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parallel-library/cps/cache_buster.py

77 lines
2.9 KiB
Python

# This file is part of the Calibre-Web (https://github.com/janeczku/calibre-web)
# Copyright (C) 2016-2019 jkrehm andy29485 OzzieIsaacs
#
# 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/>.
# Inspired by https://github.com/ChrisTM/Flask-CacheBust
# Uses query strings so CSS font files are found without having to resort to absolute URLs
import hashlib
import os
def init_cache_busting(app):
"""
Configure `app` to so that `url_for` adds a unique query string to URLs generated
for the `'static'` endpoint.
This allows setting long cache expiration values on static resources
because whenever the resource changes, so does its URL.
"""
static_folder = os.path.join(app.static_folder, '') # path to the static file folder, with trailing slash
hash_table = {} # map of file hashes
app.logger.debug('Computing cache-busting values...')
# compute file hashes
for dirpath, __, filenames in os.walk(static_folder):
for filename in filenames:
# compute version component
rooted_filename = os.path.join(dirpath, filename)
with open(rooted_filename, 'rb') as f:
file_hash = hashlib.md5(f.read()).hexdigest()[:7]
# save version to tables
file_path = rooted_filename.replace(static_folder, "")
file_path = file_path.replace("\\", "/") # Convert Windows path to web path
hash_table[file_path] = file_hash
app.logger.debug('Finished computing cache-busting values')
def bust_filename(filename):
return hash_table.get(filename, "")
def unbust_filename(filename):
return filename.split("?", 1)[0]
@app.url_defaults
def reverse_to_cache_busted_url(endpoint, values):
"""
Make `url_for` produce busted filenames when using the 'static' endpoint.
"""
if endpoint == "static":
file_hash = bust_filename(values["filename"])
if file_hash:
values["q"] = file_hash
def debusting_static_view(filename):
"""
Serve a request for a static file having a busted name.
"""
return original_static_view(filename=unbust_filename(filename))
# Replace the default static file view with our debusting view.
original_static_view = app.view_functions["static"]
app.view_functions["static"] = debusting_static_view