Merge pull request #326 from thomas-mangin/T2265

dhcp: T2265: refactor DHCP class

1 files changed, 55 insertions, 0 deletions

diff --git a/python/vyos/template.py b/python/vyos/template.py
new file mode 100644
index 000000000..e559120c0
--- /dev/null
+++ b/python/vyos/template.py
@@ -0,0 +1,55 @@
+# Copyright 2019 VyOS maintainers and contributors <maintainers@vyos.io>
+#
+# This library is free software; you can redistribute it and/or
+# modify it under the terms of the GNU Lesser General Public
+# License as published by the Free Software Foundation; either
+# version 2.1 of the License, or (at your option) any later version.
+#
+# This library 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
+# Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public
+# License along with this library.  If not, see <http://www.gnu.org/licenses/>.
+
+import os
+
+from jinja2 import Environment
+from jinja2 import FileSystemLoader
+
+from vyos.defaults import directories
+
+
+# reuse the same Environment to improve performance
+_templates_env = Environment(loader=FileSystemLoader(directories['templates']))
+_templates_mem = {}
+
+def render(destination, template, content):
+    """
+    render a template from the template directory, it will raise on any errors
+    destination: the file where the rendered template must be saved
+    template: the path to the template relative to the template folder
+    content: the dictionary to use to render the template
+
+    This classes cache the renderer, so rendering the same file multiple time
+    does not cause as too much overhead. If use everywhere, it could be changed
+    and load the template from python environement variables from an import 
+    python module generated when the debian package is build 
+    (recovering the load time and overhead caused by having the file out of the code)
+    """
+
+    # Setup a renderer for the given template
+    # This is cached and re-used for performance
+    if template not in _templates_mem:
+        _templates_mem[template] = _templates_env.get_template(template)
+    template = _templates_mem[template]
+
+    # As we are opening the file with 'w', we are performing the rendering
+    # before calling open() to not accidentally erase the file if the 
+    # templating fails
+    content = template.render(content)
+
+    # Write client config file
+    with open(destination, 'w') as f:
+        f.write(content)