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|
#!/usr/bin/env python2
#
# Decode EDI for debugging
import sys
import struct
from crc import crc16
from reedsolo import RSCodec
class Printer:
def __init__(self):
self.indent = 0
def pr(self, s):
print(" " * self.indent + s)
def hexpr(self, header, seq):
if isinstance(seq, str):
seq = bytearray(seq)
print(" " * self.indent +
header +
" ({}): ".format(len(seq)) +
" ".join("{0:02x}".format(el) for el in seq))
def inc(self):
self.indent += 1
def dec(self):
self.indent -= 1
class BufferedFile:
def __init__(self, fname):
self.buf = []
if fname == "-":
self.fd = sys.stdin
else:
self.fd = open(fname, "rb")
def read(self, n):
if not self.buf:
return self.fd.read(n)
else:
if len(self.buf) < n:
self.buf.extend(self.fd.read(n - len(self.buf)))
if len(self.buf) == n:
ret = b"".join(self.buf)
self.buf = []
else:
ret = b"".join(self.buf[:n])
del self.buf[:n]
return ret
def peek(self, n):
dat = self.fd.read(n)
self.buf.extend(dat)
return dat
p = Printer()
# keys=findex
defragmenters = {}
def decode(stream):
p.pr("start")
success = False
sync = stream.peek(2)
if len(sync) < 2:
p.pr("EOF")
return False
if sync == "PF":
if decode_pft(stream):
p.pr("PFT decode success")
success = True
else:
p.pr("PFT decode fail")
elif sync == "AF":
if decode_af(stream, is_stream=True):
p.pr("AF decode success")
success = True
else:
p.pr("AF decode fail")
return success
pft_head_struct = "!2sH3B3BH"
pft_rs_head_struct = "!2B"
pft_addr_head_struct = "!2H"
def decode_pft(stream):
p.inc()
p.pr("start decoding PF")
headerdata = stream.read(12)
header = struct.unpack(pft_head_struct, headerdata)
psync, pseq, findex1, findex2, findex3, fcount1, fcount2, fcount3, fec_ad_plen = header
findex = (findex1 << 16) | (findex2 << 8) | findex3
fcount = (fcount1 << 16) | (fcount2 << 8) | fcount3
fec = (fec_ad_plen & 0x8000) != 0x00
addr = (fec_ad_plen & 0x4000) != 0x00
plen = fec_ad_plen & 0x3FFF
# try to sync according to TS 102 821 Clause 7.4.1
if psync != "PF":
p.pr("No PF Sync")
p.dec()
return False
rs_k = 0
rs_z = 0
if fec:
rs_head = stream.read(2)
rs_k, rs_z = struct.unpack(pft_rs_head_struct, rs_head)
headerdata += rs_head
addr_source = 0
addr_dest = 0
if addr:
addr_head = stream.read(4)
addr_source, addr_dest = struct.unpack(pft_addr_head_struct, addr_head)
headerdata += addr_head
# read CRC
crc = struct.unpack("!H", stream.read(2))[0]
crc_calc = crc16(headerdata)
crc_calc ^= 0xFFFF
crc_ok = crc_calc == crc
if crc_ok:
p.pr("CRC ok")
else:
p.pr("CRC not ok!")
