thread/doc/thread_ref.qbk

[/
  (C) Copyright 2007-8 Anthony Williams.
  (C) Copyright 2011-12 Vicente J. Botet Escriba.
  Distributed under the Boost Software License, Version 1.0.
  (See accompanying file LICENSE_1_0.txt or copy at
  http://www.boost.org/LICENSE_1_0.txt).
]

[section:thread_management Thread Management]

[section:synopsis Synopsis]

  #include <boost/thread/thread.hpp>

  namespace boost 
  {
    class thread;
    void swap(thread& lhs,thread& rhs) noexcept;

    namespace this_thread 
    {
      thread::id get_id() noexcept;
      template<typename TimeDuration>
      void yield() noexcept;
      template <class Clock, class Duration>
      void sleep_until(const chrono::time_point<Clock, Duration>& abs_time); 
      template <class Rep, class Period>
      void sleep_for(const chrono::duration<Rep, Period>& rel_time);

      template<typename Callable>
      void at_thread_exit(Callable func); // EXTENSION

      void interruption_point(); // EXTENSION
      bool interruption_requested() noexcept; // EXTENSION
      bool interruption_enabled() noexcept; // EXTENSION 
      class disable_interruption; // EXTENSION
      class restore_interruption; // EXTENSION

    #if defined BOOST_THREAD_PROVIDES_DEPRECATED_FEATURES_SINCE_V3_0_0
      void sleep(TimeDuration const& rel_time);
      void sleep(system_time const& abs_time);
    #endif
    }
    class thread_group; // EXTENSION

  }

[endsect] [/section:synopsis Synopsis]

[section:tutorial Tutorial]

The __thread__ class is responsible for launching and managing threads. Each __thread__ object represents a single thread of execution,
or __not_a_thread__, and at most one __thread__ object represents a given thread of execution: objects of type __thread__ are not
copyable.

Objects of type __thread__ are movable, however, so they can be stored in move-aware containers, and returned from functions. This
allows the details of thread creation to be wrapped in a function.

    boost::thread make_thread();

    void f()
    {
        boost::thread some_thread=make_thread();
        some_thread.join();
    }

[note On compilers that support rvalue references, __thread__ provides a proper move constructor and move-assignment operator, and
therefore meets the C++0x ['MoveConstructible] and ['MoveAssignable] concepts. With such compilers, __thread__ can therefore be used
with containers that support those concepts.

For other compilers, move support is provided with a move emulation layer, so containers must explicitly detect that move emulation
layer. See <boost/thread/detail/move.hpp> for details.]

[section:launching Launching threads]

A new thread is launched by passing an object of a callable type that can be invoked with no parameters to the constructor. The
object is then copied into internal storage, and invoked on the newly-created thread of execution. If the object must not (or
cannot) be copied, then `boost::ref` can be used to pass in a reference to the function object. In this case, the user of
__boost_thread__ must ensure that the referred-to object outlives the newly-created thread of execution.

    struct callable
    {
        void operator()();
    };

    boost::thread copies_are_safe()
    {
        callable x;
        return boost::thread(x);
    } // x is destroyed, but the newly-created thread has a copy, so this is OK

    boost::thread oops()
    {
        callable x;
        return boost::thread(boost::ref(x));
    } // x is destroyed, but the newly-created thread still has a reference
      // this leads to undefined behaviour

If you wish to construct an instance of __thread__ with a function or callable object that requires arguments to be supplied,
this can be done by passing additional arguments to the __thread__ constructor:

    void find_the_question(int the_answer);

    boost::thread deep_thought_2(find_the_question,42);

The arguments are ['copied] into the internal thread structure: if a reference is required, use `boost::ref`, just as for references
to callable functions.

There is an unspecified limit on the number of additional arguments that can be passed.

[endsect]

[section:attributes Thread attributes]

Thread launched in this way are created with implementation defined thread attributes as stack size, scheduling, 
priority, ... or any platform specific attributes. It is not evident how to provide a portable interface that allows 
the user to set the platform specific attributes. Boost.Thread stay in the middle road through the class 
thread::attributes which allows to set at least in a portable way the stack size as follows:

  boost::thread::attributes attrs;
  attrs.set_size(4096*10);
  boost::thread deep_thought_2(attrs, find_the_question, 42);

Even for this simple attribute there could be portable issues as some platforms could require that the stack size 
should have a minimal size and/or be a multiple of a given page size. 
The library adapts the requested size to the platform constraints so that the user doesn't need to take care of it.

This is the single attribute that is provided in a portable way. In order to set any other thread attribute at 
construction time the user needs to use non portable code.

On PThread platforms the user will need to get the thread attributes handle and use it for whatever attribute.

Next follows how the user could set the stack size and the scheduling policy on PThread platforms.

    boost::thread::attributes attrs;
    // set portable attributes
    // ...
    attr.set_stack_size(4096*10);
    #if defined(BOOST_THREAD_PLATFORM_WIN32)
        // ... window version
    #elif defined(BOOST_THREAD_PLATFORM_PTHREAD)
        // ... pthread version
        pthread_attr_setschedpolicy(attr.get_native_handle(), SCHED_RR);
    #else
    #error "Boost threads unavailable on this platform"
    #endif
    boost::thread th(attrs, find_the_question, 42);
        
On Windows platforms it is not so simple as there is no type that compiles the thread attributes. 
There is a linked to the creation of a thread on Windows that is emulated via the thread::attributes class. This is the LPSECURITY_ATTRIBUTES lpThreadAttributes.
Boost.Thread provides a non portable set_security function so that the user can provide it before the thread creation as follows
  
[/Boost.Thread creates Windows threads that are suspended. Then it calls to the virtual function set_attributes and last it resumes the thread. 
The user needs to define a class that inherits from the class thread::attributes that defines a virtual function set_attributes to set any specific Windows thread attribute.


    class MyWinTthreadAttributes : boost::thread::attributes
    {
    public:
      void set_attributes(boost::thread::native_handle_type h)
      {
        // use any specific windows thread setting
        
      }
    };
    #if defined(BOOST_THREAD_PLATFORM_WIN32)
    
      MyWinTthreadAttributes attrs;
      // set portable attributes
      // ...
      attr.set_stack_size(4096*10);
      boost::thread th(attrs, find_the_question, 42);
    #else
    #error "Platform not supported"
    #endif

]

    #if defined(BOOST_THREAD_PLATFORM_WIN32)
      boost::thread::attributes attrs;
      // set portable attributes
      attr.set_stack_size(4096*10);
      // set non portable attribute
      LPSECURITY_ATTRIBUTES sec;
      // init sec 
      attr.set_security(sec);
      boost::thread th(attrs, find_the_question, 42);
      // Set other thread attributes using the native_handle_type.
      //...
    #else
    #error "Platform not supported"
    #endif

[endsect]

[section:exceptions Exceptions in thread functions]

If the function or callable object passed to the __thread__ constructor propagates an exception when invoked that is not of type
__thread_interrupted__, `std::terminate()` is called. 

