/usr/lib/python3/dist-packages/picklefield/fields.py is in python3-django-picklefield 1.0.0-1.
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 | """Pickle field implementation for Django."""
from base64 import b64decode, b64encode
from copy import deepcopy
from zlib import compress, decompress
from django.db import models
from django.utils.encoding import force_text
from . import DEFAULT_PROTOCOL
from .compat import dumps, loads
class PickledObject(str):
"""
A subclass of string so it can be told whether a string is a pickled
object or not (if the object is an instance of this class then it must
[well, should] be a pickled one).
Only really useful for passing pre-encoded values to ``default``
with ``dbsafe_encode``, not that doing so is necessary. If you
remove PickledObject and its references, you won't be able to pass
in pre-encoded values anymore, but you can always just pass in the
python objects themselves.
"""
class _ObjectWrapper(object):
"""
A class used to wrap object that have properties that may clash with the
ORM internals.
For example, objects with the `prepare_database_save` property such as
`django.db.Model` subclasses won't work under certain conditions and the
same apply for trying to retrieve any `callable` object.
"""
__slots__ = ('_obj',)
def __init__(self, obj):
self._obj = obj
def wrap_conflictual_object(obj):
if hasattr(obj, 'prepare_database_save') or callable(obj):
obj = _ObjectWrapper(obj)
return obj
def dbsafe_encode(value, compress_object=False, pickle_protocol=DEFAULT_PROTOCOL, copy=True):
# We use deepcopy() here to avoid a problem with cPickle, where dumps
# can generate different character streams for same lookup value if
# they are referenced differently.
# The reason this is important is because we do all of our lookups as
# simple string matches, thus the character streams must be the same
# for the lookups to work properly. See tests.py for more information.
if copy:
# Copy can be very expensive if users aren't going to perform lookups
# on the value anyway.
value = deepcopy(value)
value = dumps(value, protocol=pickle_protocol)
if compress_object:
value = compress(value)
value = b64encode(value).decode() # decode bytes to str
return PickledObject(value)
def dbsafe_decode(value, compress_object=False):
value = value.encode() # encode str to bytes
value = b64decode(value)
if compress_object:
value = decompress(value)
return loads(value)
class PickledObjectField(models.Field):
"""
A field that will accept *any* python object and store it in the
database. PickledObjectField will optionally compress its values if
declared with the keyword argument ``compress=True``.
Does not actually encode and compress ``None`` objects (although you
can still do lookups using None). This way, it is still possible to
use the ``isnull`` lookup type correctly.
"""
def __init__(self, *args, **kwargs):
self.compress = kwargs.pop('compress', False)
self.protocol = kwargs.pop('protocol', DEFAULT_PROTOCOL)
self.copy = kwargs.pop('copy', True)
kwargs.setdefault('editable', False)
super(PickledObjectField, self).__init__(*args, **kwargs)
def get_default(self):
"""
Returns the default value for this field.
The default implementation on models.Field calls force_unicode
on the default, which means you can't set arbitrary Python
objects as the default. To fix this, we just return the value
without calling force_unicode on it. Note that if you set a
callable as a default, the field will still call it. It will
*not* try to pickle and encode it.
"""
if self.has_default():
if callable(self.default):
return self.default()
return self.default
# If the field doesn't have a default, then we punt to models.Field.
return super(PickledObjectField, self).get_default()
def to_python(self, value):
"""
B64decode and unpickle the object, optionally decompressing it.
If an error is raised in de-pickling and we're sure the value is
a definite pickle, the error is allowed to propagate. If we
aren't sure if the value is a pickle or not, then we catch the
error and return the original value instead.
"""
if value is not None:
try:
value = dbsafe_decode(value, self.compress)
except:
# If the value is a definite pickle; and an error is raised in
# de-pickling it should be allowed to propogate.
if isinstance(value, PickledObject):
raise
else:
if isinstance(value, _ObjectWrapper):
return value._obj
return value
def pre_save(self, model_instance, add):
value = super(PickledObjectField, self).pre_save(model_instance, add)
return wrap_conflictual_object(value)
def from_db_value(self, value, expression, connection, context):
return self.to_python(value)
def get_db_prep_value(self, value, connection=None, prepared=False):
"""
Pickle and b64encode the object, optionally compressing it.
The pickling protocol is specified explicitly (by default 2),
rather than as -1 or HIGHEST_PROTOCOL, because we don't want the
protocol to change over time. If it did, ``exact`` and ``in``
lookups would likely fail, since pickle would now be generating
a different string.
"""
if value is not None and not isinstance(value, PickledObject):
# We call force_text here explicitly, so that the encoded string
# isn't rejected by the postgresql_psycopg2 backend. Alternatively,
# we could have just registered PickledObject with the psycopg
# marshaller (telling it to store it like it would a string), but
# since both of these methods result in the same value being stored,
# doing things this way is much easier.
value = force_text(dbsafe_encode(value, self.compress, self.protocol, self.copy))
return value
def value_to_string(self, obj):
value = self.value_from_object(obj)
return self.get_db_prep_value(value)
def get_internal_type(self):
return 'TextField'
def get_lookup(self, lookup_name):
"""
We need to limit the lookup types.
"""
if lookup_name not in ['exact', 'in', 'isnull']:
raise TypeError('Lookup type %s is not supported.' % lookup_name)
return super(PickledObjectField, self).get_lookup(lookup_name)
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