p.pr(" read 0x{:04x}, calculated 0x{:04x}".format(crc, crc_calc))
p.pr("pseq {}".format(pseq))
p.pr("findex {}".format(findex))
p.pr("fcount {}".format(fcount))
if fec:
p.pr("with fec:")
p.pr(" RSk={}".format(rs_k))
p.pr(" RSz={}".format(rs_z))
if addr:
p.pr("with transport header:")
p.pr(" source={}".format(addr_source))
p.pr(" dest={}".format(addr_dest))
p.pr("payload length={}".format(plen))
payload = stream.read(plen)
success = False
if crc_ok and fec:
# Fragmentation and
# Reed solomon decode
if pseq not in defragmenters:
defragmenters[pseq] = Defragmenter(fcount, get_rs_decoder(rs_k, rs_z))
success = defragmenters[pseq].push_fragment(findex, payload)
elif crc_ok and fcount > 1:
# Fragmentation
if pseq not in defragmenters:
defragmenters[pseq] = Defragmenter(fcount, decode_af_fragments)
success = defragmenters[pseq].push_fragment(findex, payload)
elif crc_ok and fcount == 1:
success = decode_af(payload)
p.dec()
return success
class Defragmenter():
def __init__(self, fcount, callback):
self.fragments = [None for i in range(fcount)]
self.fcount = fcount
self.cb = callback
def push_fragment(self, findex, fragment):
self.fragments[findex] = fragment
received_fragments = [f for f in self.fragments if f is not None]
p.pr("Fragments: {} (need {})".format(len(received_fragments), self.fcount))
if len(received_fragments) >= self.fcount:
return self.cb(received_fragments)
# The RS decoder should be able to handle partial lists
# of fragments. The AF decoder cannot
return True
def __repr__(self):
return "<Defragmenter with fcount={}>".format(self.fcount)
def get_rs_decoder(chunk_size, zeropad):
p.pr("Build RS decoder for chunk size={}, zero pad={}".format(chunk_size, zeropad))
def decode_rs(fragments):
p.pr("RS decode {} fragments of length {}".format(
len(fragments), len(fragments[0])))
#for f in fragments:
# p.hexpr(" ZE FRAGMENT", f);
# Transpose fragments to get an RS block
rs_block = "".join("".join(f) for f in zip(*fragments))
# chunks before protection have size chunk_size
# protection adds 48 bytes
# The tuples here are (data, parity)
#p.hexpr(" ZE RS BLOCK", "".join(rs_block))
num_chunks = len(rs_block) / chunk_size
p.pr("{} chunks".format(num_chunks))
data_size = chunk_size + 48
af_packet_size = num_chunks * chunk_size
p.pr("AF Packet size {}".format(af_packet_size))
# Cut the block into list of (data, protection) tuples
rs_chunks = [ (rs_block[i*data_size:i*data_size + chunk_size],
rs_block[i*data_size + chunk_size:(i+1)*data_size])
for i in range(num_chunks)]
#for c in rs_chunks:
# p.hexpr(" ZE CHUNK DATA", c[0]);
# p.hexpr(" ZE CHUNK PROT", c[1]);
rs_codec = RSCodec(48, fcr=1)
protection_ok = True
for chunk, protection in rs_chunks:
#p.pr(" Protection")
#p.hexpr(" OF ZE CHUNK DATA", chunk);
bchunk = bytearray(chunk)
padbytes = 255-(48 + len(chunk))
bchunk = bchunk + bytearray(0 for i in range(padbytes))
recalc_protection = rs_codec.encode(bchunk)[-48:]
if protection != recalc_protection:
p.pr(" PROTECTION ERROR")
p.hexpr(" orig", protection)
p.hexpr(" calc", recalc_protection)
protection_ok = False
else:
p.pr(" PROTECTION OK")
if protection_ok:
p.pr("Protection check: OK")
afpacket = "".join(data for (data, protection) in rs_chunks)
#p.hexpr(" ZE AF PACKET", afpacket)
if zeropad:
return decode_af(afpacket[0:-zeropad])
else:
return decode_af(afpacket)
return decode_rs
af_head_struct = "!2sLHBc"
def decode_af_fragments(fragments):
return decode_af("".join(fragments))
def decode_af(in_data, is_stream=False):
p.pr("AF Packet")
p.inc()
if is_stream:
headerdata = in_data.read(10)
else:
headerdata = in_data[:10]
if len(headerdata) != 10:
p.hexpr("AF Header", headerdata)
sync, plen, seq, ar, pt = struct.unpack(af_head_struct, headerdata)
if sync != "AF":
p.pr("No AF Sync")
p.hexpr("in", in_data)
p.dec()
return False
crc_flag = (ar & 0x80) != 0x00
revision = ar & 0x7F
if is_stream:
payload = in_data.read(plen)
crc = struct.unpack("!H", in_data.read(2))[0]
else:
payload = in_data[10:10+plen]
crc = struct.unpack("!H", in_data[10+plen:10+plen+2])[0]
crc_calc = crc16(headerdata)
crc_calc = crc16(payload, crc_calc)
crc_calc ^= 0xFFFF
crc_ok = crc_calc == crc
if crc_flag and crc_ok:
p.pr("CRC ok")
elif crc_flag:
p.pr("CRC not ok!")
