future.h
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/* Copyright (C) 2010 to 2013 Chris Vine
The library comprised in this file or of which this file is part is
distributed by Chris Vine under the GNU Lesser General Public
License as follows:
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public License
as published by the Free Software Foundation; either version 2.1 of
the License, or (at your option) any later version.
This library is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License, version 2.1, for more details.
You should have received a copy of the GNU Lesser General Public
License, version 2.1, along with this library (see the file LGPL.TXT
which came with this source code package in the src/utils sub-directory);
if not, write to the Free Software Foundation, Inc.,
51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
However, it is not intended that the object code of a program whose
source code instantiates a template from this file or uses macros or
inline functions (of any length) should by reason only of that
instantiation or use be subject to the restrictions of use in the GNU
Lesser General Public License. With that in mind, the words "and
macros, inline functions and instantiations of templates (of any
length)" shall be treated as substituted for the words "and small
macros and small inline functions (ten lines or less in length)" in
the fourth paragraph of section 5 of that licence. This does not
affect any other reason why object code may be subject to the
restrictions in that licence (nor for the avoidance of doubt does it
affect the application of section 2 of that licence to modifications
of the source code in this file).
*/
#ifndef CGU_FUTURE_H
#define CGU_FUTURE_H
#include <memory>
#include <exception>
#include <utility> // for std::move and std::forward
#include <type_traits> // for std::remove_reference and std::remove_const
#include <pthread.h>
#include <glib.h>
#include <c++-gtk-utils/thread.h>
#include <c++-gtk-utils/mutex.h>
#include <c++-gtk-utils/callback.h>
#include <c++-gtk-utils/intrusive_ptr.h>
#include <c++-gtk-utils/shared_ptr.h>
#include <c++-gtk-utils/emitter.h>
#include <c++-gtk-utils/timeout.h>
#include <c++-gtk-utils/cgu_config.h>
namespace Cgu {
namespace Thread {
struct FutureThreadError: public std::exception {
virtual const char* what() const throw() {return "FutureThreadError\n";}
};
struct FutureWhenError: public std::exception {
virtual const char* what() const throw() {return "FutureWhenError\n";}
};
/**
* @class Cgu::Thread::Future future.h c++-gtk-utils/future.h
* @brief A class representing a pthread thread which will
* provide a value.
* @sa Cgu::Thread::Thread Cgu::Thread::JoinableHandle Cgu::AsyncResult Cgu::Thread::make_future() Cgu::Thread::TaskManager
*
* The Thread::Future class will launch a worker thread, run the
* function it represents in that thread until it returns, and store
* the return value so that it can be waited on and/or extracted by
* another thread. A new Thread::Future object representing the
* function to be called is created by calling
* Cgu::Thread::Future<>::make() (a static member function) or from
* version 2.0.4 the Cgu::Thread::make_future() helper function. The
* worker thread is then started by calling run(), and the value
* extracted or waited for by calling get(). The run() method can
* only be called once, but any number of threads can wait for and/or
* extract the return value by calling the get() method. The class
* also provides a SafeEmitter @ref DoneEmitterAnchor "done_emitter"
* public object which emits when the worker thread has finished, and
* an associated when() function. In addition, from version 2.0.11 a
* move_get() method is provided, which is discussed further below.
*
* The template parameter type of Thread::Future is the type of the
* return value of the function called by the Thread::Future object.
* The return value can be any type, including any arbitrarily large
* tuple or other struct or standard C++ container (but see below
* about copying).
*
* A Thread::Future object cannot represent a function with a void
* return type - a compilation error will result if that is attempted.
* If no return value is wanted, then the Thread::Thread class can be
* used directly. (However, if in a particular usage this class is
* thought to be more convenient, the function to be represented by it
* can be wrapped by another function which provides a dummy return
* value, such as a dummy int. One possible case for this is where
* more than one thread wants to wait for the worker thread to
* terminate, as pthread_join() and so Thread::Thread::join() only
* give defined behaviour when called by one thread.) In addition, a
* Thread::Future object cannot represent a function with a non-const
* reference argument - that would not normally be safe, and a compile
* error will be generated if that is attempted. However, from
* version 2.0.0-rc3, const reference arguments can be bound to
* Thread::Future objects (this is safe, as the Thread::Future object
* will keep its own copy of the argument passed to it).
*
* The make() method and make_future() functions take a plain
* function, static member function or non-static member function,
* which can take up to three arguments in the case of a non-static
* member function, and four arguments in the case of any other
* function. In the case of a non-static member function, the
* referenced object whose member function is to be called must remain
* in existence until the worker thread has completed. Alternatively,
* a callable object such as a std::function object, a lambda or the
* return value of std::bind can be passed, which can have any number
* of arguments using lambda capture or std::bind (and which can also
* bind the referenced object of a non-static member function by
* taking a copy of it where that is necessary).
*
* It is to be noted that the target function to be represented by a
* Thread::Future object must not allow any exception other than
* Thread::Exit, an exception deriving from std::exception or a
* cancellation pseudo-exception to escape from it when it is
* executed. This includes ensuring that, for any argument of that
* function which is of class type and not taken by reference to
* const, the argument type's copy constructor does not throw anything
* other than these. (If the target function or the copy constructor
* of a value argument throws Thread::Exit or an exception deriving
* from std::exception, the exception is safely consumed and the
* Thread::Future object's error flag is set.)
*
* Where a callable object is not passed, internal moving/copying of
* arguments for the target function to be represented by the
* Thread::Future object takes place (once by invoking the rvalue move
* constructor or lvalue copy constructor, as appropriate, when make()
* or make_future() are called and, if the argument is not a const
* reference argument, once in the worker thread when run() is
* called). Therefore, if a non-trivial class object is to be
* received by the target function as an argument, it is best either
* (a) if it has a move constructor, to pass it to make() or
* make_future() as a temporary and have the target function take a
* const reference argument, or (b) for it to be constructed on free
* store and for the target function to receive it by pointer, by
* Cgu::SharedLockPtr, or by a std::shared_ptr implementation which
* has a thread-safe reference count. Note also that constructing
* callable objects using std::bind will cause copies of arguments to
* be made, as will lambda capture, so for ordinary usage it is better
* to pass a function pointer with arguments to make() or
* make_future() rather than a function object.
*
* Copying of the return value of the target function represented by
* the Thread::Future object also takes place. The run() method will
* store the return value of that function, so that it is available to
* the get() and move_get() methods and any 'when' callback, and
* therefore copy it once (unless, that is, the target function's
* return value type has a move assignment operator, in which case
* where possible that operator is called).
*
* For safety reasons, the get() method returns by value and so will
* cause the return value to be copied once more, so for return values
* comprising complex class objects which are to be abstracted using
* the get() method, it is often better if the function represented by
* the Thread::Future object allocates the return value on free store
* and returns it by pointer, by Cgu::SharedLockPtr, or by a
* std::shared_ptr implementation which has a thread-safe reference
* count. Alternatively, from version 2.0.11 a move_get() method is
* provided which will make a move operation instead of a copy if the
* return value's type implements a move constructor, but see the
* documentation on move_get() for the caveats with respect to its
* use: in particular, if move_get() is to be called by a thread, then
* get() may not normally be called by another thread, nor should the
* when() method be called.
*
* It should be noted that where the when() method is used, the return
* value is passed to the 'when' callback by reference to const and so
* without the copying carried out by the get() method: therefore, if
* the return value has a move assignment operator and the when()
* method is to be employed, and the 'when' callback only needs to
* call const methods of the return value, it may be more efficient
* not to allocate the return value on free store.
*
* This is a usage example:
*
* @code
* class Numbers {
* public:
* std::vector<long> get_primes(int n); // calculates the first n primes
* // and puts them in a vector
* ...
* };
*
* Numbers obj;
*
* // get the first 1,000 primes
* using namespace Cgu;
*
* auto future = Thread::make_future(obj, &Numbers::get_primes, 1000);
* // Thread::make_future() is a wrapper for the equivalent long-hand version required prior to version 2.0.4:
* // auto future = Thread::Future<std::vector<long>>::make(obj, &Numbers::get_primes, 1000);
*
* future->run();
* ... [ do something else ] ...
