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use alloc::{borrow::Cow, string::String, sync::Arc};
use regex_automata::{meta, util::captures, Input, PatternID};
use crate::{error::Error, RegexBuilder};
/// A compiled regular expression for searching Unicode haystacks.
///
/// A `Regex` can be used to search haystacks, split haystacks into substrings
/// or replace substrings in a haystack with a different substring. All
/// searching is done with an implicit `(?s:.)*?` at the beginning and end of
/// an pattern. To force an expression to match the whole string (or a prefix
/// or a suffix), you must use an anchor like `^` or `$` (or `\A` and `\z`).
///
/// While this crate will handle Unicode strings (whether in the regular
/// expression or in the haystack), all positions returned are **byte
/// offsets**. Every byte offset is guaranteed to be at a Unicode code point
/// boundary. That is, all offsets returned by the `Regex` API are guaranteed
/// to be ranges that can slice a `&str` without panicking. If you want to
/// relax this requirement, then you must search `&[u8]` haystacks with a
/// [`bytes::Regex`](crate::bytes::Regex).
///
/// The only methods that allocate new strings are the string replacement
/// methods. All other methods (searching and splitting) return borrowed
/// references into the haystack given.
///
/// # Example
///
/// Find the offsets of a US phone number:
///
/// ```
/// use regex::Regex;
///
/// let re = Regex::new("[0-9]{3}-[0-9]{3}-[0-9]{4}").unwrap();
/// let m = re.find("phone: 111-222-3333").unwrap();
/// assert_eq!(7..19, m.range());
/// ```
///
/// # Example: extracting capture groups
///
/// A common way to use regexes is with capture groups. That is, instead of
/// just looking for matches of an entire regex, parentheses are used to create
/// groups that represent part of the match.
///
/// For example, consider a haystack with multiple lines, and each line has
/// three whitespace delimited fields where the second field is expected to be
/// a number and the third field a boolean. To make this convenient, we use
/// the [`Captures::extract`] API to put the strings that match each group
/// into a fixed size array:
///
/// ```
/// use regex::Regex;
///
/// let hay = "
/// rabbit 54 true
/// groundhog 2 true
/// does not match
/// fox 109 false
/// ";
/// let re = Regex::new(r"(?m)^\s*(\S+)\s+([0-9]+)\s+(true|false)\s*$").unwrap();
/// let mut fields: Vec<(&str, i64, bool)> = vec![];
/// for (_, [f1, f2, f3]) in re.captures_iter(hay).map(|caps| caps.extract()) {
/// fields.push((f1, f2.parse()?, f3.parse()?));
/// }
/// assert_eq!(fields, vec![
/// ("rabbit", 54, true),
/// ("groundhog", 2, true),
/// ("fox", 109, false),
/// ]);
///
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
///
/// # Example: searching with the `Pattern` trait
///
/// **Note**: This section requires that this crate is compiled with the
/// `pattern` Cargo feature enabled, which **requires nightly Rust**.
///
/// Since `Regex` implements `Pattern` from the standard library, one can
/// use regexes with methods defined on `&str`. For example, `is_match`,
/// `find`, `find_iter` and `split` can, in some cases, be replaced with
/// `str::contains`, `str::find`, `str::match_indices` and `str::split`.
///
/// Here are some examples:
///
/// ```ignore
/// use regex::Regex;
///
/// let re = Regex::new(r"\d+").unwrap();
/// let hay = "a111b222c";
///
/// assert!(hay.contains(&re));
/// assert_eq!(hay.find(&re), Some(1));
/// assert_eq!(hay.match_indices(&re).collect::<Vec<_>>(), vec![
/// (1, "111"),
/// (5, "222"),
/// ]);
/// assert_eq!(hay.split(&re).collect::<Vec<_>>(), vec!["a", "b", "c"]);
/// ```
#[derive(Clone)]
pub struct Regex {
pub(crate) meta: meta::Regex,
pub(crate) pattern: Arc<str>,
}
impl core::fmt::Display for Regex {
/// Shows the original regular expression.
fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
write!(f, "{}", self.as_str())
}
}
impl core::fmt::Debug for Regex {
/// Shows the original regular expression.
fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
f.debug_tuple("Regex").field(&self.as_str()).finish()
}
}
impl core::str::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)
}
}
impl TryFrom<&str> for Regex {
type Error = Error;
/// Attempts to parse a string into a regular expression
fn try_from(s: &str) -> Result<Regex, Error> {
Regex::new(s)
}
}
impl TryFrom<String> for Regex {
type Error = Error;
/// Attempts to parse a string into a regular expression
fn try_from(s: String) -> 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 substrings in a haystack.
///
/// Note that regex compilation tends to be a somewhat expensive process,
/// and unlike higher level environments, compilation is not automatically
/// cached for you. One should endeavor to compile a regex once and then
/// reuse it. For example, it's a bad idea to compile the same regex
/// repeatedly in a loop.
///
/// # Errors
///
/// If an invalid pattern is given, then an error is returned.
/// An error is also returned if the pattern is valid, but would
/// produce a regex that is bigger than the configured size limit via
/// [`RegexBuilder::size_limit`]. (A reasonable size limit is enabled by
/// default.)
///
/// # Example
///
/// ```
/// use regex::Regex;
///
/// // An Invalid pattern because of an unclosed parenthesis
/// assert!(Regex::new(r"foo(bar").is_err());
/// // An invalid pattern because the regex would be too big
/// // because Unicode tends to inflate things.
/// assert!(Regex::new(r"\w{1000}").is_err());
/// // Disabling Unicode can make the regex much smaller,
/// // potentially by up to or more than an order of magnitude.
/// assert!(Regex::new(r"(?-u:\w){1000}").is_ok());
/// ```
pub fn new(re: &str) -> Result<Regex, Error> {
RegexBuilder::new(re).build()
}
/// Returns true if and only if there is a match for the regex anywhere
/// in the haystack given.
///
/// It is recommended to use this method if all you need to do is test
/// whether a match exists, since the underlying matching engine may be
/// able to do less work.
///
/// # Example
///
/// Test if some haystack contains at least one word with exactly 13
/// Unicode word characters:
///
/// ```
/// use regex::Regex;
///
/// let re = Regex::new(r"\b\w{13}\b").unwrap();
/// let hay = "I categorically deny having triskaidekaphobia.";
/// assert!(re.is_match(hay));
/// ```
#[inline]
pub fn is_match(&self, haystack: &str) -> bool {
self.is_match_at(haystack, 0)
}
/// This routine searches for the first match of this regex in the
/// haystack given, and if found, returns a [`Match`]. The `Match`
/// provides access to both the byte offsets of the match and the actual
/// substring that matched.
///
/// Note that this should only be used if you want to find the entire
/// match. If instead you just want to test the existence of a match,
/// it's potentially faster to use `Regex::is_match(hay)` instead of
/// `Regex::find(hay).is_some()`.
///
/// # Example
///
/// Find the first word with exactly 13 Unicode word characters:
///
/// ```
/// use regex::Regex;
///
/// let re = Regex::new(r"\b\w{13}\b").unwrap();
/// let hay = "I categorically deny having triskaidekaphobia.";
/// let mat = re.find(hay).unwrap();
/// assert_eq!(2..15, mat.range());
/// assert_eq!("categorically", mat.as_str());
/// ```
#[inline]
pub fn find<'h>(&self, haystack: &'h str) -> Option<Match<'h>> {
self.find_at(haystack, 0)
}
/// Returns an iterator that yields successive non-overlapping matches in
/// the given haystack. The iterator yields values of type [`Match`].
