python calls c dynamic library

import types
from ctypes import *

SDK = cdll.LoadLibrary("/home/nxy/lib/libxxx.so")

def Sm4CbcEncrypt(source,key,iv):
	
	v = c_int(0)
	p_int = pointer(v)
	p = create_string_buffer(len(source) + 64)  
	pconfig = addressof(p) 
	
	SDK.Sm4CbcEncrypt(source,len(source),pconfig,p_int,key,iv)
	result = string_at(p,v)
	p = None
	return result


def Sm4CbcDecrypt(source,key,iv):
	
	v = c_int(0)
	p_int = pointer(v)
	
	p = create_string_buffer(len(source) + 64)  
	pconfig = addressof(p) 
	
	SDK.Sm4CbcDecrypt(source,len(source),pconfig,p_int,key,iv)
	result = string_at(p,v)
	p = None
	return result


en_data = Sm4CbcEncrypt("hello","1234567890abcdef","1234567890abcdef")
print("Sm4CbcEncrypt is over")

de_data = Sm4CbcDecrypt(en_data,"1234567890abcdef","1234567890abcdef")
print("Sm4CbcDecrypt is over")

print(de_data)