p.pr(" CRC: is 0x{0:04x}, calculated 0x{1:04x}".format(crc, crc_calc))
else:
p.pr("No CRC")
p.pr("plen {}".format(plen))
p.pr("seq {}".format(seq))
p.pr("revision {}".format(revision))
p.pr("protocol type {}".format(pt))
success = False
if pt == "T":
success = decode_tag(payload)
p.dec()
return success
tag_item_head_struct = "!4sL"
def tagitems(tagpacket):
i = 0
while i+8 < len(tagpacket):
name, length = struct.unpack(tag_item_head_struct, tagpacket[i:i+8])
# length is in bits, because it's more annoying this way
assert(length % 8 == 0)
length /= 8
tag_value = tagpacket[i+8:i+8+length]
yield {'name': name, 'length': length, 'value': tag_value}
i += 8 + length
def decode_tag(tagpacket):
p.pr("Tag packet len={}".format(len(tagpacket)))
p.inc()
for item in tagitems(tagpacket):
if item['name'].startswith("*ptr"):
decode_starptr(item)
elif item['name'] == "deti":
decode_deti(item)
elif item['name'].startswith("est"):
decode_estn(item)
else:
p.pr("Tag item '{}' ({})".format(item['name'], item['length']))
p.dec()
return True
item_starptr_header_struct = "!4sHH"
def decode_starptr(item):
p.pr("TAG item {} ({})".format(item['name'], item['length']))
p.inc()
tag_value = item['value']
unpacked = struct.unpack(item_starptr_header_struct, tag_value)
protocol, major, minor = unpacked
p.pr("Protocol {}, Ver {} {}".format(
protocol, major, minor) )
p.dec()
item_deti_header_struct = "!BBBBH"
def decode_deti(item):
p.pr("TAG item {} ({})".format(item['name'], item['length']))
p.inc()
tag_value = item['value']
unpacked = struct.unpack(item_deti_header_struct, tag_value[:6])
flag_fcth, fctl, stat, mid_fp, mnsc = unpacked
atstf = flag_fcth & 0x80 != 0
if atstf:
utco, seconds, tsta1, tsta2, tsta3 = struct.unpack("!BL3B", tag_value[6:6+8])
tsta = (tsta1 << 16) | (tsta2 << 8) | tsta3
ficf = flag_fcth & 0x40 != 0
rfudf = flag_fcth & 0x20 != 0
fcth = flag_fcth & 0x1F
fct = (fcth * 250) + fctl
mid = (mid_fp >> 6) & 0x03
fp = (mid_fp >> 3) & 0x07
p.pr("FICF = {}".format(ficf))
p.pr("ATST = {}".format(atstf))
p.pr("RFUDF = {}".format(rfudf))
p.pr("FCT = {} (0x{:02x} 0x{:02x})".format(fct, fcth, fctl))
p.pr("STAT = 0x{:02x}".format(stat))
p.pr("Mode id = {}".format(mid))
p.pr("Frame phase = {}".format(fp))
p.pr("MNSC = 0x{:02x}".format(mnsc))
if atstf:
p.pr("UTCOffset = {}".format(utco))
p.pr("Seconds = {}".format(seconds))
p.pr("TSTA = {}".format(tsta))
len_fic = len(tag_value) - 2 - 4
if atstf:
len_fic -= 8
if rfudf:
len_fic -= 3
p.pr("FIC data len {}".format(len_fic))
p.dec()
item_estn_head_struct = "!HB"
def decode_estn(item):
estN = chr(ord("0") + ord(item['name'][3]))
p.pr("TAG item EST{} (len={})".format(estN, item['length']))
p.inc()
tag_value = item['value']
scid_sad, tpl_rfa = struct.unpack(item_estn_head_struct, tag_value[:3])
scid = scid_sad >> 10
sad = scid_sad & 0x3F
tpl = tpl_rfa >> 2
p.pr("SCID = {}".format(scid))
p.pr("SAD = {}".format(sad))
p.pr("TPL = {}".format(tpl))
assert(item['length'] == len(tag_value))
p.pr("MST len = {}".format(len(tag_value) - 3))
p.hexpr("MST {} data".format(scid), tag_value[3:])
p.dec()
if len(sys.argv) > 1:
filename = sys.argv[1]
edi_fd = BufferedFile(filename)
else:
edi_fd = BufferedFile("-")
while decode(edi_fd):
pass
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