///
/// # Time complexity
///
/// Note that since `find_iter` runs potentially many searches on the
/// haystack and since each search has worst case `O(m * n)` time
/// complexity, the overall worst case time complexity for iteration is
/// `O(m * n^2)`.
///
/// # Example
///
/// Find every word with exactly 13 Unicode word characters:
///
/// ```
/// use regex::Regex;
///
/// let re = Regex::new(r"\b\w{13}\b").unwrap();
/// let hay = "Retroactively relinquishing remunerations is reprehensible.";
/// let matches: Vec<_> = re.find_iter(hay).map(|m| m.as_str()).collect();
/// assert_eq!(matches, vec![
/// "Retroactively",
/// "relinquishing",
/// "remunerations",
/// "reprehensible",
/// ]);
/// ```
#[inline]
pub fn find_iter<'r, 'h>(&'r self, haystack: &'h str) -> Matches<'r, 'h> {
Matches { haystack, it: self.meta.find_iter(haystack) }
}
/// This routine searches for the first match of this regex in the haystack
/// given, and if found, returns not only the overall match but also the
/// matches of each capture group in the regex. If no match is found, then
/// `None` is returned.
///
/// Capture group `0` always corresponds to an implicit unnamed group that
/// includes the entire match. If a match is found, this group is always
/// present. Subsequent groups may be named and are numbered, starting
/// at 1, by the order in which the opening parenthesis appears in the
/// pattern. For example, in the pattern `(?<a>.(?<b>.))(?<c>.)`, `a`,
/// `b` and `c` correspond to capture group indices `1`, `2` and `3`,
/// respectively.
///
/// You should only use `captures` if you need access to the capture group
/// matches. Otherwise, [`Regex::find`] is generally faster for discovering
/// just the overall match.
///
/// # Example
///
/// Say you have some haystack with movie names and their release years,
/// like "'Citizen Kane' (1941)". It'd be nice if we could search for
/// substrings looking like that, while also extracting the movie name and
/// its release year separately. The example below shows how to do that.
///
/// ```
/// use regex::Regex;
///
/// let re = Regex::new(r"'([^']+)'\s+\((\d{4})\)").unwrap();
/// let hay = "Not my favorite movie: 'Citizen Kane' (1941).";
/// let caps = re.captures(hay).unwrap();
/// assert_eq!(caps.get(0).unwrap().as_str(), "'Citizen Kane' (1941)");
/// assert_eq!(caps.get(1).unwrap().as_str(), "Citizen Kane");
/// assert_eq!(caps.get(2).unwrap().as_str(), "1941");
/// // You can also access the groups by index using the Index notation.
/// // Note that this will panic on an invalid index. In this case, these
/// // accesses are always correct because the overall regex will only
/// // match when these capture groups match.
/// assert_eq!(&caps[0], "'Citizen Kane' (1941)");
/// assert_eq!(&caps[1], "Citizen Kane");
/// assert_eq!(&caps[2], "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:
///
/// ```
/// use regex::Regex;
///
/// let re = Regex::new(r"'(?<title>[^']+)'\s+\((?<year>\d{4})\)").unwrap();
/// let hay = "Not my favorite movie: 'Citizen Kane' (1941).";
/// let caps = re.captures(hay).unwrap();
/// assert_eq!(caps.get(0).unwrap().as_str(), "'Citizen Kane' (1941)");
/// assert_eq!(caps.name("title").unwrap().as_str(), "Citizen Kane");
/// assert_eq!(caps.name("year").unwrap().as_str(), "1941");
/// // You can also access the groups by name using the Index notation.
/// // Note that this will panic on an invalid group name. In this case,
/// // these accesses are always correct because the overall regex will
/// // only match when these capture groups match.
/// assert_eq!(&caps[0], "'Citizen Kane' (1941)");
/// assert_eq!(&caps["title"], "Citizen Kane");
/// assert_eq!(&caps["year"], "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]`.
///
/// Finally, one other way to to get the matched substrings is with the
/// [`Captures::extract`] API:
///
/// ```
/// use regex::Regex;
///
/// let re = Regex::new(r"'([^']+)'\s+\((\d{4})\)").unwrap();
/// let hay = "Not my favorite movie: 'Citizen Kane' (1941).";
/// let (full, [title, year]) = re.captures(hay).unwrap().extract();
/// assert_eq!(full, "'Citizen Kane' (1941)");
/// assert_eq!(title, "Citizen Kane");
/// assert_eq!(year, "1941");
/// ```
#[inline]
pub fn captures<'h>(&self, haystack: &'h str) -> Option<Captures<'h>> {
self.captures_at(haystack, 0)
}
/// Returns an iterator that yields successive non-overlapping matches in
/// the given haystack. The iterator yields values of type [`Captures`].
///
/// This is the same as [`Regex::find_iter`], but instead of only providing
/// access to the overall match, each value yield includes access to the
/// matches of all capture groups in the regex. Reporting this extra match
/// data is potentially costly, so callers should only use `captures_iter`
/// over `find_iter` when they actually need access to the capture group
/// matches.
///
/// # Time complexity
///
/// Note that since `captures_iter` runs potentially many searches on the
/// haystack and since each search has worst case `O(m * n)` time
/// complexity, the overall worst case time complexity for iteration is
/// `O(m * n^2)`.
///
/// # Example
///
/// We can use this to find all movie titles and their release years in
/// some haystack, where the movie is formatted like "'Title' (xxxx)":
///
/// ```
/// use regex::Regex;
///
/// let re = Regex::new(r"'([^']+)'\s+\(([0-9]{4})\)").unwrap();
/// let hay = "'Citizen Kane' (1941), 'The Wizard of Oz' (1939), 'M' (1931).";
/// let mut movies = vec![];
/// for (_, [title, year]) in re.captures_iter(hay).map(|c| c.extract()) {
/// movies.push((title, year.parse::<i64>()?));
/// }
/// assert_eq!(movies, vec![
/// ("Citizen Kane", 1941),
/// ("The Wizard of Oz", 1939),
/// ("M", 1931),
/// ]);
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
///
/// Or with named groups:
///
/// ```
/// use regex::Regex;
///
/// let re = Regex::new(r"'(?<title>[^']+)'\s+\((?<year>[0-9]{4})\)").unwrap();
/// let hay = "'Citizen Kane' (1941), 'The Wizard of Oz' (1939), 'M' (1931).";
/// let mut it = re.captures_iter(hay);
///
/// let caps = it.next().unwrap();
/// assert_eq!(&caps["title"], "Citizen Kane");
/// assert_eq!(&caps["year"], "1941");
///
/// let caps = it.next().unwrap();
/// assert_eq!(&caps["title"], "The Wizard of Oz");
/// assert_eq!(&caps["year"], "1939");
///
/// let caps = it.next().unwrap();
/// assert_eq!(&caps["title"], "M");
/// assert_eq!(&caps["year"], "1931");
/// ```
#[inline]
pub fn captures_iter<'r, 'h>(
&'r self,
haystack: &'h str,
) -> CaptureMatches<'r, 'h> {
CaptureMatches { haystack, it: self.meta.captures_iter(haystack) }
}
/// Returns an iterator of substrings of the haystack given, delimited by a
/// match of the regex. Namely, each element of the iterator corresponds to
/// a part of the haystack that *isn't* matched by the regular expression.
