struggling with printing contexts, what a mess

src/printer.rs

@@ -58,6 +58,24 @@ impl<W: io::Write> Printer<W> {
         self.write(b"\n");
     }
 
+    pub fn context<P: AsRef<Path>>(
+        &mut self,
+        path: P,
+        buf: &[u8],
+        start: usize,
+        end: usize,
+        line_number: Option<u64>,
+    ) {
+        self.write(path.as_ref().to_string_lossy().as_bytes());
+        self.write(b"-");
+        if let Some(line_number) = line_number {
+            self.write(line_number.to_string().as_bytes());
+            self.write(b"-");
+        }
+        self.write(&buf[start..end]);
+        self.write(b"\n");
+    }
+
     pub fn binary_matched<P: AsRef<Path>>(&mut self, path: P) {
         wln!(&mut self.wtr, "binary file {} matches", path.as_ref().display());
     }