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regex: add Regex::split_once method #1343

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88 changes: 88 additions & 0 deletions src/regex/bytes.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -642,6 +642,94 @@ impl Regex {
SplitN { haystack, it: self.meta.splitn(haystack, limit) }
}

/// Searches for the first match of this regex in the haystack given, and if
/// found, returns a tuple with the substring preceding the match and the
/// substring following it. If no match is found, then `None` is returned.
///
/// The matched substring itself is not returned as part of either
/// substring in the returned tuple.
///
/// # Example
///
/// To split off the first 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 got = re.split_once(hay);
/// assert_eq!(got, Some(("a", "b \t c\td e")));
/// ```
///
/// # Example: more cases
///
/// Basic usage:
///
/// ```
/// use regex::Regex;
///
/// let re = Regex::new(r" ").unwrap();
/// let hay = "Mary had a little lamb";
/// let got = re.split_once(hay);
/// assert_eq!(got, Some(("Mary", "had a little lamb")));
///
/// let re = Regex::new(r"X").unwrap();
/// let hay = "";
/// let got = re.split_once(hay);
/// assert_eq!(got, None);
///
/// let re = Regex::new(r"X").unwrap();
/// let hay = "lionXXtigerXleopard";
/// let got = re.split_once(hay);
/// assert_eq!(got, Some(("lion", "XtigerXleopard")));
///
/// let re = Regex::new(r"::").unwrap();
/// let hay = "lion::tiger::leopard";
/// let got = re.split_once(hay);
/// assert_eq!(got, Some(("lion", "tiger::leopard")));
/// ```
///
/// If the first match is at the start or end of a haystack, the
/// corresponding substring is empty.
///
/// ```
/// use regex::Regex;
///
/// let re = Regex::new(r"0").unwrap();
/// let hay = "01";
/// let got = re.split_once(hay);
/// assert_eq!(got, Some(("", "1")));
///
/// let re = Regex::new(r"0").unwrap();
/// let hay = "10";
/// let got = re.split_once(hay);
/// assert_eq!(got, Some(("1", "")));
/// ```
///
/// When the empty string is used as a regex, the resulting tuple consists
/// of the empty string followed by the complete haystack:
///
/// ```
/// use regex::Regex;
///
/// let re = Regex::new(r"").unwrap();
/// let hay = "rust";
/// let got = re.split_once(hay);
/// assert_eq!(got, Some(("", "rust")));
/// ```
#[inline]
pub fn split_once<'h>(
&self,
haystack: &'h [u8],
) -> Option<(&'h [u8], &'h [u8])> {
let m = self.find(haystack)?;
let preceding = &haystack[..m.start()];
let succeeding = &haystack[m.end()..];
Some((preceding, succeeding))
}

/// 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
Expand Down
88 changes: 88 additions & 0 deletions src/regex/string.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -633,6 +633,94 @@ impl Regex {
SplitN { haystack, it: self.meta.splitn(haystack, limit) }
}

/// Searches for the first match of this regex in the haystack given, and if
/// found, returns a tuple with the substring preceding the match and the
/// substring following it. If no match is found, then `None` is returned.
///
/// The matched substring itself is not returned as part of either
/// substring in the returned tuple.
///
/// # Example
///
/// To split off the first 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 got = re.split_once(hay);
/// assert_eq!(got, Some(("a", "b \t c\td e")));
/// ```
///
/// # Example: more cases
///
/// Basic usage:
///
/// ```
/// use regex::Regex;
///
/// let re = Regex::new(r" ").unwrap();
/// let hay = "Mary had a little lamb";
/// let got = re.split_once(hay);
/// assert_eq!(got, Some(("Mary", "had a little lamb")));
///
/// let re = Regex::new(r"X").unwrap();
/// let hay = "";
/// let got = re.split_once(hay);
/// assert_eq!(got, None);
///
/// let re = Regex::new(r"X").unwrap();
/// let hay = "lionXXtigerXleopard";
/// let got = re.split_once(hay);
/// assert_eq!(got, Some(("lion", "XtigerXleopard")));
///
/// let re = Regex::new(r"::").unwrap();
/// let hay = "lion::tiger::leopard";
/// let got = re.split_once(hay);
/// assert_eq!(got, Some(("lion", "tiger::leopard")));
/// ```
///
/// If the first match is at the start or end of a haystack, the
/// corresponding substring is empty.
///
/// ```
/// use regex::Regex;
///
/// let re = Regex::new(r"0").unwrap();
/// let hay = "01";
/// let got = re.split_once(hay);
/// assert_eq!(got, Some(("", "1")));
///
/// let re = Regex::new(r"0").unwrap();
/// let hay = "10";
/// let got = re.split_once(hay);
/// assert_eq!(got, Some(("1", "")));
/// ```
///
/// When the empty string is used as a regex, the resulting tuple consists
/// of the empty string followed by the complete haystack:
///
/// ```
/// use regex::Regex;
///
/// let re = Regex::new(r"").unwrap();
/// let hay = "rust";
/// let got = re.split_once(hay);
/// assert_eq!(got, Some(("", "rust")));
/// ```
#[inline]
pub fn split_once<'h>(
&self,
haystack: &'h str,
) -> Option<(&'h str, &'h str)> {
let m = self.find(haystack)?;
let preceding = &haystack[..m.start()];
let succeeding = &haystack[m.end()..];
Some((preceding, succeeding))
}

/// 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
Expand Down