shapefile.py

"""
shapefile.py
Provides read and write support for ESRI Shapefiles.
author: jlawhead<at>geospatialpython.com
version: 2.1.0
Compatible with Python versions 2.7-3.x
"""

__version__ = "2.1.0"

from struct import pack, unpack, calcsize, error, Struct
import os
import sys
import time
import array
import tempfile
import warnings
import io
from datetime import date


# Constants for shape types
NULL = 0
POINT = 1
POLYLINE = 3
POLYGON = 5
MULTIPOINT = 8
POINTZ = 11
POLYLINEZ = 13
POLYGONZ = 15
MULTIPOINTZ = 18
POINTM = 21
POLYLINEM = 23
POLYGONM = 25
MULTIPOINTM = 28
MULTIPATCH = 31

SHAPETYPE_LOOKUP = {
    0: 'NULL',
    1: 'POINT',
    3: 'POLYLINE',
    5: 'POLYGON',
    8: 'MULTIPOINT',
    11: 'POINTZ',
    13: 'POLYLINEZ',
    15: 'POLYGONZ',
    18: 'MULTIPOINTZ',
    21: 'POINTM',
    23: 'POLYLINEM',
    25: 'POLYGONM',
    28: 'MULTIPOINTM',
    31: 'MULTIPATCH'}

TRIANGLE_STRIP = 0
TRIANGLE_FAN = 1
OUTER_RING = 2
INNER_RING = 3
FIRST_RING = 4
RING = 5

PARTTYPE_LOOKUP = {
    0: 'TRIANGLE_STRIP',
    1: 'TRIANGLE_FAN',
    2: 'OUTER_RING',
    3: 'INNER_RING',
    4: 'FIRST_RING',
    5: 'RING'}


# Python 2-3 handling

PYTHON3 = sys.version_info[0] == 3

if PYTHON3:
    xrange = range
    izip = zip
else:
    from itertools import izip


# Helpers

MISSING = [None,'']
NODATA = -10e38 # as per the ESRI shapefile spec, only used for m-values. 

if PYTHON3:
    def b(v, encoding='utf-8', encodingErrors='strict'):
        if isinstance(v, str):
            # For python 3 encode str to bytes.
            return v.encode(encoding, encodingErrors)
        elif isinstance(v, bytes):
            # Already bytes.
            return v
        elif v is None:
            # Since we're dealing with text, interpret None as ""
            return b""
        else:
            # Force string representation.
            return str(v).encode(encoding, encodingErrors)

    def u(v, encoding='utf-8', encodingErrors='strict'):
        if isinstance(v, bytes):
            # For python 3 decode bytes to str.
            return v.decode(encoding, encodingErrors)
        elif isinstance(v, str):
            # Already str.
            return v
        elif v is None:
            # Since we're dealing with text, interpret None as ""
            return ""
        else:
            # Force string representation.
            return bytes(v).decode(encoding, encodingErrors)

    def is_string(v):
        return isinstance(v, str)

else:
    def b(v, encoding='utf-8', encodingErrors='strict'):
        if isinstance(v, unicode):
            # For python 2 encode unicode to bytes.
            return v.encode(encoding, encodingErrors)
        elif isinstance(v, bytes):
            # Already bytes.
            return v
        elif v is None:
            # Since we're dealing with text, interpret None as ""
            return ""
        else:
            # Force string representation.
            return unicode(v).encode(encoding, encodingErrors)

    def u(v, encoding='utf-8', encodingErrors='strict'):
        if isinstance(v, bytes):
            # For python 2 decode bytes to unicode.
            return v.decode(encoding, encodingErrors)
        elif isinstance(v, unicode):
            # Already unicode.
            return v
        elif v is None:
            # Since we're dealing with text, interpret None as ""
            return u""
        else:
            # Force string representation.
            return bytes(v).decode(encoding, encodingErrors)

    def is_string(v):
        return isinstance(v, basestring)


# Begin

class _Array(array.array):
    """Converts python tuples to lits of the appropritate type.
    Used to unpack different shapefile header parts."""
    def __repr__(self):
        return str(self.tolist())

def signed_area(coords):
    """Return the signed area enclosed by a ring using the linear time
    algorithm. A value >= 0 indicates a counter-clockwise oriented ring.
    """
    xs, ys = map(list, zip(*coords))
    xs.append(xs[1])
    ys.append(ys[1])
    return sum(xs[i]*(ys[i+1]-ys[i-1]) for i in range(1, len(coords)))/2.0

class Shape(object):
    def __init__(self, shapeType=NULL, points=None, parts=None, partTypes=None):
        """Stores the geometry of the different shape types
        specified in the Shapefile spec. Shape types are
        usually point, polyline, or polygons. Every shape type
        except the "Null" type contains points at some level for
        example verticies in a polygon. If a shape type has
        multiple shapes containing points within a single
        geometry record then those shapes are called parts. Parts
        are designated by their starting index in geometry record's
        list of shapes. For MultiPatch geometry, partTypes designates
        the patch type of each of the parts. 
        """
        self.shapeType = shapeType
        self.points = points or []
        self.parts = parts or []
        if partTypes:
            self.partTypes = partTypes

    @property
    def __geo_interface__(self):
        if not self.parts or not self.points:
            Exception('Invalid shape, cannot create GeoJSON representation. Shape type is "%s" but does not contain any parts and/or points.' % SHAPETYPE_LOOKUP[self.shapeType])

        if self.shapeType in [POINT, POINTM, POINTZ]:
            return {
            'type': 'Point',
            'coordinates': tuple(self.points[0])
            }
        elif self.shapeType in [MULTIPOINT, MULTIPOINTM, MULTIPOINTZ]:
            return {
            'type': 'MultiPoint',
            'coordinates': tuple([tuple(p) for p in self.points])
            }
        elif self.shapeType in [POLYLINE, POLYLINEM, POLYLINEZ]:
            if len(self.parts) == 1:
                return {
                'type': 'LineString',
                'coordinates': tuple([tuple(p) for p in self.points])
                }
            else:
                ps = None
                coordinates = []
                for part in self.parts:
                    if ps == None:
                        ps = part
                        continue
                    else:
                        coordinates.append(tuple([tuple(p) for p in self.points[ps:part]]))
                        ps = part
                else:
                    coordinates.append(tuple([tuple(p) for p in self.points[part:]]))
                return {
                'type': 'MultiLineString',
                'coordinates': tuple(coordinates)
                }
        elif self.shapeType in [POLYGON, POLYGONM, POLYGONZ]:
            if len(self.parts) == 1:
                return {
                'type': 'Polygon',
                'coordinates': (tuple([tuple(p) for p in self.points]),)
                }
            else:
                ps = None
                rings = []
                for part in self.parts:
                    if ps == None:
                        ps = part
                        continue
                    else:
                        rings.append(tuple([tuple(p) for p in self.points[ps:part]]))
                        ps = part
                else:
                    rings.append(tuple([tuple(p) for p in self.points[part:]]))
                polys = []
                poly = [rings[0]]
                for ring in rings[1:]:
                    if signed_area(ring) < 0:
                        polys.append(poly)
                        poly = [ring]
                    else:
                        poly.append(ring)
                polys.append(poly)
                if len(polys) == 1:
                    return {
                    'type': 'Polygon',
                    'coordinates': tuple(polys[0])
                    }
                elif len(polys) > 1:
                    return {
                    'type': 'MultiPolygon',
                    'coordinates': polys
                    }
        else:
            raise Exception('Shape type "%s" cannot be represented as GeoJSON.' % SHAPETYPE_LOOKUP[self.shapeType])

    @staticmethod
    def _from_geojson(geoj):
        # create empty shape
        shape = Shape()
        # set shapeType
        geojType = geoj["type"] if geoj else "Null"
        if geojType == "Null":
            shapeType = NULL
        elif geojType == "Point":
            shapeType = POINT
        elif geojType == "LineString":
            shapeType = POLYLINE
        elif geojType == "Polygon":
            shapeType = POLYGON
        elif geojType == "MultiPoint":
            shapeType = MULTIPOINT
        elif geojType == "MultiLineString":
            shapeType = POLYLINE
        elif geojType == "MultiPolygon":
            shapeType = POLYGON
        else:
            raise Exception("Cannot create Shape from GeoJSON type '%s'" % geojType)
        shape.shapeType = shapeType
        