* std::vector<long> result(future->move_get());
* std::for_each(result.begin(), result.end(), [](long l) {std::cout << l << std::endl;});
* @endcode
*
* If get_primes() were a static member function or plain function,
* the syntax would be:
*
* @code
* auto future = Thread::make_future(&Numbers::get_primes, 1000);
* @endcode
*
* The Cgu::Thread::Future::when() functions
* -----------------------------------------
*
* From version 2.0.2, the return value of the thread function
* represented by Cgu::Thread::Future can be obtained asynchronously
* using Cgu::Thread::Future::when() to execute a function in a glib
* main loop when the thread function completes. The above example
* could be reimplemented as:
*
* @code
* class Numbers {
* public:
* std::vector<long> get_primes(int n); // calculates the first n primes
* // and puts them in a vector
* ...
* };
*
* void print_primes(const std::vector<long>& result) {
* std::for_each(result.begin(), result.end(), [](long l) {std::cout << l << std::endl;});
* }
*
* Numbers obj;
*
* using namespace Cgu;
*
* auto future = Thread::make_future(obj, &Numbers::get_primes, 1000);
* future->when(Callback::make(&print_primes));
* future->run();
* @endcode
*
* In this example, the callback which prints the primes to the
* console would execute in the default program main loop once the
* thread function providing those primes returns. As an alternative
* to a free standing print_primes() function, the callback object
* could be constructed from a C++11 lambda expression using
* Cgu::Callback::lambda() (available from version 2.0.9).
*
* Lambda functions
* ----------------
*
* As mentioned above, Cgu::Thread::Future objects can be constructed
* from any callable object. For example:
*
* @code
* using namespace Cgu;
* int i = 1;
* auto f = Thread::Future<int>::make([=]() {return i + 10;});
* f->run();
* std::cout << f->get() << std::endl;
* @endcode
*
* However, if make_future() is used, prior to version 2.0.14 of the
* library, the return type parameter had to be be explicitly stated
* if the callable object was not a std::function object. From
* version 2.0.14 this is no longer necessary, as the return value
* will be deduced automatically if it is not stated:
*
* @code
* using namespace Cgu;
* int i = 1;
* auto f = Thread::make_future<int>([=]() {return i + 10;}); // prior to version 2.0.14
* //auto f = Thread::make_future([=]() {return i + 10;}); // this is fine from version 2.0.14
* f->run();
* std::cout << f->get() << std::endl;
* @endcode
*
* Overloaded functions
* --------------------
*
* Where a member function or ordinary function represented by a
* Thread::Future object is overloaded, this will cause difficulties
* in template type deduction when Thread::Future<>::make() or
* Thread::make_future() are called. With Thread::Future<>::make(),
* functions may be overloaded on numbers of argument without
* difficulty, but not with Thread::make_future(). For example:
* @code
* class Numbers {
* public:
* int calc(int i);
* int calc(int i, int j);
* ...
* };
*
* Numbers obj;
*
* using namespace Cgu;
*
* int i = 1, j = 2;
*
* auto f1 =
* Thread::Future<int>::make(obj, &Numbers::calc, i); // OK
* auto f2 =
* Thread::Future<int>::make(obj, &Numbers::calc, i, j); // OK
*
* // explicit is disambiguation required with Thread::make_future()
* auto f3 =
* Thread::make_future(obj, static_cast<int(Numbers::*)(int)>(&Numbers::calc), i);
* auto f4 =
* Thread::make_future(obj, static_cast<int(Numbers::*)(int, int)>(&Numbers::calc), i, j);
* @endcode
* Neither Thread::Future<>::make() nor Thread::make_future() can be
* overloaded on types of argument without explicit disambiguation.
* For example:
* @code
* class Numbers {
* public:
* int calc(int i);
* int calc(double d);
* ...
* };
*
* Numbers obj;
*
* using namespace Cgu;
*
* int i = 1;
* double d = 2.0;
*
* auto f1 =
* Thread::Future<int>::make(obj, static_cast<int (Numbers::*)(int)>(&Numbers::calc), i);
* auto f2 =
* Thread::Future<int>::make(obj, static_cast<int (Numbers::*)(double)>(&Numbers::calc), d);
* auto f3 =
* Thread::make_future(obj, static_cast<int (Numbers::*)(int)>(&Numbers::calc), i);
* auto f4 =
* Thread::make_future(obj, static_cast<int (Numbers::*)(double)>(&Numbers::calc), d);
* @endcode
*/
namespace FutureHelper {
// the sole purpose of this struct is to enable a callback object to
// be constructed with Callback::make_ref() which takes an argument
// which can be mutated when the callback is executed. Normally this
// would be unsafe: however in this particular use it is fine as the
// callback is only ever executed once, via Future::run().
template <class Val>
struct WhenWrapperArg {
mutable std::unique_ptr<const Cgu::Callback::CallbackArg<const Val&>> when;
// TODO: these constructors are a work-around for a bug in gcc <
// 4.6. At any API break where the required version of gcc is
// increased to gcc-4.6 or higher, remove them.
WhenWrapperArg(std::unique_ptr<const Cgu::Callback::CallbackArg<const Val&>>&& when_) :
when(std::move(when_)) {}
WhenWrapperArg(WhenWrapperArg&& w): when(std::move(w.when)) {}
};
// the sole purpose of this struct is to enable a callback object to
// be constructed with Callback::make_ref() which takes an argument
// which can be mutated when the callback is executed. Normally this
// would be unsafe: however in this particular use it is fine as the
// callback is only ever executed once, via Future::run().
template <class Val>
struct WhenWrapperArgRel {
mutable std::unique_ptr<Cgu::SafeEmitterArg<const Val&>> when;
// TODO: these constructors are a work-around for a bug in gcc <
// 4.6. At any API break where the required version of gcc is
// increased to gcc-4.6 or higher, remove them.
WhenWrapperArgRel(std::unique_ptr<Cgu::SafeEmitterArg<const Val&>>&& when_) :
when(std::move(when_)) {}
WhenWrapperArgRel(WhenWrapperArgRel&& w): when(std::move(w.when)) {}
};
} // namespace FutureHelper
template <class Val>
class Future: public IntrusiveLockCounter {
std::unique_ptr<Cgu::Thread::Thread> thread_u;
std::unique_ptr<Cgu::Callback::Callback> cb_u;
mutable Mutex mutex;
Cond cond;
Val val;
bool done;
bool running;
bool error;
bool emitter_error;
template <class T, class Ret, class... Args>
void run_wrapper(T*, Ret (T::*)(Args...), const Args&...);
template <class T, class Ret, class... Args>
void run_wrapper_const(const T*, Ret (T::*)(Args...) const, const Args&...);
template <class Ret, class... Args>
void run_wrapper_static(Ret (*)(Args...), const Args&...);
template <class Func>
void run_wrapper_functor(Func&);
void cancel_cleanup();
void execute_done(const std::unique_ptr<const Cgu::Callback::CallbackArg<const Val&>>&);
void post_done(const FutureHelper::WhenWrapperArg<Val>&,
gint, GMainContext*);
void execute_done_rel(const std::unique_ptr<Cgu::SafeEmitterArg<const Val&>>&);
void post_done_rel(const FutureHelper::WhenWrapperArgRel<Val>&,
gint, GMainContext*);
// this is a static function taking the future object by IntrusivePtr to
// ensure that the future object remains in existence whilst this
// function might execute
static void fail_cb(const Cgu::IntrusivePtr<Future<Val>>& future,
const std::unique_ptr<const Cgu::Callback::Callback>& func,
bool& ret);
// private constructor - this class can only be created with Thread::Future::make()
Future(): val(), done(false), running(false), error(false), emitter_error(false) {}
public:
// this class cannot be copied except by smart pointer
/**
* This class cannot be copied (except by smart pointer). The copy
* constructor is deleted.
*/
Future(const Future&) = delete;
/**
* This class cannot be copied (except by smart pointer). The
* assignment operator is deleted.
*/
Future& operator=(const Future&) = delete;
/**
* Constructs a new Cgu::Thread::Future object (returned by
* Cgu::IntrusivePtr<Cgu::Thread::Future<Val>>). The type parameter
* Val represents the return value of the function to be represented
* by the new object. From version 2.0.4, it will usually be more
* convenient to call the Cgu::Thread::make_future() function, which
* is a convenience wrapper for this static method.
