Simplify SliceReader

The maximum recursion limit tracked within `decode_dag_cbor_to_pyobject()`,
hence it doesn't need to be part of the SliceReader.

Author: vmx

src/lib.rs

@@ -20,16 +20,15 @@ mod marker {
     pub const F64: u8 = 0xfb;
 }
 
-// Copy from cbor4ii/src/utils.rs.
+// Based on cbor4ii/src/utils.rs.
 /// An in-memory reader.
 struct SliceReader<'a> {
     buf: &'a [u8],
-    limit: usize,
 }
 
 impl SliceReader<'_> {
     fn new(buf: &[u8]) -> SliceReader<'_> {
-        SliceReader { buf, limit: 256 }
+        SliceReader { buf }
     }
 }
 
@@ -47,21 +46,6 @@ impl<'de> dec::Read<'de> for SliceReader<'de> {
         let len = core::cmp::min(self.buf.len(), n);
         self.buf = &self.buf[len..];
     }
-
-    #[inline]
-    fn step_in(&mut self) -> bool {
-        if let Some(limit) = self.limit.checked_sub(1) {
-            self.limit = limit;
-            true
-        } else {
-            false
-        }
-    }
-
-    #[inline]
-    fn step_out(&mut self) {
-        self.limit += 1;
-    }
 }
 
 fn cid_hash_to_pydict<'py>(py: Python<'py>, cid: &Cid) -> Bound<'py, PyDict> {