mirror of
https://github.com/Hopiu/django-imagekit.git
synced 2026-03-17 05:40:25 +00:00
87 lines
2.6 KiB
Python
87 lines
2.6 KiB
Python
from django.core.exceptions import ImproperlyConfigured
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from django.utils.importlib import import_module
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class PessimisticImageCacheBackend(object):
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"""
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A very safe image cache backend. Guarantees that files will always be
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available, but at the cost of hitting the storage backend.
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"""
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def is_invalid(self, file):
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if not getattr(file, '_file', None):
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# No file on object. Have to check storage.
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return not file.storage.exists(file.name)
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return False
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def validate(self, file):
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"""
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Generates a new image by running the processors on the source file.
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"""
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if self.is_invalid(file):
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file.generate(save=True)
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def invalidate(self, file):
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file.delete(save=False)
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def clear(self, file):
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file.delete(save=False)
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class NonValidatingImageCacheBackend(object):
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"""
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A backend that is super optimistic about the existence of spec files. It
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will hit your file storage much less frequently than the pessimistic
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backend, but it is technically possible for a cache file to be missing
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after validation.
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"""
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def validate(self, file):
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"""
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NonValidatingImageCacheBackend has faith, so validate's a no-op.
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"""
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pass
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def invalidate(self, file):
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"""
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Immediately generate a new spec file upon invalidation.
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"""
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file.generate(save=True)
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def clear(self, file):
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file.delete(save=False)
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_default_image_cache_backend = None
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def get_default_image_cache_backend():
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"""
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Get the default image cache backend. Uses the same method as
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django.core.file.storage.get_storage_class
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"""
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global _default_image_cache_backend
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if not _default_image_cache_backend:
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from .settings import DEFAULT_IMAGE_CACHE_BACKEND as import_path
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try:
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dot = import_path.rindex('.')
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except ValueError:
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raise ImproperlyConfigured("%s isn't an image cache backend module." % \
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import_path)
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module, classname = import_path[:dot], import_path[dot+1:]
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try:
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mod = import_module(module)
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except ImportError, e:
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raise ImproperlyConfigured('Error importing image cache backend module %s: "%s"' % (module, e))
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try:
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cls = getattr(mod, classname)
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_default_image_cache_backend = cls()
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except AttributeError:
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raise ImproperlyConfigured('Image cache backend module "%s" does not define a "%s" class.' % (module, classname))
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return _default_image_cache_backend
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