[endsect]

[section:join Joining and detaching]

When the __thread__ object that represents a thread of execution is destroyed the thread becomes ['detached]. Once a thread is
detached, it will continue executing until the invocation of the function or callable object supplied on construction has completed,
or the program is terminated. A thread can also be detached by explicitly invoking the __detach__ member function on the __thread__
object. In this case, the __thread__ object ceases to represent the now-detached thread, and instead represents __not_a_thread__.

In order to wait for a thread of execution to finish, the __join__ or __timed_join__ member functions of the __thread__ object must be
used. __join__ will block the calling thread until the thread represented by the __thread__ object has completed. If the thread of
execution represented by the __thread__ object has already completed, or the __thread__ object represents __not_a_thread__, then __join__
returns immediately. __timed_join__ is similar, except that a call to __timed_join__ will also return if the thread being waited for
does not complete when the specified time has elapsed.

[endsect]

[section:interruption Interruption]

A running thread can be ['interrupted] by invoking the __interrupt__ member function of the corresponding __thread__ object. When the
interrupted thread next executes one of the specified __interruption_points__ (or if it is currently __blocked__ whilst executing one)
with interruption enabled, then a __thread_interrupted__ exception will be thrown in the interrupted thread. If not caught,
this will cause the execution of the interrupted thread to terminate. As with any other exception, the stack will be unwound, and
destructors for objects of automatic storage duration will be executed.

If a thread wishes to avoid being interrupted, it can create an instance of __disable_interruption__. Objects of this class disable
interruption for the thread that created them on construction, and restore the interruption state to whatever it was before on
destruction:

    void f()
    {
        // interruption enabled here
        {
            boost::this_thread::disable_interruption di;
            // interruption disabled
            {
                boost::this_thread::disable_interruption di2;
                // interruption still disabled
            } // di2 destroyed, interruption state restored
            // interruption still disabled
        } // di destroyed, interruption state restored
        // interruption now enabled
    }

The effects of an instance of __disable_interruption__ can be temporarily reversed by constructing an instance of
__restore_interruption__, passing in the __disable_interruption__ object in question. This will
restore the interruption state to what it was when the __disable_interruption__ object was constructed, and then
disable interruption again when the __restore_interruption__ object is destroyed.

    void g()
    {
        // interruption enabled here
        {
            boost::this_thread::disable_interruption di;
            // interruption disabled
            {
                boost::this_thread::restore_interruption ri(di);
                // interruption now enabled
            } // ri destroyed, interruption disable again
        } // di destroyed, interruption state restored
        // interruption now enabled
    }

At any point, the interruption state for the current thread can be queried by calling __interruption_enabled__.

[#interruption_points]

[heading Predefined Interruption Points]

The following functions are ['interruption points], which will throw __thread_interrupted__ if interruption is enabled for the
current thread, and interruption is requested for the current thread:

* [join_link `boost::thread::join()`]
* [timed_join_link `boost::thread::timed_join()`]
* `boost::__thread::__try_join_for()`,
* `boost::__thread::__try_join_until()`,
* [cond_wait_link `boost::condition_variable::wait()`]
* [cond_timed_wait_link `boost::condition_variable::timed_wait()`]
* `boost::__condition_variable::__wait_for()`
* `boost::__condition_variable::__wait_until()`
* [cond_any_wait_link `boost::condition_variable_any::wait()`]
* [cond_any_timed_wait_link `boost::condition_variable_any::timed_wait()`]
* `boost::__condition_variable_any::__cvany_wait_for()`
* `boost::__condition_variable_any::__cvany_wait_until()`
* [link thread.thread_management.thread.sleep `boost::thread::sleep()`]
* `boost::this_thread::__sleep_for()`
* `boost::this_thread::__sleep_until()`
* __interruption_point__

[endsect]

[section:id Thread IDs]

Objects of class __thread_id__ can be used to identify threads. Each running thread of execution has a unique ID obtainable
from the corresponding __thread__ by calling the `get_id()` member function, or by calling `boost::this_thread::get_id()` from
within the thread. Objects of class __thread_id__ can be copied, and used as keys in associative containers: the full range of
comparison operators is provided. Thread IDs can also be written to an output stream using the stream insertion operator, though the
output format is unspecified.

Each instance of __thread_id__ either refers to some thread, or __not_a_thread__. Instances that refer to __not_a_thread__
compare equal to each other, but not equal to any instances that refer to an actual thread of execution. The comparison operators on
__thread_id__ yield a total order for every non-equal thread ID.

[endsect]

[section:native_in Using native interfaces with Boost.Thread resources] 


__thread__ class has members `native_handle_type` and `native_handle` providing access to the underlying native handle.  
	 
This native handle can be used to change for example the scheduling. 

In general, it is not safe to use this handle with operations that can conflict with the ones provided by Boost.Thread. An example of bad usage could be detaching a thread directly as it will not change the internals of the __thread__ instance, so for example the joinable function will continue to return true, while the native thread is no more joinable. 

  thread t(fct); 
  thread::native_handle_type hnd=t.native_handle(); 
  pthread_detach(hnd); 
  assert(t.joinable()); 

[endsect]

[section:native_from Using Boost.Thread interfaces in a native thread] 
 

Any thread of execution created using the native interface is called a native thread in this documentation. 

