1 files changed, 52 insertions, 0 deletions
diff --git a/python/pyasn1/pyasn1/type/tagmap.py b/python/pyasn1/pyasn1/type/tagmap.py
new file mode 100644
index 000000000..7cec3a10e
--- /dev/null
+++ b/python/pyasn1/pyasn1/type/tagmap.py
@@ -0,0 +1,52 @@
+from pyasn1 import error
+
+class TagMap:
+    def __init__(self, posMap={}, negMap={}, defType=None):
+        self.__posMap = posMap.copy()
+        self.__negMap = negMap.copy()
+        self.__defType = defType
+        
+    def __contains__(self, tagSet):
+        return tagSet in self.__posMap or \
+               self.__defType is not None and tagSet not in self.__negMap
+
+    def __getitem__(self, tagSet):
+        if tagSet in self.__posMap:
+            return self.__posMap[tagSet]
+        elif tagSet in self.__negMap:
+            raise error.PyAsn1Error('Key in negative map')
+        elif self.__defType is not None:
+            return self.__defType
+        else:
+            raise KeyError()
+
+    def __repr__(self):
+        s = '%r/%r' % (self.__posMap, self.__negMap)
+        if self.__defType is not None:
+            s = s + '/%r' % (self.__defType,)
+        return s
+
+    def clone(self, parentType, tagMap, uniq=False):
+        if self.__defType is not None and tagMap.getDef() is not None:
+            raise error.PyAsn1Error('Duplicate default value at %s' % (self,))
+        if tagMap.getDef() is not None:
+            defType = tagMap.getDef()
+        else:
+            defType = self.__defType
+            
+        posMap = self.__posMap.copy()
+        for k in tagMap.getPosMap():
+            if uniq and k in posMap:
+                raise error.PyAsn1Error('Duplicate positive key %s' % (k,))
+            posMap[k] = parentType
+
+        negMap = self.__negMap.copy()
+        negMap.update(tagMap.getNegMap())
+        
+        return self.__class__(
+            posMap, negMap, defType,
+            )
+
+    def getPosMap(self): return self.__posMap.copy()
+    def getNegMap(self): return self.__negMap.copy()
+    def getDef(self): return self.__defType