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"""
Functions that modify an HTTP request or response in some way.
"""
# This group of functions are run as part of the response handling, after
# everything else, including all response middleware. Think of them as
# "compulsory response middleware". Be careful about what goes here, because
# it's a little fiddly to override this behavior, so they should be truly
# universally applicable.
def fix_location_header(request, response):
"""
Ensures that we always use an absolute URI in any location header in the
response. This is required by RFC 2616, section 14.30.
Code constructing response objects is free to insert relative paths, as
this function converts them to absolute paths.
"""
if 'Location' in response and request.get_host():
response['Location'] = request.build_absolute_uri(response['Location'])
return response
def conditional_content_removal(request, response):
"""
Removes the content of responses for HEAD requests, 1xx, 204 and 304
responses. Ensures compliance with RFC 2616, section 4.3.
"""
if 100 <= response.status_code < 200 or response.status_code in (204, 304):
response.content = ''
response['Content-Length'] = 0
if request.method == 'HEAD':
response.content = ''
return response
def fix_IE_for_attach(request, response):
"""
This function will prevent Django from serving a Content-Disposition header
while expecting the browser to cache it (only when the browser is IE). This
leads to IE not allowing the client to download.
"""
if 'MSIE' not in request.META.get('HTTP_USER_AGENT', '').upper():
return response
offending_headers = ('no-cache', 'no-store')
if response.has_header('Content-Disposition'):
try:
del response['Pragma']
except KeyError:
pass
if response.has_header('Cache-Control'):
cache_control_values = [value.strip() for value in
response['Cache-Control'].split(',')
if value.strip().lower() not in offending_headers]
if not len(cache_control_values):
del response['Cache-Control']
else:
response['Cache-Control'] = ', '.join(cache_control_values)
return response
def fix_IE_for_vary(request, response):
"""
This function will fix the bug reported at
http://support.microsoft.com/kb/824847/en-us?spid=8722&sid=global
by clearing the Vary header whenever the mime-type is not safe
enough for Internet Explorer to handle. Poor thing.
"""
if 'MSIE' not in request.META.get('HTTP_USER_AGENT', '').upper():
return response
# These mime-types that are decreed "Vary-safe" for IE:
safe_mime_types = ('text/html', 'text/plain', 'text/sgml')
# The first part of the Content-Type field will be the MIME type,
# everything after ';', such as character-set, can be ignored.
if response['Content-Type'].split(';')[0] not in safe_mime_types:
try:
del response['Vary']
except KeyError:
pass
return response
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