#!/usr/bin/env python3

# Written by Antonio Galea - 2010/11/18
# Updated for DFU 1.1 by Sean Cross - 2020/03/31
# Distributed under Gnu LGPL 3.0
# see http://www.gnu.org/licenses/lgpl-3.0.txt

import sys,struct,zlib,os
from optparse import OptionParser

DEFAULT_DEVICE="0x1209:0x5bf0"

def named(tuple,names):
  return dict(zip(names.split(),tuple))
def consume(fmt,data,names):
  n = struct.calcsize(fmt)
  return named(struct.unpack(fmt,data[:n]),names),data[n:]
def cstring(string):
  return string.split('\0',1)[0]
def compute_crc(data):
  return 0xFFFFFFFF & -zlib.crc32(data) -1

def parse(file,dump_images=False):
  print ('File: "%s"' % file)
  data = open(file,'rb').read()
  crc = compute_crc(data[:-4])
  data = data[len(data)-16:]
  suffix = named(struct.unpack('<4H3sBI',data[:16]),'device product vendor dfu ufd len crc')
  print ('usb: %(vendor)04x:%(product)04x, device: 0x%(device)04x, dfu: 0x%(dfu)04x, %(ufd)s, %(len)d, 0x%(crc)08x' % suffix)
  if crc != suffix['crc']:
    print ("CRC ERROR: computed crc32 is 0x%08x" % crc)
  data = data[16:]
  if data:
    print ("PARSE ERROR")

def build(file,data,device=DEFAULT_DEVICE):
  # Parse the VID and PID from the `device` argument
  v,d=map(lambda x: int(x,0) & 0xFFFF, device.split(':',1))

  # Generate the DFU suffix, consisting of these fields:
  #  Field name     | Length  |  Description
  # ================+=========+================================
  #  bcdDevice      |    2    | The release number of this firmware (0xffff - don't care)
  #  idProduct      |    2    | PID of this device
  #  idVendor       |    2    | VID of this device
  #  bcdDFU         |    2    | Version of this DFU spec (0x01 0x00)
  #  ucDfuSignature |    3    | The characters 'DFU', printed in reverse order
  #  bLength        |    1    | The length of this suffix (16 bytes)
  #  dwCRC          |    4    | A CRC32 of the data, including this suffix
  data += struct.pack('<4H3sB',0xffff,d,v,0x0100,b'UFD',16)
  crc   = compute_crc(data)
  # Append the CRC32 of the entire block
  data += struct.pack('<I',crc)
  open(file,'wb').write(data)

if __name__=="__main__":
  usage = """
%prog [-d|--dump] infile.dfu
%prog {-b|--build} file.bin [{-D|--device}=vendor:device] outfile.dfu"""
  parser = OptionParser(usage=usage)
  parser.add_option("-b", "--build", action="store", dest="binfile",
    help="build a DFU file from given BINFILE", metavar="BINFILE")
  parser.add_option("-D", "--device", action="store", dest="device",
    help="build for DEVICE, defaults to %s" % DEFAULT_DEVICE, metavar="DEVICE")
  parser.add_option("-d", "--dump", action="store_true", dest="dump_images",
    default=False, help="dump contained images to current directory")
  (options, args) = parser.parse_args()

  if options.binfile and len(args)==1:
    binfile = options.binfile
    if not os.path.isfile(binfile):
      print ("Unreadable file '%s'." % binfile)
      sys.exit(1)
    target = open(binfile,'rb').read()
    outfile = args[0]
    device = DEFAULT_DEVICE
    # If a device is specified, parse the pair into a VID:PID pair
    # in order to validate them.
    if options.device:
      device=options.device
    try:
      v,d=map(lambda x: int(x,0) & 0xFFFF, device.split(':',1))
    except:
      print ("Invalid device '%s'." % device)
      sys.exit(1)
    build(outfile,target,device)
  elif len(args)==1:
    infile = args[0]
    if not os.path.isfile(infile):
      print ("Unreadable file '%s'." % infile)
      sys.exit(1)
    parse(infile, dump_images=options.dump_images)
  else:
    parser.print_help()
    sys.exit(1)