///
/// # Time complexity
///
/// Since iterators over all matches requires running potentially many
/// searches on the haystack, and since each search has worst case
/// `O(m * n)` time complexity, the overall worst case time complexity for
/// this routine is `O(m * n^2)`.
///
/// # Example
///
/// To split a string delimited by arbitrary amounts of spaces or tabs:
///
/// ```
/// use regex::Regex;
///
/// let re = Regex::new(r"[ \t]+").unwrap();
/// let hay = "a b \t c\td e";
/// let fields: Vec<&str> = re.split(hay).collect();
/// assert_eq!(fields, vec!["a", "b", "c", "d", "e"]);
/// ```
///
/// # Example: more cases
///
/// Basic usage:
///
/// ```
/// use regex::Regex;
///
/// let re = Regex::new(r" ").unwrap();
/// let hay = "Mary had a little lamb";
/// let got: Vec<&str> = re.split(hay).collect();
/// assert_eq!(got, vec!["Mary", "had", "a", "little", "lamb"]);
///
/// let re = Regex::new(r"X").unwrap();
/// let hay = "";
/// let got: Vec<&str> = re.split(hay).collect();
/// assert_eq!(got, vec![""]);
///
/// let re = Regex::new(r"X").unwrap();
/// let hay = "lionXXtigerXleopard";
/// let got: Vec<&str> = re.split(hay).collect();
/// assert_eq!(got, vec!["lion", "", "tiger", "leopard"]);
///
/// let re = Regex::new(r"::").unwrap();
/// let hay = "lion::tiger::leopard";
/// let got: Vec<&str> = re.split(hay).collect();
/// assert_eq!(got, vec!["lion", "tiger", "leopard"]);
/// ```
///
/// If a haystack contains multiple contiguous matches, you will end up
/// with empty spans yielded by the iterator:
///
/// ```
/// use regex::Regex;
///
/// let re = Regex::new(r"X").unwrap();
/// let hay = "XXXXaXXbXc";
/// let got: Vec<&str> = re.split(hay).collect();
/// assert_eq!(got, vec!["", "", "", "", "a", "", "b", "c"]);
///
/// let re = Regex::new(r"/").unwrap();
/// let hay = "(///)";
/// let got: Vec<&str> = re.split(hay).collect();
/// assert_eq!(got, vec!["(", "", "", ")"]);
/// ```
///
/// Separators at the start or end of a haystack are neighbored by empty
/// substring.
///
/// ```
/// use regex::Regex;
///
/// let re = Regex::new(r"0").unwrap();
/// let hay = "010";
/// let got: Vec<&str> = re.split(hay).collect();
/// assert_eq!(got, vec!["", "1", ""]);
/// ```
///
/// When the empty string is used as a regex, it splits at every valid
/// UTF-8 boundary by default (which includes the beginning and end of the
/// haystack):
///
/// ```
/// use regex::Regex;
///
/// let re = Regex::new(r"").unwrap();
/// let hay = "rust";
/// let got: Vec<&str> = re.split(hay).collect();
/// assert_eq!(got, vec!["", "r", "u", "s", "t", ""]);
///
/// // Splitting by an empty string is UTF-8 aware by default!
/// let re = Regex::new(r"").unwrap();
/// let hay = "☃";
/// let got: Vec<&str> = re.split(hay).collect();
/// assert_eq!(got, vec!["", "☃", ""]);
/// ```
///
/// Contiguous separators (commonly shows up with whitespace), can lead to
/// possibly surprising behavior. For example, this code is correct:
///
/// ```
/// use regex::Regex;
///
/// let re = Regex::new(r" ").unwrap();
/// let hay = " a b c";
/// let got: Vec<&str> = re.split(hay).collect();
/// assert_eq!(got, vec!["", "", "", "", "a", "", "b", "c"]);
/// ```
///
/// It does *not* give you `["a", "b", "c"]`. For that behavior, you'd want
/// to match contiguous space characters:
///
/// ```
/// use regex::Regex;
///
/// let re = Regex::new(r" +").unwrap();
/// let hay = " a b c";
/// let got: Vec<&str> = re.split(hay).collect();
/// // N.B. This does still include a leading empty span because ' +'
/// // matches at the beginning of the haystack.
/// assert_eq!(got, vec!["", "a", "b", "c"]);
/// ```
#[inline]
pub fn split<'r, 'h>(&'r self, haystack: &'h str) -> Split<'r, 'h> {
Split { haystack, it: self.meta.split(haystack) }
}
/// Returns an iterator of at most `limit` substrings of the haystack
/// given, delimited by a match of the regex. (A `limit` of `0` will return
/// no substrings.) Namely, each element of the iterator corresponds to a
/// part of the haystack that *isn't* matched by the regular expression.
/// The remainder of the haystack that is not split will be the last
/// element in the iterator.
///
/// # Time complexity
///
/// Since iterators over all matches requires running potentially many
/// searches on the haystack, and since each search has worst case
/// `O(m * n)` time complexity, the overall worst case time complexity for
/// this routine is `O(m * n^2)`.
///
/// Although note that the worst case time here has an upper bound given
/// by the `limit` parameter.
///
/// # Example
///
/// Get the first two words in some haystack:
///
/// ```
/// use regex::Regex;
///
/// let re = Regex::new(r"\W+").unwrap();
/// let hay = "Hey! How are you?";
/// let fields: Vec<&str> = re.splitn(hay, 3).collect();
/// assert_eq!(fields, vec!["Hey", "How", "are you?"]);
/// ```
///
/// # Examples: more cases
///
/// ```
/// use regex::Regex;
///
/// let re = Regex::new(r" ").unwrap();
/// let hay = "Mary had a little lamb";
/// let got: Vec<&str> = re.splitn(hay, 3).collect();
/// assert_eq!(got, vec!["Mary", "had", "a little lamb"]);
///
/// let re = Regex::new(r"X").unwrap();
/// let hay = "";
/// let got: Vec<&str> = re.splitn(hay, 3).collect();
/// assert_eq!(got, vec![""]);
///
/// let re = Regex::new(r"X").unwrap();
/// let hay = "lionXXtigerXleopard";
/// let got: Vec<&str> = re.splitn(hay, 3).collect();
/// assert_eq!(got, vec!["lion", "", "tigerXleopard"]);
///
/// let re = Regex::new(r"::").unwrap();
/// let hay = "lion::tiger::leopard";
/// let got: Vec<&str> = re.splitn(hay, 2).collect();
/// assert_eq!(got, vec!["lion", "tiger::leopard"]);
///
/// let re = Regex::new(r"X").unwrap();
/// let hay = "abcXdef";
/// let got: Vec<&str> = re.splitn(hay, 1).collect();
/// assert_eq!(got, vec!["abcXdef"]);
///
/// let re = Regex::new(r"X").unwrap();
/// let hay = "abcdef";
/// let got: Vec<&str> = re.splitn(hay, 2).collect();
/// assert_eq!(got, vec!["abcdef"]);
///
/// let re = Regex::new(r"X").unwrap();
/// let hay = "abcXdef";
/// let got: Vec<&str> = re.splitn(hay, 0).collect();
/// assert!(got.is_empty());
/// ```
#[inline]
pub fn splitn<'r, 'h>(
&'r self,
haystack: &'h str,
limit: usize,
) -> SplitN<'r, 'h> {
SplitN { haystack, it: self.meta.splitn(haystack, limit) }
}
/// Replaces the leftmost-first match in the given haystack with the
/// replacement provided. The replacement can be a regular string (where
/// `$N` and `$name` are expanded to match capture groups) or a function
/// that takes a [`Captures`] and returns the replaced string.
