Add a tiny utility class for keeping bi-directional mappings.

Use it in websocket and socks.

1 files changed, 26 insertions, 0 deletions

diff --git a/netlib/utils.py b/netlib/utils.py
index 44bed43a..905d948f 100644
--- a/netlib/utils.py
+++ b/netlib/utils.py
@@ -65,3 +65,29 @@ def getbit(byte, offset):
     mask = 1 << offset
     if byte & mask:
         return True
+
+
+class BiDi:
+    """
+        A wee utility class for keeping bi-directional mappings, like field
+        constants in protocols:
+
+        CONST = BiDi(a=1, b=2)
+        assert CONST.a == 1
+        assert CONST[1] == "a"
+    """
+    def __init__(self, **kwargs):
+        self.names = kwargs
+        self.values = {}
+        for k, v in kwargs.items():
+            self.values[v] = k
+        if len(self.names) != len(self.values):
+            raise ValueError("Duplicate values not allowed.")
+
+    def __getattr__(self, k):
+        if k in self.names:
+            return self.names[k]
+        raise AttributeError("No such attribute: %s", k)
+
+    def __getitem__(self, k):
+        return self.values[k]