        # set points and parts
        if geojType == "Point":
            shape.points = [ geoj["coordinates"] ]
            shape.parts = [0]
        elif geojType in ("MultiPoint","LineString"):
            shape.points = geoj["coordinates"]
            shape.parts = [0]
        elif geojType in ("Polygon"):
            points = []
            parts = []
            index = 0
            for i,ext_or_hole in enumerate(geoj["coordinates"]):
                if i == 0 and not signed_area(ext_or_hole) < 0:
                    # flip exterior direction
                    ext_or_hole = list(reversed(ext_or_hole))
                elif i > 0 and not signed_area(ext_or_hole) >= 0:
                    # flip hole direction
                    ext_or_hole = list(reversed(ext_or_hole))
                points.extend(ext_or_hole)
                parts.append(index)
                index += len(ext_or_hole)
            shape.points = points
            shape.parts = parts
        elif geojType in ("MultiLineString"):
            points = []
            parts = []
            index = 0
            for linestring in geoj["coordinates"]:
                points.extend(linestring)
                parts.append(index)
                index += len(linestring)
            shape.points = points
            shape.parts = parts
        elif geojType in ("MultiPolygon"):
            points = []
            parts = []
            index = 0
            for polygon in geoj["coordinates"]:
                for i,ext_or_hole in enumerate(polygon):
                    if i == 0 and not signed_area(ext_or_hole) < 0:
                        # flip exterior direction
                        ext_or_hole = list(reversed(ext_or_hole))
                    elif i > 0 and not signed_area(ext_or_hole) >= 0:
                        # flip hole direction
                        ext_or_hole = list(reversed(ext_or_hole))
                    points.extend(ext_or_hole)
                    parts.append(index)
                    index += len(ext_or_hole)
            shape.points = points
            shape.parts = parts
        return shape

    @property
    def shapeTypeName(self):
        return SHAPETYPE_LOOKUP[self.shapeType]

class _Record(list):
    """
    A class to hold a record. Subclasses list to ensure compatibility with
    former work and allows to use all the optimazations of the builtin list.
    In addition to the list interface, the values of the record
    can also be retrieved using the fields name. Eg. if the dbf contains
    a field ID at position 0, the ID can be retrieved with the position, the field name
    as a key or the field name as an attribute.

    >>> # Create a Record with one field, normally the record is created by the Reader class
    >>> r = _Record({'ID': 0}, [0])
    >>> print(r[0])
    >>> print(r['ID'])
    >>> print(r.ID)
    """

    def __init__(self, field_positions, values, oid=None):
        """
        A Record should be created by the Reader class

        :param field_positions: A dict mapping field names to field positions
        :param values: A sequence of values
        :param oid: The object id, an int (optional)
        """
        self.__field_positions = field_positions
        if oid is not None:
            self.__oid = oid
        else:
            self.__oid = -1
        list.__init__(self, values)

    def __getattr__(self, item):
        """
        __getattr__ is called if an attribute is used that does
        not exist in the normal sense. Eg. r=Record(...), r.ID
        calls r.__getattr__('ID'), but r.index(5) calls list.index(r, 5)
        :param item: The field name, used as attribute
        :return: Value of the field
        :raises: Attribute error, if field does not exist
                and IndexError, if field exists but not values in the Record
        """
        try:
            index = self.__field_positions[item]
            return list.__getitem__(self, index)
        except KeyError:
            raise AttributeError('{} is not a field name'.format(item))
        except IndexError:
            raise IndexError('{} found as a field but not enough values available.'.format(item))

    def __setattr__(self, key, value):
        """
        Sets a value of a field attribute
        :param key: The field name
        :param value: the value of that field
        :return: None
        :raises: AttributeError, if key is not a field of the shapefile
        """
        if key.startswith('_'):  # Prevent infinite loop when setting mangled attribute
            return list.__setattr__(self, key, value)
        try:
            index = self.__field_positions[key]
            return list.__setitem__(self, index, value)
        except KeyError:
            raise AttributeError('{} is not a field name'.format(key))

    def __getitem__(self, item):
        """
        Extends the normal list item access with
        access using a fieldname

        Eg. r['ID'], r[0]
        :param item: Either the position of the value or the name of a field
        :return: the value of the field
        """
        try:
            return list.__getitem__(self, item)
        except TypeError:
            try:
                index = self.__field_positions[item]
            except KeyError:
                index = None
        if index is not None:
            return list.__getitem__(self, index)
        else:
            raise IndexError('"{}" is not a field name and not an int'.format(item))

    def __setitem__(self, key, value):
        """
        Extends the normal list item access with
        access using a fieldname

        Eg. r['ID']=2, r[0]=2
        :param key: Either the position of the value or the name of a field
        :param value: the new value of the field
        """
        try:
            return list.__setitem__(self, key, value)
        except TypeError:
            index = self.__field_positions.get(key)
            if index is not None:
                return list.__setitem__(self, index, value)
            else:
                raise IndexError('{} is not a field name and not an int'.format(key))

    @property
    def oid(self):
        """The index position of the record in the original shapefile"""
        return self.__oid

    def as_dict(self):
        """
        Returns this Record as a dictionary using the field names as keys
        :return: dict
        """
        return dict((f, self[i]) for f, i in self.__field_positions.items())

    def __repr__(self):
        return 'Record #{}: {}'.format(self.__oid, list(self))

    def __dir__(self):
        """
        Helps to show the field names in an interactive environment like IPython.
        See: http://ipython.readthedocs.io/en/stable/config/integrating.html

        :return: List of method names and fields
        """
        default = list(dir(type(self))) # default list methods and attributes of this class
        fnames = list(self.__field_positions.keys()) # plus field names (random order)
        return default + fnames 
        
class ShapeRecord(object):
    """A ShapeRecord object containing a shape along with its attributes.
    Provides the GeoJSON __geo_interface__ to return a Feature dictionary."""
    def __init__(self, shape=None, record=None):
        self.shape = shape
        self.record = record

    @property
    def __geo_interface__(self):
        return {'type': 'Feature',
                'properties': self.record.as_dict(),
                'geometry': self.shape.__geo_interface__}

class Shapes(list):
    """A class to hold a list of Shape objects. Subclasses list to ensure compatibility with
    former work and allows to use all the optimazations of the builtin list.
    In addition to the list interface, this also provides the GeoJSON __geo_interface__
    to return a GeometryCollection dictionary. """

    def __repr__(self):
        return 'Shapes: {}'.format(list(self))

    @property
    def __geo_interface__(self):
        return {'type': 'GeometryCollection',
                'geometries': [g.__geo_interface__ for g in self]}

class ShapeRecords(list):
    """A class to hold a list of ShapeRecord objects. Subclasses list to ensure compatibility with
    former work and allows to use all the optimazations of the builtin list.
    In addition to the list interface, this also provides the GeoJSON __geo_interface__
    to return a FeatureCollection dictionary. """

    def __repr__(self):
        return 'ShapeRecords: {}'.format(list(self))

    @property
    def __geo_interface__(self):
        return {'type': 'FeatureCollection',
                'features': [f.__geo_interface__ for f in self]}

class ShapefileException(Exception):
    """An exception to handle shapefile specific problems."""
    pass

class Reader(object):
    """Reads the three files of a shapefile as a unit or
    separately.  If one of the three files (.shp, .shx,
    .dbf) is missing no exception is thrown until you try
    to call a method that depends on that particular file.
    The .shx index file is used if available for efficiency
    but is not required to read the geometry from the .shp
    file. The "shapefile" argument in the constructor is the
    name of the file you want to open.

    You can instantiate a Reader without specifying a shapefile
    and then specify one later with the load() method.

