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