Implement LocatedSpan::get_line().

src/lib.rs

@@ -277,6 +277,45 @@ impl<T: AsBytes, X> LocatedSpan<T, X> {
         (column, &before_self[self.offset - (column - 1)..])
     }
 
+    /// Return the line that contains this LocatedSpan.
+    ///
+    /// The `get_column` and `get_utf8_column` functions returns
+    /// indexes that corresponds to the line returned by this function.
+    ///
+    /// ```
+    /// # extern crate nom_locate;
+    /// # extern crate nom;
+    /// # use nom_locate::LocatedSpan;
+    /// # use nom::{Slice, FindSubstring};
+    /// #
+    /// # fn main() {
+    /// let program = LocatedSpan::new(
+    ///     "Hello World!\
+    ///     \nThis is a multi-line input\
+    ///     \nthat ends after this line.\n");
+    /// let multi = program.find_substring("multi").unwrap();
+    ///
+    /// assert_eq!(
+    ///     program.slice(multi..).get_line(),
+    ///     Some("This is a multi-line input".as_ref()),
+    /// );
+    /// # }
+    /// ```
+    pub fn get_line(&self) -> Option<&[u8]> {
+        let self_bytes = self.fragment.as_bytes();
+        let self_ptr = self_bytes.as_ptr();
+        let offset = self.get_column() - 1;
+        let the_line = unsafe {
+            assert!(
+                offset <= isize::max_value() as usize,
+                "offset is too big"
+            );
+            let line_start_ptr = self_ptr.offset(-(offset as isize));
+            slice::from_raw_parts(line_start_ptr, offset + self_bytes.len())
+        };
+        the_line.split(|c| *c == b'\n').next()
+    }
+
     /// Return the column index, assuming 1 byte = 1 column.
     ///
     /// Use it for ascii text, or use get_utf8_column for UTF8.

src/tests.rs

@@ -414,3 +414,96 @@ fn it_should_display_hex() {
         "00000000\t61 62 63    \tabc\n".to_owned()
     );
 }
+
+#[test]
+fn line_of_empty_span_is_empty() {
+    assert_eq!(
+        StrSpan::new("").get_line(),
+        Some("".as_ref()),
+    );
+}
+
+#[test]
+fn line_of_single_line_start_is_whole() {
+    assert_eq!(
+        StrSpan::new("A single line").get_line(),
+        Some("A single line".as_ref()),
+    );
+}
+#[test]
+fn line_of_single_line_end_is_whole() {
+    let data = "A single line";
+    assert_eq!(
+        StrSpan::new(data).slice(data.len()..).get_line(),
+        Some("A single line".as_ref()),
+    );
+}
+
+#[test]
+fn line_of_start_is_first() {
+    assert_eq!(
+        StrSpan::new(
+            "One line of text\
+             \nFollowed by a second\
+             \nand a third\n"
+        ).get_line(),
+        Some("One line of text".as_ref()),
+    );
+}
+
+#[test]
+fn line_of_nl_is_before() {
+    let data =
+        "One line of text\
+         \nFollowed by a second\
+         \nand a third\n";
+    assert_eq!(
+        StrSpan::new(data).slice(data.find('\n').unwrap()..).get_line(),
+        Some("One line of text".as_ref()),
+    );
+}
+
+#[test]
+fn line_of_end_after_nl_is_empty() {
+    let data =
+        "One line of text\
+         \nFollowed by a second\
+         \nand a third\n";
+    assert_eq!(
+        StrSpan::new(data).slice(data.len()..).get_line(),
+        Some("".as_ref()),
+    );
+}
+
+#[test]
+fn line_of_end_no_nl_is_last() {
+    let data =
+        "One line of text\
+         \nFollowed by a second\
+         \nand a third";
+    assert_eq!(
+        StrSpan::new(data).slice(data.len()..).get_line(),
+        Some("and a third".as_ref()),
+    );
+}
+
+#[test]
+fn line_for_non_ascii_chars() {
+    // I don't really know if this Oriya text makes sense.
+    let data = StrSpan::new(
+        "Några rader text på Svenska.\
+         \nFörra raden var först, den här är i mitten\
+         \noch här är sista raden.\n");
+    let s = data.slice(data.find_substring("först").unwrap()..);
+    assert_eq!(
+        format!(
+            "{line_no:3}: {line_text}\n    {0:>lpos$}^- The match\n",
+            "",
+            line_no = s.location_line(),
+            line_text = core::str::from_utf8(s.get_line().unwrap()).unwrap(),
+            lpos = s.get_utf8_column(),
+        ),
+        "  2: Förra raden var först, den här är i mitten\
+       \n                     ^- The match\n",
+    );
+}