    Only the shapefile headers are read upon loading. Content
    within each file is only accessed when required and as
    efficiently as possible. Shapefiles are usually not large
    but they can be.
    """
    def __init__(self, *args, **kwargs):
        self.shp = None
        self.shx = None
        self.dbf = None
        self.shapeName = "Not specified"
        self._offsets = []
        self.shpLength = None
        self.numRecords = None
        self.fields = []
        self.__dbfHdrLength = 0
        self.__fieldposition_lookup = {}
        self.encoding = kwargs.pop('encoding', 'utf-8')
        self.encodingErrors = kwargs.pop('encodingErrors', 'strict')
        # See if a shapefile name was passed as an argument
        if len(args) > 0:
            if is_string(args[0]):
                self.load(args[0])
                return
        if "shp" in kwargs.keys():
            if hasattr(kwargs["shp"], "read"):
                self.shp = kwargs["shp"]
                # Copy if required
                try:
                    self.shp.seek(0)
                except (NameError, io.UnsupportedOperation):
                    self.shp = io.BytesIO(self.shp.read())
            if "shx" in kwargs.keys():
                if hasattr(kwargs["shx"], "read"):
                    self.shx = kwargs["shx"]
                    # Copy if required
                    try:
                        self.shx.seek(0)
                    except (NameError, io.UnsupportedOperation):
                        self.shx = io.BytesIO(self.shx.read())
        if "dbf" in kwargs.keys():
            if hasattr(kwargs["dbf"], "read"):
                self.dbf = kwargs["dbf"]
                # Copy if required
                try:
                    self.dbf.seek(0)
                except (NameError, io.UnsupportedOperation):
                    self.dbf = io.BytesIO(self.dbf.read())
        if self.shp or self.dbf:        
            self.load()
        else:
            raise ShapefileException("Shapefile Reader requires a shapefile or file-like object.")

    def __str__(self):
        """
        Use some general info on the shapefile as __str__
        """
        info = ['shapefile Reader']
        if self.shp:
            info.append("    {} shapes (type '{}')".format(
                len(self), SHAPETYPE_LOOKUP[self.shapeType]))
        if self.dbf:
            info.append('    {} records ({} fields)'.format(
                len(self), len(self.fields)))
        return '\n'.join(info)

    def __enter__(self):
        """
        Enter phase of context manager.
        """
        return self

    def __exit__(self, exc_type, exc_val, exc_tb):
        """
        Exit phase of context manager, close opened files.
        """
        self.close()

    def __len__(self):
        """Returns the number of shapes/records in the shapefile."""
        return self.numRecords

    def __iter__(self):
        """Iterates through the shapes/records in the shapefile."""
        for shaperec in self.iterShapeRecords():
            yield shaperec

    @property
    def __geo_interface__(self):
        fieldnames = [f[0] for f in self.fields]
        features = []
        for feat in self.iterShapeRecords():
            fdict = {'type': 'Feature',
                     'properties': dict(zip(fieldnames,feat.record)),
                     'geometry': feat.shape.__geo_interface__}
            features.append(fdict)
        return {'type': 'FeatureCollection',
                'bbox': self.bbox,
                'features': features}

    @property
    def shapeTypeName(self):
        return SHAPETYPE_LOOKUP[self.shapeType]

    def load(self, shapefile=None):
        """Opens a shapefile from a filename or file-like
        object. Normally this method would be called by the
        constructor with the file name as an argument."""
        if shapefile:
            (shapeName, ext) = os.path.splitext(shapefile)
            self.shapeName = shapeName
            self.load_shp(shapeName)
            self.load_shx(shapeName)
            self.load_dbf(shapeName)
            if not (self.shp or self.dbf):
                raise ShapefileException("Unable to open %s.dbf or %s.shp." % (shapeName, shapeName))
        if self.shp:
            self.__shpHeader()
        if self.dbf:
            self.__dbfHeader()

    def load_shp(self, shapefile_name):
        """
        Attempts to load file with .shp extension as both lower and upper case
        """
        shp_ext = 'shp'
        try:
            self.shp = open("%s.%s" % (shapefile_name, shp_ext), "rb")
        except IOError:
            try:
                self.shp = open("%s.%s" % (shapefile_name, shp_ext.upper()), "rb")
            except IOError:
                pass

    def load_shx(self, shapefile_name):
        """
        Attempts to load file with .shx extension as both lower and upper case
        """
        shx_ext = 'shx'
        try:
            self.shx = open("%s.%s" % (shapefile_name, shx_ext), "rb")
        except IOError:
            try:
                self.shx = open("%s.%s" % (shapefile_name, shx_ext.upper()), "rb")
            except IOError:
                pass

    def load_dbf(self, shapefile_name):
        """
        Attempts to load file with .dbf extension as both lower and upper case
        """
        dbf_ext = 'dbf'
        try:
            self.dbf = open("%s.%s" % (shapefile_name, dbf_ext), "rb")
        except IOError:
            try:
                self.dbf = open("%s.%s" % (shapefile_name, dbf_ext.upper()), "rb")
            except IOError:
                pass

    def __del__(self):
        self.close()

    def close(self):
        for attribute in (self.shp, self.shx, self.dbf):
            if hasattr(attribute, 'close'):
                try:
                    attribute.close()
                except IOError:
                    pass

    def __getFileObj(self, f):
        """Checks to see if the requested shapefile file object is
        available. If not a ShapefileException is raised."""
        if not f:
            raise ShapefileException("Shapefile Reader requires a shapefile or file-like object.")
        if self.shp and self.shpLength is None:
            self.load()
        if self.dbf and len(self.fields) == 0:
            self.load()
        return f

    def __restrictIndex(self, i):
        """Provides list-like handling of a record index with a clearer
        error message if the index is out of bounds."""
        if self.numRecords:
            rmax = self.numRecords - 1
            if abs(i) > rmax:
                raise IndexError("Shape or Record index out of range.")
            if i < 0: i = range(self.numRecords)[i]
        return i

    def __shpHeader(self):
        """Reads the header information from a .shp or .shx file."""
        if not self.shp:
            raise ShapefileException("Shapefile Reader requires a shapefile or file-like object. (no shp file found")
        shp = self.shp
        # File length (16-bit word * 2 = bytes)
        shp.seek(24)
        self.shpLength = unpack(">i", shp.read(4))[0] * 2
        # Shape type
        shp.seek(32)
        self.shapeType= unpack("<i", shp.read(4))[0]
        # The shapefile's bounding box (lower left, upper right)
        self.bbox = _Array('d', unpack("<4d", shp.read(32)))
        # Elevation
        self.zbox = _Array('d', unpack("<2d", shp.read(16)))
        # Measure
        self.mbox = []
        for m in _Array('d', unpack("<2d", shp.read(16))):
            # Measure values less than -10e38 are nodata values according to the spec
            if m > NODATA:
                self.mbox.append(m)
            else:
                self.mbox.append(None)

    def __shape(self):
        """Returns the header info and geometry for a single shape."""
        f = self.__getFileObj(self.shp)
        record = Shape()
        nParts = nPoints = zmin = zmax = mmin = mmax = None
        (recNum, recLength) = unpack(">2i", f.read(8))
        # Determine the start of the next record
        next = f.tell() + (2 * recLength)
        shapeType = unpack("<i", f.read(4))[0]
        record.shapeType = shapeType
        # For Null shapes create an empty points list for consistency
        if shapeType == 0:
            record.points = []
        # All shape types capable of having a bounding box
        elif shapeType in (3,5,8,13,15,18,23,25,28,31):
            record.bbox = _Array('d', unpack("<4d", f.read(32)))
        # Shape types with parts
        if shapeType in (3,5,13,15,23,25,31):
            nParts = unpack("<i", f.read(4))[0]
        # Shape types with points
        if shapeType in (3,5,8,13,15,18,23,25,28,31):
            nPoints = unpack("<i", f.read(4))[0]
        # Read parts
        if nParts:
            record.parts = _Array('i', unpack("<%si" % nParts, f.read(nParts * 4)))
        # Read part types for Multipatch - 31
        if shapeType == 31:
            record.partTypes = _Array('i', unpack("<%si" % nParts, f.read(nParts * 4)))
        # Read points - produces a list of [x,y] values
        if nPoints:
            flat = unpack("<%sd" % (2 * nPoints), f.read(16*nPoints))
            record.points = list(izip(*(iter(flat),) * 2))
        # Read z extremes and values
        if shapeType in (13,15,18,31):
            (zmin, zmax) = unpack("<2d", f.read(16))
            record.z = _Array('d', unpack("<%sd" % nPoints, f.read(nPoints * 8)))
        # Read m extremes and values
        if shapeType in (13,15,18,23,25,28,31):
            if next - f.tell() >= 16:
                (mmin, mmax) = unpack("<2d", f.read(16))
            # Measure values less than -10e38 are nodata values according to the spec
            if next - f.tell() >= nPoints * 8:
                record.m = []
                for m in _Array('d', unpack("<%sd" % nPoints, f.read(nPoints * 8))):
                    if m > NODATA:
                        record.m.append(m)
                    else:
                        record.m.append(None)
            else:
                record.m = [None for _ in range(nPoints)]
        # Read a single point
        if shapeType in (1,11,21):
            record.points = [_Array('d', unpack("<2d", f.read(16)))]
        # Read a single Z value
        if shapeType == 11:
            record.z = list(unpack("<d", f.read(8)))
        # Read a single M value
        if shapeType in (21,11):
            if next - f.tell() >= 8:
                (m,) = unpack("<d", f.read(8))
            else:
                m = NODATA
            # Measure values less than -10e38 are nodata values according to the spec
            if m > NODATA:
                record.m = [m]
            else:
                record.m = [None]
        # Seek to the end of this record as defined by the record header because
        # the shapefile spec doesn't require the actual content to meet the header
        # definition.  Probably allowed for lazy feature deletion. 
        f.seek(next)
        return record

