()
+            .map(|slot| slot.as_ref().map(|name| name.as_ref()))
+    }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        self.0.size_hint()
+    }
+}
+
+/// CaptureLocations is a low level representation of the raw offsets of each
+/// submatch.
+///
+/// You can think of this as a lower level
+/// [`Captures`](struct.Captures.html), where this type does not support
+/// named capturing groups directly and it does not borrow the text that these
+/// offsets were matched on.
+///
+/// Primarily, this type is useful when using the lower level `Regex` APIs
+/// such as `read_captures`, which permits amortizing the allocation in which
+/// capture match locations are stored.
+///
+/// In order to build a value of this type, you'll need to call the
+/// `capture_locations` method on the `Regex` being used to execute the search.
+/// The value returned can then be reused in subsequent searches.
+#[derive(Clone, Debug)]
+pub struct CaptureLocations(re_trait::Locations);
+
+/// A type alias for `CaptureLocations` for backwards compatibility.
+///
+/// Previously, we exported `CaptureLocations` as `Locations` in an
+/// undocumented API. To prevent breaking that code (e.g., in `regex-capi`),
+/// we continue re-exporting the same undocumented API.
+#[doc(hidden)]
+pub type Locations = CaptureLocations;
+
+impl CaptureLocations {
+    /// Returns the start and end positions of the Nth capture group. Returns
+    /// `None` if `i` is not a valid capture group or if the capture group did
+    /// not match anything. The positions returned are *always* byte indices
+    /// with respect to the original string matched.
+    #[inline]
+    pub fn get(&self, i: usize) -> Option<(usize, usize)> {
+        self.0.pos(i)
+    }
+
+    /// Returns the total number of capturing groups.
+    ///
+    /// This is always at least `1` since every regex has at least `1`
+    /// capturing group that corresponds to the entire match.
+    #[inline]
+    pub fn len(&self) -> usize {
+        self.0.len()
+    }
+
+    /// An alias for the `get` method for backwards compatibility.
+    ///
+    /// Previously, we exported `get` as `pos` in an undocumented API. To
+    /// prevent breaking that code (e.g., in `regex-capi`), we continue
+    /// re-exporting the same undocumented API.
+    #[doc(hidden)]
+    #[inline]
+    pub fn pos(&self, i: usize) -> Option<(usize, usize)> {
+        self.get(i)
+    }
+}
+
+/// Captures represents a group of captured byte strings for a single match.
+///
+/// The 0th capture always corresponds to the entire match. Each subsequent
+/// index corresponds to the next capture group in the regex. If a capture
+/// group is named, then the matched byte string is *also* available via the
+/// `name` method. (Note that the 0th capture is always unnamed and so must be
+/// accessed with the `get` method.)
+///
+/// Positions returned from a capture group are always byte indices.
+///
+/// `'t` is the lifetime of the matched text.
+pub struct Captures<'t> {
+    text: &'t [u8],
+    locs: re_trait::Locations,
+    named_groups: Arc<HashMap<String, usize>>,
+}
+
+impl<'t> Captures<'t> {
+    /// Returns the match associated with the capture group at index `i`. If
+    /// `i` does not correspond to a capture group, or if the capture group
+    /// did not participate in the match, then `None` is returned.
+    ///
+    /// # Examples
+    ///
+    /// Get the text of the match with a default of an empty string if this
+    /// group didn't participate in the match:
+    ///
+    /// ```rust
+    /// # use regex::bytes::Regex;
+    /// let re = Regex::new(r"[a-z]+(?:([0-9]+)|([A-Z]+))").unwrap();
+    /// let caps = re.captures(b"abc123").unwrap();
+    ///
+    /// let text1 = caps.get(1).map_or(&b""[..], |m| m.as_bytes());
+    /// let text2 = caps.get(2).map_or(&b""[..], |m| m.as_bytes());
+    /// assert_eq!(text1, &b"123"[..]);
+    /// assert_eq!(text2, &b""[..]);
+    /// ```
+    pub fn get(&self, i: usize) -> Option<Match<'t>> {
+        self.locs.pos(i).map(|(s, e)| Match::new(self.text, s, e))
+    }
+
+    /// Returns the match for the capture group named `name`. If `name` isn't a
+    /// valid capture group or didn't match anything, then `None` is returned.
+    pub fn name(&self, name: &str) -> Option<Match<'t>> {
+        self.named_groups.get(name).and_then(|&i| self.get(i))
+    }
+
+    /// An iterator that yields all capturing matches in the order in which
+    /// they appear in the regex. If a particular capture group didn't
+    /// participate in the match, then `None` is yielded for that capture.
+    ///
+    /// The first match always corresponds to the overall match of the regex.
