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      1 # (c) 2005 Ian Bicking and contributors; written for Paste (http://pythonpaste.org)
      2 # Licensed under the MIT license: http://www.opensource.org/licenses/mit-license.php
      3 
      4 # (c) 2005 Ian Bicking and contributors; written for Paste (http://pythonpaste.org)
      5 # Licensed under the MIT license: http://www.opensource.org/licenses/mit-license.php
      6 
      7 """
      8 WSGI middleware
      9 
     10 Gzip-encodes the response.
     11 """
     12 
     13 import gzip
     14 from paste.response import header_value, remove_header
     15 from paste.httpheaders import CONTENT_LENGTH
     16 import six
     17 
     18 class GzipOutput(object):
     19     pass
     20 
     21 class middleware(object):
     22 
     23     def __init__(self, application, compress_level=6):
     24         self.application = application
     25         self.compress_level = int(compress_level)
     26 
     27     def __call__(self, environ, start_response):
     28         if 'gzip' not in environ.get('HTTP_ACCEPT_ENCODING', ''):
     29             # nothing for us to do, so this middleware will
     30             # be a no-op:
     31             return self.application(environ, start_response)
     32         response = GzipResponse(start_response, self.compress_level)
     33         app_iter = self.application(environ,
     34                                     response.gzip_start_response)
     35         if app_iter is not None:
     36             response.finish_response(app_iter)
     37 
     38         return response.write()
     39 
     40 class GzipResponse(object):
     41 
     42     def __init__(self, start_response, compress_level):
     43         self.start_response = start_response
     44         self.compress_level = compress_level
     45         self.buffer = six.BytesIO()
     46         self.compressible = False
     47         self.content_length = None
     48 
     49     def gzip_start_response(self, status, headers, exc_info=None):
     50         self.headers = headers
     51         ct = header_value(headers,'content-type')
     52         ce = header_value(headers,'content-encoding')
     53         self.compressible = False
     54         if ct and (ct.startswith('text/') or ct.startswith('application/')) \
     55             and 'zip' not in ct:
     56             self.compressible = True
     57         if ce:
     58             self.compressible = False
     59         if self.compressible:
     60             headers.append(('content-encoding', 'gzip'))
     61         remove_header(headers, 'content-length')
     62         self.headers = headers
     63         self.status = status
     64         return self.buffer.write
     65 
     66     def write(self):
     67         out = self.buffer
     68         out.seek(0)
     69         s = out.getvalue()
     70         out.close()
     71         return [s]
     72 
     73     def finish_response(self, app_iter):
     74         if self.compressible:
     75             output = gzip.GzipFile(mode='wb', compresslevel=self.compress_level,
     76                 fileobj=self.buffer)
     77         else:
     78             output = self.buffer
     79         try:
     80             for s in app_iter:
     81                 output.write(s)
     82             if self.compressible:
     83                 output.close()
     84         finally:
     85             if hasattr(app_iter, 'close'):
     86                 app_iter.close()
     87         content_length = self.buffer.tell()
     88         CONTENT_LENGTH.update(self.headers, content_length)
     89         self.start_response(self.status, self.headers)
     90 
     91 def filter_factory(application, **conf):
     92     import warnings
     93     warnings.warn(
     94         'This function is deprecated; use make_gzip_middleware instead',
     95         DeprecationWarning, 2)
     96     def filter(application):
     97         return middleware(application)
     98     return filter
     99 
    100 def make_gzip_middleware(app, global_conf, compress_level=6):
    101     """
    102     Wrap the middleware, so that it applies gzipping to a response
    103     when it is supported by the browser and the content is of
    104     type ``text/*`` or ``application/*``
    105     """
    106     compress_level = int(compress_level)
    107     return middleware(app, compress_level=compress_level)
    108