Add is_valid() impl and test

1 files changed, 14 insertions, 0 deletions

diff --git a/viewstate.py b/viewstate.py
new file mode 100644
index 0000000..30da967
--- /dev/null
+++ b/viewstate.py
@@ -0,0 +1,14 @@
+from base64 import b64decode, b64encode
+
+
+class ViewState(object):
+
+    def __init__(self, base64_encoded):
+        self.base64_encoded = base64_encoded
+        self.raw = b64decode(self.base64_encoded)
+
+    def is_valid(self):
+        format_marker = b'\xff'
+        version_marker = b'\x01'
+        preamble = format_marker + version_marker
+        return self.raw[:2] == preamble