My personal writeup on the differences here: https://gist.github.com/pudquick/29fcfe09c326a9b96cf5

Pure python reimplementation of .cpio.xz content extraction from pbzx file payload originally here:

http://www.tonymacx86.com/general-help/135458-pbzx-stream-parser.html

Cleaned up C version (as the basis for my code) here, thanks to Pepijn Bruienne / @bruienne

https://gist.github.com/bruienne/029494bbcfb358098b41

import struct, sys

def seekread(f, offset=None, length=0, relative=True): if (offset != None): # offset provided, let's seek f.seek(offset, [0,1,2][relative]) if (length != 0): return f.read(length)

def parse_pbzx(pbzx_path): section = 0 xar_out_path = '%s.part%02d.cpio.xz' % (pbzx_path, section) f = open(pbzx_path, 'rb') # pbzx = f.read() # f.close() magic = seekread(f,length=4) if magic != 'pbzx': raise "Error: Not a pbzx file" # Read 8 bytes for initial flags flags = seekread(f,length=8) # Interpret the flags as a 64-bit big-endian unsigned int flags = struct.unpack('>Q', flags)[0] xar_f = open(xar_out_path, 'wb') while (flags & (1 << 24)): # Read in more flags flags = seekread(f,length=8) flags = struct.unpack('>Q', flags)[0] # Read in length f_length = seekread(f,length=8) f_length = struct.unpack('>Q', f_length)[0] xzmagic = seekread(f,length=6) if xzmagic != '\xfd7zXZ\x00': # This isn't xz content, this is actually raw decompressed cpio chunk of 16MB in size... # Let's back up ... seekread(f,offset=-6,length=0) # ... and split it out ... f_content = seekread(f,length=f_length) section += 1 decomp_out = '%s.part%02d.cpio' % (pbzx_path, section) g = open(decomp_out, 'wb') g.write(f_content) g.close() # Now to start the next section, which should hopefully be .xz (we'll just assume it is ...) xar_f.close() section += 1 new_out = '%s.part%02d.cpio.xz' % (pbzx_path, section) xar_f = open(new_out, 'wb') else: f_length -= 6 # This part needs buffering f_content = seekread(f,length=f_length) tail = seekread(f,offset=-2,length=2) xar_f.write(xzmagic) xar_f.write(f_content) if tail != 'YZ': xar_f.close() raise "Error: Footer is not xar file footer" try: f.close() xar_f.close() except: pass

def main(): result = parse_pbzx(sys.argv[1]) print "Now xz decompress the .xz chunks, then 'cat' them all together in order into a single new.cpio file"

if name == 'main': main()