Learn/pyshpLargeWriter.py at master · GeospatialPython/Learn · GitHub

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importcStringIO
importstruct
importshapefile
importrandom
importtime

classLargeWriter:
def__init__(self, filename=None, shapeType=1, hasShx=True):
self.filename=filename
self.hasShx=hasShx
# Count records for metadata
self.count=0
# Maximum number of records before disk flush
self.max=1000
self.started=False
self.minx=0
self.miny=0
self.maxx=0
self.maxy=0
self.numRecs=0
self.tmpShp=cStringIO.StringIO()
ifself.hasShx:
self.tmpShx=cStringIO.StringIO()
self.tmpDbf=cStringIO.StringIO()
self.shp=open("%s.shp"%self.filename, "wb")
ifself.hasShx:
self.shx=open("%s.shx"%self.filename, "wb")
self.dbf=open("%s.dbf"%self.filename, "wb")
self.dbfHdrLen=0
self.w=shapefile.Writer(shapeType)

defendcap(self):
"""First and last batches"""
self.started=True
self.tmpShp.seek(36)
self.xmin=struct.unpack("<d", self.tmpShp.read(8))[0]
self.ymin=struct.unpack("<d", self.tmpShp.read(8))[0]
self.xmax=struct.unpack("<d", self.tmpShp.read(8))[0]
self.ymax=struct.unpack("<d", self.tmpShp.read(8))[0]
self.tmpShp.seek(0)
ifself.hasShx:
self.tmpShx.seek(0)
self.tmpDbf.seek(8)
# The length of the dbf header will not change
self.dbfHdrLen=struct.unpack("<H", self.tmpDbf.read(2))[0]
self.tmpDbf.seek(0)
self.shp.write(self.tmpShp.read())
ifself.hasShx:
self.shx.write(self.tmpShx.read())
self.dbf.write(self.tmpDbf.read())

defbatch(self):
self.started=True
# Update shx offsets
ifself.hasShx:
self.tmpShx.seek(0,2)
shxsz=self.tmpShx.tell()
shxcur=100
adder=self.shx.tell() /2
self.tmpShx.seek(100)
whileshxcur<shxsz:
offset=struct.unpack(">i", self.tmpShx.read(4))[0]
newOffset=adder+offset
self.tmpShx.seek(-4, 1)
self.tmpShx.write(struct.pack(">i", newOffset))
self.tmpShx.seek(8, 1)
shxcur=self.tmpShx.tell()
# Get shp bounding box
self.tmpShp.seek(36)
xmin=struct.unpack("<d", self.tmpShp.read(8))[0]
ymin=struct.unpack("<d", self.tmpShp.read(8))[0]
xmax=struct.unpack("<d", self.tmpShp.read(8))[0]
ymax=struct.unpack("<d", self.tmpShp.read(8))[0]
self.xmin=min([self.xmin, xmin])
self.ymin=min([self.ymin, ymin])
self.xmax=max([self.xmax, xmax])
self.ymax=max([self.ymax, ymax])
self.tmpShp.seek(100)
self.tmpShx.seek(100)
self.tmpDbf.seek(self.dbfHdrLen)
self.shp.write(self.tmpShp.read())
ifself.hasShx:
self.shx.write(self.tmpShx.read())
self.dbf.write(self.tmpDbf.read())

defrecord(self, *recordList):
"""Count the records and save them"""
self.count+=1
self.numRecs+=1
apply(self.w.record, recordList)
ifself.count>=self.max:
ifself.hasShx:
self.w.save(shp=self.tmpShp, shx=self.tmpShx, dbf=self.tmpDbf)
else:
self.w.save(shp=self.tmpShp, dbf=self.tmpDbf)
ifnotself.started:
self.endcap()
else:
self.batch()
# Reset the buffers for the next batch
self.tmpShp=cStringIO.StringIO()
ifself.hasShx:
self.tmpShx=cStringIO.StringIO()
self.tmpDbf=cStringIO.StringIO()
self.count=0

defsave(self):
self.shp.seek(0,2)
shpLength=self.shp.tell() /2
self.shp.seek(24)
self.shp.write(struct.pack(">i", shpLength))
self.shp.seek(36)
self.shp.write(struct.pack("<4d", self.xmin,self.ymin,self.xmax,self.ymax))
ifself.hasShx:
self.shx.seek(0,2)
shxLength=self.shx.tell() /2
self.shx.seek(24)
self.shx.write(struct.pack(">i", shxLength))
self.shx.seek(36)
self.shx.write(struct.pack("<4d", self.xmin,self.ymin,self.xmax,self.ymax))
# update dbf record count
self.dbf.seek(4)
self.dbf.write(struct.pack("<L", self.numRecs))
self.shp.close()
ifself.hasShx:
self.shx.close()
self.dbf.close()

defrandom_point():
"""returns a randomly generated point"""
x=random.uniform(-180,180)
y=random.uniform(-90,90)
returnx,y

defprogress(last, count, total):
"""Print percent completed"""
percent=int((count/(total*1.0))*100.0)
ifpercent%10.0==0andpercent>last:
print"%s %% done - Shape %s/%s at %s"% (percent, count, total, time.asctime())
returnpercent


# Create a large shapefile writer with
# a filname and a shapefile type.
# 1=Point, 5=Polygon
lw=LargeWriter("giantShp", 1, hasShx=True)
#lw = LargeWriter("giantShp", 1, hasShx=False)

# Add some dbf fields
lw.w.field("ID", "C", "40")
lw.w.field("X", "C", "40")
lw.w.field("Y", "C", "40")

# Progress counter
status=0

# Number of random points to write
total=107374177

foriinrange(total):
# Progress meter
status=progress(status, i, total)
# Generate a random point
x,y=random_point()
x1,y1=random_point()
x2,y2=random_point()
x3,y3=random_point()
x4,y4=random_point()
# Call the shapefile point() method
lw.w.point(x,y)
# Call the specialized record method
lw.record(i,x,y)
#lw.w.poly(parts=[[[x,y],[x1,y1],[x2,y2],[x3,y3],[x4,y4]]])
#lw.record(i,x,y)
#x,y = random_point()
#x1,y1 = random_point()
#x2,y2 = random_point()
#x3,y3 = random_point()
#x4,y4 = random_point()
#Call the shapefile poly() method
#lw.w.poly(parts=[[[x,y],[x1,y1],[x2,y2],[x3,y3],[x4,y4]]])
#Call the specialized record method
#lw.record(i,x,y)

# Special LargeWriter save method
lw.save()