1 files changed, 143 insertions, 0 deletions
diff --git a/python/vyos/template.py b/python/vyos/template.py
new file mode 100644
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+++ b/python/vyos/template.py
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+# Copyright 2019-2020 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 functools
+import os
+
+from ipaddress import ip_network
+from jinja2 import Environment
+from jinja2 import FileSystemLoader
+from vyos.defaults import directories
+from vyos.util import chmod, chown, makedir
+
+
+# Holds template filters registered via register_filter()
+_FILTERS = {}
+
+
+# reuse Environments with identical trim_blocks setting to improve performance
+@functools.lru_cache(maxsize=2)
+def _get_environment(trim_blocks):
+    env = Environment(
+        # Don't check if template files were modified upon re-rendering
+        auto_reload=False,
+        # Cache up to this number of templates for quick re-rendering
+        cache_size=100,
+        loader=FileSystemLoader(directories["templates"]),
+        trim_blocks=trim_blocks,
+    )
+    env.filters.update(_FILTERS)
+    return env
+
+
+def register_filter(name, func=None):
+    """Register a function to be available as filter in templates under given name.
+
+    It can also be used as a decorator, see below in this module for examples.
+
+    :raise RuntimeError:
+        when trying to register a filter after a template has been rendered already
+    :raise ValueError: when trying to register a name which was taken already
+    """
+    if func is None:
+        return functools.partial(register_filter, name)
+    if _get_environment.cache_info().currsize:
+        raise RuntimeError(
+            "Filters can only be registered before rendering the first template"
+        )
+    if name in _FILTERS:
+        raise ValueError(f"A filter with name {name!r} was registered already")
+    _FILTERS[name] = func
+    return func
+
+
+def render_to_string(template, content, trim_blocks=False, formater=None):
+    """Render a template from the template directory, raise on any errors.
+
+    :param template: the path to the template relative to the template folder
+    :param content: the dictionary of variables to put into rendering context
+    :param trim_blocks: controls the trim_blocks jinja2 feature
+    :param formater:
+        if given, it has to be a callable the rendered string is passed through
+
+    The parsed template files are cached, so rendering the same file multiple times
+    does not cause as too much overhead.
+    If used everywhere, it could be changed to load the template from Python
+    environment variables from an importable Python module generated when the Debian
+    package is build (recovering the load time and overhead caused by having the
+    file out of the code).
+    """
+    template = _get_environment(bool(trim_blocks)).get_template(template)
+    rendered = template.render(content)
+    if formater is not None:
+        rendered = formater(rendered)
+    return rendered
+
+
+def render(
+    destination,
+    template,
+    content,
+    trim_blocks=False,
+    formater=None,
+    permission=None,
+    user=None,
+    group=None,
+):
+    """Render a template from the template directory to a file, raise on any errors.
+
+    :param destination: path to the file to save the rendered template in
+    :param permission: permission bitmask to set for the output file
+    :param user: user to own the output file
+    :param group: group to own the output file
+
+    All other parameters are as for :func:`render_to_string`.
+    """
+    # Create the directory if it does not exist
+    folder = os.path.dirname(destination)
+    makedir(folder, user, group)
+
+    # As we are opening the file with 'w', we are performing the rendering before
+    # calling open() to not accidentally erase the file if rendering fails
+    rendered = render_to_string(template, content, trim_blocks, formater)
+
+    # Write to file
+    with open(destination, "w") as file:
+        chmod(file.fileno(), permission)
+        chown(file.fileno(), user, group)
+        file.write(rendered)
+
+
+##################################
+# Custom template filters follow #
+##################################
+
+
+@register_filter("address_from_cidr")
+def vyos_address_from_cidr(text):
+    """ Take an IPv4/IPv6 CIDR prefix and convert the network to an "address".
+    Example:
+    192.0.2.0/24 -> 192.0.2.0, 2001:db8::/48 -> 2001:db8::
+    """
+    return ip_network(text).network_address
+
+
+@register_filter("netmask_from_cidr")
+def vyos_netmask_from_cidr(text):
+    """ Take an IPv4/IPv6 CIDR prefix and convert the prefix length to a "subnet mask".
+    Example:
+    192.0.2.0/24 -> 255.255.255.0, 2001:db8::/48 -> ffff:ffff:ffff::
+    """
+    return ip_network(text).netmask