c++ - 以下程序的格式说明符可能是什么？

Question

void TASK(Task100ms_Raster)
{
    int a,b,c;
    struct timespec start, stop;
    uint32 StartTime, StopTime;
    uint32 duration100ms;

    if( clock_gettime( CLOCK_REALTIME, &start) == -1 ) {
       perror( "clock gettime" );
    }

    StartTime =start.tv_sec + 0.0000001 * start.tv_nsec;
    printf("start time is %lu", StartTime);

    printf("value is %d",c);
    printf("ETAS1\n");
    if( (StopTime = clock_gettime( CLOCK_REALTIME, &stop)) == -1 )
    {
      perror( "clock gettime" );
    }
    StopTime =  stop.tv_sec + 0.0000001 * stop.tv_nsec;
    printf("stop time is %lu", StopTime);

    duration100ms = StopTime -StartTime;
    printf( "time difference is= %lu\n", duration100ms );
}

我创建了一个计时器，它计算开始时间、停止时间和时间差。我对开始时间、停止时间和 suration100ms 的格式说明符感到困惑。但是 struct timespec start, stop;类型为http://www.qnx.com/developers/docs/6.3.0SP3/neutrino/lib_ref/t/timespec.html那么获得结果的正确格式说明符可能是什么。有人指导我。

Answer 1

您正在进行浮点计算来计算秒数，但将结果存储在整数中:

StartTime = start.tv_sec + 0.0000001 * start.tv_nsec;

这会将结果截断为整数。您应该将 StartTime 设为 double，并按如下方式打印:

double StartTime = start.tv_sec + 1e-9 * start.tv_nsec;

printf("start time is %f\n", StartTime);

我认为计算差异时转换为 float 更有利于精度:

double duration = StopTime.tv_sec - StartTime.tv_sec +
                  1E-9 * (StopTime.tv_nsec - StartTime.tv_nsec);

如果您必须将持续时间设置为以 100 毫秒为单位的整数，您可以这样做:

duration = 10000 * (StopTime.tv_sec - StartTime.tv_sec) + 
           (StopTime.tv_nsec - StartTime.tv_nsec) / 100000000;