ctypes variable length structures

Question

Ever since I read Dave Beazley\'s post on binary I/O handling (http://dabeaz.blogspot.com/2009/08/python-binary-io-handling.html) I\'ve wanted to create a Python library for

Answer 1

And now, for something completly different - If all you need is dealing with the Data, possibly the "most Pythonic" way is not trying to use ctypes to handle raw data in memory at all.

This approach just uses struct.pack and .unpack to serialiase/unserialize teh data as it moves on/off the your app. The "Points" class can accept the raw bytes, and creates python objects from that, and can serialize the data trough a "get_data" method. Otherwise, it is just am ordinary python list.

import struct

class Point(object):
    def __init__(self, x=0.0, y=0.0, z= 0.0):
        self.x, self.y, self.z = x,y,z
    def get_data(self):
        return struct.pack("ffffd", self.x, self.y, self.z)


class Points(list):
    def __init__(self, data=None):
        if data is None:
            return
        pointsize = struct.calcsize("ffffd")
        for index in xrange(struct.calcsize("i"), len(data) - struct.calcsize("i"), pointsize):
            point_data = struct.unpack("ffffd", data[index: index + pointsize])
            self.append(Point(*point_data))

    def get_data(self):
        return struct.pack("i", len(self)) + "".join(p.get_data() for p in self)