將時間戳字符串轉換為“HH:MM:SS.microseconds”格式的建議

Psb 发表于 Dev

psb

我得到了std::vector<std::string>一個字符串格式的時間戳列表（假設我們有一個現成的）std::vector<std::string> = {"12:27:37.740002", "19:37:17.314002", "20:00:07.140902",...}。沒有日期，沒有時區。將這些字符串解析為某種 C++ 類型（std::chrono::time_point？）以便稍後能夠執行一些比較和排序的更好方法是什麼。

例如：比較值，從"20:00:07.140902"和解析值，從解析"20:00:07.000000"。

C++17 沒問題，但我不能使用任何第三方庫（Boost、Date 等）。保持微秒精度至關重要。

佩皮恩·克萊默

您可以完全使用 C++ 標準庫功能構建此功能。要解析字符串，請使用 std::regex。對於時間相關的數據類型使用 std::chrono

例子：

#include <stdexcept>
#include <regex>
#include <chrono>
#include <iostream>

auto parse_to_timepoint(const std::string& input)
{
    // setup a regular expression to parse the input string
    // https://regex101.com/
    // each part between () is a group and will end up in the match
    // [0-2] will match any character from 0 to 2 etc..
    // [0-9]{6} will match exactly 6 digits
    static const std::regex rx{ "([0-2][0-9]):([0-5][0-9]):([0-5][0-9])\\.([0-9]{6})" };
    std::smatch match;

    if (!std::regex_search(input, match, rx))
    {
        throw std::invalid_argument("input string is not a valid time string");
    }

    // convert each matched group to the corresponding value
    // note match[0] is the complete matched string by the regular expression
    // we only need the groups which start at index 1
    const auto& hours = std::stoul(match[1]);
    const auto& minutes = std::stoul(match[2]);
    const auto& seconds = std::stoul(match[3]);
    const auto& microseconds = std::stoul(match[4]);
    
    // build up a duration
    std::chrono::high_resolution_clock::duration duration{};
    duration += std::chrono::hours(hours);
    duration += std::chrono::minutes(minutes);
    duration += std::chrono::seconds(seconds);
    duration += std::chrono::microseconds(microseconds);

    // then return a time_point (note this will not help you with correctly handling day boundaries)
    // since there is no date in the input string
    return std::chrono::high_resolution_clock::time_point{ duration };
}

int main()
{
    std::string input1{ "20:00:07.140902" };
    std::string input2{ "20:00:07.000000" };

    auto tp1 = parse_to_timepoint(input1);
    auto tp2 = parse_to_timepoint(input2);

    std::cout << "start time = " << ((tp1 < tp2) ? input1 : input2) << "\n";
    std::cout << "end time = " << ((tp1 >= tp2) ? input1 : input2) << "\n";

    return 0;
}