The first example of a native thread of execution is the main thread.  

The user can access to some synchronization functions related to the native current thread using the `boost::this_thread` `yield`, `sleep`, __sleep_for, __sleep_until, functions. 


  int main() { 
    // ... 
    boost::this_thread::sleep_for(boost::chrono::milliseconds(10)); 
    // ... 
  } 


Of course all the synchronization facilities provided by Boost.Thread are also available on native threads. 

The `boost::this_thread` interrupt related functions behave in a degraded mode when called from a thread created using the native interface, i.e. `boost::this_thread::interruption_enabled()` returns false. As consequence the use of `boost::this_thread::disable_interruption` and `boost::this_thread::restore_interruption` will do nothing and calls to `boost::this_thread::interruption_point()` will be just ignored.  

As the single way to interrupt a thread is through a __thread__ instance, `interruption_request()` wiil returns false for the native threads. 

[heading `pthread_exit` POSIX limitation]

`pthread_exit` in glibc/NPTL causes a "forced unwind" that is almost like a C++ exception, but not quite. On Mac OS X, for example, `pthread_exit` unwinds without calling C++ destructors.

This behavior is incompatible with the current Boost.Thread design, so the use of this function in a POSIX thread result in undefined behavior of any Boost.Thread function.

[endsect]

[endsect] [/section:tutorial Tutorial]

[section:thread Class `thread`]

    #include <boost/thread/thread.hpp>

    class thread
    {
    public:
        thread() noexcept;
        thread(const thread&) = delete;
        thread& operator=(const thread&) = delete;

        thread(thread&&) noexcept;
        thread& operator=(thread&&) noexcept;
        ~thread();

        template <class F>
        explicit thread(F f);
        template <class F>
        thread(F &&f);

        template <class F,class A1,class A2,...>
        thread(F f,A1 a1,A2 a2,...);
        // template <class F, class ...Args> 
        // explicit thread(F&& f, Args&&... args); // NOT YET IMPLEMENTED

        template <class F>
        explicit thread(attributes& attrs, F f); // EXTENSION
        template <class F>
        thread(attributes& attrs, F &&f); // EXTENSION
        // template <class F, class ...Args> 
        // explicit thread(attributes& attrs, F&& f, Args&&... args); // NOT YET IMPLEMENTED

        // move support
        thread(thread && x) noexcept;
        thread& operator=(thread && x) noexcept;

        void swap(thread& x) noexcept;

        class id;
        class attributes; // EXTENSION

        id get_id() const noexcept;

        bool joinable() const noexcept;
        void join();
        template <class Rep, class Period>
        bool try_join_for(const chrono::duration<Rep, Period>& rel_time); // EXTENSION
        template <class Clock, class Duration>
        bool try_join_until(const chrono::time_point<Clock, Duration>& t); // EXTENSION

        void detach();

        static unsigned hardware_concurrency() noexcept;

        typedef platform-specific-type native_handle_type;
        native_handle_type native_handle();

        void interrupt(); // EXTENSION
        bool interruption_requested() const noexcept; // EXTENSION


    #if defined BOOST_THREAD_PROVIDES_DEPRECATED_FEATURES_SINCE_V3_0_0 || defined BOOST_THREAD_DONT_USE_CHRONO
        bool timed_join(const system_time& wait_until);
        template<typename TimeDuration>
        bool timed_join(TimeDuration const& rel_time); 
    #endif

    #if defined BOOST_THREAD_PROVIDES_DEPRECATED_FEATURES_SINCE_V3_0_0
        bool operator==(const thread& other) const;
        bool operator!=(const thread& other) const;

        static void yield();
        static void sleep(const system_time& xt);
    #endif

    };

    void swap(thread& lhs,thread& rhs) noexcept;

[section:default_constructor Default Constructor]

    thread() noexcept;

[variablelist

[[Effects:] [Constructs a __thread__ instance that refers to __not_a_thread__.]]

[[Postconditions:] [`this->get_id()==thread::id()`]]

[[Throws:] [Nothing]]

]

[endsect]

[section:move_constructor Move Constructor]

    thread(thread&& other) noexcept;

[variablelist

[[Effects:] [Transfers ownership of the thread managed by `other` (if any) to the newly constructed __thread__ instance.]]

[[Postconditions:] [`other.get_id()==thread::id()` and `get_id()` returns the value of `other.get_id()` prior to the construction]]

[[Throws:] [Nothing]]

]

[endsect]

[section:move_assignment Move assignment operator]

    thread& operator=(thread&& other) noexcept;

[variablelist

[[Effects:] [Transfers ownership of the thread managed by `other` (if
any) to `*this`. Version 2: If there was a thread previously associated with
`*this` then that thread is detached, Version 3: If the thread is joinable calls to std::terminate.]]

[[Postconditions:] [`other->get_id()==thread::id()` and `get_id()` returns the value of `other.get_id()` prior to the assignment.]]

[[Throws:] [Nothing]]

]

[endsect]

[section:callable_constructor Thread Constructor]

    template<typename Callable>
    thread(Callable func);

[variablelist

[[Requires:] [`Callable` must by Copyable and `func()` must be a valid expression.]]

[[Effects:] [`func` is copied into storage managed internally by the thread library, and that copy is invoked on a newly-created
thread of execution. If this invocation results in an exception being propagated into the internals of the thread library that is
not of type __thread_interrupted__, then `std::terminate()` will be called. Any return value from this invocation is ignored.]]

[[Postconditions:] [`*this` refers to the newly created thread of execution and `this->get_id()!=thread::id()`.]]

[[Throws:] [__thread_resource_error__ if an error occurs. ]]

[[Error Conditions:] [

[*resource_unavailable_try_again] : the system lacked the necessary resources to create an- other thread, or the system-imposed limit on the number of threads in a process would be exceeded. 

]]

]

[endsect]

[section:attr_callable_constructor Thread Attributes Constructor EXTENSION]

    template<typename Callable>
    thread(attributes& attrs, Callable func);

[variablelist

[[Preconditions:] [`Callable` must by copyable.]]

