from ctypes import byref, c_int from datetime import date, datetime, time from django.contrib.gis.gdal.error import OGRException from django.contrib.gis.gdal.prototypes.ds import \ get_feat_field_defn, get_field_as_datetime, get_field_as_double, \ get_field_as_integer, get_field_as_string, get_field_name, get_field_precision, \ get_field_type, get_field_type_name, get_field_width # For more information, see the OGR C API source code: # http://www.gdal.org/ogr/ogr__api_8h.html # # The OGR_Fld_* routines are relevant here. class Field(object): "A class that wraps an OGR Field, needs to be instantiated from a Feature object." #### Python 'magic' routines #### def __init__(self, feat, index): """ Initializes on the feature pointer and the integer index of the field within the feature. """ # Setting the feature pointer and index. self._feat = feat self._index = index # Getting the pointer for this field. fld = get_feat_field_defn(feat, index) if not fld: raise OGRException('Cannot create OGR Field, invalid pointer given.') self._ptr = fld # Setting the class depending upon the OGR Field Type (OFT) self.__class__ = FIELD_CLASSES[self.type] # OFTReal with no precision should be an OFTInteger. if isinstance(self, OFTReal) and self.precision == 0: self.__class__ = OFTInteger def __str__(self): "Returns the string representation of the Field." return str(self.value).strip() #### Field Methods #### def as_double(self): "Retrieves the Field's value as a double (float)." return get_field_as_double(self._feat, self._index) def as_int(self): "Retrieves the Field's value as an integer." return get_field_as_integer(self._feat, self._index) def as_string(self): "Retrieves the Field's value as a string." return get_field_as_string(self._feat, self._index) def as_datetime(self): "Retrieves the Field's value as a tuple of date & time components." yy, mm, dd, hh, mn, ss, tz = [c_int() for i in range(7)] status = get_field_as_datetime(self._feat, self._index, byref(yy), byref(mm), byref(dd), byref(hh), byref(mn), byref(ss), byref(tz)) if status: return (yy, mm, dd, hh, mn, ss, tz) else: raise OGRException('Unable to retrieve date & time information from the field.') #### Field Properties #### @property def name(self): "Returns the name of this Field." return get_field_name(self._ptr) @property def precision(self): "Returns the precision of this Field." return get_field_precision(self._ptr) @property def type(self): "Returns the OGR type of this Field." return get_field_type(self._ptr) @property def type_name(self): "Return the OGR field type name for this Field." return get_field_type_name(self.type) @property def value(self): "Returns the value of this Field." # Default is to get the field as a string. return self.as_string() @property def width(self): "Returns the width of this Field." return get_field_width(self._ptr) ### The Field sub-classes for each OGR Field type. ### class OFTInteger(Field): @property def value(self): "Returns an integer contained in this field." return self.as_int() @property def type(self): """ GDAL uses OFTReals to represent OFTIntegers in created shapefiles -- forcing the type here since the underlying field type may actually be OFTReal. """ return 0 class OFTReal(Field): @property def value(self): "Returns a float contained in this field." return self.as_double() # String & Binary fields, just subclasses class OFTString(Field): pass class OFTWideString(Field): pass class OFTBinary(Field): pass # OFTDate, OFTTime, OFTDateTime fields. class OFTDate(Field): @property def value(self): "Returns a Python `date` object for the OFTDate field." yy, mm, dd, hh, mn, ss, tz = self.as_datetime() try: return date(yy.value, mm.value, dd.value) except ValueError: return None class OFTDateTime(Field): @property def value(self): "Returns a Python `datetime` object for this OFTDateTime field." yy, mm, dd, hh, mn, ss, tz = self.as_datetime() # TODO: Adapt timezone information. # See http://lists.maptools.org/pipermail/gdal-dev/2006-February/007990.html # The `tz` variable has values of: 0=unknown, 1=localtime (ambiguous), # 100=GMT, 104=GMT+1, 80=GMT-5, etc. try: return datetime(yy.value, mm.value, dd.value, hh.value, mn.value, ss.value) except ValueError: return None class OFTTime(Field): @property def value(self): "Returns a Python `time` object for this OFTTime field." yy, mm, dd, hh, mn, ss, tz = self.as_datetime() try: return time(hh.value, mn.value, ss.value) except ValueError: return None # List fields are also just subclasses class OFTIntegerList(Field): pass class OFTRealList(Field): pass class OFTStringList(Field): pass class OFTWideStringList(Field): pass # Class mapping dictionary for OFT Types FIELD_CLASSES = { 0 : OFTInteger, 1 : OFTIntegerList, 2 : OFTReal, 3 : OFTRealList, 4 : OFTString, 5 : OFTStringList, 6 : OFTWideString, 7 : OFTWideStringList, 8 : OFTBinary, 9 : OFTDate, 10 : OFTTime, 11 : OFTDateTime, }