"""
Created on Mon Jun 11 18:02:27 2012
@author: pietro
"""
import ctypes
import grass.lib.gis as libgis
import grass.lib.raster as libraster
import grass.lib.segment as libseg
from grass.pygrass.raster.raster_type import TYPE as RTYPE
[docs]class Segment(object):
def __init__(self, srows=64, scols=64, maxmem=100):
self.srows = srows
self.scols = scols
self.maxmem = maxmem
self.c_seg = ctypes.pointer(libseg.SEGMENT())
[docs] def rows(self):
return libraster.Rast_window_rows()
[docs] def cols(self):
return libraster.Rast_window_cols()
[docs] def nseg(self):
rows = self.rows()
cols = self.cols()
return int(
((rows + self.srows - 1) / self.srows)
* ((cols + self.scols - 1) / self.scols)
)
[docs] def segments_in_mem(self):
if self.maxmem > 0 and self.maxmem < 100:
seg_in_mem = (self.maxmem * self.nseg()) / 100
else:
seg_in_mem = 4 * (self.rows() / self.srows + self.cols() / self.scols + 2)
if seg_in_mem == 0:
seg_in_mem = 1
return seg_in_mem
[docs] def open(self, mapobj):
"""Open a segment it is necessary to pass a RasterSegment object."""
self.val = RTYPE[mapobj.mtype]["grass def"]()
size = ctypes.sizeof(RTYPE[mapobj.mtype]["ctypes"])
file_name = libgis.G_tempfile()
libseg.Segment_open(
self.c_seg,
file_name,
self.rows(),
self.cols(),
self.srows,
self.scols,
size,
self.nseg(),
)
self.flush()
[docs] def init(self, mapobj, file_name=""):
if file_name == "":
file_name = mapobj.temp_file.name
mapobj.temp_file = open(file_name, "w")
libseg.Segment_init(self.c_seg, mapobj.temp_file.fileno(), self.segments_in_mem)
[docs] def get_row(self, row_index, buf):
"""Return the row using, the `segment` method"""
libseg.Segment_get_row(self.c_seg, buf.p, row_index)
return buf
[docs] def put_row(self, row_index, buf):
"""Write the row using the `segment` method"""
libseg.Segment_put_row(self.c_seg, buf.p, row_index)
[docs] def get(self, row_index, col_index):
"""Return the value of the map"""
libseg.Segment_get(self.c_seg, ctypes.byref(self.val), row_index, col_index)
return self.val.value
[docs] def put(self, row_index, col_index):
"""Write the value to the map"""
libseg.Segment_put(self.c_seg, ctypes.byref(self.val), row_index, col_index)
[docs] def get_seg_number(self, row_index, col_index):
"""Return the segment number"""
return row_index / self.srows * self.cols / self.scols + col_index / self.scols
[docs] def flush(self):
"""Flush pending updates to disk.
Forces all pending updates generated by Segment_put() to be written to
the segment file seg. Must be called after the final Segment_put()
to force all pending updates to disk. Must also be called before the
first call to Segment_get_row."""
libseg.Segment_flush(self.c_seg)
[docs] def close(self):
"""Free memory allocated to segment and delete temp file."""
libseg.Segment_close(self.c_seg)
[docs] def release(self):
"""Free memory allocated to segment.
Releases the allocated memory associated with the segment file seg.
Note: Does not close the file. Does not flush the data which may be
pending from previous Segment_put() calls."""
libseg.Segment_release(self.c_seg)
