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authorNeels Hofmeyr <neels@hofmeyr.de>2017-03-28 12:16:58 +0200
committerNeels Hofmeyr <neels@hofmeyr.de>2017-03-28 12:37:17 +0200
commitdae3d3c47906379061d57854fd140e8a7a12a25c (patch)
tree120abdd29437f4d78e971685aa21300439c6f449 /src/osmo_gsm_tester/config.py
parent0f2f19e9aa736f86a5a7cc3cbd2f5b1e325b0202 (diff)
initial import0.1
The original osmo-gsm-tester was an internal development at sysmocom, mostly by D. Laszlo Sitzer <dlsitzer@sysmocom.de>, of which this public osmo-gsm-tester is a refactoring / rewrite. This imports an early state of the refactoring and is not functional yet. Bits from the earlier osmo-gsm-tester will be added as needed. The earlier commit history is not imported.
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+# osmo_gsm_tester: read and validate config files
+#
+# Copyright (C) 2016-2017 by sysmocom - s.f.m.c. GmbH
+#
+# Author: Neels Hofmeyr <neels@hofmeyr.de>
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as
+# published by the Free Software Foundation, either version 3 of the
+# License, or (at your option) any later version.
+#
+# 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 Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+# discussion for choice of config file format:
+#
+# Python syntax is insane, because it allows the config file to run arbitrary
+# python commands.
+#
+# INI file format is nice and simple, but it doesn't allow having the same
+# section numerous times (e.g. to define several modems or BTS models) and does
+# not support nesting.
+#
+# JSON has too much braces and quotes to be easy to type
+#
+# YAML formatting is lean, but too powerful. The normal load() allows arbitrary
+# code execution. There is safe_load(). But YAML also allows several
+# alternative ways of formatting, better to have just one authoritative style.
+# Also it would be better to receive every setting as simple string rather than
+# e.g. an IMSI as an integer.
+#
+# The Python ConfigParserShootout page has numerous contestants, but it we want
+# to use widely used, standardized parsing code without re-inventing the wheel.
+# https://wiki.python.org/moin/ConfigParserShootout
+#
+# The optimum would be a stripped down YAML format.
+# In the lack of that, we shall go with yaml.load_safe() + a round trip
+# (feeding back to itself), converting keys to lowercase and values to string.
+
+import yaml
+import re
+import os
+
+from . import log
+
+def read(path, schema=None):
+ with log.Origin(path):
+ with open(path, 'r') as f:
+ config = yaml.safe_load(f)
+ config = _standardize(config)
+ if schema:
+ validate(config, schema)
+ return config
+
+def tostr(config):
+ return _tostr(_standardize(config))
+
+def _tostr(config):
+ return yaml.dump(config, default_flow_style=False)
+
+def _standardize_item(item):
+ if isinstance(item, (tuple, list)):
+ return [_standardize_item(i) for i in item]
+ if isinstance(item, dict):
+ return dict([(key.lower(), _standardize_item(val)) for key,val in item.items()])
+ return str(item)
+
+def _standardize(config):
+ config = yaml.safe_load(_tostr(_standardize_item(config)))
+ return config
+
+
+KEY_RE = re.compile('[a-zA-Z][a-zA-Z0-9_]*')
+
+def band(val):
+ if val in ('GSM-1800', 'GSM-1900'):
+ return
+ raise ValueError('Unknown GSM band: %r' % val)
+
+INT = 'int'
+STR = 'str'
+BAND = 'band'
+SCHEMA_TYPES = {
+ INT: int,
+ STR: str,
+ BAND: band,
+ }
+
+def is_dict(l):
+ return isinstance(l, dict)
+
+def is_list(l):
+ return isinstance(l, (list, tuple))
+
+def validate(config, schema):
+ '''Make sure the given config dict adheres to the schema.
+ The schema is a dict of 'dict paths' in dot-notation with permitted
+ value type. All leaf nodes are validated, nesting dicts are implicit.
+
+ validate( { 'a': 123, 'b': { 'b1': 'foo', 'b2': [ 1, 2, 3 ] } },
+ { 'a': int,
+ 'b.b1': str,
+ 'b.b2[]': int } )
+
+ Raise a ValueError in case the schema is violated.
+ '''
+
+ def validate_item(path, value, schema):
+ want_type = schema.get(path)
+
+ if is_list(value):
+ if want_type:
+ raise ValueError('config item is a list, should be %r: %r' % (want_type, path))
+ path = path + '[]'
+ want_type = schema.get(path)
+
+ if not want_type:
+ if is_dict(value):
+ nest(path, value, schema)
+ return
+ if is_list(value) and value:
+ for list_v in value:
+ validate_item(path, list_v, schema)
+ return
+ raise ValueError('config item not known: %r' % path)
+
+ if want_type not in SCHEMA_TYPES:
+ raise ValueError('unknown type %r at %r' % (want_type, path))
+
+ if is_dict(value):
+ raise ValueError('config item is dict but should be a leaf node of type %r: %r'
+ % (want_type, path))
+
+ if is_list(value):
+ for list_v in value:
+ validate_item(path, list_v, schema)
+ return
+
+ with log.Origin(item=path):
+ type_validator = SCHEMA_TYPES.get(want_type)
+ type_validator(value)
+
+ def nest(parent_path, config, schema):
+ if parent_path:
+ parent_path = parent_path + '.'
+ else:
+ parent_path = ''
+ for k,v in config.items():
+ if not KEY_RE.fullmatch(k):
+ raise ValueError('invalid config key: %r' % k)
+ path = parent_path + k
+ validate_item(path, v, schema)
+
+ nest(None, config, schema)
+
+# vim: expandtab tabstop=4 shiftwidth=4