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# Authors: William Fagan
# Copyright (c) 2013-2017 William Fagan
# License: The MIT License (MIT)
import sys
import functools
from gzip import GzipFile
import zlib
from io import BytesIO
from collections import defaultdict
try:
import brotlicffi as brotli
except ImportError:
import brotli
import zstandard
from flask import request, after_this_request, current_app
if sys.version_info[:2] == (2, 6):
class GzipFile(GzipFile):
""" Backport of context manager support for python 2.6"""
def __enter__(self):
if self.fileobj is None:
raise ValueError("I/O operation on closed GzipFile object")
return self
def __exit__(self, *args):
self.close()
class DictCache(object):
def __init__(self):
self.data = {}
def get(self, key):
return self.data.get(key)
def set(self, key, value):
self.data[key] = value
class Compress(object):
"""
The Compress object allows your application to use Flask-Compress.
When initialising a Compress object you may optionally provide your
:class:`flask.Flask` application object if it is ready. Otherwise,
you may provide it later by using the :meth:`init_app` method.
:param app: optional :class:`flask.Flask` application object
:type app: :class:`flask.Flask` or None
"""
def __init__(self, app=None):
"""
An alternative way to pass your :class:`flask.Flask` application
object to Flask-Compress. :meth:`init_app` also takes care of some
default `settings`_.
:param app: the :class:`flask.Flask` application object.
"""
self.app = app
if app is not None:
self.init_app(app)
def init_app(self, app):
defaults = [
('COMPRESS_MIMETYPES', [
'application/javascript', # Obsolete (RFC 9239)
'application/json',
'text/css',
'text/html',
'text/javascript',
'text/xml',
]),
('COMPRESS_LEVEL', 6),
('COMPRESS_BR_LEVEL', 4),
('COMPRESS_BR_MODE', 0),
('COMPRESS_BR_WINDOW', 22),
('COMPRESS_BR_BLOCK', 0),
('COMPRESS_ZSTD_LEVEL', 3),
('COMPRESS_DEFLATE_LEVEL', -1),
('COMPRESS_MIN_SIZE', 500),
('COMPRESS_CACHE_KEY', None),
('COMPRESS_CACHE_BACKEND', None),
('COMPRESS_REGISTER', True),
('COMPRESS_STREAMS', True),
('COMPRESS_ALGORITHM', ['zstd', 'br', 'gzip', 'deflate']),
]
for k, v in defaults:
app.config.setdefault(k, v)
backend = app.config['COMPRESS_CACHE_BACKEND']
self.cache = backend() if backend else None
self.cache_key = app.config['COMPRESS_CACHE_KEY']
algo = app.config['COMPRESS_ALGORITHM']
if isinstance(algo, str):
self.enabled_algorithms = [i.strip() for i in algo.split(',')]
else:
self.enabled_algorithms = list(algo)
if (app.config['COMPRESS_REGISTER'] and
app.config['COMPRESS_MIMETYPES']):
app.after_request(self.after_request)
def _choose_compress_algorithm(self, accept_encoding_header):
"""
Determine which compression algorithm we're going to use based on the
client request. The `Accept-Encoding` header may list one or more desired
algorithms, together with a "quality factor" for each one (higher quality
means the client prefers that algorithm more).
:param accept_encoding_header: Content of the `Accept-Encoding` header
:return: name of a compression algorithm (`gzip`, `deflate`, `br`, 'zstd') or `None` if
the client and server don't agree on any.