    def __shapeIndex(self, i=None):
        """Returns the offset in a .shp file for a shape based on information
        in the .shx index file."""
        shx = self.shx
        if not shx:
            return None
        if not self._offsets:
            # File length (16-bit word * 2 = bytes) - header length
            shx.seek(24)
            shxRecordLength = (unpack(">i", shx.read(4))[0] * 2) - 100
            numRecords = shxRecordLength // 8
            # Jump to the first record.
            shx.seek(100)
            shxRecords = _Array('i')
            # Each offset consists of two nrs, only the first one matters
            shxRecords.fromfile(shx, 2 * numRecords)
            if sys.byteorder != 'big':
                 shxRecords.byteswap()
            self._offsets = [2 * el for el in shxRecords[::2]]
        if not i == None:
            return self._offsets[i]

    def shape(self, i=0):
        """Returns a shape object for a shape in the the geometry
        record file."""
        shp = self.__getFileObj(self.shp)
        i = self.__restrictIndex(i)
        offset = self.__shapeIndex(i)
        if not offset:
            # Shx index not available so iterate the full list.
            for j,k in enumerate(self.iterShapes()):
                if j == i:
                    return k
        shp.seek(offset)
        return self.__shape()

    def shapes(self):
        """Returns all shapes in a shapefile."""
        shp = self.__getFileObj(self.shp)
        # Found shapefiles which report incorrect
        # shp file length in the header. Can't trust
        # that so we seek to the end of the file
        # and figure it out.
        shp.seek(0,2)
        self.shpLength = shp.tell()
        shp.seek(100)
        shapes = Shapes()
        while shp.tell() < self.shpLength:
            shapes.append(self.__shape())
        return shapes

    def iterShapes(self):
        """Serves up shapes in a shapefile as an iterator. Useful
        for handling large shapefiles."""
        shp = self.__getFileObj(self.shp)
        shp.seek(0,2)
        self.shpLength = shp.tell()
        shp.seek(100)
        while shp.tell() < self.shpLength:
            yield self.__shape()    

    def __dbfHeader(self):
        """Reads a dbf header. Xbase-related code borrows heavily from ActiveState Python Cookbook Recipe 362715 by Raymond Hettinger"""
        if not self.dbf:
            raise ShapefileException("Shapefile Reader requires a shapefile or file-like object. (no dbf file found)")
        dbf = self.dbf
        # read relevant header parts
        self.numRecords, self.__dbfHdrLength, self.__recordLength = \
                unpack("<xxxxLHH20x", dbf.read(32))
        # read fields
        numFields = (self.__dbfHdrLength - 33) // 32
        for field in range(numFields):
            fieldDesc = list(unpack("<11sc4xBB14x", dbf.read(32)))
            name = 0
            idx = 0
            if b"\x00" in fieldDesc[name]:
                idx = fieldDesc[name].index(b"\x00")
            else:
                idx = len(fieldDesc[name]) - 1
            fieldDesc[name] = fieldDesc[name][:idx]
            fieldDesc[name] = u(fieldDesc[name], self.encoding, self.encodingErrors)
            fieldDesc[name] = fieldDesc[name].lstrip()
            fieldDesc[1] = u(fieldDesc[1], 'ascii')
            self.fields.append(fieldDesc)
        terminator = dbf.read(1)
        if terminator != b"\r":
            raise ShapefileException("Shapefile dbf header lacks expected terminator. (likely corrupt?)")
        self.fields.insert(0, ('DeletionFlag', 'C', 1, 0))
        fmt,fmtSize = self.__recordFmt()
        self.__recStruct = Struct(fmt)

        # Store the field positions
        self.__fieldposition_lookup = dict((f[0], i) for i, f in enumerate(self.fields[1:]))

    def __recordFmt(self):
        """Calculates the format and size of a .dbf record."""
        if self.numRecords is None:
            self.__dbfHeader()
        fmt = ''.join(['%ds' % fieldinfo[2] for fieldinfo in self.fields])
        fmtSize = calcsize(fmt)
        # total size of fields should add up to recordlength from the header
        while fmtSize < self.__recordLength:
            # if not, pad byte until reaches recordlength
            fmt += "x" 
            fmtSize += 1
        return (fmt, fmtSize)

    def __record(self, oid=None):
        """Reads and returns a dbf record row as a list of values."""
        f = self.__getFileObj(self.dbf)
        recordContents = self.__recStruct.unpack(f.read(self.__recStruct.size))
        if recordContents[0] != b' ':
            # deleted record
            return None
        record = []
        for (name, typ, size, deci), value in zip(self.fields, recordContents):
            if name == 'DeletionFlag':
                continue
            elif typ in ("N","F"):
                # numeric or float: number stored as a string, right justified, and padded with blanks to the width of the field. 
                value = value.split(b'\0')[0]
                value = value.replace(b'*', b'')  # QGIS NULL is all '*' chars
                if value == b'':
                    value = None
                elif deci:
                    try:
                        value = float(value)
                    except ValueError:
                        #not parseable as float, set to None
                        value = None
                else:
                    # force to int
                    try:
                        # first try to force directly to int.
                        # forcing a large int to float and back to int
                        # will lose information and result in wrong nr.
                        value = int(value) 
                    except ValueError:
                        # forcing directly to int failed, so was probably a float.
                        try:
                            value = int(float(value))
                        except ValueError:
                            #not parseable as int, set to None
                            value = None
            elif typ == 'D':
                # date: 8 bytes - date stored as a string in the format YYYYMMDD.
                if value.count(b'0') == len(value):  # QGIS NULL is all '0' chars
                    value = None
                else:
                    try:
                        y, m, d = int(value[:4]), int(value[4:6]), int(value[6:8])
                        value = date(y, m, d)
                    except:
                        value = value.strip()
            elif typ == 'L':
                # logical: 1 byte - initialized to 0x20 (space) otherwise T or F.
                if value == b" ":
                    value = None # space means missing or not yet set
                else:
                    if value in b'YyTt1':
                        value = True
                    elif value in b'NnFf0':
                        value = False
                    else:
                        value = None # unknown value is set to missing
            else:
                # anything else is forced to string/unicode
                value = u(value, self.encoding, self.encodingErrors)
                value = value.strip()
            record.append(value)

        return _Record(self.__fieldposition_lookup, record, oid)

    def record(self, i=0):
        """Returns a specific dbf record based on the supplied index."""
        f = self.__getFileObj(self.dbf)
        if self.numRecords is None:
            self.__dbfHeader()
        i = self.__restrictIndex(i)
        recSize = self.__recStruct.size
        f.seek(0)
        f.seek(self.__dbfHdrLength + (i * recSize))
        return self.__record(oid=i)

    def records(self):
        """Returns all records in a dbf file."""
        if self.numRecords is None:
            self.__dbfHeader()
        records = []
        f = self.__getFileObj(self.dbf)
        f.seek(self.__dbfHdrLength)
        for i in range(self.numRecords):
            r = self.__record(oid=i)
            if r:
                records.append(r)
        return records

