python/lib/django_1_4/django/contrib/gis/gdal/driver.py

   1 # prerequisites imports
   2 from ctypes import c_void_p
   3 from django.contrib.gis.gdal.base import GDALBase
   4 from django.contrib.gis.gdal.error import OGRException
   5 from django.contrib.gis.gdal.prototypes import ds as capi
   6
   7 # For more information, see the OGR C API source code:
   8 #  http://www.gdal.org/ogr/ogr__api_8h.html
   9 #
  10 # The OGR_Dr_* routines are relevant here.
  11 class Driver(GDALBase):
  12     "Wraps an OGR Data Source Driver."
  13
  14     # Case-insensitive aliases for OGR Drivers.
  15     _alias = {'esri' : 'ESRI Shapefile',
  16               'shp' : 'ESRI Shapefile',
  17               'shape' : 'ESRI Shapefile',
  18               'tiger' : 'TIGER',
  19               'tiger/line' : 'TIGER',
  20               }
  21
  22     def __init__(self, dr_input):
  23         "Initializes an OGR driver on either a string or integer input."
  24
  25         if isinstance(dr_input, basestring):
  26             # If a string name of the driver was passed in
  27             self._register()
  28
  29             # Checking the alias dictionary (case-insensitive) to see if an alias
  30             #  exists for the given driver.
  31             if dr_input.lower() in self._alias:
  32                 name = self._alias[dr_input.lower()]
  33             else:
  34                 name = dr_input
  35
  36             # Attempting to get the OGR driver by the string name.
  37             dr = capi.get_driver_by_name(name)
  38         elif isinstance(dr_input, int):
  39             self._register()
  40             dr = capi.get_driver(dr_input)
  41         elif isinstance(dr_input, c_void_p):
  42             dr = dr_input
  43         else:
  44             raise OGRException('Unrecognized input type for OGR Driver: %s' % str(type(dr_input)))
  45
  46         # Making sure we get a valid pointer to the OGR Driver
  47         if not dr:
  48             raise OGRException('Could not initialize OGR Driver on input: %s' % str(dr_input))
  49         self.ptr = dr
  50
  51     def __str__(self):
  52         "Returns the string name of the OGR Driver."
  53         return capi.get_driver_name(self.ptr)
  54
  55     def _register(self):
  56         "Attempts to register all the data source drivers."
  57         # Only register all if the driver count is 0 (or else all drivers
  58         # will be registered over and over again)
  59         if not self.driver_count: capi.register_all()
  60
  61     # Driver properties
  62     @property
  63     def driver_count(self):
  64         "Returns the number of OGR data source drivers registered."
  65         return capi.get_driver_count()