Fix smallest CBOR integer

Author: MarshalX

pytests/test_dag_cbor.py

@@ -135,3 +135,13 @@ def test_recursion_limit_exceed_on_nested_maps() -> None:
         libipld.decode_dag_cbor(dag_cbor)
 
     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_smallest_negative_int() -> None:
+    result = libipld.decode_dag_cbor(bytes.fromhex('3bffffffffffffffff'))
+    assert result == -(2**64)

src/lib.rs

@@ -122,7 +122,7 @@ fn decode_dag_cbor_to_pyobject<R: Read + Seek>(
     let major = decode::read_major(r)?;
     Ok(match major.kind() {
         MajorKind::UnsignedInt => decode::read_uint(r, major)?.into_pyobject(py)?.into(),
-        MajorKind::NegativeInt => (-1 - decode::read_uint(r, major)? as i64).into_pyobject(py)?.into(),
+        MajorKind::NegativeInt => (-1 - decode::read_uint(r, major)? as i128).into_pyobject(py)?.into(),
         MajorKind::ByteString => {
             let len = decode::read_uint(r, major)?;
             PyBytes::new(py, &decode::read_bytes(r, len)?).into_pyobject(py)?.into()