    def iterRecords(self):
        """Serves up records in a dbf file as an iterator.
        Useful for large shapefiles or dbf files."""
        if self.numRecords is None:
            self.__dbfHeader()
        f = self.__getFileObj(self.dbf)
        f.seek(self.__dbfHdrLength)
        for i in xrange(self.numRecords):
            r = self.__record()
            if r:
                yield r

    def shapeRecord(self, i=0):
        """Returns a combination geometry and attribute record for the
        supplied record index."""
        i = self.__restrictIndex(i)
        return ShapeRecord(shape=self.shape(i), record=self.record(i))

    def shapeRecords(self):
        """Returns a list of combination geometry/attribute records for
        all records in a shapefile."""
        return ShapeRecords([ShapeRecord(shape=rec[0], record=rec[1]) \
                                for rec in zip(self.shapes(), self.records())])

    def iterShapeRecords(self):
        """Returns a generator of combination geometry/attribute records for
        all records in a shapefile."""
        for shape, record in izip(self.iterShapes(), self.iterRecords()):
            yield ShapeRecord(shape=shape, record=record)


class Writer(object):
    """Provides write support for ESRI Shapefiles."""
    def __init__(self, target=None, shapeType=None, autoBalance=False, **kwargs):
        self.target = target
        self.autoBalance = autoBalance
        self.fields = []
        self.shapeType = shapeType
        self.shp = self.shx = self.dbf = None
        if target:
            self.shp = self.__getFileObj(os.path.splitext(target)[0] + '.shp')
            self.shx = self.__getFileObj(os.path.splitext(target)[0] + '.shx')
            self.dbf = self.__getFileObj(os.path.splitext(target)[0] + '.dbf')
        elif kwargs.get('shp') or kwargs.get('shx') or kwargs.get('dbf'):
            shp,shx,dbf = kwargs.get('shp'), kwargs.get('shx'), kwargs.get('dbf')
            if shp:
                self.shp = self.__getFileObj(shp)
            if shx:
                self.shx = self.__getFileObj(shx)
            if dbf:
                self.dbf = self.__getFileObj(dbf)
        else:
            raise Exception('Either the target filepath, or any of shp, shx, or dbf must be set to create a shapefile.')
        # Initiate with empty headers, to be finalized upon closing
        if self.shp: self.shp.write(b'9'*100) 
        if self.shx: self.shx.write(b'9'*100) 
        # Geometry record offsets and lengths for writing shx file.
        self.recNum = 0
        self.shpNum = 0
        self._bbox = None
        self._zbox = None
        self._mbox = None
        # Use deletion flags in dbf? Default is false (0).
        self.deletionFlag = 0
        # Encoding
        self.encoding = kwargs.pop('encoding', 'utf-8')
        self.encodingErrors = kwargs.pop('encodingErrors', 'strict')

    def __len__(self):
        """Returns the current number of features written to the shapefile. 
        If shapes and records are unbalanced, the length is considered the highest
        of the two."""
        return max(self.recNum, self.shpNum) 

    def __enter__(self):
        """
        Enter phase of context manager.
        """
        return self

    def __exit__(self, exc_type, exc_val, exc_tb):
        """
        Exit phase of context manager, finish writing and close the files.
        """
        self.close()

    def __del__(self):
        self.close()

    def close(self):
        """
        Write final shp, shx, and dbf headers, close opened files.
        """
        # Check if any of the files have already been closed
        shp_open = self.shp and not (hasattr(self.shp, 'closed') and self.shp.closed)
        shx_open = self.shx and not (hasattr(self.shx, 'closed') and self.shx.closed)
        dbf_open = self.dbf and not (hasattr(self.dbf, 'closed') and self.dbf.closed)
            
        # Balance if already not balanced
        if self.shp and shp_open and self.dbf and dbf_open:
            if self.autoBalance:
                self.balance()
            if self.recNum != self.shpNum:
                raise ShapefileException("When saving both the dbf and shp file, "
                                         "the number of records (%s) must correspond "
                                         "with the number of shapes (%s)" % (self.recNum, self.shpNum))
        # Fill in the blank headers
        if self.shp and shp_open:
            self.__shapefileHeader(self.shp, headerType='shp')
        if self.shx and shx_open:
            self.__shapefileHeader(self.shx, headerType='shx')

        # Update the dbf header with final length etc
        if self.dbf and dbf_open:
            self.__dbfHeader()

        # Close files, if target is a filepath
        if self.target:
            for attribute in (self.shp, self.shx, self.dbf):
                if hasattr(attribute, 'close'):
                    try:
                        attribute.close()
                    except IOError:
                        pass

    def __getFileObj(self, f):
        """Safety handler to verify file-like objects"""
        if not f:
            raise ShapefileException("No file-like object available.")
        elif hasattr(f, "write"):
            return f
        else:
            pth = os.path.split(f)[0]
            if pth and not os.path.exists(pth):
                os.makedirs(pth)
            return open(f, "wb+")

    def __shpFileLength(self):
        """Calculates the file length of the shp file."""
        # Remember starting position
        start = self.shp.tell()
        # Calculate size of all shapes
        self.shp.seek(0,2)
        size = self.shp.tell()
        # Calculate size as 16-bit words
        size //= 2
        # Return to start
        self.shp.seek(start)
        return size

    def __bbox(self, s):
        x = []
        y = []
        if len(s.points) > 0:
            px, py = list(zip(*s.points))[:2]
            x.extend(px)
            y.extend(py)
        else:
            # this should not happen.
            # any shape that is not null should have at least one point, and only those should be sent here. 
            # could also mean that earlier code failed to add points to a non-null shape. 
            raise Exception("Cannot create bbox. Expected a valid shape with at least one point. Got a shape of type '%s' and 0 points." % s.shapeType)
        bbox = [min(x), min(y), max(x), max(y)]
        # update global
        if self._bbox:
            # compare with existing
            self._bbox = [min(bbox[0],self._bbox[0]), min(bbox[1],self._bbox[1]), max(bbox[2],self._bbox[2]), max(bbox[3],self._bbox[3])]
        else:
            # first time bbox is being set
            self._bbox = bbox
        return bbox

    def __zbox(self, s):
        z = []
        for p in s.points:
            try:
                z.append(p[2])
            except IndexError:
                # point did not have z value
                # setting it to 0 is probably ok, since it means all are on the same elavation
                z.append(0)
        zbox = [min(z), max(z)]
        # update global
        if self._zbox:
            # compare with existing
            self._zbox = [min(zbox[0],self._zbox[0]), max(zbox[1],self._zbox[1])]
        else:
            # first time zbox is being set
            self._zbox = zbox
        return zbox

    def __mbox(self, s):
        mpos = 3 if s.shapeType in (11,13,15,18,31) else 2
        m = []
        for p in s.points:
            try:
                if p[mpos] is not None:
                    # mbox should only be calculated on valid m values
                    m.append(p[mpos])
            except IndexError:
                # point did not have m value so is missing
                # mbox should only be calculated on valid m values
                pass
        if not m:
            # only if none of the shapes had m values, should mbox be set to missing m values
            m.append(NODATA)
        mbox = [min(m), max(m)]
        # update global
        if self._mbox:
            # compare with existing
            self._mbox = [min(mbox[0],self._mbox[0]), max(mbox[1],self._mbox[1])]
        else:
            # first time mbox is being set
            self._mbox = mbox
        return mbox