///
/// If no match is found, then the haystack is returned unchanged. In that
/// case, this implementation will likely return a `Cow::Borrowed` value
/// such that no allocation is performed.
///
/// # Replacement string syntax
///
/// All instances of `$ref` in the replacement string are replaced with
/// the substring corresponding to the capture group identified by `ref`.
///
/// `ref` 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 `ref` 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. For example, `$1a` looks up the
/// capture group named `1a` and not the capture group at index `1`. To
/// exert more precise control over the name, use braces, e.g., `${1}a`.
///
/// To write a literal `$` use `$$`.
///
/// # Example
///
/// Note that this function is polymorphic with respect to the replacement.
/// In typical usage, this can just be a normal string:
///
/// ```
/// use regex::Regex;
///
/// let re = Regex::new(r"[^01]+").unwrap();
/// assert_eq!(re.replace("1078910", ""), "1010");
/// ```
///
/// But anything satisfying the [`Replacer`] trait will work. For example,
/// a closure of type `|&Captures| -> String` provides direct access to the
/// captures corresponding to a match. This allows one to access capturing
/// group matches easily:
///
/// ```
/// use regex::{Captures, Regex};
///
/// let re = Regex::new(r"([^,\s]+),\s+(\S+)").unwrap();
/// let result = re.replace("Springsteen, Bruce", |caps: &Captures| {
/// format!("{} {}", &caps[2], &caps[1])
/// });
/// assert_eq!(result, "Bruce Springsteen");
/// ```
///
/// But this is a bit cumbersome to use all the time. Instead, a simple
/// syntax is supported (as described above) that expands `$name` into the
/// corresponding capture group. Here's the last example, but using this
/// expansion technique with named capture groups:
///
/// ```
/// use regex::Regex;
///
/// let re = Regex::new(r"(?<last>[^,\s]+),\s+(?<first>\S+)").unwrap();
/// let result = re.replace("Springsteen, Bruce", "$first $last");
/// assert_eq!(result, "Bruce Springsteen");
/// ```
///
/// Note that using `$2` instead of `$first` or `$1` instead of `$last`
/// would produce the same result. To write a literal `$` use `$$`.
///
/// Sometimes the replacement string requires use of curly braces to
/// delineate a capture group replacement when it is adjacent to some other
/// literal text. For example, if we wanted to join two words together with
/// an underscore:
///
/// ```
/// use regex::Regex;
///
/// let re = Regex::new(r"(?<first>\w+)\s+(?<second>\w+)").unwrap();
/// let result = re.replace("deep fried", "${first}_$second");
/// assert_eq!(result, "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
/// string with [`NoExpand`]:
///
/// ```
/// use regex::{NoExpand, Regex};
///
/// let re = Regex::new(r"(?<last>[^,\s]+),\s+(\S+)").unwrap();
/// let result = re.replace("Springsteen, Bruce", NoExpand("$2 $last"));
/// assert_eq!(result, "$2 $last");
/// ```
///
/// Using `NoExpand` may also be faster, since the replacement string won't
/// need to be parsed for the `$` syntax.
#[inline]
pub fn replace<'h, R: Replacer>(
&self,
haystack: &'h str,
rep: R,
) -> Cow<'h, str> {
self.replacen(haystack, 1, rep)
}
/// Replaces all non-overlapping matches in the haystack with the
/// replacement provided. This is the same as calling `replacen` with
/// `limit` set to `0`.
///
/// The documentation for [`Regex::replace`] goes into more detail about
/// what kinds of replacement strings are supported.
///
/// # Time complexity
///
/// Since iterators over all matches requires running potentially many
/// searches on the haystack, and since each search has worst case
/// `O(m * n)` time complexity, the overall worst case time complexity for
/// this routine is `O(m * n^2)`.
///
/// # Fallibility
///
/// If you need to write a replacement routine where any individual
/// replacement might "fail," doing so with this API isn't really feasible
/// because there's no way to stop the search process if a replacement
/// fails. Instead, if you need this functionality, you should consider
/// implementing your own replacement routine:
///
/// ```
/// use regex::{Captures, Regex};
///
/// fn replace_all<E>(
/// re: &Regex,
/// haystack: &str,
/// replacement: impl Fn(&Captures) -> Result<String, E>,
/// ) -> Result<String, E> {
/// let mut new = String::with_capacity(haystack.len());
/// let mut last_match = 0;
/// for caps in re.captures_iter(haystack) {
/// let m = caps.get(0).unwrap();
/// new.push_str(&haystack[last_match..m.start()]);
/// new.push_str(&replacement(&caps)?);
/// last_match = m.end();
/// }
/// new.push_str(&haystack[last_match..]);
/// Ok(new)
/// }
///
/// // Let's replace each word with the number of bytes in that word.
/// // But if we see a word that is "too long," we'll give up.
/// let re = Regex::new(r"\w+").unwrap();
/// let replacement = |caps: &Captures| -> Result<String, &'static str> {
/// if caps[0].len() >= 5 {
/// return Err("word too long");
/// }
/// Ok(caps[0].len().to_string())
/// };
/// assert_eq!(
/// Ok("2 3 3 3?".to_string()),
/// replace_all(&re, "hi how are you?", &replacement),
/// );
/// assert!(replace_all(&re, "hi there", &replacement).is_err());
/// ```
///
/// # Example
///
/// This example shows how to flip the order of whitespace (excluding line
/// terminators) delimited fields, and normalizes the whitespace that
/// delimits the fields:
///
/// ```
/// use regex::Regex;
///
/// let re = Regex::new(r"(?m)^(\S+)[\s--\r\n]+(\S+)$").unwrap();
/// let hay = "
/// Greetings 1973
/// Wild\t1973
/// BornToRun\t\t\t\t1975
/// Darkness 1978
/// TheRiver 1980
/// ";
/// let new = re.replace_all(hay, "$2 $1");
/// assert_eq!(new, "
/// 1973 Greetings
/// 1973 Wild
/// 1975 BornToRun
/// 1978 Darkness
/// 1980 TheRiver
/// ");
/// ```
#[inline]
pub fn replace_all<'h, R: Replacer>(
&self,
haystack: &'h str,
rep: R,
) -> Cow<'h, str> {
self.replacen(haystack, 0, rep)
}
/// Replaces at most `limit` non-overlapping matches in the haystack with
/// the replacement provided. If `limit` is `0`, then all non-overlapping
/// matches are replaced. That is, `Regex::replace_all(hay, rep)` is
/// equivalent to `Regex::replacen(hay, 0, rep)`.
///
/// The documentation for [`Regex::replace`] goes into more detail about
/// what kinds of replacement strings are supported.
///
/// # Time complexity
///
/// Since iterators over all matches requires running potentially many
/// searches on the haystack, and since each search has worst case
/// `O(m * n)` time complexity, the overall worst case time complexity for
/// this routine is `O(m * n^2)`.
