New scanner methods

1 files changed, 41 insertions, 0 deletions

diff --git a/src/scanner.rs b/src/scanner.rs
index 6c82041..a68199c 100644
--- a/src/scanner.rs
+++ b/src/scanner.rs
@@ -182,6 +182,47 @@ impl Scanner {
 		self.goto(position)
 	}
 
+	/// Increase the position by one, if possible. If the new position would be
+	/// outside of the range of the source, then `None` is returned. Otherwise,
+	/// the character that was passed over is returned.
+	///
+	/// # Example
+	///
+	/// ```
+	/// use snob::Scanner;
+	///
+	/// let mut scanner = Scanner::new("Hello, world");
+	/// let c = scanner.advance_char();
+	/// assert_eq!(scanner.position(), 1);
+	/// assert_eq!(c, 'H');
+	/// ```
+	pub fn advance_char(&mut self) -> Option<char> {
+		let char = self.source.get(self.position)?;
+		self.position = self.position.checked_add(1)?;
+		Some(*char)
+	}
+
+	/// Increases the position by the given `amount`, or advances to the end of
+	/// the source if the new position would be outside of the range of the
+	/// source. This returnes the subslice of the string from the old position
+	/// to the new position.
+	///
+	/// ```
+	/// use snob::Scanner;
+	///
+	/// let mut scanner = Scanner::new("Hello, world!");
+	/// let substr = scanner.advance_or_goto_end(20);
+	/// assert_eq!(scanner.position(), 13);
+	/// assert_eq!(substr, String::from("Hello, world!"))
+	/// ```
+	pub fn advance_or_goto_end(&mut self, amount: isize) -> String {
+		let position = self
+			.position
+			.checked_add_signed(amount)
+			.unwrap_or(self.len());
+		self.goto(position).expect("a valid position")
+	}
+
 	/// Looks for the given `substring` in the remainder of the scanner. If the
 	/// substring is found, the position of the first character in the
 	/// substring is returned. Otherwise, `None` is returned.