timestamp interval rdd

import struct
from ctypes import *
import numpy as np
def get_timespan(fn):
    with open(fn, "rb") as fp:
        fp.seek(1024)
        data = True
        first = None
        last = None
        while data:
            data = fp.read(16)
            if data:
                if not first:
                    first = struct.unpack('dd', data)[0]
                last = struct.unpack('dd', data)[0]
        #print(first, last)
        return (round(first, 2), round(last+0.01, 2))


def make_timestamp_rdd(span, step, outfile):
    offset = struct.pack("I", 1024)
    padding = struct.pack("I", 0)
    samples = struct.pack("Q", 0)
    first_val = struct.pack("f", span[0])
    last_val = struct.pack("f", span[1])
    min_val = struct.pack("f", 0)
    max_val = struct.pack("f", 0)
    header_data = offset + padding + samples + first_val + last_val + min_val + max_val
    with open(outfile, "wb") as fp:
        fp.write(header_data)
        fp.write('\x00'*(1024-32))
        ts = span[0]
        samples = 0
        while ts <= span[1]:
            fp.write(struct.pack('dd', ts,samples))
            ts += step
            samples += 1
        fp.seek(8)
        fp.write(struct.pack("Q", samples))
        fp.seek(16)
        fp.write(struct.pack("f", samples))
        fp.seek(24)
        fp.write(struct.pack("f", samples))
        print('{} samples written to {}'.format(samples, outfile))
    return


span = get_timespan("Test_Point_PIDD_Out.rdd")
make_timestamp_rdd(span, 0.01, "timestamp.rdd")