* @exception std::bad_alloc It might throw std::bad_alloc if memory
* is exhausted and the system throws in that case. (This exception
* will not be thrown if the library has been installed using the
* \--with-glib-memory-slices-no-compat configuration option: instead
* glib will terminate the program if it is unable to obtain memory
* from the operating system.)
* @exception Cgu::Thread::MutexError It might throw
* Cgu::Thread::MutexError if initialisation of the contained mutex
* fails. (It is often not worth checking for this, as it means
* either memory is exhausted or pthread has run out of other
* resources to create new mutexes.)
* @exception Cgu::Thread::CondError It might throw
* Cgu::Thread::CondError if initialisation of the contained condition
* variable fails. (It is often not worth checking for this, as it
* means either memory is exhausted or pthread has run out of other
* resources to create new condition variables.)
* @note This method will also throw if the default constructor of the
* return value type throws.
*/
template <class Ret, class T>
static Cgu::IntrusivePtr<Cgu::Thread::Future<Val>> make(T& t,
Ret (T::*func)());
/**
* Constructs a new Cgu::Thread::Future object (returned by
* Cgu::IntrusivePtr<Cgu::Thread::Future<Val>>). The type parameter
* Val represents the return value of the function to be represented
* by the new object. From version 2.0.4, it will usually be more
* convenient to call the Cgu::Thread::make_future() function, which
* is a convenience wrapper for this static method.
* @exception std::bad_alloc It might throw std::bad_alloc if memory
* is exhausted and the system throws in that case. (This exception
* will not be thrown if the library has been installed using the
* \--with-glib-memory-slices-no-compat configuration option: instead
* glib will terminate the program if it is unable to obtain memory
* from the operating system.)
* @exception Cgu::Thread::MutexError It might throw
* Cgu::Thread::MutexError if initialisation of the contained mutex
* fails. (It is often not worth checking for this, as it means
* either memory is exhausted or pthread has run out of other
* resources to create new mutexes.)
* @exception Cgu::Thread::CondError It might throw
* Cgu::Thread::CondError if initialisation of the contained condition
* variable fails. (It is often not worth checking for this, as it
* means either memory is exhausted or pthread has run out of other
* resources to create new condition variables.)
* @note This method will also throw if the copy or move constructor
* of the bound argument throws, or the default constructor of the
* return value type throws.
*/
template <class Ret, class Param1, class Arg1, class T>
static Cgu::IntrusivePtr<Cgu::Thread::Future<Val>> make(T& t,
Ret (T::*func)(Param1),
Arg1&& arg1);
/**
* Constructs a new Cgu::Thread::Future object (returned by
* Cgu::IntrusivePtr<Cgu::Thread::Future<Val>>). The type parameter
* Val represents the return value of the function to be represented
* by the new object. From version 2.0.4, it will usually be more
* convenient to call the Cgu::Thread::make_future() function, which
* is a convenience wrapper for this static method.
* @exception std::bad_alloc It might throw std::bad_alloc if memory
* is exhausted and the system throws in that case. (This exception
* will not be thrown if the library has been installed using the
* \--with-glib-memory-slices-no-compat configuration option: instead
* glib will terminate the program if it is unable to obtain memory
* from the operating system.)
* @exception Cgu::Thread::MutexError It might throw
* Cgu::Thread::MutexError if initialisation of the contained mutex
* fails. (It is often not worth checking for this, as it means
* either memory is exhausted or pthread has run out of other
* resources to create new mutexes.)
* @exception Cgu::Thread::CondError It might throw
* Cgu::Thread::CondError if initialisation of the contained condition
* variable fails. (It is often not worth checking for this, as it
* means either memory is exhausted or pthread has run out of other
* resources to create new condition variables.)
* @note This method will also throw if the copy or move constructor
* of a bound argument throws, or the default constructor of the
* return value type throws.
*/
template <class Ret, class Param1, class Param2, class Arg1, class Arg2, class T>
static Cgu::IntrusivePtr<Cgu::Thread::Future<Val>> make(T& t,
Ret (T::*func)(Param1, Param2),
Arg1&& arg1,
Arg2&& arg2);
/**
* Constructs a new Cgu::Thread::Future object (returned by
* Cgu::IntrusivePtr<Cgu::Thread::Future<Val>>). The type parameter
* Val represents the return value of the function to be represented
* by the new object. From version 2.0.4, it will usually be more
* convenient to call the Cgu::Thread::make_future() function, which
* is a convenience wrapper for this static method.
* @exception std::bad_alloc It might throw std::bad_alloc if memory
* is exhausted and the system throws in that case. (This exception
* will not be thrown if the library has been installed using the
* \--with-glib-memory-slices-no-compat configuration option: instead
* glib will terminate the program if it is unable to obtain memory
* from the operating system.)
* @exception Cgu::Thread::MutexError It might throw
* Cgu::Thread::MutexError if initialisation of the contained mutex
* fails. (It is often not worth checking for this, as it means
* either memory is exhausted or pthread has run out of other
* resources to create new mutexes.)
* @exception Cgu::Thread::CondError It might throw
* Cgu::Thread::CondError if initialisation of the contained condition
* variable fails. (It is often not worth checking for this, as it
* means either memory is exhausted or pthread has run out of other
* resources to create new condition variables.)
* @note This method will also throw if the copy or move constructor
* of a bound argument throws, or the default constructor of the
* return value type throws.
*/
template <class Ret, class Param1, class Param2, class Param3,
class Arg1, class Arg2, class Arg3, class T>
static Cgu::IntrusivePtr<Cgu::Thread::Future<Val>> make(T& t,
Ret (T::*func)(Param1, Param2, Param3),
Arg1&& arg1,
Arg2&& arg2,
Arg3&& arg3);
/**
* Constructs a new Cgu::Thread::Future object (returned by
* Cgu::IntrusivePtr<Cgu::Thread::Future<Val>>). The type parameter
* Val represents the return value of the function to be represented
* by the new object. From version 2.0.4, it will usually be more
* convenient to call the Cgu::Thread::make_future() function, which
* is a convenience wrapper for this static method.
* @exception std::bad_alloc It might throw std::bad_alloc if memory
* is exhausted and the system throws in that case. (This exception
* will not be thrown if the library has been installed using the
* \--with-glib-memory-slices-no-compat configuration option: instead
* glib will terminate the program if it is unable to obtain memory
* from the operating system.)
* @exception Cgu::Thread::MutexError It might throw
* Cgu::Thread::MutexError if initialisation of the contained mutex
* fails. (It is often not worth checking for this, as it means
* either memory is exhausted or pthread has run out of other
* resources to create new mutexes.)
* @exception Cgu::Thread::CondError It might throw
* Cgu::Thread::CondError if initialisation of the contained condition
* variable fails. (It is often not worth checking for this, as it
* means either memory is exhausted or pthread has run out of other
* resources to create new condition variables.)
* @note This method will also throw if the default constructor of the
* return value type throws.
*/
template <class Ret, class T>
static Cgu::IntrusivePtr<Cgu::Thread::Future<Val>> make(const T& t,
Ret (T::*func)() const);
/**
* Constructs a new Cgu::Thread::Future object (returned by
* Cgu::IntrusivePtr<Cgu::Thread::Future<Val>>). The type parameter
* Val represents the return value of the function to be represented
* by the new object. From version 2.0.4, it will usually be more
* convenient to call the Cgu::Thread::make_future() function, which
* is a convenience wrapper for this static method.
* @exception std::bad_alloc It might throw std::bad_alloc if memory
* is exhausted and the system throws in that case. (This exception
* will not be thrown if the library has been installed using the
* \--with-glib-memory-slices-no-compat configuration option: instead
* glib will terminate the program if it is unable to obtain memory
* from the operating system.)
* @exception Cgu::Thread::MutexError It might throw
* Cgu::Thread::MutexError if initialisation of the contained mutex
* fails. (It is often not worth checking for this, as it means
* either memory is exhausted or pthread has run out of other
* resources to create new mutexes.)
* @exception Cgu::Thread::CondError It might throw
* Cgu::Thread::CondError if initialisation of the contained condition
* variable fails. (It is often not worth checking for this, as it
* means either memory is exhausted or pthread has run out of other
* resources to create new condition variables.)
* @note This method will also throw if the copy or move constructor
* of the bound argument throws, or the default constructor of the
* return value type throws.