///
/// Although note that the worst case time here has an upper bound given
/// by the `limit` parameter.
///
/// # Fallibility
///
/// See the corresponding section in the docs for [`Regex::replace_all`]
/// for tips on how to deal with a replacement routine that can fail.
///
/// # Example
///
/// This example shows how to flip the order of whitespace (excluding line
/// terminators) delimited fields, and normalizes the whitespace that
/// delimits the fields. But we only do it for the first two matches.
///
/// ```
/// use regex::Regex;
///
/// let re = Regex::new(r"(?m)^(\S+)[\s--\r\n]+(\S+)$").unwrap();
/// let hay = "
/// Greetings 1973
/// Wild\t1973
/// BornToRun\t\t\t\t1975
/// Darkness 1978
/// TheRiver 1980
/// ";
/// let new = re.replacen(hay, 2, "$2 $1");
/// assert_eq!(new, "
/// 1973 Greetings
/// 1973 Wild
/// BornToRun\t\t\t\t1975
/// Darkness 1978
/// TheRiver 1980
/// ");
/// ```
#[inline]
pub fn replacen<'h, R: Replacer>(
&self,
haystack: &'h str,
limit: usize,
mut rep: R,
) -> Cow<'h, str> {
// If we know that the replacement doesn't have any capture expansions,
// then we can use the fast path. The fast path can make a tremendous
// difference:
//
// 1) We use `find_iter` instead of `captures_iter`. Not asking for
// captures generally makes the regex engines faster.
// 2) We don't need to look up all of the capture groups and do
// replacements inside the replacement string. We just push it
// at each match and be done with it.
if let Some(rep) = rep.no_expansion() {
let mut it = self.find_iter(haystack).enumerate().peekable();
if it.peek().is_none() {
return Cow::Borrowed(haystack);
}
let mut new = String::with_capacity(haystack.len());
let mut last_match = 0;
for (i, m) in it {
new.push_str(&haystack[last_match..m.start()]);
new.push_str(&rep);
last_match = m.end();
if limit > 0 && i >= limit - 1 {
break;
}
}
new.push_str(&haystack[last_match..]);
return Cow::Owned(new);
}
// The slower path, which we use if the replacement may need access to
// capture groups.
let mut it = self.captures_iter(haystack).enumerate().peekable();
if it.peek().is_none() {
return Cow::Borrowed(haystack);
}
let mut new = String::with_capacity(haystack.len());
let mut last_match = 0;
for (i, cap) in it {
// unwrap on 0 is OK because captures only reports matches
let m = cap.get(0).unwrap();
new.push_str(&haystack[last_match..m.start()]);
rep.replace_append(&cap, &mut new);
last_match = m.end();
if limit > 0 && i >= limit - 1 {
break;
}
}
new.push_str(&haystack[last_match..]);
Cow::Owned(new)
}
}
/// A group of advanced or "lower level" search methods. Some methods permit
/// starting the search at a position greater than `0` in the haystack. Other
/// methods permit reusing allocations, for example, when extracting the
/// matches for capture groups.
impl Regex {
/// Returns the end byte offset of the first match in the haystack given.
///
/// This method may have the same performance characteristics as
/// `is_match`. Behaviorlly, it doesn't just report whether it match
/// occurs, but also the end offset for a match. In particular, the offset
/// returned *may be shorter* than the proper end of the leftmost-first
/// match that you would find via [`Regex::find`].
///
/// Note that it is not guaranteed that this routine finds the shortest or
/// "earliest" possible match. Instead, the main idea of this API is that
/// it returns the offset at the point at which the internal regex engine
/// has determined that a match has occurred. This may vary depending on
/// which internal regex engine is used, and thus, the offset itself may
/// change based on internal heuristics.
///
/// # Example
///
/// Typically, `a+` would match the entire first sequence of `a` in some
/// haystack, but `shortest_match` *may* give up as soon as it sees the
/// first `a`.
///
/// ```
/// use regex::Regex;
///
/// let re = Regex::new(r"a+").unwrap();
/// let offset = re.shortest_match("aaaaa").unwrap();
/// assert_eq!(offset, 1);
/// ```
#[inline]
pub fn shortest_match(&self, haystack: &str) -> Option<usize> {
self.shortest_match_at(haystack, 0)
}
/// Returns the same as [`Regex::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`.
///
/// If a match is found, the offset returned is relative to the beginning
/// of the haystack, not the beginning of the search.
///
/// # Panics
///
/// This panics when `start >= haystack.len() + 1`.
///
/// # Example
///
/// This example shows the significance of `start` by demonstrating how it
/// can be used to permit look-around assertions in a regex to take the
/// surrounding context into account.
///
/// ```
/// use regex::Regex;
///
/// let re = Regex::new(r"\bchew\b").unwrap();
/// let hay = "eschew";
/// // We get a match here, but it's probably not intended.
/// assert_eq!(re.shortest_match(&hay[2..]), Some(4));
/// // No match because the assertions take the context into account.
/// assert_eq!(re.shortest_match_at(hay, 2), None);
/// ```
#[inline]
pub fn shortest_match_at(
&self,
haystack: &str,
start: usize,
) -> Option<usize> {
let input =
Input::new(haystack).earliest(true).span(start..haystack.len());
self.meta.search_half(&input).map(|hm| hm.offset())
}
/// Returns the same as [`Regex::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`.
///
/// # Panics
///
/// This panics when `start >= haystack.len() + 1`.
///
/// # Example
///
/// This example shows the significance of `start` by demonstrating how it
/// can be used to permit look-around assertions in a regex to take the
/// surrounding context into account.
///
/// ```
/// use regex::Regex;
///
/// let re = Regex::new(r"\bchew\b").unwrap();
/// let hay = "eschew";
/// // We get a match here, but it's probably not intended.
/// assert!(re.is_match(&hay[2..]));
/// // No match because the assertions take the context into account.
/// assert!(!re.is_match_at(hay, 2));
/// ```
#[inline]
pub fn is_match_at(&self, haystack: &str, start: usize) -> bool {
let input =
Input::new(haystack).earliest(true).span(start..haystack.len());
self.meta.search_half(&input).is_some()
}
/// Returns the same as [`Regex::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`.
///
/// # Panics
///
/// This panics when `start >= haystack.len() + 1`.
///
/// # Example
///
/// This example shows the significance of `start` by demonstrating how it
/// can be used to permit look-around assertions in a regex to take the
/// surrounding context into account.
///
/// ```
/// use regex::Regex;
///
/// let re = Regex::new(r"\bchew\b").unwrap();
/// let hay = "eschew";
/// // We get a match here, but it's probably not intended.
/// assert_eq!(re.find(&hay[2..]).map(|m| m.range()), Some(0..4));
/// // No match because the assertions take the context into account.
/// assert_eq!(re.find_at(hay, 2), None);
/// ```
#[inline]
pub fn find_at<'h>(
&self,
haystack: &'h str,
start: usize,
) -> Option<Match<'h>> {
let input = Input::new(haystack).span(start..haystack.len());
self.meta
.search(&input)
.map(|m| Match::new(haystack, m.start(), m.end()))
}
/// Returns the same as [`Regex::captures`], 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`.
///
/// # Panics
///
/// This panics when `start >= haystack.len() + 1`.
