Changeset 9184 for src/django_gheat/gheat

Timestamp:

May 12, 2011, 12:05:59 PM (14 years ago)

Author:

rick

Message:

Implemented cross database tile caching method, using base64 storage.

File:

• src/django_gheat/gheat/models.py (modified) (1 diff)

src/django_gheat/gheat/models.py

@@ -1 @@
-from django.db import models
 from gheat import managers
 import datetime
+import binascii
+import hashlib
+
+from django.core import validators
+from django.db import models
+from django.dispatch import receiver
+from django.utils.encoding import smart_unicode
+from django.utils.translation import ugettext_lazy as _
+
+class BinaryField(models.Field):
+  MAGIC = '###MAGIC###'
+  description = _('Binary object using base64 (up to %(max_length)s)')
+
+  __metaclass__ = models.SubfieldBase
+
+  def __init__(self, *args, **kwargs):
+    # base64 roughly max the binary size with with 4 times
+    kwargs['max_length'] = kwargs['max_length'] * 4 + len(self.MAGIC)
+    super(BinaryField, self).__init__(*args, **kwargs)
+    self.validators.append(validators.MaxLengthValidator(self.max_length))
+
+  def to_python(self,value):
+    if value.startswith(self.MAGIC):
+      return binascii.a2b_base64(value[len(self.MAGIC):])
+    else:
+      return value
+
+  def get_db_prep_value(self, value, connection, prepared=False):
+    target = self.MAGIC + binascii.b2a_base64(value)
+    if len(target) > self.max_length:
+      raise ValueError(len(target))
+    return target
+
+  def get_prep_lookup(self, lookup_type, value):
+    raise TypeError('Lookup type %r not supported.' % lookup_type)
+
+  def get_internal_type(self):
+    return 'TextField'
+
+class TileCache(models.Model):
+  key = models.CharField(max_length=34,unique=True)
+  data = BinaryField(max_length=10000)
+  creation_time = models.DateTimeField(auto_now_add=True)
+
+  def __unicode__(self):
+    return self.key
+
+  @staticmethod
+  def make_key(source):
+    return hashlib.md5(source).hexdigest()
+
 
 class Accespoint(models.Model):