*/
template <class Ret, class Param1, class Arg1, class T>
static Cgu::IntrusivePtr<Cgu::Thread::Future<Val>> make(const T& t,
Ret (T::*func)(Param1) const,
Arg1&& arg1);
/**
* Constructs a new Cgu::Thread::Future object (returned by
* Cgu::IntrusivePtr<Cgu::Thread::Future<Val>>). The type parameter
* Val represents the return value of the function to be represented
* by the new object. From version 2.0.4, it will usually be more
* convenient to call the Cgu::Thread::make_future() function, which
* is a convenience wrapper for this static method.
* @exception std::bad_alloc It might throw std::bad_alloc if memory
* is exhausted and the system throws in that case. (This exception
* will not be thrown if the library has been installed using the
* \--with-glib-memory-slices-no-compat configuration option: instead
* glib will terminate the program if it is unable to obtain memory
* from the operating system.)
* @exception Cgu::Thread::MutexError It might throw
* Cgu::Thread::MutexError if initialisation of the contained mutex
* fails. (It is often not worth checking for this, as it means
* either memory is exhausted or pthread has run out of other
* resources to create new mutexes.)
* @exception Cgu::Thread::CondError It might throw
* Cgu::Thread::CondError if initialisation of the contained condition
* variable fails. (It is often not worth checking for this, as it
* means either memory is exhausted or pthread has run out of other
* resources to create new condition variables.)
* @note This method will also throw if the copy or move constructor
* of a bound argument throws, or the default constructor of the
* return value type throws.
*/
template <class Ret, class Param1, class Param2, class Arg1, class Arg2, class T>
static Cgu::IntrusivePtr<Cgu::Thread::Future<Val>> make(const T& t,
Ret (T::*func)(Param1, Param2) const,
Arg1&& arg1,
Arg2&& arg2);
/**
* Constructs a new Cgu::Thread::Future object (returned by
* Cgu::IntrusivePtr<Cgu::Thread::Future<Val>>). The type parameter
* Val represents the return value of the function to be represented
* by the new object. From version 2.0.4, it will usually be more
* convenient to call the Cgu::Thread::make_future() function, which
* is a convenience wrapper for this static method.
* @exception std::bad_alloc It might throw std::bad_alloc if memory
* is exhausted and the system throws in that case. (This exception
* will not be thrown if the library has been installed using the
* \--with-glib-memory-slices-no-compat configuration option: instead
* glib will terminate the program if it is unable to obtain memory
* from the operating system.)
* @exception Cgu::Thread::MutexError It might throw
* Cgu::Thread::MutexError if initialisation of the contained mutex
* fails. (It is often not worth checking for this, as it means
* either memory is exhausted or pthread has run out of other
* resources to create new mutexes.)
* @exception Cgu::Thread::CondError It might throw
* Cgu::Thread::CondError if initialisation of the contained condition
* variable fails. (It is often not worth checking for this, as it
* means either memory is exhausted or pthread has run out of other
* resources to create new condition variables.)
* @note This method will also throw if the copy or move constructor
* of a bound argument throws, or the default constructor of the
* return value type throws.
*/
template <class Ret, class Param1, class Param2, class Param3,
class Arg1, class Arg2, class Arg3, class T>
static Cgu::IntrusivePtr<Cgu::Thread::Future<Val>> make(const T& t,
Ret (T::*func)(Param1, Param2, Param3) const,
Arg1&& arg1,
Arg2&& arg2,
Arg3&& arg3);
/**
* Constructs a new Cgu::Thread::Future object (returned by
* Cgu::IntrusivePtr<Cgu::Thread::Future<Val>>). The type parameter
* Val represents the return value of the function to be represented
* by the new object. From version 2.0.4, it will usually be more
* convenient to call the Cgu::Thread::make_future() function, which
* is a convenience wrapper for this static method.
* @exception std::bad_alloc It might throw std::bad_alloc if memory
* is exhausted and the system throws in that case. (This exception
* will not be thrown if the library has been installed using the
* \--with-glib-memory-slices-no-compat configuration option: instead
* glib will terminate the program if it is unable to obtain memory
* from the operating system.)
* @exception Cgu::Thread::MutexError It might throw
* Cgu::Thread::MutexError if initialisation of the contained mutex
* fails. (It is often not worth checking for this, as it means
* either memory is exhausted or pthread has run out of other
* resources to create new mutexes.)
* @exception Cgu::Thread::CondError It might throw
* Cgu::Thread::CondError if initialisation of the contained condition
* variable fails. (It is often not worth checking for this, as it
* means either memory is exhausted or pthread has run out of other
* resources to create new condition variables.)
* @note This method will also throw if the default constructor of the
* return value type throws.
*/
template <class Ret>
static Cgu::IntrusivePtr<Cgu::Thread::Future<Val>> make(Ret (*func)());
/**
* Constructs a new Cgu::Thread::Future object (returned by
* Cgu::IntrusivePtr<Cgu::Thread::Future<Val>>). The type parameter
* Val represents the return value of the function to be represented
* by the new object. From version 2.0.4, it will usually be more
* convenient to call the Cgu::Thread::make_future() function, which
* is a convenience wrapper for this static method.
* @exception std::bad_alloc It might throw std::bad_alloc if memory
* is exhausted and the system throws in that case. (This exception
* will not be thrown if the library has been installed using the
* \--with-glib-memory-slices-no-compat configuration option: instead
* glib will terminate the program if it is unable to obtain memory
* from the operating system.)
* @exception Cgu::Thread::MutexError It might throw
* Cgu::Thread::MutexError if initialisation of the contained mutex
* fails. (It is often not worth checking for this, as it means
* either memory is exhausted or pthread has run out of other
* resources to create new mutexes.)
* @exception Cgu::Thread::CondError It might throw
* Cgu::Thread::CondError if initialisation of the contained condition
* variable fails. (It is often not worth checking for this, as it
* means either memory is exhausted or pthread has run out of other
* resources to create new condition variables.)
* @note This method will also throw if the copy or move constructor
* of the bound argument throws, or the default constructor of the
* return value type throws.
*/
template <class Ret, class Param1, class Arg1>
static Cgu::IntrusivePtr<Cgu::Thread::Future<Val>> make(Ret (*func)(Param1),
Arg1&& arg1);
/**
* Constructs a new Cgu::Thread::Future object (returned by
* Cgu::IntrusivePtr<Cgu::Thread::Future<Val>>). The type parameter
* Val represents the return value of the function to be represented
* by the new object. From version 2.0.4, it will usually be more
* convenient to call the Cgu::Thread::make_future() function, which
* is a convenience wrapper for this static method.
* @exception std::bad_alloc It might throw std::bad_alloc if memory
* is exhausted and the system throws in that case. (This exception
* will not be thrown if the library has been installed using the
* \--with-glib-memory-slices-no-compat configuration option: instead
* glib will terminate the program if it is unable to obtain memory
* from the operating system.)
* @exception Cgu::Thread::MutexError It might throw
* Cgu::Thread::MutexError if initialisation of the contained mutex
* fails. (It is often not worth checking for this, as it means
* either memory is exhausted or pthread has run out of other
* resources to create new mutexes.)
* @exception Cgu::Thread::CondError It might throw
* Cgu::Thread::CondError if initialisation of the contained condition
* variable fails. (It is often not worth checking for this, as it
* means either memory is exhausted or pthread has run out of other
* resources to create new condition variables.)
* @note This method will also throw if the copy or move constructor
* of a bound argument throws, or the default constructor of the
* return value type throws.
*/
template <class Ret, class Param1, class Param2, class Arg1, class Arg2>
static Cgu::IntrusivePtr<Cgu::Thread::Future<Val>> make(Ret (*func)(Param1, Param2),
Arg1&& arg1,
Arg2&& arg2);
/**
* Constructs a new Cgu::Thread::Future object (returned by
* Cgu::IntrusivePtr<Cgu::Thread::Future<Val>>). The type parameter
* Val represents the return value of the function to be represented
* by the new object. From version 2.0.4, it will usually be more
* convenient to call the Cgu::Thread::make_future() function, which
* is a convenience wrapper for this static method.
* @exception std::bad_alloc It might throw std::bad_alloc if memory
* is exhausted and the system throws in that case. (This exception
* will not be thrown if the library has been installed using the
* \--with-glib-memory-slices-no-compat configuration option: instead
* glib will terminate the program if it is unable to obtain memory
* from the operating system.)
