How to decode the password in Accinfo.ini?

Here is the C code -
static void PasswordDecode(char * szPassword)
{
char szEncode[1024];
char strDecodePass[_MAX_BUF_LEN + 1]={""}, strPass[_MAX_BUF_LEN + 1]={""};
strcpy(strDecodePass, szPassword);
for(unsigned int i = 0; i < strlen(strDecodePass)/3; i ++)
{
char szCode[_MAX_BUF_LEN + 1];
strcpy(szCode, strDecodePass + i * 3);
szCode[3] = 0;
int nCode = atoi(szCode);
nCode = 999 - nCode;
sprintf(szEncode, "%c", nCode);
strcat(strPass, szEncode);
}

strcpy(szPassword, strPass);

return;
};