How Can I Parse Date Strings and Perform Time Calculations Using C 11\'s std::chrono?

Parsing Date Strings with C 11's std::chrono

When dealing with historical date strings, it's often necessary to parse them into C date representations for various computations. C 11's std::chrono namespace provides powerful tools for time handling.

Parsing a Date String

To parse a date string of the format "Thu Jan 9 12:35:34 2014," we can leverage the std::stringstream and std::get_time functions:

std::stringstream ss("Jan 9 2014 12:35:34");
std::tm tm = {};
ss >> std::get_time(&tm, "%b %d %Y %H:%M:%S");

This parses the string into a std::tm struct, which contains the individual time components.

Converting to a std::chrono::time_point

To obtain a std::chrono::time_point representing the parsed date, we use std::chrono::system_clock::from_time_t:

auto tp = std::chrono::system_clock::from_time_t(std::mktime(&tm));

Calculating Elapsed Time

With the std::chrono::time_point, we can easily calculate elapsed time from the specified historic date:

auto now = std::chrono::system_clock::now();
auto duration = now - tp;

Accessing Time Components

std::chrono::duration provides access to individual time components:

• duration.count() returns the total count of time units (seconds by default)
• duration.seconds() retrieves seconds
• duration.minutes() obtains minutes
• duration.hours() fetches hours
• duration.days() provides days

C 11 Support

GCC prior to version 5 does not implement std::get_time. However, an alternative using strptime is also available:

std::tm tm = {};
strptime("Thu Jan 9 2014 12:35:34", "%a %b %d %Y %H:%M:%S", &tm);

The above is the detailed content of How Can I Parse Date Strings and Perform Time Calculations Using C 11\'s std::chrono?. For more information, please follow other related articles on the PHP Chinese website!