* @exception Cgu::Thread::MutexError It might throw
* Cgu::Thread::MutexError if initialisation of the contained mutex
* fails. (It is often not worth checking for this, as it means
* either memory is exhausted or pthread has run out of other
* resources to create new mutexes.)
* @exception Cgu::Thread::CondError It might throw
* Cgu::Thread::CondError if initialisation of the contained condition
* variable fails. (It is often not worth checking for this, as it
* means either memory is exhausted or pthread has run out of other
* resources to create new condition variables.)
* @note This method will also throw if the copy or move constructor
* of a bound argument throws, or the default constructor of the
* return value type throws.
*/
template <class Ret, class Param1, class Param2, class Param3,
class Arg1, class Arg2, class Arg3>
static Cgu::IntrusivePtr<Cgu::Thread::Future<Val>> make(Ret (*func)(Param1, Param2, Param3),
Arg1&& arg1,
Arg2&& arg2,
Arg3&& arg3);
/**
* Constructs a new Cgu::Thread::Future object (returned by
* Cgu::IntrusivePtr<Cgu::Thread::Future<Val>>). The type parameter
* Val represents the return value of the function to be represented
* by the new object. From version 2.0.4, it will usually be more
* convenient to call the Cgu::Thread::make_future() function, which
* is a convenience wrapper for this static method.
* @exception std::bad_alloc It might throw std::bad_alloc if memory
* is exhausted and the system throws in that case. (This exception
* will not be thrown if the library has been installed using the
* \--with-glib-memory-slices-no-compat configuration option: instead
* glib will terminate the program if it is unable to obtain memory
* from the operating system.)
* @exception Cgu::Thread::MutexError It might throw
* Cgu::Thread::MutexError if initialisation of the contained mutex
* fails. (It is often not worth checking for this, as it means
* either memory is exhausted or pthread has run out of other
* resources to create new mutexes.)
* @exception Cgu::Thread::CondError It might throw
* Cgu::Thread::CondError if initialisation of the contained condition
* variable fails. (It is often not worth checking for this, as it
* means either memory is exhausted or pthread has run out of other
* resources to create new condition variables.)
* @note This method will also throw if the copy or move constructor
* of a bound argument throws, or the default constructor of the
* return value type throws.
*/
template <class Ret, class Param1, class Param2, class Param3, class Param4,
class Arg1, class Arg2, class Arg3, class Arg4>
static Cgu::IntrusivePtr<Cgu::Thread::Future<Val>> make(Ret (*func)(Param1, Param2, Param3, Param4),
Arg1&& arg1,
Arg2&& arg2,
Arg3&& arg3,
Arg4&& arg4);
/**
* Constructs a new Cgu::Thread::Future object (returned by
* Cgu::IntrusivePtr<Cgu::Thread::Future<Val>>). The type parameter
* Val represents the return value of the function to be represented
* by the new object. From version 2.0.4, it will usually be more
* convenient to call the Cgu::Thread::make_future() function, which
* is a convenience wrapper for this static method.
* @exception std::bad_alloc It might throw std::bad_alloc if memory
* is exhausted and the system throws in that case. (This exception
* will not be thrown if the library has been installed using the
* \--with-glib-memory-slices-no-compat configuration option: instead
* glib will terminate the program if it is unable to obtain memory
* from the operating system.)
* @exception Cgu::Thread::MutexError It might throw
* Cgu::Thread::MutexError if initialisation of the contained mutex
* fails. (It is often not worth checking for this, as it means
* either memory is exhausted or pthread has run out of other
* resources to create new mutexes.)
* @exception Cgu::Thread::CondError It might throw
* Cgu::Thread::CondError if initialisation of the contained condition
* variable fails. (It is often not worth checking for this, as it
* means either memory is exhausted or pthread has run out of other
* resources to create new condition variables.)
* @note 1. This method will also throw if the copy or move
* constructor of the callable object passed as an argument throws, or
* the default constructor of the return value type throws.
* @note 2. If the callable object passed as an argument has both
* const and non-const operator()() methods, the non-const version
* will be called even if the callable object passed is a const
* object.
*/
template <class Func>
static Cgu::IntrusivePtr<Cgu::Thread::Future<Val>> make(Func&& functor);
/**
* Runs the function represented by this Cgu::Thread::Future object in
* a new worker thread. That function will only be run once. If this
* is the first time this method has been called, it will start the
* worker thread and return true, and if it has previously been
* called, this method will do nothing and return false. This method
* is thread safe and may be called by a different thread from the one
* which called make().
* @return true if this is the first time this method has been called,
* or false if this method has previously been called.
* @exception Cgu::Thread::FutureThreadError This method might throw
* Cgu::Thread::FutureThreadError if it has not previously been called
* and the thread did not start properly. If it does throw, this
* Cgu::Thread::Future object is defunct and further attempts to call
* this method will return immediately with a false value. (It is
* often not worth checking for this exception, as it means either
* memory is exhausted, the pthread thread limit has been reached or
* pthread has run out of other resources to start new threads.)
* @exception std::bad_alloc This method might throw std::bad_alloc if
* it has not previously been called, and memory is exhausted and the
* system throws in that case. If it does throw, this
* Cgu::Thread::Future object is defunct and further attempts to call
* this method will return immediately with a false value. (This
* exception will not be thrown if the library has been installed
* using the \--with-glib-memory-slices-no-compat configuration
* option: instead glib will terminate the program if it is unable to
* obtain memory from the operating system.)
* @note 1. Any Cgu::Thread::Exit exception, or any uncaught exception
* derived from std::exception, which is thrown from the worker thread
* will be caught and consumed and the error flag will be set. The
* worker thread will safely terminate and unwind the stack in so
* doing.
* @note 2. As this wrapper class can provide error reporting in a way
* that Cgu::Thread::Thread of itself cannot, it would be desirable to
* consume any other uncaught exceptions. However, this cannot be
* done: annoyingly, NPTL's forced stack unwinding does not allow this
* if thread cancellation is to be made available. If an uncaught
* exception propagates out of a thread when the thread exits, the
* C++11 standard will cause std::terminate() to be called and so
* terminate the entire program. Accordingly, a user must make sure
* that no exceptions, other than Cgu::Thread::Exit or those derived
* from std::exception or any cancellation pseudo-exception, can
* propagate from the function which this Cgu::Thread::Future object
* represents.
* @note 3. If the worker thread is cancelled by a call to cancel()
* while in the middle of executing the function which this
* Cgu::Thread::Future object represents, the error flag will be set.
*/
bool run();
/**
* Gets the stored value obtained from the function which is
* represented by this object. If the worker thread launched by the
* call to run() has not completed, then this method will block until
* it has completed. If run() has not been called, then run() will be
* called (and this method will block until the launched worker thread
* completes). If the function which is represented by this object
* throws Cgu::Thread::Exit or an uncaught exception derived from
* std::exception, then the exception will have been consumed by this
* Cgu::Thread::Future object and the error flag will have been set.
* The error flag will also have been set if the worker thread is
* cancelled or the thread wrapper in this Cgu::Thread::Future object
* threw std::bad_alloc. This method is thread safe and may be called
* by any thread (and by more than one thread). It is a cancellation
* point if it blocks, and from version 2.0.11 is cancellation safe if
* the stack unwinds on cancellation. It is also strongly exception
* safe: no data will be lost if extracting the value fails.
* @return The value obtained from the function which is represented
* by this object
* @exception Cgu::Thread::FutureThreadError This method might throw
* Cgu::Thread::FutureThreadError if run() has not previously been
* called and the thread did not start properly when this function
* called run().
* @exception std::bad_alloc This method might throw std::bad_alloc if
* run() has not previously been called, memory is exhausted and the
* system throws in that case. (This exception will not be thrown if
* the library has been installed using the
* \--with-glib-memory-slices-no-compat configuration option: instead
* glib will terminate the program if it is unable to obtain memory
* from the operating system.)
* @note 1. This method might also throw if the copy constructor of
* the returned value type throws.