    @property
    def shapeTypeName(self):
        return SHAPETYPE_LOOKUP[self.shapeType]

    def bbox(self):
        """Returns the current bounding box for the shapefile which is
        the lower-left and upper-right corners. It does not contain the
        elevation or measure extremes."""
        return self._bbox

    def zbox(self):
        """Returns the current z extremes for the shapefile."""
        return self._zbox

    def mbox(self):
        """Returns the current m extremes for the shapefile."""
        return self._mbox

    def __shapefileHeader(self, fileObj, headerType='shp'):
        """Writes the specified header type to the specified file-like object.
        Several of the shapefile formats are so similar that a single generic
        method to read or write them is warranted."""
        f = self.__getFileObj(fileObj)
        f.seek(0)
        # File code, Unused bytes
        f.write(pack(">6i", 9994,0,0,0,0,0))
        # File length (Bytes / 2 = 16-bit words)
        if headerType == 'shp':
            f.write(pack(">i", self.__shpFileLength()))
        elif headerType == 'shx':
            f.write(pack('>i', ((100 + (self.shpNum * 8)) // 2)))
        # Version, Shape type
        if self.shapeType is None:
            self.shapeType = NULL
        f.write(pack("<2i", 1000, self.shapeType))
        # The shapefile's bounding box (lower left, upper right)
        if self.shapeType != 0:
            try:
                bbox = self.bbox()
                if bbox is None:
                    # The bbox is initialized with None, so this would mean the shapefile contains no valid geometries.
                    # In such cases of empty shapefiles, ESRI spec says the bbox values are 'unspecified'.
                    # Not sure what that means, so for now just setting to 0s, which is the same behavior as in previous versions.
                    # This would also make sense since the Z and M bounds are similarly set to 0 for non-Z/M type shapefiles.
                    bbox = [0,0,0,0] 
                f.write(pack("<4d", *bbox))
            except error:
                raise ShapefileException("Failed to write shapefile bounding box. Floats required.")
        else:
            f.write(pack("<4d", 0,0,0,0))
        # Elevation
        if self.shapeType in (11,13,15,18):
            # Z values are present in Z type
            zbox = self.zbox()
        else:
            # As per the ESRI shapefile spec, the zbox for non-Z type shapefiles are set to 0s
            zbox = [0,0]
        # Measure
        if self.shapeType in (11,13,15,18,21,23,25,28,31):
            # M values are present in M or Z type
            mbox = self.mbox()
        else:
            # As per the ESRI shapefile spec, the mbox for non-M type shapefiles are set to 0s
            mbox = [0,0]
        # Try writing
        try:
            f.write(pack("<4d", zbox[0], zbox[1], mbox[0], mbox[1]))
        except error:
            raise ShapefileException("Failed to write shapefile elevation and measure values. Floats required.")

    def __dbfHeader(self):
        """Writes the dbf header and field descriptors."""
        f = self.__getFileObj(self.dbf)
        f.seek(0)
        version = 3
        year, month, day = time.localtime()[:3]
        year -= 1900
        # Remove deletion flag placeholder from fields
        for field in self.fields:
            if field[0].startswith("Deletion"):
                self.fields.remove(field)
        numRecs = self.recNum
        numFields = len(self.fields)
        headerLength = numFields * 32 + 33
        if headerLength >= 65535:
            raise ShapefileException(
                    "Shapefile dbf header length exceeds maximum length.")
        recordLength = sum([int(field[2]) for field in self.fields]) + 1
        header = pack('<BBBBLHH20x', version, year, month, day, numRecs,
                headerLength, recordLength)
        f.write(header)
        # Field descriptors
        for field in self.fields:
            name, fieldType, size, decimal = field
            name = b(name, self.encoding, self.encodingErrors)
            name = name.replace(b' ', b'_')
            name = name.ljust(11).replace(b' ', b'\x00')
            fieldType = b(fieldType, 'ascii')
            size = int(size)
            fld = pack('<11sc4xBB14x', name, fieldType, size, decimal)
            f.write(fld)
        # Terminator
        f.write(b'\r')

    def shape(self, s):
        # Balance if already not balanced
        if self.autoBalance and self.recNum < self.shpNum:
            self.balance()
        # Check is shape or import from geojson
        if not isinstance(s, Shape):
            if hasattr(s, "__geo_interface__"):
                s = s.__geo_interface__
            if isinstance(s, dict):
                s = Shape._from_geojson(s)
            else:
                raise Exception("Can only write Shape objects, GeoJSON dictionaries, "
                                "or objects with the __geo_interface__, "
                                "not: %r" % s)
        # Write to file
        offset,length = self.__shpRecord(s)
        self.__shxRecord(offset, length)

    def __shpRecord(self, s):
        f = self.__getFileObj(self.shp)
        offset = f.tell()
        # Record number, Content length place holder
        self.shpNum += 1
        f.write(pack(">2i", self.shpNum, 0))
        start = f.tell()
        # Shape Type
        if self.shapeType is None and s.shapeType != NULL:
            self.shapeType = s.shapeType
        if s.shapeType != NULL and s.shapeType != self.shapeType:
            raise Exception("The shape's type (%s) must match the type of the shapefile (%s)." % (s.shapeType, self.shapeType))
        f.write(pack("<i", s.shapeType))

        # For point just update bbox of the whole shapefile
        if s.shapeType in (1,11,21):
            self.__bbox(s)
        # All shape types capable of having a bounding box
        if s.shapeType in (3,5,8,13,15,18,23,25,28,31):
            try:
                f.write(pack("<4d", *self.__bbox(s)))
            except error:
                raise ShapefileException("Failed to write bounding box for record %s. Expected floats." % self.shpNum)
        # Shape types with parts
        if s.shapeType in (3,5,13,15,23,25,31):
            # Number of parts
            f.write(pack("<i", len(s.parts)))
        # Shape types with multiple points per record
        if s.shapeType in (3,5,8,13,15,18,23,25,28,31):
            # Number of points
            f.write(pack("<i", len(s.points)))
        # Write part indexes
        if s.shapeType in (3,5,13,15,23,25,31):
            for p in s.parts:
                f.write(pack("<i", p))
        # Part types for Multipatch (31)
        if s.shapeType == 31:
            for pt in s.partTypes:
                f.write(pack("<i", pt))
        # Write points for multiple-point records
        if s.shapeType in (3,5,8,13,15,18,23,25,28,31):
            try:
                [f.write(pack("<2d", *p[:2])) for p in s.points]
            except error:
                raise ShapefileException("Failed to write points for record %s. Expected floats." % self.shpNum)
        # Write z extremes and values
        # Note: missing z values are autoset to 0, but not sure if this is ideal.
        if s.shapeType in (13,15,18,31):
            try:
                f.write(pack("<2d", *self.__zbox(s)))
            except error:
                raise ShapefileException("Failed to write elevation extremes for record %s. Expected floats." % self.shpNum)
            try:
                if hasattr(s,"z"):
                    # if z values are stored in attribute
                    f.write(pack("<%sd" % len(s.z), *s.z))
                else:
                    # if z values are stored as 3rd dimension
                    [f.write(pack("<d", p[2] if len(p) > 2 else 0)) for p in s.points]  
            except error:
                raise ShapefileException("Failed to write elevation values for record %s. Expected floats." % self.shpNum)
        # Write m extremes and values
        # When reading a file, pyshp converts NODATA m values to None, so here we make sure to convert them back to NODATA
        # Note: missing m values are autoset to NODATA.
        if s.shapeType in (13,15,18,23,25,28,31):
            try:
                f.write(pack("<2d", *self.__mbox(s)))
            except error:
                raise ShapefileException("Failed to write measure extremes for record %s. Expected floats" % self.shpNum)
            try:
                if hasattr(s,"m"): 
                    # if m values are stored in attribute
                    f.write(pack("<%sd" % len(s.m), *[m if m is not None else NODATA for m in s.m]))
                else:
                    # if m values are stored as 3rd/4th dimension
                    # 0-index position of m value is 3 if z type (x,y,z,m), or 2 if m type (x,y,m)
                    mpos = 3 if s.shapeType in (13,15,18,31) else 2
                    [f.write(pack("<d", p[mpos] if len(p) > mpos and p[mpos] is not None else NODATA)) for p in s.points]
            except error:
                raise ShapefileException("Failed to write measure values for record %s. Expected floats" % self.shpNum)
        # Write a single point
        if s.shapeType in (1,11,21):
            try:
                f.write(pack("<2d", s.points[0][0], s.points[0][1]))
            except error:
                raise ShapefileException("Failed to write point for record %s. Expected floats." % self.shpNum)
        # Write a single Z value
        # Note: missing z values are autoset to 0, but not sure if this is ideal.
        if s.shapeType == 11:
            # update the global z box
            self.__zbox(s)
            # then write value
            if hasattr(s, "z"):
                # if z values are stored in attribute
                try:
                    if not s.z:
                        s.z = (0,)
                    f.write(pack("<d", s.z[0]))
                except error:
                    raise ShapefileException("Failed to write elevation value for record %s. Expected floats." % self.shpNum)
            else:
                # if z values are stored as 3rd dimension
                try:
                    if len(s.points[0]) < 3:
                        s.points[0].append(0)
                    f.write(pack("<d", s.points[0][2]))
                except error:
                    raise ShapefileException("Failed to write elevation value for record %s. Expected floats." % self.shpNum)
        # Write a single M value
        # Note: missing m values are autoset to NODATA.
        if s.shapeType in (11,21):
            # update the global m box
            self.__mbox(s)
            # then write value
            if hasattr(s, "m"):
                # if m values are stored in attribute
                try:
                    if not s.m or s.m[0] is None:
                        s.m = (NODATA,) 
                    f.write(pack("<1d", s.m[0]))
                except error:
                    raise ShapefileException("Failed to write measure value for record %s. Expected floats." % self.shpNum)
            else:
                # if m values are stored as 3rd/4th dimension
                # 0-index position of m value is 3 if z type (x,y,z,m), or 2 if m type (x,y,m)
                try:
                    mpos = 3 if s.shapeType == 11 else 2
                    if len(s.points[0]) < mpos+1:
                        s.points[0].append(NODATA)
                    elif s.points[0][mpos] is None:
                        s.points[0][mpos] = NODATA
                    f.write(pack("<1d", s.points[0][mpos]))
                except error:
                    raise ShapefileException("Failed to write measure value for record %s. Expected floats." % self.shpNum)
        # Finalize record length as 16-bit words
        finish = f.tell()
        length = (finish - start) // 2
        # start - 4 bytes is the content length field
        f.seek(start-4)
        f.write(pack(">i", length))
        f.seek(finish)
        return offset,length

