将毫秒转换为GNU端口的时间规格 [英] Convert milliseconds to timespec for GNU port

问题描述

我想将毫秒转换为GNU Linux使用的timespec结构。我已经尝试了以下代码来实现同样的目的。

I want to convert milliseconds into timespec structure used by GNU Linux. I have tried following code for the same.

  timespec GetTimeSpecValue(unsigned long milisec)
  {
    struct timespec req;
    //long sec = (milisecondtime /1000);
    time_t sec = (time_t)(milisec/1000);
    req->tv_sec = sec;
    req->tv_nsec = 0;
    return req;
  }

运行此代码会给我以下错误。

Running this code gives me the following error.

在'GetTimeSpecValue'之前的'='，'，'，';'，'asm'或'__attribute __'

expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’ before ‘GetTimeSpecValue’

我还在代码中包含了 time.h 文件。

I have also include time.h file in the code.

推荐答案

timespec 结构以两部分表示时间-秒和纳秒。因此，从毫秒转换的算法非常简单。一秒有千毫秒，一毫秒有千微秒，一微秒有千微秒，对此我们非常感谢： SI 。因此，我们首先需要将毫秒除以一千以得到秒数。举例来说，假设1500毫秒/ 1000 = 1.5秒。给定整数算术（不是浮点数），其余部分将被丢弃（即1500/1000等于1，而不是1.5）。然后，我们需要取一个表示绝对小于一秒的毫秒数的余数，并将其乘以一百万以将其转换为纳秒。要获得除以1000的余数，我们使用模块运算符（％）（即 1500％1000等于500 ）。例如，让我们将4321毫秒转换为秒和纳秒：

The timespec structure represents time in two portions — seconds and nanoseconds. Thus, the algorithm for conversion from milliseconds is pretty darn simple. One seconds has thousand milliseconds, one milliseconds has a thousand microseconds and one microsecond has a thousand nanoseconds, for which we are grateful to SI. Therefore, we first need to divide milliseconds by a thousand to get a number of seconds. Say, for example, 1500 milliseconds / 1000 = 1.5 seconds. Given integer arithmetics (not a floating point), the remainder is dropped (i.e. 1500 / 1000 is equal to just 1, not 1.5). Then we need to take a remainder that denotes a number of milliseconds that is definitely less than one second, and multiply it by a million to convert it to nanoseconds. To get a remainder of dividing by 1000, we use a module operator (%) (i.e. 1500 % 1000 is equal to 500). For example, let's convert 4321 milliseconds to seconds and nanoseconds:

1. 4321（毫秒）/ 1000 = 4（秒）


2. 4321（毫秒）％1000 = 321（毫秒）


3. 321（毫秒）* 1000000 = 321000000（纳秒）

了解上述内容后，剩下的唯一事情就是编写一点C代码。很少有您做不到的事情：

Knowing the above, the only thing that is left is to write a little bit of C code. There are few things that you didn't get right:

1. 在C语言中，必须在结构数据类型前加上结构。例如，不是说 timespec ，而是说 struct timespec 。但是，在C ++中，您不必这样做（不幸的是，在我看来）。


2. 您无法从C函数中返回结构。因此，您需要传递一个结构通过将指针指向一个对该结构有作用的函数。

1. In C, you have to prefix structure data types with struct. For example, instead of saying timespec you say struct timespec. In C++, however, you don't have to do it (unfortunately, in my opinion).
2. You cannot return structures from the function in C. Therefore, you need to pass a structure by pointer into a function that does something with that structure.

编辑：这与（从C中的函数返回一个 struct ）。

好的，足够多的谈话。下面是一个简单的C代码示例：

OK, enough talking. Below is a simple C code example:

#include <time.h>
#include <stdlib.h>
#include <stdio.h>

static void ms2ts(struct timespec *ts, unsigned long ms)
{
    ts->tv_sec = ms / 1000;
    ts->tv_nsec = (ms % 1000) * 1000000;
}

static void print_ts(unsigned long ms)
{
    struct timespec ts;
    ms2ts(&ts, ms);
    printf("%lu milliseconds is %ld seconds and %ld nanoseconds.\n",
           ms, ts.tv_sec, ts.tv_nsec);
}

int main()
{
    print_ts(1000);
    print_ts(2500);
    print_ts(4321);
    return EXIT_SUCCESS;
}

希望它会有所帮助。祝你好运！

Hope it helps. Good Luck!

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