[[Effects:] [`func` is copied into storage managed internally by the thread library, and that copy is invoked on a newly-created
thread of execution with the specified attributes. If this invocation results in an exception being propagated into the internals of the thread library that is
not of type __thread_interrupted__, then `std::terminate()` will be called. Any return value from this invocation is ignored. 
If the attributes declare the native thread as detached, the boost::thread will be detached.]]

[[Postconditions:] [`*this` refers to the newly created thread of execution and `this->get_id()!=thread::id()`.]]

[[Throws:] [__thread_resource_error__ if an error occurs. ]]

[[Error Conditions:] [

[*resource_unavailable_try_again] : the system lacked the necessary resources to create an- other thread, or the system-imposed limit on the number of threads in a process would be exceeded. 

]]

]

[endsect]

[section:callable_move_constructor Thread Callable Move Constructor]

    template<typename Callable>
    thread(Callable &&func);

[variablelist

[[Preconditions:] [`Callable` must by Movable.]]

[[Effects:] [`func` is moved into storage managed internally by the thread library, and that copy is invoked on a newly-created
thread of execution. If this invocation results in an exception being propagated into the internals of the thread library that is
not of type __thread_interrupted__, then `std::terminate()` will be called. Any return value from this invocation is ignored.]]

[[Postconditions:] [`*this` refers to the newly created thread of execution and `this->get_id()!=thread::id()`.]]

[[Throws:] [__thread_resource_error__ if an error occurs. ]]

[[Error Conditions:] [

[*resource_unavailable_try_again] : the system lacked the necessary resources to create an- other thread, or the system-imposed limit on the number of threads in a process would be exceeded. 

]]

]

[endsect]

[section:attr_callable_move_constructor Thread Attributes Move Constructor EXTENSION]

    template<typename Callable>
    thread(attributes& attrs, Callable func);

[variablelist

[[Preconditions:] [`Callable` must by copyable.]]

[[Effects:] [`func` is copied into storage managed internally by the thread library, and that copy is invoked on a newly-created
thread of execution with the specified attributes. If this invocation results in an exception being propagated into the internals of the thread library that is
not of type __thread_interrupted__, then `std::terminate()` will be called. Any return value from this invocation is ignored. 
If the attributes declare the native thread as detached, the boost::thread will be detached.]]

[[Postconditions:] [`*this` refers to the newly created thread of execution and `this->get_id()!=thread::id()`.]]

[[Throws:] [__thread_resource_error__ if an error occurs. ]]

[[Error Conditions:] [

[*resource_unavailable_try_again] : the system lacked the necessary resources to create an- other thread, or the system-imposed limit on the number of threads in a process would be exceeded. 

]]

]

[endsect]


[section:multiple_argument_constructor Thread Constructor with arguments]

    template <class F,class A1,class A2,...>
    thread(F f,A1 a1,A2 a2,...);

[variablelist

[[Preconditions:] [`F` and each `A`n must by copyable or movable.]]

[[Effects:] [As if [link
thread.thread_management.thread.callable_constructor
`thread(boost::bind(f,a1,a2,...))`. Consequently, `f` and each `a`n
are copied into internal storage for access by the new thread.]]]

[[Postconditions:] [`*this` refers to the newly created thread of execution.]]

[[Throws:] [__thread_resource_error__ if an error occurs.]]

[[Error Conditions:] [

[*resource_unavailable_try_again] : the system lacked the necessary resources to create an- other thread, or the system-imposed limit on the number of threads in a process would be exceeded. 

]]

[[Note:] [Currently up to nine additional arguments `a1` to `a9` can be specified in addition to the function `f`.]]

]

[endsect]

[section:destructor Thread Destructor]

    ~thread();

[variablelist

[[Effects:] [Version 2: If `*this` has an associated thread of execution, calls __detach__, Version 3: If the thread is joinable calls to std::terminate. Destroys `*this`.]]

[[Throws:] [Nothing.]]

]

[endsect]

[/
[section:v2_destructor V3 Thread Destructor]

    ~thread();

[variablelist

[[Effects:] [If `*this` has an associated thread of execution, calls terminate. Destroys `*this`.]]

[[Note:] [Either implicitly detaching or joining a `joinable()` thread in its destructor could result in difficult to debug correctness (for `detach`) or performance (for `join`) bugs encountered only when an exception is raised. Thus the programmer must ensure that the destructor is never executed while the thread is still joinable.]]


[[Throws:] [Nothing.]]

]

[endsect]
]

[section:joinable Member function `joinable()`]

    bool joinable() const noexcept;

[variablelist

[[Returns:] [`true` if `*this` refers to a thread of execution, `false` otherwise.]]

[[Throws:] [Nothing]]

]


[endsect]

[section:join Member function `join()`]

    void join();

[variablelist

[[Preconditions:] [the thread is joinable.]]

[[Effects:] [If `*this` refers to a thread of execution, waits for that thread of execution to complete.]]

[[Postconditions:] [If `*this` refers to a thread of execution on entry, that thread of execution has completed. `*this` no longer refers to any thread of execution.]]

[[Throws:] [__thread_interrupted__ if the current thread of execution is interrupted or `system_error`]]

[[Error Conditions:] [

[*resource_deadlock_would_occur]: if deadlock is detected or this->get_id() == boost::this_thread::get_id().

[*invalid_argument]: if the thread is not joinable and BOOST_THREAD_TRROW_IF_PRECONDITION_NOT_SATISFIED is defined.


[/
[*no_such_process]: if the thread is not valid.

] 

]]

[[Notes:] [`join()` is one of the predefined __interruption_points__.]]

]

[endsect]

[section:timed_join Member function `timed_join()`]

    bool timed_join(const system_time& wait_until);

    template<typename TimeDuration>
    bool timed_join(TimeDuration const& rel_time);

[variablelist

[[Preconditions:] [the thread is joinable.]]

[[Effects:] [If `*this` refers to a thread of execution, waits for that thread of execution to complete, the time `wait_until` has
been reach or the specified duration `rel_time` has elapsed. If `*this` doesn't refer to a thread of execution, returns immediately.]]

[[Returns:] [`true` if `*this` refers to a thread of execution on entry, and that thread of execution has completed before the call
times out, `false` otherwise.]]