    def __shxRecord(self, offset, length):
         """Writes the shx records."""
         f = self.__getFileObj(self.shx)
         f.write(pack(">i", offset // 2))
         f.write(pack(">i", length))

    def record(self, *recordList, **recordDict):
        """Creates a dbf attribute record. You can submit either a sequence of
        field values or keyword arguments of field names and values. Before
        adding records you must add fields for the record values using the
        fields() method. If the record values exceed the number of fields the
        extra ones won't be added. In the case of using keyword arguments to specify
        field/value pairs only fields matching the already registered fields
        will be added."""
        # Balance if already not balanced
        if self.autoBalance and self.recNum > self.shpNum:
            self.balance()
            
        record = []
        fieldCount = len(self.fields)
        # Compensate for deletion flag
        if self.fields[0][0].startswith("Deletion"): fieldCount -= 1
        if recordList:
            record = [recordList[i] for i in range(fieldCount)]
        elif recordDict:
            for field in self.fields:
                if field[0] in recordDict:
                    val = recordDict[field[0]]
                    if val is None:
                        record.append("")
                    else:
                        record.append(val)
        else:
            # Blank fields for empty record
            record = ["" for i in range(fieldCount)]
        self.__dbfRecord(record)

    def __dbfRecord(self, record):
        """Writes the dbf records."""
        f = self.__getFileObj(self.dbf)
        if self.recNum == 0:
            # first records, so all fields should be set
            # allowing us to write the dbf header
            # cannot change the fields after this point
            self.__dbfHeader()
        # begin
        self.recNum += 1
        if not self.fields[0][0].startswith("Deletion"):
            f.write(b' ') # deletion flag
        for (fieldName, fieldType, size, deci), value in zip(self.fields, record):
            fieldType = fieldType.upper()
            size = int(size)
            if fieldType in ("N","F"):
                # numeric or float: number stored as a string, right justified, and padded with blanks to the width of the field.
                if value in MISSING:
                    value = b"*"*size # QGIS NULL
                elif not deci:
                    # force to int
                    try:
                        # first try to force directly to int.
                        # forcing a large int to float and back to int
                        # will lose information and result in wrong nr.
                        value = int(value) 
                    except ValueError:
                        # forcing directly to int failed, so was probably a float.
                        value = int(float(value))
                    value = format(value, "d")[:size].rjust(size) # caps the size if exceeds the field size
                else:
                    value = float(value)
                    value = format(value, ".%sf"%deci)[:size].rjust(size) # caps the size if exceeds the field size
            elif fieldType == "D":
                # date: 8 bytes - date stored as a string in the format YYYYMMDD.
                if isinstance(value, date):
                    value = '{:04d}{:02d}{:02d}'.format(value.year, value.month, value.day)
                elif isinstance(value, list) and len(value) == 3:
                    value = '{:04d}{:02d}{:02d}'.format(*value)
                elif value in MISSING:
                    value = b'0' * 8 # QGIS NULL for date type
                elif is_string(value) and len(value) == 8:
                    pass # value is already a date string
                else:
                    raise ShapefileException("Date values must be either a datetime.date object, a list, a YYYYMMDD string, or a missing value.")
            elif fieldType == 'L':
                # logical: 1 byte - initialized to 0x20 (space) otherwise T or F.
                if value in MISSING:
                    value = b' ' # missing is set to space
                elif value in [True,1]:
                    value = b'T'
                elif value in [False,0]:
                    value = b'F'
                else:
                    value = b' ' # unknown is set to space
            else:
                # anything else is forced to string, truncated to the length of the field
                value = b(value, self.encoding, self.encodingErrors)[:size].ljust(size)
            if not isinstance(value, bytes):
                # just in case some of the numeric format() and date strftime() results are still in unicode (Python 3 only)
                value = b(value, 'ascii', self.encodingErrors) # should be default ascii encoding
            if len(value) != size:
                raise ShapefileException(
                    "Shapefile Writer unable to pack incorrect sized value"
                    " (size %d) into field '%s' (size %d)." % (len(value), fieldName, size))
            f.write(value)

    def balance(self):
        """Adds corresponding empty attributes or null geometry records depending
        on which type of record was created to make sure all three files
        are in synch."""
        while self.recNum > self.shpNum:
            self.null()
        while self.recNum < self.shpNum:
            self.record()


    def null(self):
        """Creates a null shape."""
        self.shape(Shape(NULL))


    def point(self, x, y):
        """Creates a POINT shape."""
        shapeType = POINT
        pointShape = Shape(shapeType)
        pointShape.points.append([x, y])
        self.shape(pointShape)

    def pointm(self, x, y, m=None):
        """Creates a POINTM shape.
        If the m (measure) value is not set, it defaults to NoData."""
        shapeType = POINTM
        pointShape = Shape(shapeType)
        pointShape.points.append([x, y, m])
        self.shape(pointShape)

    def pointz(self, x, y, z=0, m=None):
        """Creates a POINTZ shape.
        If the z (elevation) value is not set, it defaults to 0.
        If the m (measure) value is not set, it defaults to NoData."""
        shapeType = POINTZ
        pointShape = Shape(shapeType)
        pointShape.points.append([x, y, z, m])
        self.shape(pointShape)
        

    def multipoint(self, points):
        """Creates a MULTIPOINT shape.
        Points is a list of xy values."""
        shapeType = MULTIPOINT
        points = [points] # nest the points inside a list to be compatible with the generic shapeparts method
        self._shapeparts(parts=points, shapeType=shapeType)

    def multipointm(self, points):
        """Creates a MULTIPOINTM shape.
        Points is a list of xym values.
        If the m (measure) value is not included, it defaults to None (NoData)."""
        shapeType = MULTIPOINTM
        points = [points] # nest the points inside a list to be compatible with the generic shapeparts method
        self._shapeparts(parts=points, shapeType=shapeType)

    def multipointz(self, points):
        """Creates a MULTIPOINTZ shape.
        Points is a list of xyzm values.
        If the z (elevation) value is not included, it defaults to 0.
        If the m (measure) value is not included, it defaults to None (NoData)."""
        shapeType = MULTIPOINTZ
        points = [points] # nest the points inside a list to be compatible with the generic shapeparts method
        self._shapeparts(parts=points, shapeType=shapeType)


    def line(self, lines):
        """Creates a POLYLINE shape.
        Lines is a collection of lines, each made up of a list of xy values."""
        shapeType = POLYLINE
        self._shapeparts(parts=lines, shapeType=shapeType)