* @note 2. Question: Couldn't this method return the stored value by
* lvalue reference to const? Answer: It could. However, because of
* return value optimization, which will be implemented by any
* compiler capable of compiling this library, no advantage would be
* gained by doing so when initializing a local variable with the
* return value of this method (the copy constructor will only be
* called once whether returning by value or const reference). The
* advantage of returning by value is that the call to the copy
* constructor is forced to be within this Thread::Future object's
* mutex, so different threads' calls to the copy constructor are
* serialized, and also with blocked cancellation, so this method is
* cancellation safe. All calls to this method by different threads
* are therefore isolated and we do not have to worry about the thread
* safety of direct access to the stored value via its const methods
* outside the mutex (which would not be thread safe if the stored
* value has data members declared mutable) nor about the cancellation
* safety of the copy constructor. Of course, for objects which do
* not have mutable data, a hit arises by returning by value in cases
* where it is not intended to initialize a local variable at all nor
* to cancel a thread: where, say, only const methods are to be called
* on the return value (which could be done directly if this method
* returned by const reference). However, in many use cases this will
* be mitigated by the move_get() method.
*/
Val get();
/**
* Gets the stored value obtained from the function which is
* represented by this object by a move operation, if the return type
* implements a move constructor (otherwise this method does the same
* as the get() method). It is provided as an option for cases where
* a move is required for efficiency reasons, but although it may be
* called by any thread, a move from this Thread::Future object may
* normally only be made once (except where the return type has been
* designed to be moved more than once for the limited purpose of
* inspecting a flag indicating whether its value is valid or not).
* If this method is to be called then no calls to get() by another
* thread should normally be made and no calls to when() should be
* made. If the worker thread launched by the call to run() has not
* completed, then this method will block until it has completed. If
* run() has not been called, then run() will be called (and this
* method will block until the launched worker thread completes). If
* the function which is represented by this object throws
* Cgu::Thread::Exit or an uncaught exception derived from
* std::exception, then the exception will have been consumed by this
* Cgu::Thread::Future object and the error flag will have been set.
* The error flag will also have been set if the worker thread is
* cancelled or the thread wrapper in this Cgu::Thread::Future object
* threw std::bad_alloc. This method is a cancellation point if it
* blocks, and is cancellation safe if the stack unwinds on
* cancellation. This method is only exception safe if the return
* type's move constructor is exception safe.
* @return The value obtained from the function which is represented
* by this object
* @exception Cgu::Thread::FutureThreadError This method might throw
* Cgu::Thread::FutureThreadError if run() has not previously been
* called and the thread did not start properly when this function
* called run().
* @exception std::bad_alloc This method might throw std::bad_alloc if
* run() has not previously been called, memory is exhausted and the
* system throws in that case. (This exception will not be thrown if
* the library has been installed using the
* \--with-glib-memory-slices-no-compat configuration option: instead
* glib will terminate the program if it is unable to obtain memory
* from the operating system.)
* @note 1. This method might also throw if the copy or move
* constructor of the returned value type throws.
* @note 2. Question: Couldn't this method return the stored value by
* rvalue reference? Answer: It could. However, because of return
* value optimization, which will be implemented by any compiler
* capable of compiling this library, no advantage would be gained by
* doing so when initializing a local variable with the return value
* of this method (the move constructor will only be called once, and
* no call will be made to the copy constructor, whether returning by
* value or rvalue reference). The advantage of returning by value is
* that the call to the move constructor is forced to be within this
* Thread::Future object's mutex, so different threads' calls to the
* move constructor are serialized, and also with blocked
* cancellation, so this method is cancellation safe. All calls to
* this method by different threads are therefore isolated and we do
* not have to worry about the thread safety of the mutating first
* call to this method, nor about direct access to the stored value
* via a rvalue reference outside the mutex nor the cancellation
* safety of the move constructor.
*
* Since 2.0.11
*/
Val move_get();
/**
* Cancels the worker thread in which the function represented by this
* object runs, if that function has not yet finished. If this method
* is called and the worker thread is still running and is cancelled
* in response to a call to this method, then the error flag will be
* set so that a method calling get() or move_get() can examine
* whether the result is valid. If run() has not yet been called or
* the worker thread has already finished executing the function
* represented by this object then this function does nothing and
* returns false. This method is thread safe and may be called by any
* thread. It will not throw.
* @return true if run() has previously been called and the worker
* thread has not yet finished executing the function represented by
* this object, otherwise false (in which case this method does
* nothing).
* @note 1. Use this method with care. When cancelling a thread not
* all thread implementations will unwind the stack, and so run the
* destructors of local objects. This is discussed further in the
* documentation on Cgu::Thread::Thread::cancel().
* @note 2. This method might return true because the worker thread
* has not yet finished, but the error flag might still not be set.
* This is because the worker thread may not meet a cancellation point
* before it ends naturally. It is the error flag which indicates
* definitively whether the worker thread terminated prematurely in
* response to a call to this method.
*/
bool cancel();
/**
* A utility enabling the value returned by the thread function
* represented by this Cgu::Thread::Future object to be dealt with
* asynchronously rather than by (or in addition to) a call to the
* get() method. It causes the callback passed as an argument to this
* method (referred to below as the 'when' callback) to be executed by
* a thread's main loop if and when the thread function represented by
* this Cgu::Thread::Future object finishes correctly - the 'when'
* callback is passed that thread function's return value when it is
* invoked. This method is thread safe, and may be called by any
* thread.
*
* This functionality is implemented by connecting an internal
* dispatching callback to the done_emitter object.
*
* The 'when' callback should take a single unbound argument
* comprising a const reference to the return type of the thread
* function represented by this Cgu::Thread::Future object. (So, in
* the case of a Future<int> object, the callback function should take
* a const int& argument as the unbound argument.) The 'when'
* callback can have any number of bound arguments, except that a
* bound argument may not include a copy of this Cgu::Thread::Future
* object held by intrusive pointer as returned by the make() methods
* (that would result in this Cgu::Thread::Future object owning, via
* done_emitter, a reference to itself and so become incapable of
* being freed). The 'when' callback may, however, take a pointer to
* this Cgu::Thread::Future object, as obtained by the
* Cgu::IntrusivePtr::get() method, because this Cgu::Thread::Future
* object is guaranteed to remain in existence until the callback has
* completed executing.
*
* This method cannot be called after the thread function represented
* by this Cgu::Thread::Future object has completed (either
* successfully or unsuccessfully) so that is_done() would return
* true, and if this is attempted a Cgu::Thread::FutureWhenError
* exception will be thrown. Therefore, generally this method should
* be called before the run() method has been called.
*
* Once the run() method has been called, this Cgu::Thread::Future
* object will always stay in existence until the thread function
* represented by it has completed (whether correctly, by cancellation
* or by a thrown exception), and any 'when' callback (and any other
* callbacks connected to the done_emitter object) and any 'fail'
* callback have completed. Accordingly it is safe to use this method
* even if the intrusive pointer object returned by the make() methods
* will go out of scope before the 'when' callback has executed: the
* callback will execute correctly irrespective of that.
*
* Summary: use of this method is safe and has been implemented in a
* way which does not give rise to timing issues.
*
* If memory is exhausted and std::bad_alloc is thrown by the thread
* wrapper of Cgu::Thread::Future after run() is called or by
* done_emitter when emitting, or if the thread function represented
* by this Cgu::Thread::Future object throws Cgu::Thread::Exit, exits
* with an uncaught exception deriving from std::exception or is
* cancelled, or if the copy constructor of a non-reference argument
* of the function represented by the 'when' callback throws, or any
* other callback has been connected to done_emitter before this
* method is called which exits with an uncaught exception, then the
* 'when' callback will not execute (instead the exception concerned
* will be consumed and an error indicated). With many systems, swap
* memory combined with memory over-commit makes it pointless to check
* for std::bad_alloc (and even more so in programs using glib, as
* glib aborts a program where it cannot obtain memory from the
* operating system). So subject to that, if the user program is
* designed so that the thread function represented by this
* Cgu::Thread::Future object does not exit with uncaught exceptions,
* does not throw Cgu::Thread::Exit and is not cancelled, and so that
* the 'when' callback does not exit with an uncaught exception (and
* the function represented by that callback either takes no arguments
* of class type by value or the copy constructors of any of its value
* arguments do not throw), and if this method is called before any
* other callbacks are connected to done_emitter, the possibility of
* failure can be disregarded.
