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Add time_generator_v7::operator() overload for caller provided time point #195

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Merged
pdimov merged 1 commit into from
Jul 24, 2026
Merged

Add time_generator_v7::operator() overload for caller provided time point #195

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8 changes: 8 additions & 0 deletions doc/uuid/time_generator_v7.adoc
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Original file line number Diff line number Diff line change
Expand Up @@ -31,6 +31,7 @@ public:
time_generator_v7& operator=( time_generator_v7&& rhs ) noexcept;

result_type operator()() noexcept;
result_type operator()( std::chrono::time_point<std::chrono::system_clock> const& time_point ) noexcept;
};

}} // namespace boost::uuids
Expand Down Expand Up @@ -100,3 +101,10 @@ Remarks: :: `operator()` generates a monotonically increasing sequence of UUIDs,
* The system clock never goes backwards.
* The system clock has at least millisecond resolution.
* No more than 64 UUIDs are generated per microsecond (no more than one every 16 nanoseconds).

```
result_type operator()( std::chrono::time_point<std::chrono::system_clock> const& time_point ) noexcept;
```

Effects: :: The same as `operator()()` but allows the caller to provide the system time
Remarks: :: The same as `operator()()`
16 changes: 11 additions & 5 deletions include/boost/uuid/time_generator_v7.hpp
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Expand Up @@ -46,10 +46,11 @@ class time_generator_v7
time_generator_v7& operator=( time_generator_v7&& rhs ) noexcept;

result_type operator()() noexcept;
result_type operator()( std::chrono::time_point<std::chrono::system_clock> const& time_point ) noexcept;

private:

static state_type get_new_state( state_type const& oldst ) noexcept;
static state_type get_new_state( state_type const& oldst, std::chrono::time_point<std::chrono::system_clock> const& time_point = std::chrono::system_clock::now() ) noexcept;
};

// constructors
Expand Down Expand Up @@ -91,10 +92,10 @@ inline time_generator_v7& time_generator_v7::operator=( time_generator_v7&& rhs

// get_new_state

inline time_generator_v7::state_type time_generator_v7::get_new_state( state_type const& oldst ) noexcept
inline time_generator_v7::state_type time_generator_v7::get_new_state( state_type const& oldst, std::chrono::time_point<std::chrono::system_clock> const& time_point ) noexcept
{
// `now()` in microseconds
std::uint64_t now_in_us = static_cast<std::uint64_t>( std::chrono::time_point_cast< std::chrono::microseconds >( std::chrono::system_clock::now() ).time_since_epoch().count() );
std::uint64_t now_in_us = static_cast<std::uint64_t>( std::chrono::time_point_cast< std::chrono::microseconds >( time_point ).time_since_epoch().count() );

std::uint64_t time_ms = now_in_us / 1000; // timestamp, ms part
std::uint64_t time_us = now_in_us % 1000; // timestamp, us part
Expand All @@ -119,7 +120,7 @@ inline time_generator_v7::state_type time_generator_v7::get_new_state( state_typ

// operator()

inline time_generator_v7::result_type time_generator_v7::operator()() noexcept
inline time_generator_v7::result_type time_generator_v7::operator()( std::chrono::time_point<std::chrono::system_clock> const& time_point ) noexcept
{
uuid result;

Expand All @@ -131,7 +132,7 @@ inline time_generator_v7::result_type time_generator_v7::operator()() noexcept
detail::store_native_u32( result.data + 12, dist( rng_ ) );

// get new timestamp
state_ = get_new_state( state_ );
state_ = get_new_state( state_, time_point );

std::uint64_t time_ms = state_ >> 16; // timestamp, ms part
std::uint64_t time_us = ( state_ & 0xFFFF ) >> 6; // timestamp, us part
Expand All @@ -147,6 +148,11 @@ inline time_generator_v7::result_type time_generator_v7::operator()() noexcept
return result;
}

inline time_generator_v7::result_type time_generator_v7::operator()() noexcept
{
return operator()(std::chrono::system_clock::now());
}

}} // namespace boost::uuids

#endif // BOOST_UUID_TIME_GENERATOR_V7_HPP_INCLUDED
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