"""
# A flag denoting that client requested using any (`*`) algorithm,
# in case a specific one is not supported by the server
fallback_to_any = False
# Map quality factors to requested algorithm names.
algos_by_quality = defaultdict(set)
# Set of supported algorithms
server_algos_set = set(self.enabled_algorithms)
for part in accept_encoding_header.lower().split(','):
part = part.strip()
if ';q=' in part:
# If the client associated a quality factor with an algorithm,
# try to parse it. We could do the matching using a regex, but
# the format is so simple that it would be overkill.
algo = part.split(';')[0].strip()
try:
quality = float(part.split('=')[1].strip())
except ValueError:
quality = 1.0
else:
# Otherwise, use the default quality
algo = part
quality = 1.0
if algo == '*':
if quality > 0:
fallback_to_any = True
elif algo == 'identity': # identity means 'no compression asked'
algos_by_quality[quality].add(None)
elif algo in server_algos_set:
algos_by_quality[quality].add(algo)
# Choose the algorithm with the highest quality factor that the server supports.
#
# If there are multiple equally good options, choose the first supported algorithm
# from server configuration.
#
# If the server doesn't support any algorithm that the client requested but
# there's a special wildcard algorithm request (`*`), choose the first supported
# algorithm.
for _, viable_algos in sorted(algos_by_quality.items(), reverse=True):
if len(viable_algos) == 1:
return viable_algos.pop()
elif len(viable_algos) > 1:
for server_algo in self.enabled_algorithms:
if server_algo in viable_algos:
return server_algo
if fallback_to_any:
return self.enabled_algorithms[0]
return None
def after_request(self, response):
app = self.app or current_app
vary = response.headers.get('Vary')
if not vary:
response.headers['Vary'] = 'Accept-Encoding'
elif 'accept-encoding' not in vary.lower():
response.headers['Vary'] = '{}, Accept-Encoding'.format(vary)
accept_encoding = request.headers.get('Accept-Encoding', '')
chosen_algorithm = self._choose_compress_algorithm(accept_encoding)
if (chosen_algorithm is None or
response.mimetype not in app.config["COMPRESS_MIMETYPES"] or
response.status_code < 200 or
response.status_code >= 300 or
(response.is_streamed and app.config["COMPRESS_STREAMS"] is False) or
"Content-Encoding" in response.headers or
(response.content_length is not None and
response.content_length < app.config["COMPRESS_MIN_SIZE"])):
return response
response.direct_passthrough = False
if self.cache is not None:
key = self.cache_key(request)
compressed_content = self.cache.get(key)
if compressed_content is None:
compressed_content = self.compress(app, response, chosen_algorithm)
self.cache.set(key, compressed_content)
else:
compressed_content = self.compress(app, response, chosen_algorithm)
response.set_data(compressed_content)
response.headers['Content-Encoding'] = chosen_algorithm
response.headers['Content-Length'] = response.content_length
# "123456789" => "123456789:gzip" - A strong ETag validator
# W/"123456789" => W/"123456789:gzip" - A weak ETag validator
etag = response.headers.get('ETag')
if etag:
response.headers['ETag'] = '{0}:{1}"'.format(etag[:-1], chosen_algorithm)
return response
def compressed(self):
def decorator(f):
@functools.wraps(f)
def decorated_function(*args, **kwargs):
@after_this_request
def compressor(response):
return self.after_request(response)
return f(*args, **kwargs)
return decorated_function
return decorator
def compress(self, app, response, algorithm):
if algorithm == 'gzip':
gzip_buffer = BytesIO()
with GzipFile(mode='wb',
compresslevel=app.config['COMPRESS_LEVEL'],
fileobj=gzip_buffer) as gzip_file:
gzip_file.write(response.get_data())
return gzip_buffer.getvalue()
elif algorithm == 'deflate':
return zlib.compress(response.get_data(),
app.config['COMPRESS_DEFLATE_LEVEL'])
elif algorithm == 'br':
return brotli.compress(response.get_data(),
mode=app.config['COMPRESS_BR_MODE'],
quality=app.config['COMPRESS_BR_LEVEL'],
lgwin=app.config['COMPRESS_BR_WINDOW'],
lgblock=app.config['COMPRESS_BR_BLOCK'])
elif algorithm == 'zstd':
return zstandard.ZstdCompressor(app.config['COMPRESS_ZSTD_LEVEL']).compress(response.get_data())