Add debug assertions for the start and len invariants

Author: pvdrz

src/exec/use_pty/pipe/ring_buffer.rs

@@ -51,6 +51,9 @@ impl RingBuffer {
 
         self.len += inserted_len;
 
+        debug_assert!(self.start < Self::LEN);
+        debug_assert!(self.len <= Self::LEN);
+
         Ok(inserted_len)
     }
 
@@ -82,10 +85,13 @@ impl RingBuffer {
         };
 
         self.start += removed_len;
-        self.start %= self.storage.len();
+        self.start %= Self::LEN;
 
         self.len -= removed_len;
 
+        debug_assert!(self.start < Self::LEN);
+        debug_assert!(self.len <= Self::LEN);
+
         Ok(removed_len)
     }
 }