[[Postconditions:] [If `*this` refers to a thread of execution on entry, and `timed_join` returns `true`, that thread of execution
has completed, and `*this` no longer refers to any thread of execution. If this call to `timed_join` returns `false`, `*this` is
unchanged.]]

[[Throws:] [__thread_interrupted__ if the current thread of execution is interrupted or `system_error`]]

[[Error Conditions:] [

[*resource_deadlock_would_occur]: if deadlock is detected or this->get_id() == boost::this_thread::get_id().

[*invalid_argument]: if the thread is not joinable and BOOST_THREAD_TRROW_IF_PRECONDITION_NOT_SATISFIED is defined.


[/
[*no_such_process]: if the thread is not valid.
] 

]]

[[Notes:] [`timed_join()` is one of the predefined __interruption_points__.]]

]

[endsect]

[section:try_join_for Member function `try_join_for()` EXTENSION]

        template <class Rep, class Period>
        bool try_join_for(const chrono::duration<Rep, Period>& rel_time);

[variablelist

[[Preconditions:] [the thread is joinable.]]

[[Effects:] [If `*this` refers to a thread of execution, waits for that thread of execution to complete, 
the specified duration `rel_time` has elapsed. If `*this` doesn't refer to a thread of execution, returns immediately.]]

[[Returns:] [`true` if `*this` refers to a thread of execution on entry, and that thread of execution has completed before the call
times out, `false` otherwise.]]

[[Postconditions:] [If `*this` refers to a thread of execution on entry, and `try_join_for` returns `true`, that thread of execution
has completed, and `*this` no longer refers to any thread of execution. If this call to `try_join_for` returns `false`, `*this` is
unchanged.]]

[[Throws:] [__thread_interrupted__ if the current thread of execution is interrupted or `system_error`]]

[[Error Conditions:] [

[*resource_deadlock_would_occur]: if deadlock is detected or this->get_id() == boost::this_thread::get_id().

[*invalid_argument]: if the thread is not joinable and BOOST_THREAD_TRROW_IF_PRECONDITION_NOT_SATISFIED is defined.


[/
[*no_such_process]: if the thread is not valid.
] 

]]

[[Notes:] [`try_join_for()` is one of the predefined __interruption_points__.]]

]

[endsect]

[section:try_join_until Member function `try_join_until()` EXTENSION]

        template <class Clock, class Duration>
        bool try_join_until(const chrono::time_point<Clock, Duration>& abs_time);

[variablelist

[[Preconditions:] [the thread is joinable.]]

[[Effects:] [If `*this` refers to a thread of execution, waits for that thread of execution to complete, the time `abs_time` has
been reach. If `*this` doesn't refer to a thread of execution, returns immediately.]]

[[Returns:] [`true` if `*this` refers to a thread of execution on entry, and that thread of execution has completed before the call
times out, `false` otherwise.]]

[[Postconditions:] [If `*this` refers to a thread of execution on entry, and `try_join_until` returns `true`, that thread of execution
has completed, and `*this` no longer refers to any thread of execution. If this call to `try_join_until` returns `false`, `*this` is
unchanged.]]

[[Throws:] [__thread_interrupted__ if the current thread of execution is interrupted or `system_error`]]

[[Error Conditions:] [

[*resource_deadlock_would_occur]: if deadlock is detected or this->get_id() == boost::this_thread::get_id().

[*invalid_argument]: if the thread is not joinable and BOOST_THREAD_TRROW_IF_PRECONDITION_NOT_SATISFIED is defined.


[/
[*no_such_process]: if the thread is not valid.

] 

]]

[[Notes:] [`try_join_until()` is one of the predefined __interruption_points__.]]

]

[endsect]



[section:detach Member function `detach()`]

    void detach();

[variablelist

[[Preconditions:] [the thread is joinable.]]

[[Effects:] [The thread of execution becomes detached, and no longer has an associated __thread__ object.]]

[[Postconditions:] [`*this` no longer refers to any thread of execution.]]

[[Throws:] [`system_error`]]

[[Error Conditions:] [

[*no_such_process]: if the thread is not valid.

[*invalid_argument]: if the thread is not joinable and BOOST_THREAD_TRROW_IF_PRECONDITION_NOT_SATISFIED is defined.

]]

]

[endsect]


[section:get_id Member function `get_id()`]

    thread::id get_id() const noexcept;

[variablelist

[[Returns:] [If `*this` refers to a thread of execution, an instance of __thread_id__ that represents that thread. Otherwise returns
a default-constructed __thread_id__.]]

[[Throws:] [Nothing]]

]

[endsect]

[section:interrupt Member function `interrupt()`]

    void interrupt();

[variablelist

[[Effects:] [If `*this` refers to a thread of execution, request that the thread will be interrupted the next time it enters one of
the predefined __interruption_points__ with interruption enabled, or if it is currently __blocked__ in a call to one of the
predefined __interruption_points__ with interruption enabled .]]

[[Throws:] [Nothing]]

]
        

[endsect]

[section:hardware_concurrency Static member function `hardware_concurrency()`]

    unsigned hardware_concurrency() noexecpt;

[variablelist

[[Returns:] [The number of hardware threads available on the current system (e.g. number of CPUs or cores or hyperthreading units),
or 0 if this information is not available.]]

[[Throws:] [Nothing]]

]

[endsect]

[section:nativehandle Member function `native_handle()`]

    typedef platform-specific-type native_handle_type;
    native_handle_type native_handle();

[variablelist

[[Effects:] [Returns an instance of `native_handle_type` that can be used with platform-specific APIs to manipulate the underlying
implementation. If no such instance exists, `native_handle()` and `native_handle_type` are not present.]]

[[Throws:] [Nothing.]]

]

[endsect]

[section:equals `operator==` DEPRECATED V3]

    bool operator==(const thread& other) const;

[variablelist

[[Returns:] [`get_id()==other.get_id()`]]

[[See:] [Use `a.__get_id()==b.__get_id()` instead]]

]

[endsect]

[section:not_equals `operator!=` DEPRECATED V3]

    bool operator!=(const thread& other) const;

[variablelist

[[Returns:] [`get_id()!=other.get_id()`]]

[[See:] [Use `a.__get_id()!=b.__get_id()` instead`]]

]

[endsect]

[section:sleep Static member function `sleep()`]

    void sleep(system_time const& abs_time);

[variablelist

[[Effects:] [Suspends the current thread until the specified time has been reached.]]