*
* In cases where that is not true and detecting whether a failure has
* occurred is required, a fail() method is provided. It should be
* noted that a callback handed to the fail() method will not execute
* in a case of error if the error comprises the 'when' callback
* exiting with an uncaught exception when it is executed by the main
* loop, or the copy constructor of any value argument of the function
* represented by the 'when' callback throwing (such exceptions would
* be consumed internally in order to protect the main loop and a
* g_critical message issued). If the 'when' callback might exit with
* an uncaught exception when executing or have the copy constructor
* of a value argument throw, and doing something other than consuming
* the exception and issuing a g_critical message is required, then a
* different approach is to start a new thread to wait on the get()
* method which can act on the result of is_error() directly.
*
* If glib < 2.32 is used, the glib main loop must have been made
* thread-safe by a call to g_thread_init() before this function is
* called. glib >= 2.32 does not require g_thread_init() to be called
* in order to be thread safe.
*
* @param cb The 'when' callback (the callback to be executed when the
* function represented by this Cgu::Thread::Future object has
* successfully completed). Ownership is taken of this object, and it
* will be deleted when it has been finished with.
* @param priority The priority to be given to the 'when' callback in
* the main loop after the thread function represented by this
* Cgu::Thread::Future object has successfully completed. In
* ascending order of priorities, priorities are G_PRIORITY_LOW,
* G_PRIORITY_DEFAULT_IDLE, G_PRIORITY_HIGH_IDLE, G_PRIORITY_DEFAULT
* and G_PRIORITY_HIGH. The default is G_PRIORITY_DEFAULT. This
* determines the order in which the callback will appear in the event
* list in the main loop, not the priority which the OS will adopt.
* @param context The glib main context of the thread in whose main
* loop the 'when' callback is to be executed (the default of NULL
* will cause the callback to be executed in the main program loop).
* @return The internal dispatching callback created by this method
* and connected to done_emitter. It is made available as a return
* value so that if wanted it can be disconnected programmatically
* from done_emitter, or block()/unblock() can be called on it (but if
* that is to be done, it must be done before the thread function
* represented by this Cgu::Thread::Future object has completed in
* order for it to be effective).
* @exception Cgu::Thread::FutureWhenError This method will throw
* Cgu::Thread::FutureWhenError if it is called after the thread
* function represented by this Cgu::Thread::Future object has
* completed. If it does so, the 'when' callback will be disposed of.
* @exception std::bad_alloc This method might throw std::bad_alloc if
* memory is exhausted and the system throws in that case. If it does
* so, the 'when' callback will be disposed of.
* @note The return value of the function represented by this
* Cgu::Thread::Future object is stored and passed as an argument to
* the 'when' callback by const reference. If other threads might
* concurrently call this object's get() method, which copies the
* stored value, the stored type's copy constructor must be thread
* safe with respect to the stored type's const methods. This would
* be relevant if the stored type has data members declared mutable
* which would be copied by its copy constructor.
*
* Since 2.0.2
*/
Cgu::Callback::SafeFunctor when(const Cgu::Callback::CallbackArg<const Val&>* cb,
gint priority = G_PRIORITY_DEFAULT,
GMainContext* context = 0);
/**
* This is a version of the utility enabling the value returned by the
* thread function represented by this Cgu::Thread::Future object to
* be dealt with asynchronously, which takes a Releaser object for
* automatic disconnection of the callback passed as an argument to
* this method (referred to below as the 'when' callback), if the
* object having the 'when' callback function as a member is
* destroyed. For this to be race free, the lifetime of that object
* must be controlled by the thread in whose main loop the 'when'
* callback will execute.
*
* If the 'when' callback has not been released, this method causes it
* to be executed by a thread's main loop if and when the thread
* function represented by this Cgu::Thread::Future object finishes
* correctly - the 'when' callback is passed that thread function's
* return value when it is invoked. This method is thread safe, and
* may be called by any thread.
*
* This functionality is implemented by connecting an internal
* dispatching callback to the done_emitter object.
*
* The 'when' callback should take a single unbound argument
* comprising a const reference to the return type of the thread
* function represented by this Cgu::Thread::Future object. (So, in
* the case of a Future<int> object, the callback function should take
* a const int& argument as the unbound argument.) The 'when'
* callback can have any number of bound arguments, except that a
* bound argument may not include a copy of this Cgu::Thread::Future
* object held by intrusive pointer as returned by the make() methods
* (that would result in this Cgu::Thread::Future object owning, via
* done_emitter, a reference to itself and so become incapable of
* being freed). The 'when' callback may, however, take a pointer to
* this Cgu::Thread::Future object, as obtained by the
* Cgu::IntrusivePtr::get() method, because this Cgu::Thread::Future
* object is guaranteed to remain in existence until the callback has
* completed executing.
*
* This method cannot be called after the thread function represented
* by this Cgu::Thread::Future object has completed (either
* successfully or unsuccessfully) so that is_done() would return
* true, and if this is attempted a Cgu::Thread::FutureWhenError
* exception will be thrown. Therefore, generally this method should
* be called before the run() method has been called.
*
* The documentation for the version of this method which does not
* take a Releaser object gives further details of how this method is
* used.
*
* If glib < 2.32 is used, the glib main loop must have been made
* thread-safe by a call to g_thread_init() before this function is
* called. glib >= 2.32 does not require g_thread_init() to be called
* in order to be thread safe.
*
* @param cb The 'when' callback (the callback to be executed when the
* function represented by this Cgu::Thread::Future object has
* successfully completed). Ownership is taken of this object, and it
* will be deleted when it has been finished with.
* @param r A Releaser object for automatic disconnection of the
* 'when' callback if the object of which the callback function is a
* member is destroyed.
* @param priority The priority to be given to the 'when' callback in
* the main loop after the thread function represented by this
* Cgu::Thread::Future object has successfully completed. In
* ascending order of priorities, priorities are G_PRIORITY_LOW,
* G_PRIORITY_DEFAULT_IDLE, G_PRIORITY_HIGH_IDLE, G_PRIORITY_DEFAULT
* and G_PRIORITY_HIGH. The default is G_PRIORITY_DEFAULT. This
* determines the order in which the callback will appear in the event
* list in the main loop, not the priority which the OS will adopt.
* @param context The glib main context of the thread in whose main
* loop the 'when' callback is to be executed (the default of NULL
* will cause the callback to be executed in the main program loop).
* @return The internal dispatching callback created by this method
* and connected to done_emitter. It is made available as a return
* value so that if wanted it can be disconnected programmatically
* from done_emitter, or block()/unblock() can be called on it (but if
* that is to be done, it must be done before the thread function
* represented by this Cgu::Thread::Future object has completed in
* order for it to be effective).
* @exception Cgu::Thread::FutureWhenError This method will throw
* Cgu::Thread::FutureWhenError if it is called after the thread
* function represented by this Cgu::Thread::Future object has
* completed. If it does so, the 'when' callback will be disposed of.
* @exception std::bad_alloc This method might throw std::bad_alloc if
* memory is exhausted and the system throws in that case. If it does
* so, the 'when' callback will be disposed of.
* @exception Cgu::Thread::MutexError This method will throw
* Cgu:Thread::MutexError if initialisation of the mutex in a
* SafeEmitterArg object constructed by this method fails. If it does
* so, the 'when' callback will be disposed of. (It is often not
* worth checking for this, as it means either memory is exhausted or
* pthread has run out of other resources to create new mutexes.)
* @note 1. The return value of the function represented by this
* Cgu::Thread::Future object is stored and passed as an argument to
* the 'when' callback by const reference. If other threads might
* concurrently call this object's get() method, which copies the
* stored value, the stored type's copy constructor must be thread
* safe with respect to the stored type's const methods. This would
* be relevant if the stored type has data members declared mutable
* which would be copied by its copy constructor.
* @note 2. By virtue of the Releaser object, it is in theory possible
* (if memory is exhausted and the system throws in that case) that an
* internal SafeEmitterArg object will throw std::bad_alloc when
* emitting/executing the 'when' callback in the glib main loop, with
* the result that the relevant callback will not execute (instead the
* exception will be consumed and a g_critical() warning will be
* issued). This is rarely of any relevance because glib will abort
* the program if it is itself unable to obtain memory from the
* operating system. However, where it is relevant, design the
* program so that it is not necessary to provide a releaser object.
