我正在编写一个程序，在用相机拍摄的图像上加上时间戳。为此，我使用的是Windows 7系统时间。我在下面的代码中使用了GetSystemTimeAsFileTime()：
FILETIME ft;
GetSystemTimeAsFileTime(&ft);
long long ll_now = (LONGLONG)ft.dwLowDateTime + ((LONGLONG)(ft.dwHighDateTime) << 32LL);
我想要做的是以毫秒的分辨率获得当天（0- 86400）的秒数，因此它将类似于12345.678。这是正确的方法吗？如果是这样，如何转换此整数以获取当天的秒数？我将在字符串中显示时间，并使用fstream将时间放在文本文件中。
由于
答案 0 :(得分：0)
我不知道C++但是#include <ctime>
#include <chrono>
#include <string>
#include <sstream>
#include <iomanip>
std::string stamp_secs_dot_ms()
{
using namespace std::chrono;
auto now = system_clock::now();
// tt stores time in seconds since epoch
std::time_t tt = system_clock::to_time_t(now);
// broken time as of now
std::tm bt = *std::localtime(&tt);
// alter broken time to the beginning of today
bt.tm_hour = 0;
bt.tm_min = 0;
bt.tm_sec = 0;
// convert broken time back into std::time_t
tt = std::mktime(&bt);
// start of today in system_clock units
auto start_of_today = system_clock::from_time_t(tt);
// today's duration in system clock units
auto length_of_today = now - start_of_today;
// seconds since start of today
seconds secs = duration_cast<seconds>(length_of_today); // whole seconds
// milliseconds since start of today
milliseconds ms = duration_cast<milliseconds>(length_of_today);
// subtract the number of seconds from the number of milliseconds
// to get the current millisecond
ms -= secs;
// build output string
std::ostringstream oss;
oss.fill('0');
oss << std::setw(5) << secs.count();
oss << '.' << std::setw(3) << ms.count();
return oss.str();
}
int main()
{
std::cout << stamp_secs_dot_ms() << '\n';
}
标准库（自C ++ 11以来）可以像这样使用：
13641.509
示例输出：
Caused by: org.postgresql.util.PSQLException: This connection has been closed.
at org.postgresql.jdbc2.AbstractJdbc2Connection.checkClosed(AbstractJdbc2Connection.java:822)
at org.postgresql.jdbc2.AbstractJdbc2Connection.rollback(AbstractJdbc2Connection.java:839)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:497)
at com.ibatis.common.jdbc.SimpleDataSource$SimplePooledConnection.invoke(SimpleDataSource.java:958)
at com.sun.proxy.$Proxy0.rollback(Unknown Source)
at com.ibatis.sqlmap.engine.transaction.jdbc.JdbcTransaction.rollback(JdbcTransaction.java:72)
at com.ibatis.sqlmap.engine.transaction.TransactionManager.end(TransactionManager.java:87)
at com.ibatis.sqlmap.engine.impl.SqlMapExecutorDelegate.endTransaction(SqlMapExecutorDelegate.java:734)
at com.ibatis.sqlmap.engine.impl.SqlMapSessionImpl.endTransaction(SqlMapSessionImpl.java:176)
at com.ibatis.sqlmap.engine.impl.SqlMapClientImpl.endTransaction(SqlMapClientImpl.java:153)
at com.ibatis.sqlmap.engine.impl.SqlMapExecutorDelegate.autoEndTransaction(SqlMapExecutorDelegate.java:835)
at com.ibatis.sqlmap.engine.impl.SqlMapExecutorDelegate.insert(SqlMapExecutorDelegate.java:410)
at com.ibatis.sqlmap.engine.impl.SqlMapSessionImpl.insert(SqlMapSessionImpl.java:82)
at com.ibatis.sqlmap.engine.impl.SqlMapClientImpl.insert(SqlMapClientImpl.java:58)
at mblib.dao.TrxLogDAO.insertLog(TrxLogDAO.java:32)
... 10 more