fix largest unsigned int roundtrip

Author: MarshalX

pytests/test_dag_cbor.py

@@ -137,11 +137,21 @@ def test_recursion_limit_exceed_on_nested_maps() -> None:
     assert 'in DAG-CBOR decoding' in str(exc_info.value)
 
 
-def test_dag_cbor_decode_largest_unsigned_int() -> None:
-    result = libipld.decode_dag_cbor(bytes.fromhex('1bffffffffffffffff'))
-    assert result == 2**64 - 1
+def test_dag_cbor_decode_largest_unsigned_int_roundtrip() -> None:
+    data = bytes.fromhex('1bffffffffffffffff')
 
+    decoded_result = libipld.decode_dag_cbor(data)
+    assert decoded_result == 2**64 - 1
 
-def test_dag_cbor_decode_smallest_negative_int() -> None:
-    result = libipld.decode_dag_cbor(bytes.fromhex('3bffffffffffffffff'))
-    assert result == -(2**64)
+    encoded_result = libipld.encode_dag_cbor(decoded_result)
+    assert encoded_result == data
+
+
+def test_dag_cbor_decode_smallest_negative_int_roundtrip() -> None:
+    data = bytes.fromhex('3bffffffffffffffff')
+
+    decoded_result = libipld.decode_dag_cbor(data)
+    assert decoded_result == -(2**64)
+
+    encoded_result = libipld.encode_dag_cbor(decoded_result)
+    assert encoded_result == data

src/lib.rs

@@ -231,7 +231,7 @@ fn encode_dag_cbor_from_pyobject<'py, W: Write>(
 
         Ok(())
     } else if obj.is_instance_of::<PyInt>() {
-        let i: i64 = obj.extract()?;
+        let i: i128 = obj.extract()?;
 
         if i.is_negative() {
             encode::write_u64(w, MajorKind::NegativeInt, -(i + 1) as u64)?