add fuzzer

tests/fuzz.rs

@@ -0,0 +1,50 @@
+use core::slice;
+use gentoo_utils::{Parseable, atom::Atom};
+use mon::{Parser, ParserFinishedError, input::InputIter};
+use std::{
+    io::Write,
+    process::{Command, Stdio},
+};
+
+#[allow(clippy::missing_safety_doc, clippy::needless_return)]
+#[unsafe(no_mangle)]
+pub unsafe extern "C" fn LLVMFuzzerTestOneInput(input: *const u8, len: usize) -> i32 {
+    let slice = unsafe { slice::from_raw_parts(input, len) };
+
+    let atom = match str::from_utf8(slice) {
+        Ok(str) => str.trim(),
+        _ => return -1,
+    };
+
+    let mut proc = Command::new("atom.py")
+        .stdin(Stdio::piped())
+        .spawn()
+        .unwrap();
+
+    proc.stdin
+        .as_mut()
+        .unwrap()
+        .write_all(atom.as_bytes())
+        .unwrap();
+
+    let status = proc.wait().unwrap();
+
+    let result = Atom::parser().check_finished(InputIter::new(atom));
+
+    match (status.success(), result) {
+        (true, Ok(_)) => {
+            eprintln!("agreement that {atom} is valid");
+            return 0;
+        }
+        (true, Err(ParserFinishedError::Err(it) | ParserFinishedError::Unfinished(it))) => {
+            panic!("gentoo-utils rejected valid atom: {atom}: {}", it.rest());
+        }
+        (false, Err(_)) => {
+            eprintln!("agreement that {atom} is invalid");
+            return -1;
+        }
+        (false, Ok(_)) => {
+            panic!("gentoo-utils accepted invalid atom: {atom}");
+        }
+    }
+}