///
/// # Example
///
/// This example shows the significance of `start` by demonstrating how it
/// can be used to permit look-around assertions in a regex to take the
/// surrounding context into account.
///
/// ```
/// use regex::Regex;
///
/// let re = Regex::new(r"\bchew\b").unwrap();
/// let hay = "eschew";
/// // We get a match here, but it's probably not intended.
/// assert_eq!(&re.captures(&hay[2..]).unwrap()[0], "chew");
/// // No match because the assertions take the context into account.
/// assert!(re.captures_at(hay, 2).is_none());
/// ```
#[inline]
pub fn captures_at<'h>(
&self,
haystack: &'h str,
start: usize,
) -> Option<Captures<'h>> {
let input = Input::new(haystack).span(start..haystack.len());
let mut caps = self.meta.create_captures();
self.meta.search_captures(&input, &mut caps);
if caps.is_match() {
let static_captures_len = self.static_captures_len();
Some(Captures { haystack, caps, static_captures_len })
} else {
None
}
}
/// This is like [`Regex::captures`], but writes the byte offsets of each
/// capture group match into the locations given.
///
/// A [`CaptureLocations`] stores the same byte offsets as a [`Captures`],
/// but does *not* store a reference to the haystack. This makes its API
/// a bit lower level and less convenient. But in exchange, callers
/// may allocate their own `CaptureLocations` and reuse it for multiple
/// searches. This may be helpful if allocating a `Captures` shows up in a
/// profile as too costly.
///
/// To create a `CaptureLocations` value, use the
/// [`Regex::capture_locations`] method.
///
/// This also returns the overall match if one was found. When a match is
/// found, its offsets are also always stored in `locs` at index `0`.
///
/// # Panics
///
/// This routine may panic if the given `CaptureLocations` was not created
/// by this regex.
///
/// # Example
///
/// ```
/// use regex::Regex;
///
/// let re = Regex::new(r"^([a-z]+)=(\S*)$").unwrap();
/// let mut locs = re.capture_locations();
/// assert!(re.captures_read(&mut locs, "id=foo123").is_some());
/// assert_eq!(Some((0, 9)), locs.get(0));
/// assert_eq!(Some((0, 2)), locs.get(1));
/// assert_eq!(Some((3, 9)), locs.get(2));
/// ```
#[inline]
pub fn captures_read<'h>(
&self,
locs: &mut CaptureLocations,
haystack: &'h str,
) -> Option<Match<'h>> {
self.captures_read_at(locs, haystack, 0)
}
/// Returns the same as [`Regex::captures_read`], 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`.
///
/// # Panics
///
/// This panics when `start >= haystack.len() + 1`.
///
/// This routine may also panic if the given `CaptureLocations` was not
/// created by this regex.
///
/// # Example
///
/// This example shows the significance of `start` by demonstrating how it
/// can be used to permit look-around assertions in a regex to take the
/// surrounding context into account.
///
/// ```
/// use regex::Regex;
///
/// let re = Regex::new(r"\bchew\b").unwrap();
/// let hay = "eschew";
/// let mut locs = re.capture_locations();
/// // We get a match here, but it's probably not intended.
/// assert!(re.captures_read(&mut locs, &hay[2..]).is_some());
/// // No match because the assertions take the context into account.
/// assert!(re.captures_read_at(&mut locs, hay, 2).is_none());
/// ```
#[inline]
pub fn captures_read_at<'h>(
&self,
locs: &mut CaptureLocations,
haystack: &'h str,
start: usize,
) -> Option<Match<'h>> {
let input = Input::new(haystack).span(start..haystack.len());
self.meta.search_captures(&input, &mut locs.0);
locs.0.get_match().map(|m| Match::new(haystack, m.start(), m.end()))
}
/// 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)]
#[inline]
pub fn read_captures_at<'h>(
&self,
locs: &mut CaptureLocations,
haystack: &'h str,
start: usize,
) -> Option<Match<'h>> {
self.captures_read_at(locs, haystack, start)
}
}
/// Auxiliary methods.
impl Regex {
/// Returns the original string of this regex.
///
/// # Example
///
/// ```
/// use regex::Regex;
///
/// let re = Regex::new(r"foo\w+bar").unwrap();
/// assert_eq!(re.as_str(), r"foo\w+bar");
/// ```
#[inline]
pub fn as_str(&self) -> &str {
&self.pattern
}
/// Returns an iterator over the capture names in this regex.
///
/// The iterator returned yields elements of type `Option<&str>`. That is,
/// the iterator yields values for all capture groups, even ones that are
/// unnamed. The order of the groups corresponds to the order of the group's
/// corresponding opening parenthesis.
///
/// The first element of the iterator always yields the group corresponding
/// to the overall match, and this group is always unnamed. Therefore, the
/// iterator always yields at least one group.
///
/// # Example
///
/// This shows basic usage with a mix of named and unnamed capture groups:
///
/// ```
/// use regex::Regex;
///
/// let re = Regex::new(r"(?<a>.(?<b>.))(.)(?:.)(?<c>.)").unwrap();
/// let mut names = re.capture_names();
/// assert_eq!(names.next(), Some(None));
/// assert_eq!(names.next(), Some(Some("a")));
/// assert_eq!(names.next(), Some(Some("b")));
/// assert_eq!(names.next(), Some(None));
/// // the '(?:.)' group is non-capturing and so doesn't appear here!
/// assert_eq!(names.next(), Some(Some("c")));
/// assert_eq!(names.next(), None);
/// ```
///
/// The iterator always yields at least one element, even for regexes with
/// no capture groups and even for regexes that can never match:
///
/// ```
/// use regex::Regex;
///
/// let re = Regex::new(r"").unwrap();
/// let mut names = re.capture_names();
/// assert_eq!(names.next(), Some(None));
/// assert_eq!(names.next(), None);
///
/// let re = Regex::new(r"[a&&b]").unwrap();
/// let mut names = re.capture_names();
/// assert_eq!(names.next(), Some(None));
/// assert_eq!(names.next(), None);
/// ```
#[inline]
pub fn capture_names(&self) -> CaptureNames<'_> {
CaptureNames(self.meta.group_info().pattern_names(PatternID::ZERO))
}
/// Returns the number of captures groups in this regex.
///
/// This includes all named and unnamed groups, including the implicit
/// unnamed group that is always present and corresponds to the entire
/// match.
///
/// Since the implicit unnamed group is always included in this length, the
/// length returned is guaranteed to be greater than zero.
///
/// # Example
///
/// ```
/// use regex::Regex;
///
/// let re = Regex::new(r"foo").unwrap();
/// assert_eq!(1, re.captures_len());
///
/// let re = Regex::new(r"(foo)").unwrap();
/// assert_eq!(2, re.captures_len());
///
/// let re = Regex::new(r"(?<a>.(?<b>.))(.)(?:.)(?<c>.)").unwrap();
/// assert_eq!(5, re.captures_len());
///
/// let re = Regex::new(r"[a&&b]").unwrap();
/// assert_eq!(1, re.captures_len());
/// ```
#[inline]
pub fn captures_len(&self) -> usize {
self.meta.group_info().group_len(PatternID::ZERO)
}
/// Returns the total number of capturing groups that appear in every
/// possible match.
///
/// If the number of capture groups can vary depending on the match, then
/// this returns `None`. That is, a value is only returned when the number
/// of matching groups is invariant or "static."
