#!/usr/bin/python

import sys, struct

# do we make a 32 or 16 bits bytes swap?
targetswap = 16

bytestoconsider = int(targetswap / 8)
if targetswap == 32:
    pack = '>I'
    unpack = '<I'
else:
    pack = '>H'
    unpack = '<H'

if len(sys.argv) > 1:
    baseName = sys.argv[1]
    try:
        with open(baseName, mode='rb') as InFile:
            OutFile = open("%s.bs" % (baseName), "wb")
            file_data = InFile.read()
            sz = len(file_data)
            if sz % bytestoconsider:
                print("Be carefull, %d bytes will not be present in destination" % (sz % bytestoconsider))
            for i in range(0, (sz // bytestoconsider) * bytestoconsider, bytestoconsider):
                val = struct.unpack(unpack,file_data[i:i+bytestoconsider])
                swapped = struct.pack(pack, val[0])
                OutFile.write(swapped)
        OutFile.close()
    except:
        print("Cannot open file '%s'!" % (baseName))
else:
    print("Please give the source file name as parameter")