英文:
How do you convert a very large (>max(int64)) nanosecond unix timestamp to time.Time
问题
我有一个大于int64可以容纳的最大值的uint64纳秒级Unix时间戳。由于我不能再使用接受int64参数的time.Unix()函数，我该如何将这个时间戳转换为Time类型而不丢失数据呢？
英文:
I have a uint64 nanosecond unix timestamp which is larger than than the max value a int64 can hold. Since I can no longer use the time.Unix() function which takes int64, how can I convert this timestamp to a Time without losing data?
答案1
得分: 6
time.Unix() 函数接受两个参数：
func Unix(sec int64, nsec int64) Time
如果你有 int64 类型的纳秒数，可以将 sec 参数设为 0，将纳秒数设为 nsec 参数。例如：
nsec := int64(1623840300988135567)
t := time.Unix(0, nsec)
fmt.Println(t) // 2021-06-16 10:45:00.988135567 +0000 UTC
传递超出范围 [0, 999999999] 的纳秒数也是有效的。
如果你有一个无法适应 int64 类型的纳秒数，可以将其分为两部分：秒数和剩余的纳秒数。分割的方法是将其除以 1e9（即一秒钟的纳秒数）并取余数。
例如：
x := uint64(math.MaxInt64)
t = time.Unix(0, int64(x))
fmt.Println(t)
x += uint64(time.Hour)
t = time.Unix(int64(x/1e9), int64(x%1e9))
fmt.Println(t)
将 time.Hour 加到 math.MaxInt64 上显然无法适应 int64 类型。然而，上述代码可以正常运行并输出：
2262-04-11 23:47:16.854775807 +0000 UTC
2262-04-12 00:47:16.854775807 +0000 UTC
在 Go Playground 上尝试一下吧。
英文:
The time.Unix() function takes 2 arguments:
func Unix(sec int64, nsec int64) Time
If you have the int64 nanoseconds, you may pass 0 for sec, and the nanoseconds value for nsec. For example:
nsec := int64(1623840300988135567)
t := time.Unix(0, nsec)
fmt.Println(t) // 2021-06-16 10:45:00.988135567 +0000 UTC
It is valid to pass nanoseconds value outside the range [0, 999999999].
If you have a nanoseconds value not fitting into int64, then simply break it into 2 parts: seconds and remaining nanoseconds. Breaking it is simply dividing by and getting the remainder of dividing by 1e9 (which is the number of nanoseconds in a sec).
For example:
x := uint64(math.MaxInt64)
t = time.Unix(0, int64(x))
fmt.Println(t)
x += uint64(time.Hour)
t = time.Unix(int64(x/1e9), int64(x%1e9))
fmt.Println(t)
Adding time.Hour to math.MaxInt64 clearly doesn't fit into int64. Yet the above code runs fine and outputs:
2262-04-11 23:47:16.854775807 +0000 UTC
2262-04-12 00:47:16.854775807 +0000 UTC
Try it on the Go Playground.
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