basic setup for BSON module, including some test code (that doesn't pass yet

bson.py

@@ -0,0 +1,61 @@
+"""Tools for dealing with Mongo's BSON data representation.
+
+Generally not needed to be used by application developers."""
+
+import unittest
+import types
+
+class InvalidBSON(Exception):
+    """Raised when trying to create a BSON object from invalid data.
+    """
+
+
+def is_valid(bson):
+    """Validate that the given string represents valid BSON data.
+
+    Returns True if the data represents a valid BSON object (which must be a
+    subclass of str), False otherwise.
+
+    Arguments:
+    - `bson`: the data to be validated
+    """
+    if not isinstance(bson, types.StringType):
+        return False
+    return True
+
+
+class BSON(str):
+    """BSON data.
+
+    Represents binary data storable in and retrievable from Mongo.
+    """
+    def __new__(cls, bson):
+        """Initialize a new BSON object with some data
+
+        The data given must be a string instance and represent a valid BSON
+        object, otherwise an InvalidBSON exception is raised.
+
+        Arguments:
+        - `bson`: the initial data
+        """
+        if not is_valid(bson):
+            raise InvalidBSON()
+
+        return str.__new__(cls, bson)
+
+
+class TestBSON(unittest.TestCase):
+    def setUp(self):
+        pass
+
+    def testValidate(self):
+        self.assertFalse(is_valid(100))
+        self.assertFalse(is_valid(u"test"))
+        self.assertFalse(is_valid(10.4))
+        self.assertFalse(is_valid("test"))
+        # The simplest valid BSON document
+        self.assertTrue(is_valid("\x05\x00\x00\x00\x00"))
+
+
+if __name__ == "__main__":
+    unittest.main()