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 + (len(self._shapes) * 8)) // 2)))
# Version, Shape type
f.write(pack("<2i", 1000, self.shapeType))
# The shapefile's bounding box (lower left, upper right)
if self.shapeType != 0:
try:
f.write(pack("<4d", *self.bbox()))
except error:
raise ShapefileException(
"Failed to write shapefile bounding box. Floats required.")
else:
f.write(pack("<4d", 0, 0, 0, 0))
# Elevation
z = self.zbox()
# Measure
m = self.mbox()
try:
f.write(pack("<4d", z[0], z[1], m[0], m[1]))
except error:
raise ShapefileException(
"Failed to write shapefile elevation and measure values. Floats required."
)
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
# 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"]
if hasattr(self.shp, "seek"):
self.shp.seek(0)
if "shx" in kwargs.keys():
if hasattr(kwargs["shx"], "read"):
self.shx = kwargs["shx"]
if hasattr(self.shx, "seek"):
self.shx.seek(0)
if "dbf" in kwargs.keys():
if hasattr(kwargs["dbf"], "read"):
self.dbf = kwargs["dbf"]
if hasattr(self.dbf, "seek"):
self.dbf.seek(0)
if self.shp or self.dbf:
self.load()
else:
raise ShapefileException(
"Shapefile Reader requires a shapefile or file-like object.")
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 __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 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 object or file name as an
argument."""
if shapefile:
shapeName, ext = os.path.splitext(shapefile)
self.shapeName = shapeName
try:
self.shp = open("%s.shp" % shapeName, "rb")
except IOError:
raise ShapefileException("Unable to open %s.shp" % shapeName)
try:
self.shx = open("%s.shx" % shapeName, "rb")
except IOError:
raise ShapefileException("Unable to open %s.shx" % shapeName)
try:
self.dbf = open("%s.dbf" % shapeName, "rb")
except IOError:
raise ShapefileException("Unable to open %s.dbf" % shapeName)
if self.shp:
self.__shpHeader()
if self.dbf:
self.__dbfHeader()
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.elevation = Array('d', unpack("<2d", shp.read(16)))
# Measure
self.measure = Array('d', unpack("<2d", shp.read(16)))
def __shpRecords(self):
"""Write the shp records"""
f = self.__getFileObj(self.shp)
f.seek(100)
recNum = 1
for s in self._shapes:
self._offsets.append(f.tell())
# Record number, Content length place holder
f.write(pack(">2i", recNum, 0))
recNum += 1
start = f.tell()
# Shape Type
if self.shapeType != 31:
s.shapeType = self.shapeType
f.write(pack("<i", s.shapeType))
# 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(
"Falied to write bounding box for record %s. Expected floats."
% recNum)
# 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, 23, 25, 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, 23, 25, 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."
% recNum)
# Write z extremes and values
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."
% recNum)
try:
if hasattr(s, "z"):
f.write(pack("<%sd" % len(s.z), *s.z))
else:
[f.write(pack("<d", p[2])) for p in s.points]
except error:
raise ShapefileException(
"Failed to write elevation values for record %s. Expected floats."
% recNum)
# Write m extremes and values
if s.shapeType in (13, 15, 18, 23, 25, 28, 31):
try:
if hasattr(s, "m"):
f.write(pack("<%sd" % len(s.m), *s.m))
else:
f.write(pack("<2d", *self.__mbox([s])))
except error:
raise ShapefileException(
"Failed to write measure extremes for record %s. Expected floats"
% recNum)
try:
[f.write(pack("<d", p[3])) for p in s.points]
except error:
raise ShapefileException(
"Failed to write measure values for record %s. Expected floats"
% recNum)
# 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."
% recNum)
# Write a single Z value
if s.shapeType == 11:
if hasattr(s, "z"):
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."
% recNum)
else:
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."
% recNum)
# Write a single M value
if s.shapeType in (11, 21):
if hasattr(s, "m"):
try:
if not s.m:
s.m = (0, )
f.write(pack("<1d", s.m[0]))
except error:
raise ShapefileException(
"Failed to write measure value for record %s. Expected floats."
% recNum)
else:
try:
if len(s.points[0]) < 4:
s.points[0].append(0)
f.write(pack("<1d", s.points[0][3]))
except error:
raise ShapefileException(
"Failed to write measure value for record %s. Expected floats."
% recNum)
# Finalize record length as 16-bit words
finish = f.tell()
length = (finish - start) // 2
self._lengths.append(length)
# start - 4 bytes is the content length field
f.seek(start - 4)
f.write(pack(">i", length))
f.seek(finish)
def assertFile(self, attr):
# attr should be 'shp', 'dbf', or 'shx'
if not getattr(self, attr, None):
raise ShapefileException(
"Shapefile Reader requires a shapefile or file-like object."
"(no %s file found)" % attr)