///
/// Note that like [`Regex::captures_len`], this **does** include the
/// implicit capturing group corresponding to the entire match. Therefore,
/// when a non-None value is returned, it is guaranteed to be at least `1`.
/// Stated differently, a return value of `Some(0)` is impossible.
///
/// # Example
///
/// This shows a few cases where a static number of capture groups is
/// available and a few cases where it is not.
///
/// ```
/// use regex::Regex;
///
/// let len = |pattern| {
/// Regex::new(pattern).map(|re| re.static_captures_len())
/// };
///
/// assert_eq!(Some(1), len("a")?);
/// assert_eq!(Some(2), len("(a)")?);
/// assert_eq!(Some(2), len("(a)|(b)")?);
/// assert_eq!(Some(3), len("(a)(b)|(c)(d)")?);
/// assert_eq!(None, len("(a)|b")?);
/// assert_eq!(None, len("a|(b)")?);
/// assert_eq!(None, len("(b)*")?);
/// assert_eq!(Some(2), len("(b)+")?);
///
/// # Ok::<(), Box<dyn std::error::Error>>(())
/// ```
#[inline]
pub fn static_captures_len(&self) -> Option<usize> {
self.meta.static_captures_len()
}
/// Returns a fresh allocated set of capture locations that can
/// be reused in multiple calls to [`Regex::captures_read`] or
/// [`Regex::captures_read_at`].
///
/// The returned locations can be used for any subsequent search for this
/// particular regex. There is no guarantee that it is correct to use for
/// other regexes, even if they have the same number of capture groups.
///
/// # Example
///
/// ```
/// use regex::Regex;
///
/// let re = Regex::new(r"(.)(.)(\w+)").unwrap();
/// let mut locs = re.capture_locations();
/// assert!(re.captures_read(&mut locs, "Padron").is_some());
/// assert_eq!(locs.get(0), Some((0, 6)));
/// assert_eq!(locs.get(1), Some((0, 1)));
/// assert_eq!(locs.get(2), Some((1, 2)));
/// assert_eq!(locs.get(3), Some((2, 6)));
/// ```
#[inline]
pub fn capture_locations(&self) -> CaptureLocations {
CaptureLocations(self.meta.create_captures())
}
/// An alias for `capture_locations` to preserve backward compatibility.
///
/// The `regex-capi` crate used this method, so to avoid breaking that
/// crate, we continue to export it as an undocumented API.
#[doc(hidden)]
#[inline]
pub fn locations(&self) -> CaptureLocations {
self.capture_locations()
}
}
/// Represents a single match of a regex in a haystack.
///
/// A `Match` contains both the start and end byte offsets of the match and the
/// actual substring corresponding to the range of those byte offsets. It is
/// guaranteed that `start <= end`. When `start == end`, the match is empty.
///
/// Since this `Match` can only be produced by the top-level `Regex` APIs
/// that only support searching UTF-8 encoded strings, the byte offsets for a
/// `Match` are guaranteed to fall on valid UTF-8 codepoint boundaries. That
/// is, slicing a `&str` with [`Match::range`] is guaranteed to never panic.
///
/// Values with this type are created by [`Regex::find`] or
/// [`Regex::find_iter`]. Other APIs can create `Match` values too. For
/// example, [`Captures::get`].
///
/// The lifetime parameter `'h` refers to the lifetime of the matched of the
/// haystack that this match was produced from.
///
/// # Numbering
///
/// The byte offsets in a `Match` form a half-open interval. That is, the
/// start of the range is inclusive and the end of the range is exclusive.
/// For example, given a haystack `abcFOOxyz` and a match of `FOO`, its byte
/// offset range starts at `3` and ends at `6`. `3` corresponds to `F` and
/// `6` corresponds to `x`, which is one past the end of the match. This
/// corresponds to the same kind of slicing that Rust uses.
///
/// For more on why this was chosen over other schemes (aside from being
/// consistent with how Rust the language works), see [this discussion] and
/// [Dijkstra's note on a related topic][note].
///
/// [this discussion]:
https://github.com/rust-lang/regex/discussions/866
/// [note]:
https://www.cs.utexas.edu/users/EWD/transcriptions/EWD08xx/EWD831.html
///
/// # Example
///
/// This example shows the value of each of the methods on `Match` for a
/// particular search.
///
/// ```
/// use regex::Regex;
///
/// let re = Regex::new(r"\p{Greek}+").unwrap();
/// let hay = "Greek: αβγδ";
/// let m = re.find(hay).unwrap();
/// assert_eq!(7, m.start());
/// assert_eq!(15, m.end());
/// assert!(!m.is_empty());
/// assert_eq!(8, m.len());
/// assert_eq!(7..15, m.range());
/// assert_eq!("αβγδ", m.as_str());
/// ```
#[derive(Copy, Clone, Eq, PartialEq)]
pub struct Match<'h> {
haystack: &'h str,
start: usize,
end: usize,
}
impl<'h> Match<'h> {
/// Returns the byte offset of the start of the match in the haystack. The
/// start of the match corresponds to the position where the match begins
/// and includes the first byte in the match.
///
/// It is guaranteed that `Match::start() <= Match::end()`.
///
/// This is guaranteed to fall on a valid UTF-8 codepoint boundary. That
/// is, it will never be an offset that appears between the UTF-8 code
/// units of a UTF-8 encoded Unicode scalar value. Consequently, it is
/// always safe to slice the corresponding haystack using this offset.
#[inline]
pub fn start(&self) -> usize {
self.start
}
/// Returns the byte offset of the end of the match in the haystack. The
/// end of the match corresponds to the byte immediately following the last
/// byte in the match. This means that `&slice[start..end]` works as one
/// would expect.
///
/// It is guaranteed that `Match::start() <= Match::end()`.
///
/// This is guaranteed to fall on a valid UTF-8 codepoint boundary. That
/// is, it will never be an offset that appears between the UTF-8 code
/// units of a UTF-8 encoded Unicode scalar value. Consequently, it is
/// always safe to slice the corresponding haystack using this offset.
#[inline]
pub fn end(&self) -> usize {
self.end
}
/// Returns true if and only if this match has a length of zero.
///
/// Note that an empty match can only occur when the regex itself can
/// match the empty string. Here are some examples of regexes that can
/// all match the empty string: `^`, `^$`, `\b`, `a?`, `a*`, `a{0}`,
/// `(foo|\d+|quux)?`.
#[inline]
pub fn is_empty(&self) -> bool {
self.start == self.end
}
/// Returns the length, in bytes, of this match.
#[inline]
pub fn len(&self) -> usize {
self.end - self.start
}
/// Returns the range over the starting and ending byte offsets of the
/// match in the haystack.
///
/// It is always correct to slice the original haystack searched with this
/// range. That is, because the offsets are guaranteed to fall on valid
/// UTF-8 boundaries, the range returned is always valid.
#[inline]
pub fn range(&self) -> core::ops::Range<usize> {
self.start..self.end
}
/// Returns the substring of the haystack that matched.
#[inline]
pub fn as_str(&self) -> &'h str {
&self.haystack[self.range()]
}
/// Creates a new match from the given haystack and byte offsets.