    def linem(self, lines):
        """Creates a POLYLINEM shape.
        Lines is a collection of lines, each made up of a list of xym values.
        If the m (measure) value is not included, it defaults to None (NoData)."""
        shapeType = POLYLINEM
        self._shapeparts(parts=lines, shapeType=shapeType)

    def linez(self, lines):
        """Creates a POLYLINEZ shape.
        Lines is a collection of lines, each made up of a list of xyzm values.
        If the z (elevation) value is not included, it defaults to 0.
        If the m (measure) value is not included, it defaults to None (NoData)."""
        shapeType = POLYLINEZ
        self._shapeparts(parts=lines, shapeType=shapeType)


    def poly(self, polys):
        """Creates a POLYGON shape.
        Polys is a collection of polygons, each made up of a list of xy values.
        Note that for ordinary polygons the coordinates must run in a clockwise direction.
        If some of the polygons are holes, these must run in a counterclockwise direction."""
        shapeType = POLYGON
        self._shapeparts(parts=polys, shapeType=shapeType)

    def polym(self, polys):
        """Creates a POLYGONM shape.
        Polys is a collection of polygons, each made up of a list of xym values.
        Note that for ordinary polygons the coordinates must run in a clockwise direction.
        If some of the polygons are holes, these must run in a counterclockwise direction.
        If the m (measure) value is not included, it defaults to None (NoData)."""
        shapeType = POLYGONM
        self._shapeparts(parts=polys, shapeType=shapeType)

    def polyz(self, polys):
        """Creates a POLYGONZ shape.
        Polys is a collection of polygons, each made up of a list of xyzm values.
        Note that for ordinary polygons the coordinates must run in a clockwise direction.
        If some of the polygons are holes, these must run in a counterclockwise direction.
        If the z (elevation) value is not included, it defaults to 0.
        If the m (measure) value is not included, it defaults to None (NoData)."""
        shapeType = POLYGONZ
        self._shapeparts(parts=polys, shapeType=shapeType)


    def multipatch(self, parts, partTypes):
        """Creates a MULTIPATCH shape.
        Parts is a collection of 3D surface patches, each made up of a list of xyzm values.
        PartTypes is a list of types that define each of the surface patches.
        The types can be any of the following module constants: TRIANGLE_STRIP,
        TRIANGLE_FAN, OUTER_RING, INNER_RING, FIRST_RING, or RING.
        If the z (elavation) value is not included, it defaults to 0.
        If the m (measure) value is not included, it defaults to None (NoData)."""
        shapeType = MULTIPATCH
        polyShape = Shape(shapeType)
        polyShape.parts = []
        polyShape.points = []
        for part in parts:
            # set part index position
            polyShape.parts.append(len(polyShape.points))
            # add points
            for point in part:
                # Ensure point is list
                if not isinstance(point, list):
                    point = list(point)
                polyShape.points.append(point)
        polyShape.partTypes = partTypes
        # write the shape
        self.shape(polyShape)


    def _shapeparts(self, parts, shapeType):
        """Internal method for adding a shape that has multiple collections of points (parts):
        lines, polygons, and multipoint shapes.
        """
        polyShape = Shape(shapeType)
        polyShape.parts = []
        polyShape.points = []
        for part in parts:
            # set part index position
            polyShape.parts.append(len(polyShape.points))
            # add points
            for point in part:
                # Ensure point is list
                if not isinstance(point, list):
                    point = list(point)
                polyShape.points.append(point)
        # write the shape
        self.shape(polyShape)

    def field(self, name, fieldType="C", size="50", decimal=0):
        """Adds a dbf field descriptor to the shapefile."""
        if fieldType == "D":
            size = "8"
            decimal = 0
        elif fieldType == "L":
            size = "1"
            decimal = 0
        if len(self.fields) >= 2046:
            raise ShapefileException(
                "Shapefile Writer reached maximum number of fields: 2046.")
        self.fields.append((name, fieldType, size, decimal))

##    def saveShp(self, target):
##        """Save an shp file."""
##        if not hasattr(target, "write"):
##            target = os.path.splitext(target)[0] + '.shp'
##        self.shp = self.__getFileObj(target)
##        self.__shapefileHeader(self.shp, headerType='shp')
##        self.shp.seek(100)
##        self._shp.seek(0)
##        chunk = True
##        while chunk:
##            chunk = self._shp.read(self.bufsize)
##            self.shp.write(chunk)
##
##    def saveShx(self, target):
##        """Save an shx file."""
##        if not hasattr(target, "write"):
##            target = os.path.splitext(target)[0] + '.shx'
##        self.shx = self.__getFileObj(target)
##        self.__shapefileHeader(self.shx, headerType='shx')
##        self.shx.seek(100)
##        self._shx.seek(0)
##        chunk = True
##        while chunk:
##            chunk = self._shx.read(self.bufsize)
##            self.shx.write(chunk)
##
##    def saveDbf(self, target):
##        """Save a dbf file."""
##        if not hasattr(target, "write"):
##            target = os.path.splitext(target)[0] + '.dbf'
##        self.dbf = self.__getFileObj(target)
##        self.__dbfHeader() # writes to .dbf
##        self._dbf.seek(0)
##        chunk = True
##        while chunk:
##            chunk = self._dbf.read(self.bufsize)
##            self.dbf.write(chunk)

##    def save(self, target=None, shp=None, shx=None, dbf=None):
##        """Save the shapefile data to three files or
##        three file-like objects. SHP and DBF files can also
##        be written exclusively using saveShp, saveShx, and saveDbf respectively.
##        If target is specified but not shp, shx, or dbf then the target path and
##        file name are used.  If no options or specified, a unique base file name
##        is generated to save the files and the base file name is returned as a 
##        string. 
##        """
##        # Balance if already not balanced
##        if shp and dbf:
##            if self.autoBalance:
##                self.balance()
##            if self.recNum != self.shpNum:
##                raise ShapefileException("When saving both the dbf and shp file, "
##                                         "the number of records (%s) must correspond "
##                                         "with the number of shapes (%s)" % (self.recNum, self.shpNum))
##        # Save
##        if shp:
##            self.saveShp(shp)
##        if shx:
##            self.saveShx(shx)
##        if dbf:
##            self.saveDbf(dbf)
##        # Create a unique file name if one is not defined
##        if not shp and not shx and not dbf:
##            generated = False
##            if not target:
##                temp = tempfile.NamedTemporaryFile(prefix="shapefile_",dir=os.getcwd())
##                target = temp.name
##                generated = True         
##            self.saveShp(target)
##            self.shp.close()
##            self.saveShx(target)
##            self.shx.close()
##            self.saveDbf(target)
##            self.dbf.close()
##            if generated:
##                return target

# Begin Testing
def test(**kwargs):
    import doctest
    doctest.NORMALIZE_WHITESPACE = 1
    verbosity = kwargs.get('verbose', 0)
    if verbosity == 0:
        print('Running doctests...')

    # ignore py2-3 unicode differences
    import re
    class Py23DocChecker(doctest.OutputChecker):
        def check_output(self, want, got, optionflags):
            if sys.version_info[0] == 2:
                got = re.sub("u'(.*?)'", "'\\1'", got)
                got = re.sub('u"(.*?)"', '"\\1"', got)
            res = doctest.OutputChecker.check_output(self, want, got, optionflags)
            return res
        def summarize(self):
            doctest.OutputChecker.summarize(True)

    # run tests
    runner = doctest.DocTestRunner(checker=Py23DocChecker(), verbose=verbosity)
    with open("README.md","rb") as fobj:
        test = doctest.DocTestParser().get_doctest(string=fobj.read().decode("utf8").replace('\r\n','\n'), globs={}, name="README", filename="README.md", lineno=0)
    failure_count, test_count = runner.run(test)

    # print results
    if verbosity:
        runner.summarize(True)
    else:
        if failure_count == 0:
            print('All test passed successfully')
        elif failure_count > 0:
            runner.summarize(verbosity)

    return failure_count
    
if __name__ == "__main__":
    """
    Doctests are contained in the file 'README.md', and are tested using the built-in
    testing libraries. 
    """
    failure_count = test()
    sys.exit(failure_count)