Limit line length to 100 MB to not exhaust system memory on /dev/zero

Closes sharkdp#636

CHANGELOG.md

@@ -12,6 +12,7 @@
 - Python syntax highlighting no longer suffers from abysmal performance in specific scenarios. See #1688 (@keith-hall)
 - First line not shown in diff context. See #1891 (@divagant-martian)
 - Do not ignore syntaxes that handle file names with a `*.conf` extension. See #1703 (@cbolgiano)
+- Limit line length to 100 MB to not exhaust system memory on `/dev/zero`. See #1972 (@Enselic)
 
 ## Performance
 

src/input.rs

@@ -251,7 +251,7 @@ pub(crate) struct InputReader<'a> {
 impl<'a> InputReader<'a> {
     fn new<R: BufRead + 'a>(mut reader: R) -> InputReader<'a> {
         let mut first_line = vec![];
-        reader.read_until(b'\n', &mut first_line).ok();
+        Self::read_line_safely(&mut reader, &mut first_line).ok();
 
         let content_type = if first_line.is_empty() {
             None
@@ -276,14 +276,26 @@ impl<'a> InputReader<'a> {
             return Ok(true);
         }
 
-        let res = self.inner.read_until(b'\n', buf).map(|size| size > 0)?;
+        let res = Self::read_line_safely(&mut self.inner, buf).map(|size| size > 0)?;
 
         if self.content_type == Some(ContentType::UTF_16LE) {
             let _ = self.inner.read_until(0x00, buf);
         }
 
         Ok(res)
     }
+
+    fn read_line_safely<R: BufRead + 'a>(reader: &mut R, buf: &mut Vec<u8>) -> io::Result<usize> {
+        let limit = 100_000_000_usize;
+
+        match reader.take(limit as u64).read_until(b'\n', buf) {
+            Ok(n) if n == limit => Err(io::Error::new(
+                io::ErrorKind::Other,
+                "Lines longer than 100 MB are not supported",
+            )),
+            r => r,
+        }
+    }
 }
 
 #[test]

tests/integration_tests.rs

@@ -344,6 +344,18 @@ fn no_args_doesnt_break() {
     assert!(exit_status.success());
 }
 
+#[cfg(unix)]
+#[test]
+fn dev_zero() {
+    bat()
+        .arg("/dev/zero")
+        .assert()
+        .failure()
+        .stderr(predicate::str::contains(
+            "Lines longer than 100 MB are not supported",
+        ));
+}
+
 #[test]
 fn tabs_numbers() {
     bat()