[[Throws:] [__thread_interrupted__ if the current thread of execution is interrupted.]]

[[Notes:] [`sleep()` is one of the predefined __interruption_points__.]]

[[See:] [Use `this_thread::__sleep_for()` or `this_thread::__sleep_until()`]]

]

[endsect]

[section:yield Static member function `yield()`]

    void yield();

[variablelist

[[Effects:] [See [link thread.thread_management.this_thread.yield `boost::this_thread::yield()`].]]

[[See:] [Use `this_thread::__yield()`]]

]

[endsect]

[section:swap Member function `swap()`]

    void swap(thread& other) noexcept;

[variablelist

[[Effects:] [Exchanges the threads of execution associated with `*this` and `other`, so `*this` is associated with the thread of
execution associated with `other` prior to the call, and vice-versa.]]

[[Postconditions:] [`this->get_id()` returns the same value as `other.get_id()` prior to the call. `other.get_id()` returns the same
value as `this->get_id()` prior to the call.]]

[[Throws:] [Nothing.]]

]

[endsect]

[section:non_member_swap Non-member function `swap()`]

    #include <boost/thread/thread.hpp>

    void swap(thread& lhs,thread& rhs) noexcept;

[variablelist

[[Effects:] [[link thread.thread_management.thread.swap `lhs.swap(rhs)`].]]

]

[endsect]


[section:id Class `boost::thread::id`]

    #include <boost/thread/thread.hpp>

    class thread::id
    {
    public:
        id() noexcept;

        bool operator==(const id& y) const noexcept;
        bool operator!=(const id& y) const noexcept;
        bool operator<(const id& y) const noexcept;
        bool operator>(const id& y) const noexcept;
        bool operator<=(const id& y) const noexcept;
        bool operator>=(const id& y) const noexcept;

        template<class charT, class traits>
        friend std::basic_ostream<charT, traits>& 
        operator<<(std::basic_ostream<charT, traits>& os, const id& x);
    };

[section:constructor Default constructor]

    id() noexcept;

[variablelist

[[Effects:] [Constructs a __thread_id__ instance that represents __not_a_thread__.]]

[[Throws:] [Nothing]]

]

[endsect]

[section:is_equal `operator==`]

    bool operator==(const id& y) const noexcept;

[variablelist

[[Returns:] [`true` if `*this` and `y` both represent the same thread of execution, or both represent __not_a_thread__, `false`
otherwise.]]

[[Throws:] [Nothing]]

]

[endsect]

[section:not_equal `operator!=`]

    bool operator!=(const id& y) const noexcept;

[variablelist

[[Returns:] [`true` if `*this` and `y` represent different threads of execution, or one represents a thread of execution, and
the other represent __not_a_thread__, `false` otherwise.]]

[[Throws:] [Nothing]]

]

[endsect]

[section:less_than `operator<`]

    bool operator<(const id& y) const noexcept;

[variablelist

[[Returns:] [`true` if `*this!=y` is `true` and the implementation-defined total order of __thread_id__ values places `*this` before
`y`, `false` otherwise.]]

[[Throws:] [Nothing]]

[[Note:] [A __thread_id__ instance representing __not_a_thread__ will always compare less than an instance representing a thread of
execution.]]

]

[endsect]


[section:greater_than `operator>`]

    bool operator>(const id& y) const noexcept;

[variablelist

[[Returns:] [`y<*this`]]

[[Throws:] [Nothing]]

]

[endsect]

[section:less_than_or_equal `operator<=`]

    bool operator<=(const id& y) const noexcept;

[variablelist

[[Returns:] [`!(y<*this)`]]

[[Throws:] [Nothing]]

]

[endsect]

[section:greater_than_or_equal `operator>=`]

    bool operator>=(const id& y) const noexcept;

[variablelist

[[Returns:] [`!(*this<y)`]]

[[Throws:] [Nothing]]

]

[endsect]

[section:stream_out Friend `operator<<`]

    template<class charT, class traits>
    friend std::basic_ostream<charT, traits>& 
    operator<<(std::basic_ostream<charT, traits>& os, const id& x);

[variablelist

[[Effects:] [Writes a representation of the __thread_id__ instance `x` to the stream `os`, such that the representation of two
instances of __thread_id__ `a` and `b` is the same if `a==b`, and different if `a!=b`.]]

[[Returns:] [`os`]]

]

[endsect]


[endsect]

[section:attributes Class `boost::thread::attributes` EXTENSION]

    class thread::attributes {
    public:
        attributes() noexcept;
        ~ attributes()=default;
        // stack
        void set_stack_size(std::size_t size) noexcept;
        std::size_t get_stack_size() const noexcept;

    #if defined BOOST_THREAD_DEFINES_THREAD_ATTRIBUTES_NATIVE_HANDLE
        typedef platform-specific-type native_handle_type;
        native_handle_type* native_handle() noexcept;
        const native_handle_type* native_handle() const noexcept;
    #endif

    };

[section:constructor Default constructor]

    thread_attributes() noexcept;

[variablelist

[[Effects:] [Constructs a thread atrributes instance with its default values.]]

[[Throws:] [Nothing]]

]

[endsect]

[section: set_stack_size Member function `set_stack_size()`]

        void set_stack_size(std::size_t size) noexcept;

[variablelist

[[Effects:] [Stores the stack size to be used to create a thread. This is an hint that the implementation can choose a better size if to small or too big or not aligned to a page.]]

[[Postconditions:] [`this-> get_stack_size()` returns the chosen stack size.]]

[[Throws:] [Nothing.]]

]

[endsect]

[section:get_stack_size Member function `get_stack_size()`]

        std::size_t get_stack_size() const noexcept;

[variablelist

[[Returns:] [The stack size to be used on the creation of a thread. Note that this function can return 0 meaning the default.]]

[[Throws:] [Nothing.]]

