double 小数点位数截取

double setDoublePrecision(double dInDate, int iPrecision = 4)
{
    char buf[512] = {0};
	char szPrecision[32] = {0};
    sprintf(szPrecision, "%s%df", "%.", iPrecision);
    sprintf(buf, szPrecision, dInDate);

    return atof(buf);
}