+    pub fn iter<'c>(&'c self) -> SubCaptureMatches<'c, 't> {
+        SubCaptureMatches { caps: self, it: self.locs.iter() }
+    }
+
+    /// Expands all instances of `$name` in `replacement` to the corresponding
+    /// capture group `name`, and writes them to the `dst` buffer given.
+    ///
+    /// `name` may be an integer corresponding to the index of the
+    /// capture group (counted by order of opening parenthesis where `0` is the
+    /// entire match) or it can be a name (consisting of letters, digits or
+    /// underscores) corresponding to a named capture group.
+    ///
+    /// If `name` isn't a valid capture group (whether the name doesn't exist
+    /// or isn't a valid index), then it is replaced with the empty string.
+    ///
+    /// The longest possible name is used. e.g., `$1a` looks up the capture
+    /// group named `1a` and not the capture group at index `1`. To exert more
+    /// precise control over the name, use braces, e.g., `${1}a`.
+    ///
+    /// To write a literal `$` use `$$`.
+    pub fn expand(&self, replacement: &[u8], dst: &mut Vec<u8>) {
+        expand_bytes(self, replacement, dst)
+    }
+
+    /// Returns the number of captured groups.
+    ///
+    /// This is always at least `1`, since every regex has at least one capture
+    /// group that corresponds to the full match.
+    #[inline]
+    pub fn len(&self) -> usize {
+        self.locs.len()
+    }
+}
+
+impl<'t> fmt::Debug for Captures<'t> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_tuple("Captures").field(&CapturesDebug(self)).finish()
+    }
+}
+
+struct CapturesDebug<'c, 't: 'c>(&'c Captures<'t>);
+
+impl<'c, 't> fmt::Debug for CapturesDebug<'c, 't> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        fn escape_bytes(bytes: &[u8]) -> String {
+            let mut s = String::new();
+            for &b in bytes {
+                s.push_str(&escape_byte(b));
+            }
+            s
+        }
+
+        fn escape_byte(byte: u8) -> String {
+            use std::ascii::escape_default;
+
+            let escaped: Vec<u8> = escape_default(byte).collect();
+            String::from_utf8_lossy(&escaped).into_owned()
+        }
+
+        // We'd like to show something nice here, even if it means an
+        // allocation to build a reverse index.
+        let slot_to_name: HashMap<&usize, &String> =
+            self.0.named_groups.iter().map(|(a, b)| (b, a)).collect();
+        let mut map = f.debug_map();
+        for (slot, m) in self.0.locs.iter().enumerate() {
+            let m = m.map(|(s, e)| escape_bytes(&self.0.text[s..e]));
+            if let Some(name) = slot_to_name.get(&slot) {
+                map.entry(&name, &m);
+            } else {
+                map.entry(&slot, &m);
+            }
+        }
+        map.finish()
+    }
+}
+
+/// Get a group by index.
+///
+/// `'t` is the lifetime of the matched text.
+///
+/// The text can't outlive the `Captures` object if this method is
+/// used, because of how `Index` is defined (normally `a[i]` is part
+/// of `a` and can't outlive it); to do that, use `get()` instead.
+///
+/// # Panics
+///
+/// If there is no group at the given index.
+impl<'t> Index<usize> for Captures<'t> {
+    type Output = [u8];
+
+    fn index(&self, i: usize) -> &[u8] {
+        self.get(i)
+            .map(|m| m.as_bytes())
+            .unwrap_or_else(|| panic!("no group at index '{}'", i))
+    }
+}
+
+/// Get a group by name.
+///
+/// `'t` is the lifetime of the matched text and `'i` is the lifetime
+/// of the group name (the index).
+///
+/// The text can't outlive the `Captures` object if this method is
+/// used, because of how `Index` is defined (normally `a[i]` is part
+/// of `a` and can't outlive it); to do that, use `name` instead.
+///
+/// # Panics
+///
+/// If there is no group named by the given value.
+impl<'t, 'i> Index<&'i str> for Captures<'t> {
+    type Output = [u8];
+
+    fn index<'a>(&'a self, name: &'i str) -> &'a [u8] {
+        self.name(name)
+            .map(|m| m.as_bytes())
+            .unwrap_or_else(|| panic!("no group named '{}'", name))
+    }
+}
+
+/// An iterator that yields all capturing matches in the order in which they
+/// appear in the regex.
+///
+/// If a particular capture group didn't participate in the match, then `None`
+/// is yielded for that capture. The first match always corresponds to the
+/// overall match of the regex.
+///
+/// The lifetime `'c` corresponds to the lifetime of the `Captures` value, and
+/// the lifetime `'t` corresponds to the originally matched text.
