1 files changed, 107 insertions, 0 deletions
diff --git a/host/utils/rfnoc/yaml_utils.py b/host/utils/rfnoc/yaml_utils.py
new file mode 100644
index 000000000..e64556334
--- /dev/null
+++ b/host/utils/rfnoc/yaml_utils.py
@@ -0,0 +1,107 @@
+"""
+Copyright 2019 Ettus Research, A National Instrument Brand
+
+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, 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 General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <http://www.gnu.org/licenses/>.
+"""
+
+import json
+import logging
+import os
+import sys
+from ruamel import yaml
+
+# Allow jsonschema import to fail. If not available no schema validation will
+# be done (but warning will be printed for each skipped validation).
+try:
+    import jsonschema
+except ImportError:
+    logging.warning("Module jsonschema is not installed. Configuration files "
+                    "will not be validated against their schema.")
+
+
+def find_schema(schema_name, config_path):
+    """
+    Recursive search for schema file. Only looks for a file with appropriate
+    name without checking for content or accessibility.
+    This check will be performed later when trying to load the schema.
+    :param schema_name: name of schema file to search for
+    :param config_path: root path to start search in
+    :return: full path to schema file if found, None else
+    """
+    for root, _, _ in os.walk(config_path):
+        filename = os.path.join(root, schema_name)
+        if os.path.isfile(filename):
+            return filename
+    return None
+
+
+def validate_config(config, config_path):
+    """
+    Try to validate config.
+
+    config contains a configuration loaded from a yaml file. config is assumed
+    to be a dictionary which contains a key 'schema' which determines
+    which schema to validate against. The schema (json formatted) needs to be
+    located in config_path or any sub folder of it.
+    If "jsonschema" module cannot be loaded validation is skipped and config
+    is assumed to be valid. This way a configuration can also be loaded if
+    "jsonschema" is not available.
+    The method raises ValueError if no schema is defined in config or the
+    schema defined in config cannot be found. The validation itself may throw
+    a jsonschema.exceptions.ValidationError if config does not confirm to its
+    schema.
+    :param config: a dictionary to validate (loaded from yaml file).
+    :param config_path: a path holding schema definitions
+    """
+    if "jsonschema" not in sys.modules:
+        logging.warning("Skip schema validation (missing module jsonschema).")
+        return
+
+    if not "schema" in config:
+        raise ValueError("Missing schema in configuration.")
+
+    schema_name = config["schema"]
+    logging.debug("Validate against schema %s.", schema_name)
+
+    schema_file = find_schema('%s.json' % schema_name, config_path)
+    if not schema_file:
+        raise ValueError("Unknown schema %s." % schema_name)
+
+    logging.debug("Using schema file %s.", schema_file)
+
+    with open(schema_file) as stream:
+        jsonschema.validate(instance=config, schema=json.load(stream))
+        logging.debug("Configuration successful validated.")
+
+
+def load_config(config_file, config_path):
+    """
+    Wrapper method to unify loading of configuration files.
+    Beside loading the configuration (yaml file format) itself from config_file
+    this method also validates the configuration against a schema. The root
+    element of the configuration must load to a dictionary which contains a
+    "schema" key. The value of schema points to a file named {value}.json which
+    must be located in config_path or one of its sub folders.
+    .. seealso:: validate_config.
+    :param config_file: configuration to load
+    :param config_path: root path of schema definition files
+    :return:
+    """
+    logging.debug("Load configuration %s.", config_file)
+    with open(config_file) as stream:
+        rt_yaml = yaml.YAML(typ='rt')
+        config = rt_yaml.load(stream)
+        logging.debug("Configuration successful loaded.")
+        validate_config(config, config_path)
+        return config