make endianness conversion between big endian and little endian

invert_endianness.py

def invert_endianness(number):
    new_bits = []
    
    total_bits = number.bit_length()
    check_len = True
    bits = 8
    
    while(check_len):
        if (bits - total_bits) >= 0:
            check_len = False
        else:
            bits *= 2
    
    shift_back = bits - 8
    
    shift = 8
    mask = 0xFF
    bits = bits//8
    new_endian = 0x00000000

    for i in range(bits):
        if i==0:
            new_bits.append(number & mask)
        else:
            new_bits.append((number >> shift) & mask)
            shift += 8
            
    for i in range(bits):
        new_endian |= (new_bits[i] << shift_back)
        shift_back -= 8
        
    return new_endian

big_endian = 0x00020804
print('0x{0:0{1}X}'.format(big_endian,8))
print('0x{0:0{1}X}'.format(invert_endianness(big_endian),8))

big_endian = 0x0000010000040880
print('0x{0:0{1}X}'.format(big_endian,16))
print('0x{0:0{1}X}'.format(invert_endianness(big_endian),16))