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compressed_textfield.py
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compressed_textfield.py
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from base64 import binascii
from django.db import models
from django.utils.text import compress_string
from django.db.models.signals import post_init
from django.utils.encoding import smart_unicode
from south.modelsinspector import add_introspection_rules
add_introspection_rules([], ["^utils\.compressed_textfield\.StoryField"])
add_introspection_rules([], ["^utils\.compressed_textfield\.CompressedTextField"])
def uncompress_string(s):
'''helper function to reverse django.utils.text.compress_string'''
import cStringIO, gzip
try:
zbuf = cStringIO.StringIO(s)
zfile = gzip.GzipFile(fileobj=zbuf)
ret = zfile.read()
zfile.close()
except:
ret = s
return ret
class StoryField(models.TextField):
__metaclass__ = models.SubfieldBase
def to_python(self, value):
if not value:
return None
# print 'From DB: %s %s' % (len(value), value[:25],)
try:
return unicode(value.decode('base64').decode('zlib'))
except:
return value
def get_prep_save(self, value):
if value:
# print "Pre To DB: %s %s" % (len(value), value[:25])
value = value.encode('zlib').encode('base64')
# print "Post To DB: %s %s" % (len(value), value[:25])
return super(StoryField, self).get_prep_save(value)
class CompressedTextField(models.TextField):
'''transparently compress data before hitting the db and uncompress after fetching'''
def get_db_prep_save(self, value):
if value is not None:
value = compress_string(value)
return models.TextField.get_db_prep_save(self, value)
def _get_val_from_obj(self, obj):
if obj:
return uncompress_string(getattr(obj, self.attname))
else:
return self.get_default()
def post_init(self, instance=None, **kwargs):
value = self._get_val_from_obj(instance)
if value:
setattr(instance, self.attname, value)
def contribute_to_class(self, cls, name):
super(CompressedTextField, self).contribute_to_class(cls, name)
post_init.connect(self.post_init, sender=cls)
def get_internal_type(self):
return "TextField"
def db_type(self):
from django.conf import settings
db_types = {'mysql':'longblob','sqlite3':'blob'}
try:
return db_types[settings.DATABASE_ENGINE]
except KeyError:
raise Exception, '%s currently works only with: %s'%(self.__class__.__name__,','.join(db_types.keys()))