void* memcpy(void* pvTo, const void* pvForm, size_t size)
{
 assert((pvTo!= NULL) && (pvFrom!= NULL));//使用断言防止传递空地址
 unsigned char* pbTo = (unsigned char*)pvTo;//防止改变pvTo的地址
 unsigned char* pbFrom = (unsigned char*)pvFrom;//防止改变pvFrom的地址
 while(size-- > 0)
 {
  *pbTo++ = *pbFrom++;
 }
 return pvTo;
}

char* strcpy(char* pDest, const char* pSrc)
{
 assert((pDest != NULL) && (pSrc != NULL));
 char *pTmp = pDest;
 while ((*pDest++ = *pSrc++) != '\0')
  ;
 return pTmp;
}