def _etag_is_valid(image_attrs, check_etag, is_original):
"""
Returns a tuple of (True, last_modified_time) if the current ETag for the
image described by image_attrs matches the given ETag.
Returns (False, new_modified_time) if the current ETag value is different.
"""
modified_time = image_engine.get_image_original_modified_time(image_attrs) \
if is_original else \
image_engine.get_image_modified_time(image_attrs)
if modified_time == 0:
# Return False to re-generate the image and re-store the modified time
return (False, 0)
current_etag = etag(
str(modified_time),
image_attrs.get_cache_key()
)
return ((current_etag == check_etag), modified_time)
def _add_http_caching_headers(response, image_attrs, last_modified_time, expiry_seconds):
"""
Sets the standard client-side cache control headers expected for an HTTP
200 or 304 response. The last modified time should be given as number of
seconds since the epoch. The expiry time is as described for ImageWrapper.
"""
# This (and others below) auto-converted to correct format by Werkzeug
response.date = time.time()
if expiry_seconds != 0:
if expiry_seconds > 0:
response.cache_control.public = True
response.cache_control.max_age = expiry_seconds
response.expires = int(time.time() + expiry_seconds)
else:
response.cache_control.public = True
response.cache_control.no_cache = True
response.expires = 0
if expiry_seconds >= 0:
response.headers['ETag'] = etag(
str(last_modified_time),
image_attrs.get_cache_key()
)
