我需要根據 RFC 5905由以下結構表示爲boost::posix_time::ptime
轉換成NTP 日期郵票:轉換的boost ::了posix_time ::的ptime到NTP時間戳
struct NtpDatestamp {
std::int32_t era_number;
std::uint32_t seconds_since_era_epoch;
std::uint64_t fraction_of_second;
};
RFC 5905條規定如下:
要轉換系統時間以任何形式向NTP日期和時間戳的格式 要求從黃金時期秒
s
到系統0號時間確定。爲了確定整數era
和timestamp
給出s
,era = s/2^(32) and timestamp = s - era * 2^(32),
它適用於正面和負面的日期。爲了確定給定的時代 和時間戳
s
,s = era * 2^(32) + timestamp.
所以我嘗試了以下內容:
const auto system_time = boost::posix_time::time_from_string("1899-12-31 00:00:00.000");
const boost::posix_time::ptime prime_epoch{boost::gregorian::date{1900, 1, 1}};
// Calculate the number of seconds from the prime epoch to the system time.
const boost::posix_time::time_duration time_duration{system_time - prime_epoch};
const std::int64_t s{time_duration.total_seconds()};
const std::int32_t era_number{static_cast<std::int32_t>(s/std::pow(2, 32))};
const std::uint64_t seconds_since_era_epoch{static_cast<std::uint64_t>(s - s/std::pow(2, 32) * std::pow(2, 32))};
// The fraction of a NTP Datestamp is measured in Attoseconds.
const std::uint64_t fraction_of_second{static_cast<std::uint64_t>(time_duration.total_microseconds() * 1e12)};
但是,讓不正確的結果。
我完全被這個(其實很簡單)的問題困擾着。
有人可以引導我進入正確的方向嗎?我如何獲得時代號碼,時代補償和分數 NTP日期戳boost::posix_time::ptime
?
編輯: RFC 5905中的計算不夠準確,或者我誤解了它們。多虧了意見,我已經改變了計算如下(此時一個完整的例子):
#include <cmath>
#include <cstdint>
#include <iostream>
#include <boost/date_time.hpp>
int main() {
const auto system_time =
boost::posix_time::time_from_string("1899-12-31 00:00:00.000");
const boost::posix_time::ptime prime_epoch{
boost::gregorian::date{1900, 1, 1}};
// Calculate the number of seconds from the prime epoch to the system time.
const boost::posix_time::time_duration time_duration{prime_epoch -
system_time};
// s is correctly determined now.
std::int64_t s{time_duration.total_seconds()};
if (prime_epoch > system_time) {
// boost::posix_time::time_duration does not take the sign into account.
s *= -1;
}
// TODO(wolters): The following calculations do not return the correct
// results, but the RFC 5905 states them
const std::int32_t era{static_cast<std::int32_t>(s/std::pow(2, 32))};
const std::uint64_t timestamp{
static_cast<std::uint64_t>(s - era * std::pow(2, 32))};
// The fraction of a NTP Datestamp is measured in Attoseconds.
// TODO(wolters): `boost::posix_time::ptime` does NOT resolve to attoseconds,
// but doesn't the target format expect the value to be specified as
// attoseconds? Doesn't the following depend on Boost compile options?
const std::uint64_t fraction{
static_cast<std::uint64_t>(time_duration.fractional_seconds())};
std::cout << "s = " << std::dec << s << '\n';
// TODO(wolters): This does still not match the expected results; taken from
// Figure 4 of https://www.ietf.org/rfc/rfc5905.txt
std::cout << "Era (expected: -1) = " << std::dec << era << '\n';
std::cout << "Timestamp (expected: 4294880896) = " << std::dec << timestamp
<< '\n';
std::cout << "Fraction (expected: 0) = " << std::dec << fraction << '\n';
}
s
現在可以正確地計算,但其他的計算是錯誤的。我想我完全錯過了一些重要的東西......
一個問題:seconds_since_era_epoch應該計算的S - era_number * 2^32,但你計算的方式,它會永遠是零。 – lrm29
第二個問題:fraction_of_second應該使用time_duration.fractional_seconds() 第三個問題:ptime無法解析爲attoseconds ... – lrm29