1 files changed, 60 insertions, 0 deletions
diff --git a/distbuild/route_map.py b/distbuild/route_map.py
new file mode 100644
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+++ b/distbuild/route_map.py
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+# distbuild/route_map.py -- map message ids for routing purposes
+#
+# Copyright (C) 2014  Codethink Limited
+# 
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; version 2 of the License.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License along
+# with this program; if not, write to the Free Software Foundation, Inc.,
+# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA..
+
+
+class RouteMap(object):
+
+    '''Map message identifiers for routing purposes.
+    
+    Various state machines need to handle requests coming from multiple
+    sources, and they need to keep track of which responses should be
+    sent to which requestors. This class provides tools for keeping
+    track of that.
+    
+    Each message is expected to have a unique identifier of some sort.
+    The incoming request message has one, and all responses to it need
+    to keep that. An incoming request might be converted into one or more
+    outgoing requests, each with its own unique id. The responses to all
+    of those need to be mapped back to the original incoming request.
+    
+    For this class, we care about "incoming id" and "outgoing id".
+    There can be multiple outgoing identifiers for one incoming one.
+    
+    '''
+    
+    def __init__(self):
+        self._routes = {}
+    
+    def add(self, incoming_id, outgoing_id):
+        assert (outgoing_id not in self._routes or 
+                self._routes[outgoing_id] == incoming_id)
+        self._routes[outgoing_id] = incoming_id
+        
+    def get_incoming_id(self, outgoing_id):
+        '''Get the incoming id corresponding to an outgoing one.
+        
+        Raise KeyError if not found.
+        
+        '''
+
+        return self._routes[outgoing_id]
+
+    def get_outgoing_ids(self, incoming_id):
+        return [o for (o, i) in self._routes.iteritems() if i == incoming_id]
+
+    def remove(self, outgoing_id):
+        del self._routes[outgoing_id]