]

[endsect]

[section:nativehandle Member function `native_handle()`]

    typedef platform-specific-type native_handle_type;
        typedef platform-specific-type native_handle_type;
        native_handle_type* native_handle() noexcept;
        const native_handle_type* native_handle() const noexcept;

[variablelist

[[Effects:] [Returns an instance of `native_handle_type` that can be used with platform-specific APIs to manipulate the underlying
thread attributes implementation. If no such instance exists, `native_handle()` and `native_handle_type` are not present and `BOOST_THREAD_DEFINES_THREAD_ATTRIBUTES_NATIVE_HANDLE` is not defined.]]

[[Throws:] [Nothing.]]

]

[endsect]
[endsect] [/ thread::attributes ]
[endsect] [/ thread ]

[section:this_thread Namespace `this_thread`]


  namespace boost {
    namespace this_thread {
      thread::id get_id() noexcept;
      template<typename TimeDuration>
      void yield() noexcept;
      template <class Clock, class Duration>
      void sleep_until(const chrono::time_point<Clock, Duration>& abs_time); 
      template <class Rep, class Period>
      void sleep_for(const chrono::duration<Rep, Period>& rel_time);

      template<typename Callable>
      void at_thread_exit(Callable func); // EXTENSION

      void interruption_point(); // EXTENSION
      bool interruption_requested() noexcept; // EXTENSION
      bool interruption_enabled() noexcept; // EXTENSION
      class disable_interruption; // EXTENSION
      class restore_interruption; // EXTENSION

    #if defined BOOST_THREAD_PROVIDES_DEPRECATED_FEATURES_SINCE_V3_0_0 || defined BOOST_THREAD_DONT_USE_CHRONO
      void sleep(TimeDuration const& rel_time);
      void sleep(system_time const& abs_time) 
    #endif
    }
  }

[section:get_id Non-member function `get_id()`]

    #include <boost/thread/thread.hpp>

    namespace this_thread
    {
        thread::id get_id() noexcept;
    }

[variablelist

[[Returns:] [An instance of __thread_id__ that represents that currently executing thread.]]

[[Throws:] [__thread_resource_error__ if an error occurs.]]

]

[endsect]

[section:interruption_point Non-member function `interruption_point()` EXTENSION]

    #include <boost/thread/thread.hpp>

    namespace this_thread
    {
        void interruption_point();
    }

[variablelist

[[Effects:] [Check to see if the current thread has been interrupted.]]

[[Throws:] [__thread_interrupted__ if __interruption_enabled__ and __interruption_requested__ both return `true`.]]

]

[endsect]

[section:interruption_requested Non-member function `interruption_requested()` EXTENSION]

    #include <boost/thread/thread.hpp>

    namespace this_thread
    {
        bool interruption_requested() noexcept;
    }

[variablelist

[[Returns:] [`true` if interruption has been requested for the current thread, `false` otherwise.]]

[[Throws:] [Nothing.]]

]

[endsect]

[section:interruption_enabled Non-member function `interruption_enabled()` EXTENSION]

    #include <boost/thread/thread.hpp>

    namespace this_thread
    {
        bool interruption_enabled() noexcept;
    }

[variablelist

[[Returns:] [`true` if interruption has been enabled for the current thread, `false` otherwise.]]

[[Throws:] [Nothing.]]

]

[endsect]

[section:sleep Non-member function `sleep()`]

    #include <boost/thread/thread.hpp>

    namespace this_thread
    {
        template<typename TimeDuration>
        void sleep(TimeDuration const& rel_time);
        void sleep(system_time const& abs_time)
    }

[variablelist

[[Effects:] [Suspends the current thread until the time period
specified by `rel_time` has elapsed or the time point specified by
`abs_time` has been reached.]]

[[Throws:] [__thread_interrupted__ if the current thread of execution is interrupted.]]

[[Notes:] [`sleep()` is one of the predefined __interruption_points__.]]

[[See:] [Use `__sleep_for()` and `__sleep_until()` instead.]]

]

[endsect]

[section:sleep_until Non-member function `sleep_until()`]

    #include <boost/thread/thread.hpp>

    namespace this_thread
    {
      template <class Clock, class Duration>
      void sleep_until(const chrono::time_point<Clock, Duration>& abs_time); 
    }

[variablelist

[[Effects:] [Suspends the current thread until the time period
specified by `rel_time` has elapsed or the time point specified by
`abs_time` has been reached.]]

[[Throws:] [Nothing if Clock satisfies the TrivialClock requirements and operations of Duration
do not throw exceptions. __thread_interrupted__ if the current thread of execution is interrupted. ]]

[[Notes:] [`sleep_until()` is one of the predefined __interruption_points__.]]

]

[endsect]

[section:sleep_for Non-member function `sleep_for()`]

    #include <boost/thread/thread.hpp>

    namespace this_thread
    {
      template <class Rep, class Period>
      void sleep_for(const chrono::duration<Rep, Period>& rel_time);
    }

[variablelist

[[Effects:] [Suspends the current thread until the time point specified by
`abs_time` has been reached.]]

[[Throws:] [Nothing if operations of chrono::duration<Rep, Period> do not throw exceptions. __thread_interrupted__ if the current thread of execution is interrupted.]]

[[Notes:] [`sleep_for()` is one of the predefined __interruption_points__.]]

]

[endsect]


[section:yield Non-member function `yield()`]

    #include <boost/thread/thread.hpp>

    namespace this_thread
    {
        void yield() noexcept;
    }

[variablelist

[[Effects:] [Gives up the remainder of the current thread's time slice, to allow other threads to run.]]

[[Throws:] [Nothing.]]

]

[endsect]

[section:disable_interruption Class `disable_interruption` EXTENSION]

    #include <boost/thread/thread.hpp>

    namespace this_thread
    {
        class disable_interruption
        {
        public:
            disable_interruption(const disable_interruption&) = delete;
            disable_interruption& operator=(const disable_interruption&) = delete;
            disable_interruption() noexcept;
            ~disable_interruption() noexcept;
        };
    }

`boost::this_thread::disable_interruption` disables interruption for the current thread on construction, and restores the prior
interruption state on destruction. Instances of `disable_interruption` cannot be copied or moved.

