From 15bc07a8fe5d72bff673429f70b60fb8990fe3b4 Mon Sep 17 00:00:00 2001
From: Yuval Adam <yuval@y3xz.com>
Date: Thu, 24 Mar 2016 01:41:47 +0200
Subject: Add is_valid() impl and test

---
 README.md    |  6 ++++++
 test.py      | 13 +++++++++++++
 viewstate.py | 14 ++++++++++++++
 3 files changed, 33 insertions(+)
 create mode 100644 test.py
 create mode 100644 viewstate.py

diff --git a/README.md b/README.md
index d1f8de4..b59ed74 100644
--- a/README.md
+++ b/README.md
@@ -9,6 +9,12 @@ from viewstate import ViewState
 vs = ViewState(base64EncodedViewState)
 ```
 
+## Test
+
+```python
+python test.py
+```
+
 ## References
 
  - https://github.com/mutantzombie/JavaScript-ViewState-Parser
diff --git a/test.py b/test.py
new file mode 100644
index 0000000..84249b2
--- /dev/null
+++ b/test.py
@@ -0,0 +1,13 @@
+import unittest
+
+from viewstate import ViewState
+
+class TestViewState(unittest.TestCase):
+
+    def test_is_valid(self):
+        with open('samples/ngcs.sample', 'r') as f:
+            vs = ViewState(f.read())
+            self.assertTrue(vs.is_valid())
+
+if __name__ == '__main__':
+    unittest.main()
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
-- 
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