chromium中的TimeTicks和TimeDelta
TimeTicks
vs TimeDelta
base::TimeTicks
- 表示一个抽象的时间,用于跟踪时间量。
- 大部分时间都是递增的,
TimeTicks
可以 “静止”(例如,如果计算机被暂停)。 - 在内部是以微秒表示,它们不能被转换为人类可读的时间。
base::TimeDelta
- 代表一个时间长度,内部表示为微秒。
media/filters/video_renderer_algorithm.cc
中的代码实例:
const base::TimeTicks end_time = std::min(deadline_max, frame.end_time);
const base::TimeDelta duration =
end_time - std::max(deadline_min, frame.start_time);
定义TimeDelta类型
在chromium中,base::TimeDelta定义在base/time/time.h
文件中,在v8子目录中看到还有一个v8/src/base/platform/time.h
,所以如果看错了,如果使用FromNanoseconds的函数创建TimeDleta的时候会报错:
// TimeDelta ------------------------------------------------------------------
class V8_BASE_EXPORT TimeDelta final {
public:
constexpr TimeDelta() : delta_(0) {}
// Converts units of time to TimeDeltas.
static constexpr TimeDelta FromDays(int days) {
return TimeDelta(days * TimeConstants::kMicrosecondsPerDay);
}
static constexpr TimeDelta FromHours(int hours) {
return TimeDelta(hours * TimeConstants::kMicrosecondsPerHour);
}
static constexpr TimeDelta FromMinutes(int minutes) {
return TimeDelta(minutes * TimeConstants::kMicrosecondsPerMinute);
}
static constexpr TimeDelta FromSeconds(int64_t seconds) {
return TimeDelta(seconds * TimeConstants::kMicrosecondsPerSecond);
}
static constexpr TimeDelta FromMilliseconds(int64_t milliseconds) {
return TimeDelta(milliseconds * TimeConstants::kMicrosecondsPerMillisecond);
}
static constexpr TimeDelta FromMicroseconds(int64_t microseconds) {
return TimeDelta(microseconds);
}
static constexpr TimeDelta FromNanoseconds(int64_t nanoseconds) {
return TimeDelta(nanoseconds / TimeConstants::kNanosecondsPerMicrosecond);
}
正确的是base/time/time.h,代码如下:
template <typename T>
constexpr TimeDelta Days(T n) {
return TimeDelta::FromInternalValue(MakeClampedNum(n) *
Time::kMicrosecondsPerDay);
}
template <typename T>
constexpr TimeDelta Hours(T n) {
return TimeDelta::FromInternalValue(MakeClampedNum(n) *
Time::kMicrosecondsPerHour);
}
template <typename T>
constexpr TimeDelta Minutes(T n) {
return TimeDelta::FromInternalValue(MakeClampedNum(n) *
Time::kMicrosecondsPerMinute);
}
template <typename T>
constexpr TimeDelta Seconds(T n) {
return TimeDelta::FromInternalValue(MakeClampedNum(n) *
Time::kMicrosecondsPerSecond);
}
template <typename T>
constexpr TimeDelta Milliseconds(T n) {
return TimeDelta::FromInternalValue(MakeClampedNum(n) *
Time::kMicrosecondsPerMillisecond);
}
template <typename T>
constexpr TimeDelta Microseconds(T n) {
return TimeDelta::FromInternalValue(MakeClampedNum(n));
}
template <typename T>
constexpr TimeDelta Nanoseconds(T n) {
return TimeDelta::FromInternalValue(MakeClampedNum(n) /
Time::kNanosecondsPerMicrosecond);
}
像这样,构造一个base::TimeDelta类型的时间对象:
base::TimeDelta timestamp = base::Nanoseconds(ptsNs);