1 from ctypes import byref, c_int

     2 from datetime import date, datetime, time

     3 from django.contrib.gis.gdal.error import OGRException

     4 from django.contrib.gis.gdal.prototypes.ds import \

     5     get_feat_field_defn, get_field_as_datetime, get_field_as_double, \

     6     get_field_as_integer, get_field_as_string, get_field_name, get_field_precision, \

     7     get_field_type, get_field_type_name, get_field_width

     8 

     9 # For more information, see the OGR C API source code:

    10 #  http://www.gdal.org/ogr/ogr__api_8h.html

    11 #

    12 # The OGR_Fld_* routines are relevant here.

    13 class Field(object):

    14     "A class that wraps an OGR Field, needs to be instantiated from a Feature object."

    15 

    16     #### Python 'magic' routines ####

    17     def __init__(self, feat, index):

    18         """

    19         Initializes on the feature pointer and the integer index of

    20         the field within the feature.

    21         """

    22         # Setting the feature pointer and index.

    23         self._feat = feat

    24         self._index = index

    25         

    26         # Getting the pointer for this field.

    27         fld = get_feat_field_defn(feat, index)

    28         if not fld:

    29             raise OGRException('Cannot create OGR Field, invalid pointer given.')

    30         self._ptr = fld

    31 

    32         # Setting the class depending upon the OGR Field Type (OFT)

    33         self.__class__ = FIELD_CLASSES[self.type]

    34 

    35         # OFTReal with no precision should be an OFTInteger.

    36         if isinstance(self, OFTReal) and self.precision == 0:

    37             self.__class__ = OFTInteger

    38 

    39     def __str__(self):

    40         "Returns the string representation of the Field."

    41         return str(self.value).strip()

    42 

    43     #### Field Methods ####

    44     def as_double(self):

    45         "Retrieves the Field's value as a double (float)."

    46         return get_field_as_double(self._feat, self._index)

    47 

    48     def as_int(self):

    49         "Retrieves the Field's value as an integer."

    50         return get_field_as_integer(self._feat, self._index)

    51 

    52     def as_string(self):

    53         "Retrieves the Field's value as a string."

    54         return get_field_as_string(self._feat, self._index)

    55 

    56     def as_datetime(self):

    57         "Retrieves the Field's value as a tuple of date & time components."

    58         yy, mm, dd, hh, mn, ss, tz = [c_int() for i in range(7)]

    59         status = get_field_as_datetime(self._feat, self._index, byref(yy), byref(mm), byref(dd),

    60                                        byref(hh), byref(mn), byref(ss), byref(tz))

    61         if status:

    62             return (yy, mm, dd, hh, mn, ss, tz)

    63         else:

    64             raise OGRException('Unable to retrieve date & time information from the field.')

    65 

    66     #### Field Properties ####

    67     @property

    68     def name(self):

    69         "Returns the name of this Field."

    70         return get_field_name(self._ptr)

    71 

    72     @property

    73     def precision(self):

    74         "Returns the precision of this Field."

    75         return get_field_precision(self._ptr)

    76 

    77     @property

    78     def type(self):

    79         "Returns the OGR type of this Field."

    80         return get_field_type(self._ptr)

    81 

    82     @property

    83     def type_name(self):

    84         "Return the OGR field type name for this Field."

    85         return get_field_type_name(self.type)

    86 

    87     @property

    88     def value(self):

    89         "Returns the value of this Field."

    90         # Default is to get the field as a string.

    91         return self.as_string()

    92 

    93     @property

    94     def width(self):

    95         "Returns the width of this Field."

    96         return get_field_width(self._ptr)

    97 

    98 ### The Field sub-classes for each OGR Field type. ###

    99 class OFTInteger(Field):

   100     @property

   101     def value(self):

   102         "Returns an integer contained in this field."

   103         return self.as_int()

   104 

   105     @property

   106     def type(self):

   107         """

   108         GDAL uses OFTReals to represent OFTIntegers in created

   109         shapefiles -- forcing the type here since the underlying field

   110         type may actually be OFTReal.

   111         """

   112         return 0

   113 

   114 class OFTReal(Field):

   115     @property

   116     def value(self):

   117         "Returns a float contained in this field."

   118         return self.as_double()

   119 

   120 # String & Binary fields, just subclasses

   121 class OFTString(Field): pass

   122 class OFTWideString(Field): pass

   123 class OFTBinary(Field): pass

   124 

   125 # OFTDate, OFTTime, OFTDateTime fields.

   126 class OFTDate(Field):

   127     @property

   128     def value(self):

   129         "Returns a Python `date` object for the OFTDate field."

   130         yy, mm, dd, hh, mn, ss, tz = self.as_datetime()

   131         try:

   132             return date(yy.value, mm.value, dd.value)

   133         except ValueError:

   134             return None

   135 

   136 class OFTDateTime(Field):

   137     @property

   138     def value(self):

   139         "Returns a Python `datetime` object for this OFTDateTime field."

   140         yy, mm, dd, hh, mn, ss, tz = self.as_datetime()

   141         # TODO: Adapt timezone information.

   142         #  See http://lists.maptools.org/pipermail/gdal-dev/2006-February/007990.html

   143         #  The `tz` variable has values of: 0=unknown, 1=localtime (ambiguous), 

   144         #  100=GMT, 104=GMT+1, 80=GMT-5, etc.

   145         try:

   146             return datetime(yy.value, mm.value, dd.value, hh.value, mn.value, ss.value)

   147         except ValueError:

   148             return None

   149 

   150 class OFTTime(Field):

   151     @property

   152     def value(self):

   153         "Returns a Python `time` object for this OFTTime field."

   154         yy, mm, dd, hh, mn, ss, tz = self.as_datetime()

   155         try:

   156             return time(hh.value, mn.value, ss.value)

   157         except ValueError:

   158             return None

   159 

   160 # List fields are also just subclasses

   161 class OFTIntegerList(Field): pass

   162 class OFTRealList(Field): pass

   163 class OFTStringList(Field): pass

   164 class OFTWideStringList(Field): pass

   165 

   166 # Class mapping dictionary for OFT Types

   167 FIELD_CLASSES = { 0 : OFTInteger,

   168                   1 : OFTIntegerList,

   169                   2 : OFTReal,

   170                   3 : OFTRealList,

   171                   4 : OFTString,

   172                   5 : OFTStringList,

   173                   6 : OFTWideString,

   174                   7 : OFTWideStringList,

   175                   8 : OFTBinary,

   176                   9 : OFTDate,

   177                  10 : OFTTime,

   178                  11 : OFTDateTime,

   179                   }