diff --git a/synapse/streams/config.py b/synapse/streams/config.py
new file mode 100644
index 0000000000..2434844d80
--- /dev/null
+++ b/synapse/streams/config.py
@@ -0,0 +1,84 @@
+# -*- coding: utf-8 -*-
+# Copyright 2014 matrix.org
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from synapse.api.errors import SynapseError
+from synapse.types import StreamToken
+
+import logging
+
+
+logger = logging.getLogger(__name__)
+
+
+class PaginationConfig(object):
+
+ """A configuration object which stores pagination parameters."""
+
+ def __init__(self, from_token=None, to_token=None, direction='f',
+ limit=0):
+ self.from_token = from_token
+ self.to_token = to_token
+ self.direction = 'f' if direction == 'f' else 'b'
+ self.limit = int(limit)
+
+ @classmethod
+ def from_request(cls, request, raise_invalid_params=True):
+ def get_param(name, default=None):
+ lst = request.args.get(name, [])
+ if len(lst) > 1:
+ raise SynapseError(
+ 400, "%s must be specified only once" % (name,)
+ )
+ elif len(lst) == 1:
+ return lst[0]
+ else:
+ return default
+
+ direction = get_param("dir", 'f')
+ if direction not in ['f', 'b']:
+ raise SynapseError(400, "'dir' parameter is invalid.")
+
+ from_tok = get_param("from")
+ to_tok = get_param("to")
+
+ try:
+ if from_tok == "END":
+ from_tok = None # For backwards compat.
+ elif from_tok:
+ from_tok = StreamToken.from_string(from_tok)
+ except:
+ raise SynapseError(400, "'from' paramater is invalid")
+
+ try:
+ if to_tok:
+ to_tok = StreamToken.from_string(to_tok)
+ except:
+ raise SynapseError(400, "'to' paramater is invalid")
+
+ limit = get_param("limit", "0")
+ if not limit.isdigit():
+ raise SynapseError(400, "'limit' parameter must be an integer.")
+
+ try:
+ return PaginationConfig(from_tok, to_tok, direction, limit)
+ except:
+ logger.exception("Failed to create pagination config")
+ raise SynapseError(400, "Invalid request.")
+
+ def __str__(self):
+ return (
+ "<PaginationConfig from_tok=%s, to_tok=%s, "
+ "direction=%s, limit=%s>"
+ ) % (self.from_tok, self.to_tok, self.direction, self.limit)
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