pygrass.raster.rowio — GRASS Python Library documentation

# Source code for pygrass.raster.rowio

    """
    Created on Mon Jun 18 13:22:38 2012

    @author: pietro
    """

    import ctypes

    import grass.lib.rowio as librowio
    import grass.lib.raster as librast

    from grass.pygrass.errors import GrassError
    from grass.pygrass.raster.raster_type import TYPE as RTYPE

    CMPFUNC = ctypes.CFUNCTYPE(
        ctypes.c_int, ctypes.c_int, ctypes.c_void_p, ctypes.c_int, ctypes.c_int
    )

    def getmaprow_CELL(fd, buf, row, l):
        librast.Rast_get_c_row(fd, ctypes.cast(buf, ctypes.POINTER(librast.CELL)), row)
        return 1

    def getmaprow_FCELL(fd, buf, row, l):
        librast.Rast_get_f_row(fd, ctypes.cast(buf, ctypes.POINTER(librast.FCELL)), row)
        return 1

    def getmaprow_DCELL(fd, buf, row, l):
        librast.Rast_get_d_row(fd, ctypes.cast(buf, ctypes.POINTER(librast.DCELL)), row)
        return 1

    get_row = {
        "CELL": CMPFUNC(getmaprow_CELL),
        "FCELL": CMPFUNC(getmaprow_FCELL),
        "DCELL": CMPFUNC(getmaprow_DCELL),
    }

    class RowIO:
        def __init__(self):
            self.c_rowio = librowio.ROWIO()
            self.fd = None
            self.rows = None
            self.cols = None
            self.mtype = None
            self.row_size = None

        def open(self, fd, rows, cols, mtype):
            self.fd = fd
            self.rows = rows
            self.cols = cols
            self.mtype = mtype
            self.row_size = ctypes.sizeof(RTYPE[mtype]["grass def"] * cols)
            if (
                librowio.Rowio_setup(
                    ctypes.byref(self.c_rowio),
                    self.fd,
                    self.rows,
                    self.row_size,
                    get_row[self.mtype],
                    get_row[self.mtype],
                )
                == -1
            ):
                raise GrassError("Fatal error, Rowio not setup correctly.")

        def release(self):
            librowio.Rowio_release(ctypes.byref(self.c_rowio))
            self.fd = None
            self.rows = None
            self.cols = None
            self.mtype = None

        def get(self, row_index, buf):
            rowio_buf = librowio.Rowio_get(ctypes.byref(self.c_rowio), row_index)
            ctypes.memmove(buf.p, rowio_buf, self.row_size)
            return buf

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