+pub struct SubCaptureMatches<'c, 't: 'c> {
+    caps: &'c Captures<'t>,
+    it: SubCapturesPosIter<'c>,
+}
+
+impl<'c, 't> Iterator for SubCaptureMatches<'c, 't> {
+    type Item = Option<Match<'t>>;
+
+    fn next(&mut self) -> Option<Option<Match<'t>>> {
+        self.it
+            .next()
+            .map(|cap| cap.map(|(s, e)| Match::new(self.caps.text, s, e)))
+    }
+}
+
+/// Replacer describes types that can be used to replace matches in a byte
+/// string.
+///
+/// In general, users of this crate shouldn't need to implement this trait,
+/// since implementations are already provided for `&[u8]` and
+/// `FnMut(&Captures) -> Vec<u8>` (or any `FnMut(&Captures) -> T`
+/// where `T: AsRef<[u8]>`), which covers most use cases.
+pub trait Replacer {
+    /// Appends text to `dst` to replace the current match.
+    ///
+    /// The current match is represented by `caps`, which is guaranteed to
+    /// have a match at capture group `0`.
+    ///
+    /// For example, a no-op replacement would be
+    /// `dst.extend(&caps[0])`.
+    fn replace_append(&mut self, caps: &Captures, dst: &mut Vec<u8>);
+
+    /// Return a fixed unchanging replacement byte string.
+    ///
+    /// When doing replacements, if access to `Captures` is not needed (e.g.,
+    /// the replacement byte string does not need `$` expansion), then it can
+    /// be beneficial to avoid finding sub-captures.
+    ///
+    /// In general, this is called once for every call to `replacen`.
+    fn no_expansion<'r>(&'r mut self) -> Option<Cow<'r, [u8]>> {
+        None
+    }
+
+    /// Return a `Replacer` that borrows and wraps this `Replacer`.
+    ///
+    /// This is useful when you want to take a generic `Replacer` (which might
+    /// not be cloneable) and use it without consuming it, so it can be used
+    /// more than once.
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// use regex::bytes::{Regex, Replacer};
+    ///
+    /// fn replace_all_twice<R: Replacer>(
+    ///     re: Regex,
+    ///     src: &[u8],
+    ///     mut rep: R,
+    /// ) -> Vec<u8> {
+    ///     let dst = re.replace_all(src, rep.by_ref());
+    ///     let dst = re.replace_all(&dst, rep.by_ref());
+    ///     dst.into_owned()
+    /// }
+    /// ```
+    fn by_ref<'r>(&'r mut self) -> ReplacerRef<'r, Self> {
+        ReplacerRef(self)
+    }
+}
+
+/// By-reference adaptor for a `Replacer`
+///
+/// Returned by [`Replacer::by_ref`](trait.Replacer.html#method.by_ref).
+#[derive(Debug)]
+pub struct ReplacerRef<'a, R: ?Sized + 'a>(&'a mut R);
+
+impl<'a, R: Replacer + ?Sized + 'a> Replacer for ReplacerRef<'a, R> {
+    fn replace_append(&mut self, caps: &Captures, dst: &mut Vec<u8>) {
+        self.0.replace_append(caps, dst)
+    }
+    fn no_expansion<'r>(&'r mut self) -> Option<Cow<'r, [u8]>> {
+        self.0.no_expansion()
+    }
+}
+
+impl<'a> Replacer for &'a [u8] {
+    fn replace_append(&mut self, caps: &Captures, dst: &mut Vec<u8>) {
+        caps.expand(*self, dst);
+    }
+
+    fn no_expansion(&mut self) -> Option<Cow<[u8]>> {
+        match find_byte(b'$', *self) {
+            Some(_) => None,
+            None => Some(Cow::Borrowed(*self)),
+        }
+    }
+}
+
+impl<F, T> Replacer for F
+where
+    F: FnMut(&Captures) -> T,
+    T: AsRef<[u8]>,
+{
+    fn replace_append(&mut self, caps: &Captures, dst: &mut Vec<u8>) {
+        dst.extend_from_slice((*self)(caps).as_ref());
+    }
+}
+
+/// `NoExpand` indicates literal byte string replacement.
+///
+/// It can be used with `replace` and `replace_all` to do a literal byte string
+/// replacement without expanding `$name` to their corresponding capture
+/// groups. This can be both convenient (to avoid escaping `$`, for example)
+/// and performant (since capture groups don't need to be found).
+///
+/// `'t` is the lifetime of the literal text.
+pub struct NoExpand<'t>(pub &'t [u8]);
+
+impl<'t> Replacer for NoExpand<'t> {
+    fn replace_append(&mut self, _: &Captures, dst: &mut Vec<u8>) {
+        dst.extend_from_slice(self.0);
+    }
+
+    fn no_expansion(&mut self) -> Option<Cow<[u8]>> {
+        Some(Cow::Borrowed(self.0))
+    }
+}