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diff --git a/src/mailman/rest/helpers.py b/src/mailman/rest/helpers.py
new file mode 100644
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+++ b/src/mailman/rest/helpers.py
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+# Copyright (C) 2010 by the Free Software Foundation, Inc.
+#
+# This file is part of GNU Mailman.
+#
+# GNU Mailman 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, either version 3 of the License, or (at your option)
+# any later version.
+#
+# GNU Mailman 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
+# GNU Mailman.  If not, see <http://www.gnu.org/licenses/>.
+
+"""Web service helpers."""
+
+from __future__ import absolute_import, unicode_literals
+
+__metaclass__ = type
+__all__ = [
+    'etag',
+    'path_to',
+    ]
+
+
+import json
+import hashlib
+
+from lazr.config import as_boolean
+from mailman.config import config
+
+
+
+def path_to(resource):
+    """Return the url path to a resource.
+
+    :param resource: The canonical path to the resource, relative to the
+        system base URI.
+    :type resource: string
+    :return: The full path to the resource.
+    :rtype: string
+    """
+    return '{0}://{1}:{2}/{3}/{4}'.format(
+        ('https' if as_boolean(config.webservice.use_https) else 'http'),
+        config.webservice.hostname,
+        config.webservice.port,
+        config.webservice.api_version,
+        (resource[1:] if resource.startswith('/') else resource),
+        )
+
+
+
+def etag(resource):
+    """Calculate the etag and return a JSON representation.
+
+    The input is a dictionary representing the resource.  This dictionary must
+    not contain an `http_etag` key.  This function calculates the etag by
+    using the sha1 hexdigest of the repr of the dictionary.  It then inserts
+    this value under the `http_etag` key, and returns the JSON representation
+    of the modified dictionary.
+
+    :param resource: The original resource representation.
+    :type resource: dictionary
+    :return: JSON representation of the modified dictionary.
+    :rtype string
+    """
+    assert 'http_etag' not in resource, 'Resource already etagged'
+    etag = hashlib.sha1(repr(resource)).hexdigest()
+    resource['http_etag'] = '"{0}"'.format(etag)
+    return json.dumps(resource)