[section:constructor Constructor]

    disable_interruption() noexcept;

[variablelist

[[Effects:] [Stores the current state of __interruption_enabled__ and disables interruption for the current thread.]]

[[Postconditions:] [__interruption_enabled__ returns `false` for the current thread.]]

[[Throws:] [Nothing.]]

]

[endsect]

[section:destructor Destructor]

    ~disable_interruption() noexcept;

[variablelist

[[Preconditions:] [Must be called from the same thread from which `*this` was constructed.]]

[[Effects:] [Restores the current state of __interruption_enabled__ for the current thread to that prior to the construction of `*this`.]]

[[Postconditions:] [__interruption_enabled__ for the current thread returns the value stored in the constructor of `*this`.]]

[[Throws:] [Nothing.]]

]

[endsect]

[endsect]

[section:restore_interruption Class `restore_interruption` EXTENSION]

    #include <boost/thread/thread.hpp>

    namespace this_thread
    {
        class restore_interruption
        {
        public:
            restore_interruption(const restore_interruption&) = delete;
            restore_interruption& operator=(const restore_interruption&) = delete;
            explicit restore_interruption(disable_interruption& disabler) noexcept;
            ~restore_interruption() noexcept;
        };
    }

On construction of an instance of `boost::this_thread::restore_interruption`, the interruption state for the current thread is
restored to the interruption state stored by the constructor of the supplied instance of __disable_interruption__. When the instance
is destroyed, interruption is again disabled. Instances of `restore_interruption` cannot be copied or moved.

[section:constructor Constructor]

    explicit restore_interruption(disable_interruption& disabler) noexcept;

[variablelist

[[Preconditions:] [Must be called from the same thread from which `disabler` was constructed.]]

[[Effects:] [Restores the current state of __interruption_enabled__ for the current thread to that prior to the construction of `disabler`.]]

[[Postconditions:] [__interruption_enabled__ for the current thread returns the value stored in the constructor of `disabler`.]]

[[Throws:] [Nothing.]]

]

[endsect]

[section:destructor Destructor]

    ~restore_interruption() noexcept;

[variablelist

[[Preconditions:] [Must be called from the same thread from which `*this` was constructed.]]

[[Effects:] [Disables interruption for the current thread.]]

[[Postconditions:] [__interruption_enabled__ for the current thread returns `false`.]]

[[Throws:] [Nothing.]]

]

[endsect]

[endsect]

[section:atthreadexit Non-member function template `at_thread_exit()` EXTENSION]

    #include <boost/thread/thread.hpp>

    template<typename Callable>
    void at_thread_exit(Callable func);

[variablelist

[[Effects:] [A copy of `func` is placed in
thread-specific storage. This copy is invoked when the current thread
exits (even if the thread has been interrupted).]]

[[Postconditions:] [A copy of `func` has been saved for invocation on thread exit.]]

[[Throws:] [`std::bad_alloc` if memory cannot be allocated for the copy of the function, __thread_resource_error__ if any other
error occurs within the thread library. Any exception thrown whilst copying `func` into internal storage.]]

[[Note:] [This function is *not* called if the thread was terminated
forcefully using platform-specific APIs, or if the thread is
terminated due to a call to `exit()`, `abort()` or
`std::terminate()`. In particular, returning from `main()` is
equivalent to call to `exit()`, so will not call any functions
registered with `at_thread_exit()`]]

]

[endsect]

[endsect]

[section:threadgroup Class `thread_group`]

    #include <boost/thread/thread.hpp>

    class thread_group:
        private noncopyable
    {
    public:
        thread_group();
        ~thread_group();

        template<typename F>
        thread* create_thread(F threadfunc);
        void add_thread(thread* thrd);
        void remove_thread(thread* thrd);
        void join_all();
        void interrupt_all();
        int size() const;
    };

`thread_group` provides for a collection of threads that are related in some fashion. New threads can be added to the group with
`add_thread` and `create_thread` member functions. `thread_group` is not copyable or movable.

[section:constructor Constructor]

    thread_group();

[variablelist

[[Effects:] [Create a new thread group with no threads.]]

]

[endsect]

[section:destructor Destructor]

    ~thread_group();

[variablelist

[[Effects:] [Destroy `*this` and `delete` all __thread__ objects in the group.]]

]

[endsect]

[section:create_thread Member function `create_thread()`]

    template<typename F>
    thread* create_thread(F threadfunc);

[variablelist

[[Effects:] [Create a new __thread__ object as-if by `new thread(threadfunc)` and add it to the group.]]

[[Postcondition:] [`this->size()` is increased by one, the new thread is running.]]

[[Returns:] [A pointer to the new __thread__ object.]]

]

[endsect]

[section:add_thread Member function `add_thread()`]

    void add_thread(thread* thrd);

[variablelist

[[Precondition:] [The expression `delete thrd` is well-formed and will not result in undefined behaviour.]]

[[Effects:] [Take ownership of the __thread__ object pointed to by `thrd` and add it to the group.]]

[[Postcondition:] [`this->size()` is increased by one.]]

]

[endsect]

[section:remove_thread Member function `remove_thread()`]

    void remove_thread(thread* thrd);

[variablelist

[[Effects:] [If `thrd` is a member of the group, remove it without calling `delete`.]]

[[Postcondition:] [If `thrd` was a member of the group, `this->size()` is decreased by one.]]

]

[endsect]

[section:join_all Member function `join_all()`]

    void join_all();

[variablelist

[[Effects:] [Call `join()` on each __thread__ object in the group.]]

[[Postcondition:] [Every thread in the group has terminated.]]

[[Note:] [Since __join__ is one of the predefined __interruption_points__, `join_all()` is also an interruption point.]]

]

[endsect]

[section:interrupt_all Member function `interrupt_all()`]

    void interrupt_all();

[variablelist

[[Effects:] [Call `interrupt()` on each __thread__ object in the group.]]

]

[endsect]

[section:size Member function `size()`]

    int size();

[variablelist

[[Returns:] [The number of threads in the group.]]

[[Throws:] [Nothing.]]

]

[endsect]


[endsect]

[endsect]