ofproto: detect supported OFP versions automatically.

And add helper functions to get OFP modules/class for a given OFP version.

Signed-off-by: Isaku Yamahata <yamahata@valinux.co.jp>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>

ryu/ofproto/__init__.py

@@ -0,0 +1,59 @@
+# Copyright (C) 2013 Nippon Telegraph and Telephone Corporation.
+# Copyright (C) 2013 Isaku Yamahata <yamahata at private email ne jp>
+#
+# 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.
+
+import glob
+import inspect
+import os.path
+
+from ryu import utils
+
+
+_OFPROTO_DIR = os.path.dirname(__file__)
+_OFPROTO_PARSER_FILE_NAMES = glob.glob(os.path.join(
+    _OFPROTO_DIR, 'ofproto_v[0-9]*_[0-9]*_parser.py'))
+_OFPROTO_PARSER_FILE_NAMES = [os.path.basename(name)
+                              for name in _OFPROTO_PARSER_FILE_NAMES]
+
+
+_OFPROTO_MODULES = {}
+for parser_file_name in _OFPROTO_PARSER_FILE_NAMES:
+    # drop lasting '.py'
+    parser_mod_name = __name__ + '.' + parser_file_name[:-3]
+    consts_mod_name = parser_mod_name[:-7]      # drop lasting '_parser'
+    try:
+        parser_mod = utils.import_module(parser_mod_name)
+        consts_mod = utils.import_module(consts_mod_name)
+    except:
+        continue
+
+    assert consts_mod.OFP_VERSION not in _OFPROTO_MODULES
+    _OFPROTO_MODULES[consts_mod.OFP_VERSION] = (consts_mod, parser_mod)
+
+
+def get_ofp_module(ofp_version):
+    """get modules pair for the constants and parser of OF-wire of
+    a given OF version.
+    """
+    return _OFPROTO_MODULES[ofp_version]
+
+
+def get_ofp_cls(ofp_version, name):
+    """get class for name of a given OF version"""
+    (_consts_mod, parser_mod) = get_ofp_module(ofp_version)
+    for i in inspect.getmembers(parser_mod, inspect.isclass):
+        if i[0] == name:
+            return i[1]
+    return None