diff --git a/src/pymsi/package.py b/src/pymsi/package.py
index 43ecaee..8249542 100644
--- a/src/pymsi/package.py
+++ b/src/pymsi/package.py
@@ -1,5 +1,6 @@
 import copy
 import io
+import mmap
 from pathlib import Path
 from typing import Iterator, Optional, Union
 
@@ -18,13 +19,14 @@
 
 
 class Package:
-    def __init__(self, path_or_bytesio: Union[Path, io.BytesIO]):
-        if isinstance(path_or_bytesio, io.BytesIO):
-            self.path = None
-            self.file = path_or_bytesio
-        else:
+    # TODO: consider typing.BinaryIO
+    def __init__(self, path_or_bytesio: Union[Path, io.BytesIO, mmap.mmap]):
+        if isinstance(path_or_bytesio, Path):
             self.path = path_or_bytesio.resolve(True)
             self.file = self.path.open("rb")
+        else:
+            self.path = None
+            self.file = path_or_bytesio
         self.tables = {}
         self.ole = None
         self.summary = None
diff --git a/tests/io.py b/tests/io.py
new file mode 100644
index 0000000..6636c2f
--- /dev/null
+++ b/tests/io.py
@@ -0,0 +1,49 @@
+import mmap
+from pathlib import Path
+
+import pytest
+
+import pymsi
+
+
+def read_package(path_or_bytesio):
+    with pymsi.Package(path_or_bytesio) as package:
+        msi = pymsi.Msi(package)
+        return msi
+
+
+# Function to read a package using Path
+def read_package_path(file_path):
+    path = Path(file_path)
+    return read_package(path)
+
+
+# Function to read a package using with open
+def read_package_with_open(file_path):
+    with open(file_path, "rb") as f:
+        return read_package(f)
+
+
+# Function to read a package using mmap
+def read_package_mmap(file_path):
+    with open(file_path, "r+b") as f:
+        mm = mmap.mmap(f.fileno(), 0)
+        return read_package(mm)
+
+
+# Test cases
+@pytest.mark.parametrize(
+    "read_package_func", [read_package_path, read_package_with_open, read_package_mmap]
+)
+def test_read_package(read_package_func):
+    test_file = "powertoys.msi"
+
+    msi = read_package_func(test_file)
+
+    size = (msi.package.ole.nb_sect * msi.package.ole.sector_size) + 512
+
+    print(size)
+
+
+if __name__ == "__main__":
+    pytest.main()