calibre-web/cps/cache_buster.py

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# 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, dirnames, filenames in os.walk(static_folder):
for filename in filenames:
# compute version component
rooted_filename = os.path.join(dirpath, filename)
with open(rooted_filename, 'r') as f:
version = 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] = version
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':
values["q"] = bust_filename(values['filename'])
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