"converts the bitfield 001110010110...100 to the respective string"

	"""Converts array of bits set to an hex-string."""

	octets = [0] * (24 * 7 / 8)

	# convert list of bit numbers to bit-string

	# bitstring = '0' * 168

	bitstring = ''.join( map( lambda x: x in logontimes and '1' or '0', range( 168 ) ) )

	# for idx in logontimes:

	# 	bitstring[ idx ] = '1'

	logontimes = bitstring

	# consecutive bytes mean consecutive 8-hrs-intervals, but the leftmost bit stands for

	# consecutive bytes mean consecutive 8-hrs-intervals, but the MSB stands for

	# the last hour in that interval, the 2nd but leftmost bit for the second-but-last

	# the last hour in that interval, the 2nd leftmost bit for the second-to-last

	# See http://ma.ph-freiburg.de/tng/tng-technical/2003-04/msg00015.html for details.

	# See <http://ma.ph-freiburg.de/tng/tng-technical/2003-04/msg00015.html> for details.

	for hour in logontimes:

	newtimes = ""

		idx, bit = divmod(hour, 8)

	for i in range(0,21):

		octets[idx] |= 1 << bit

		bitlist=list(logontimes[(i*8):(i*8)+8])

	return ''.join(['%02x' % _ for _ in octets])

		bitlist.reverse()

		newtimes+="".join(bitlist)

	logontimes = newtimes

	# create a hexnumber from each 8-bit-segment

	ret=""

	for i in range(0,21):

	        val=0

	        exp=7

	        for j in range((i*8), (i*8)+8):

	                if not (logontimes[j]=="0"):

	                        val+=2**exp

	                exp-=1

		# we now have: 0<=val<=255

	        hx=hex(val)[2:4]

	        if len(hx)==1: hx="0"+hx

	        ret+=hx

	return ret

	"converts the string to a bit array"

	"""Converts hex-string to an array of bits set."""

	times = logontimes[0].ljust(42, '0')[:42]

	times=logontimes[0][:42]

	assert len(times) == 24 * 7 / 4

	while len(times)<42:

	octets = [int(times[i : i + 2], 16) for i in range(0, len(times), 2)]

		times=times

	assert len(octets) == 24 * 7 / 8

        ret=""

	return [idx * 8 + bit

        for i in range(0,42,2):

			for (idx, value) in enumerate(octets)

                val=int(times[i:i+2],16)

			for bit in range(8)

                ret+=intToBinary(val)

			if value & (1 << bit)]

	# reverse order of the bits in each byte. See above for details

	newtime = ""

	for i in range(0, 21):

		bitlist=list(ret[(i*8):(i*8)+8])

		bitlist.reverse()

		newtime+="".join(bitlist)

	# convert bit-string to list

	return filter( lambda i: newtime[ i ] == '1', range( 168 ) )

def intToBinary(val):

        ret=""

        while val>0:

                ret=str(val&1)+ret

                val=val>>1

        # pad with leading 0s until length is n*8

        if ret=="": ret="0"

        while not (len(ret)%8==0):

                ret="0"+ret

        return ret