Jurek-Data

#!/usr/bin/env python

from datetime import datetime
from time import mktime
import os

def v_to_n(wind, vbatt, ibatt):
    """ Merge three values into one 16-bit integer """
    return ((wind + 10)<<10) + ((vbatt + 10)<<5) + (ibatt + 10)

def n_to_v(n):
    """ Convert 16-bit integer into three values """
    wind = (n>>10) - 10
    n -= (wind + 10) << 10
    vbatt = (n>>5) - 10
    n -= (vbatt + 10) << 5
    ibatt = n - 10
    return (wind, vbatt, ibatt)

def n_to_c(n):
    """ Convert 16-bit integer into two bytes """
    a = n >> 8
    b = n - (a<<8)
    return chr(a) + chr(b)

def c_to_n(c):
    """ Convert two bytes into 16-bit integer """
    a = ord(c[0])
    b = ord(c[1])
    return (a<<8) + b

def writedata(datadir, c):
    """ Write two bytes to correct place """

    # Start of day and tiemstamp now
    sod = int(mktime(datetime.utcnow().date().timetuple()))
    now = int(mktime(datetime.utcnow().timetuple()))

    # Diff from now to start of day
    diff = now - sod

    # Open file
    with open(os.path.join(datadir, str(sod)), "a+b") as f:
        # Get file size and append zeroes if necessary
        f.seek(0, 2)
        missing = 2*diff - f.tell() - 2
        if missing > 0:
            f.write(chr(0) * missing)
        # Write data and close
        f.write(c)

def readdata(datadir, t):
    """ Read two bytes from correct position """

    # Start of day and given timestamp
    now = int(mktime(t.timetuple()))
    sod = int(mktime(t.date().timetuple()))

    # Open file
    with open(os.path.join(datadir, str(sod)), "r+b") as f:
        # Seek to correct position and read two bytes
        f.seek(2*(now - sod) - 2)
        return f.read(2)

Code under MirOS or Simplified BSD license