c11时间库一个小例子

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#pragma once
#include <chrono>
#include <string>
#include <iostream>
#include <ctime>
#include <iomanip>
 
#define NAMESPACE(x) namespace x{
#define NAMESPACEEND(x) }
 
 
NAMESPACE(DEF)
 
const int kMicroSecondsPerSecond = 1000 * 1000;
 
class Timestamp
{
public:
    Timestamp() {};
    void TimestampSet(const Timestamp& t) {
        time_ = t.time_;
    };
 
    bool valid() const { return time_.time_since_epoch().count() > 0; }
    int64_t MicroSecondsSinceEpoch() const { return time_.time_since_epoch().count(); }
    void Now() { time_  = std::chrono::system_clock::now();};
    std::string Timestamp::ToFormattedString() const;
    std::string ToString() const {
        char buf[32] = { 0 };
        auto s1 = std::chrono::duration_cast<std::chrono::microseconds>
                 (time_.time_since_epoch()).count();    
        snprintf(buf, sizeof(buf) - 1, "%lld.%06lld", s1 / kMicroSecondsPerSecond, s1 % kMicroSecondsPerSecond);
        //printf("buf %s\n", buf);
        return buf;
    };
    const std::chrono::time_point<std::chrono::system_clock>&
        Time() { return time_; };
private:
    std::chrono::time_point<std::chrono::system_clock>  time_;
};
 
inline bool operator<(Timestamp lhs, Timestamp rhs)
{
    return lhs.Time() < rhs.Time();
}
 
inline bool operator==(Timestamp lhs, Timestamp rhs)
{
    return lhs.Time() == rhs.Time();
}
 
inline bool operator>(Timestamp lhs, Timestamp rhs)
{
    return lhs.Time() > rhs.Time();
}
 
inline bool operator>=(Timestamp lhs, Timestamp rhs)
{
    return lhs.Time() >= rhs.Time();
}
 
inline int64_t timeDifference(Timestamp high, Timestamp low)
{
    return  (high.Time() - low.Time()).count();
}
 
 
 
std::string Timestamp::ToFormattedString() const
{
    auto t = std::chrono::system_clock::to_time_t(time_);
 
    char mbstr[100] = {0};
    if (std::strftime(mbstr, sizeof(mbstr), "%Y_%m_%d_%H_%M_%S", std::localtime(&t)))
    {
        return mbstr;
    }
 
    return mbstr;
}
 
NAMESPACEEND(DEF)
 
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