#[inline]
fn new(haystack: &'h str, start: usize, end: usize) -> Match<'h> {
Match { haystack, start, end }
}
}
impl<'h> core::fmt::Debug for Match<'h> {
fn fmt(&self, f: &mut core::fmt::Formatter) -> core::fmt::Result {
f.debug_struct("Match")
.field("start", &self.start)
.field("end", &self.end)
.field("string", &self.as_str())
.finish()
}
}
impl<'h> From<Match<'h>> for &'h str {
fn from(m: Match<'h>) -> &'h str {
m.as_str()
}
}
impl<'h> From<Match<'h>> for core::ops::Range<usize> {
fn from(m: Match<'h>) -> core::ops::Range<usize> {
m.range()
}
}
/// Represents the capture groups for a single match.
///
/// Capture groups refer to parts of a regex enclosed in parentheses. They can
/// be optionally named. The purpose of capture groups is to be able to
/// reference different parts of a match based on the original pattern. For
/// example, say you want to match the individual letters in a 5-letter word:
///
/// ```text
/// (?<first>\w)(\w)(?:\w)\w(?<last>\w)
/// ```
///
/// This regex has 4 capture groups:
///
/// * The group at index `0` corresponds to the overall match. It is always
/// present in every match and never has a name.
/// * The group at index `1` with name `first` corresponding to the first
/// letter.
/// * The group at index `2` with no name corresponding to the second letter.
/// * The group at index `3` with name `last` corresponding to the fifth and
/// last letter.
///
/// Notice that `(?:\w)` was not listed above as a capture group despite it
/// being enclosed in parentheses. That's because `(?:pattern)` is a special
/// syntax that permits grouping but *without* capturing. The reason for not
/// treating it as a capture is that tracking and reporting capture groups
/// requires additional state that may lead to slower searches. So using as few
/// capture groups as possible can help performance. (Although the difference
/// in performance of a couple of capture groups is likely immaterial.)
///
/// Values with this type are created by [`Regex::captures`] or
/// [`Regex::captures_iter`].
///
/// `'h` is the lifetime of the haystack that these captures were matched from.
///
/// # Example
///
/// ```
/// use regex::Regex;
///
/// let re = Regex::new(r"(?<first>\w)(\w)(?:\w)\w(?<last>\w)").unwrap();
/// let caps = re.captures("toady").unwrap();
/// assert_eq!("toady", &caps[0]);
/// assert_eq!("t", &caps["first"]);
/// assert_eq!("o", &caps[2]);
/// assert_eq!("y", &caps["last"]);
/// ```
pub struct Captures<'h> {
haystack: &'h str,
caps: captures::Captures,
static_captures_len: Option<usize>,
}
impl<'h> Captures<'h> {
/// 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.
///
/// When `i == 0`, this is guaranteed to return a non-`None` value.
///
/// # Examples
///
/// Get the substring that matched with a default of an empty string if the
/// group didn't participate in the match:
///
/// ```
/// use regex::Regex;
///
/// let re = Regex::new(r"[a-z]+(?:([0-9]+)|([A-Z]+))").unwrap();
/// let caps = re.captures("abc123").unwrap();
///
/// let substr1 = caps.get(1).map_or("", |m| m.as_str());
/// let substr2 = caps.get(2).map_or("", |m| m.as_str());
/// assert_eq!(substr1, "123");
/// assert_eq!(substr2, "");
/// ```
#[inline]
pub fn get(&self, i: usize) -> Option<Match<'h>> {
self.caps
.get_group(i)
.map(|sp| Match::new(self.haystack, sp.start, sp.end))
}
/// Returns the `Match` associated with the capture group named `name`. If
/// `name` isn't a valid capture group or it refers to a group that didn't
/// match, then `None` is returned.
///
/// Note that unlike `caps["name"]`, this returns a `Match` whose lifetime
/// matches the lifetime of the haystack in this `Captures` value.
/// Conversely, the substring returned by `caps["name"]` has a lifetime
/// of the `Captures` value, which is likely shorter than the lifetime of
/// the haystack. In some cases, it may be necessary to use this method to
/// access the matching substring instead of the `caps["name"]` notation.
///
/// # Examples
///
/// Get the substring that matched with a default of an empty string if the
/// group didn't participate in the match:
///
/// ```
/// use regex::Regex;
///
/// let re = Regex::new(
/// r"[a-z]+(?:(?<numbers>[0-9]+)|(?<letters>[A-Z]+))",
/// ).unwrap();
/// let caps = re.captures("abc123").unwrap();
///
/// let numbers = caps.name("numbers").map_or("", |m| m.as_str());
/// let letters = caps.name("letters").map_or("", |m| m.as_str());
/// assert_eq!(numbers, "123");
/// assert_eq!(letters, "");
/// ```
#[inline]
pub fn name(&self, name: &str) -> Option<Match<'h>> {
self.caps
.get_group_by_name(name)
.map(|sp| Match::new(self.haystack, sp.start, sp.end))
}
/// This is a convenience routine for extracting the substrings
/// corresponding to matching capture groups.
///
/// This returns a tuple where the first element corresponds to the full
/// substring of the haystack that matched the regex. The second element is
/// an array of substrings, with each corresponding to the to the substring
/// that matched for a particular capture group.
///
/// # Panics
///
/// This panics if the number of possible matching groups in this
/// `Captures` value is not fixed to `N` in all circumstances.
/// More precisely, this routine only works when `N` is equivalent to
/// [`Regex::static_captures_len`].
///
/// Stated more plainly, if the number of matching capture groups in a
/// regex can vary from match to match, then this function always panics.
///
/// For example, `(a)(b)|(c)` could produce two matching capture groups
/// or one matching capture group for any given match. Therefore, one
/// cannot use `extract` with such a pattern.
///
/// But a pattern like `(a)(b)|(c)(d)` can be used with `extract` because
/// the number of capture groups in every match is always equivalent,
/// even if the capture _indices_ in each match are not.
///
/// # Example
///
/// ```
/// use regex::Regex;
///
/// let re = Regex::new(r"([0-9]{4})-([0-9]{2})-([0-9]{2})").unwrap();
/// let hay = "On 2010-03-14, I became a Tenneessee lamb.";
/// let Some((full, [year, month, day])) =
/// re.captures(hay).map(|caps| caps.extract()) else { return };
/// assert_eq!("2010-03-14", full);
/// assert_eq!("2010", year);
/// assert_eq!("03", month);
/// assert_eq!("14", day);
/// ```
///
/// # Example: iteration
///
/// This example shows how to use this method when iterating over all
/// `Captures` matches in a haystack.
///
/// ```
/// use regex::Regex;
///
/// let re = Regex::new(r"([0-9]{4})-([0-9]{2})-([0-9]{2})").unwrap();
/// let hay = "1973-01-05, 1975-08-25 and 1980-10-18";
///
/// let mut dates: Vec<(&str, &str, &str)> = vec![];
/// for (_, [y, m, d]) in re.captures_iter(hay).map(|c| c.extract()) {
/// dates.push((y, m, d));
/// }
/// assert_eq!(dates, vec![
/// ("1973", "01", "05"),
/// ("1975", "08", "25"),
/// ("1980", "10", "18"),
/// ]);
/// ```
///
/// # Example: parsing different formats
///
/// This API is particularly useful when you need to extract a particular
/// value that might occur in a different format. Consider, for example,
/// an identifier that might be in double quotes or single quotes:
///
/// ```
/// use regex::Regex;
///
/// let re = Regex::new(r#"id:(?:"([^"]+)"|'([^']+)')"#).unwrap();
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