*
* Since 2.0.2
*/
Cgu::Callback::SafeFunctor when(const Cgu::Callback::CallbackArg<const Val&>* cb,
Cgu::Releaser& r,
gint priority = G_PRIORITY_DEFAULT,
GMainContext* context = 0);
/**
* A utility intended to be used where relevant in conjunction with
* the when() methods. It enables a callback to be executed in a glib
* main loop (referred to below as the 'fail' callback) if memory is
* exhausted and std::bad_alloc was thrown by the thread wrapper of
* Cgu::Thread::Future after calling run() or by done_emitter when
* emitting, or if the thread function represented by this
* Cgu::Thread::Future object threw Cgu::Thread::Exit, exited with an
* uncaught exception deriving from std::exception or was cancelled
* (or that function took an argument of class type by value whose
* copy constructor threw such an exception), or any callback
* connected to done_emitter exited with an uncaught exception. It
* therefore enables errors to be detected and acted on without having
* a thread wait on the get() method in order to test is_error() or
* is_emitter_error().
*
* It is implemented by attaching a timeout to the main loop which
* polls at 100 millisecond intervals and tests is_done()/is_error()
* and is_emitter_done()/is_emitter_error(). The timeout is
* automatically removed by the implementation once it has been
* detected that an error has occurred and the 'fail' callback is
* executed, or if the thread function represented by this Cgu::Future
* object and all done_emitter emissions (including execution of any
* 'when' callback) have completed successfully.
*
* This method can be called before or after the run() method has been
* called, and whether or not the thread function represented by this
* Cgu::Thread::Future object has completed.
*
* Once this method has been called, this Cgu::Thread::Future object
* will always stay in existence until the timeout has been
* automatically removed by the implementation. Accordingly it is
* safe to use this method even if the intrusive pointer object
* returned by the make() methods will go out of scope before the
* 'fail' callback has executed: the callback will execute correctly
* irrespective of that.
*
* This method does not have a priority argument: as a polling timeout
* is created, a particular priority will normally have no
* significance (in fact, the 'fail' callback will execute in the main
* loop with a priority of G_PRIORITY_DEFAULT). If in a special case
* a different polling interval than 100 milliseconds or a different
* priority is required, users can attach their own polling timeouts
* to a main loop and carry out the tests by hand.
*
* Four other points should be noted. First, if as well as the when()
* method being called some other callback has been connected to
* done_emitter, and that other callback throws, the 'fail' callback
* will execute. Therefore, if the particular program design requires
* that the 'fail' callback should only execute if the 'when' callback
* is not executed (and the 'when' callback only execute if the 'fail'
* callback does not execute), no other callbacks which throw should
* be connected to done_emitter.
*
* Secondly, as mentioned in the documentation on the when() method,
* if the 'when' callback exits with an uncaught exception upon being
* executed by the main loop or the function it represents takes an
* argument by value whose copy constructor throws, the 'fail'
* callback will not execute (the exception will have been consumed
* internally in order to protect the main loop and a g_critical
* message issued).
*
* Thirdly, avoid if possible having the 'fail' callback represent a
* function which either might throw or takes an argument by value
* whose copy constructor might throw (such an exception would be
* consumed internally in order to protect the main loop and a
* g_critical message issued, but no other error indication apart from
* the g_critical message will be provided).
*
* Fourthly, unlike the 'when' callback, a copy of this
* Cgu::Thread::Future object held by intrusive pointer as returned by
* the make() methods may safely be bound to the 'fail' callback,
* which would enable the 'fail' callback to determine whether it is
* is_error() or is_emitter_error() which returns false.
*
* If glib < 2.32 is used, the glib main loop must have been made
* thread-safe by a call to g_thread_init() before this function is
* called. glib >= 2.32 does not require g_thread_init() to be called
* in order to be thread safe.
*
* @param cb The 'fail' callback (the callback to be executed if the
* thread function represented by this Cgu::Thread::Future object or a
* done_emitter emission has failed to complete). Ownership is taken
* of this object, and it will be deleted when it has been finished
* with.
* @param context The glib main context of the thread in whose main
* loop the 'fail' callback is to be executed (the default of NULL
* will cause the functor to be executed in the main program loop).
* @exception std::bad_alloc This method might throw std::bad_alloc if
* memory is exhausted and the system throws in that case. If it does
* so, the 'fail' callback will be disposed of.
*
* Since 2.0.2
*/
void fail(const Cgu::Callback::Callback* cb,
GMainContext* context = 0);
/**
* This is a version of the fail() utility for use in conjunction with
* the when() methods, which takes a Releaser object for automatic
* disconnection of the callback functor passed as an argument to this
* method if the object having the callback function as a member is
* destroyed. For this to be race free, the lifetime of that object
* must be controlled by the thread in whose main loop the 'fail'
* callback will execute.
*
* This method enables a callback to be executed in a glib main loop
* if memory is exhausted and std::bad_alloc was thrown by the thread
* wrapper of Cgu::Thread::Future after calling run() or by
* done_emitter when emitting, or if the thread function represented
* by this Cgu::Thread::Future object threw Cgu::Thread::Exit, exited
* with an uncaught exception deriving from std::exception or was
* cancelled (or that function took an argument of class type by value
* whose copy constructor threw such an exception), or any callback
* connected to done_emitter exited with an uncaught exception. It
* therefore enables errors to be detected and acted on without having
* a thread wait on the get() method in order to test is_error() or
* is_emitter_error().
*
* This method can be called before or after the run() method has been
* called, and whether or not the thread function represented by this
* Cgu::Thread::Future object has completed.
*
* The documentation for the version of this method which does not
* take a Releaser object gives further details of how this method is
* used.
*
* If glib < 2.32 is used, the glib main loop must have been made
* thread-safe by a call to g_thread_init() before this function is
* called. glib >= 2.32 does not require g_thread_init() to be called
* in order to be thread safe.
*
* @param cb The 'fail' callback (the callback to be executed if the
* thread function represented by this Cgu::Thread::Future object or a
* done_emitter emission has failed to complete). Ownership is taken
* of this object, and it will be deleted when it has been finished
* with.
* @param r A Releaser object for automatic disconnection of the
* 'fail' callback if the object of which the callback function is a
* member is destroyed.
* @param context The glib main context of the thread in whose main
* loop the 'fail' callback is to be executed (the default of NULL
* will cause the functor to be executed in the main program loop).
* @exception std::bad_alloc This method might throw std::bad_alloc if
* memory is exhausted and the system throws in that case. If it does
* so, the 'fail' callback will be disposed of.
* @exception Cgu::Thread::MutexError This method will throw
* Cgu:Thread::MutexError if initialisation of the mutex in a
* SafeEmitterArg object constructed by Cgu::start_timeout() fails.
* If it does so, the 'fail' callback will be disposed of. (It is
* often not worth checking for this, as it means either memory is
* exhausted or pthread has run out of other resources to create new
* mutexes.)
* @note By virtue of the Releaser object, it is in theory possible
* (if memory is exhausted and the system throws in that case) that an
* internal SafeEmitterArg object will throw std::bad_alloc when
* emitting/executing the 'fail' callback in the glib main loop, with
* the result that the relevant callback will not execute (instead the
* exception will be consumed and a g_critical() warning will be
* issued). This is rarely of any relevance because glib will abort
* the program if it is itself unable to obtain memory from the
* operating system. However, where it is relevant, design the
* program so that it is not necessary to provide a releaser object.
*
* Since 2.0.2
*/
void fail(const Cgu::Callback::Callback* cb,
Cgu::Releaser& r,
GMainContext* context = 0);
/**
* @return true if the function represented by this
* Cgu::Thread::Future object has finished, either by returning
* normally, by cancellation or by virtue of having thrown
* Cgu::Thread::Exit or some exception derived from std::exception.
* Once this method returns true, then it is guaranteed that the get()
* or move_get() method will not block (except as incidental to any
* contention between threads calling get()). Once this method has
* returned true or get() or move_get() has unblocked, then the result
* of is_error() is definitive. This method is thread safe and may be
* called by any thread. It will not throw.
* @note This method will return true even though any callbacks
* connected to done_emitter are still executing or waiting to
* execute. From version 2.0.2 the is_emitter_done() method will
* indicate when done_emitter callbacks (if any) have also completed.
*/
bool is_done() const;
/**
* @return true if both the function represented by this
* Cgu::Thread::Future object has finished and any callbacks connected
* to done_emitter have completed. Once this method returns true,
* then the result of is_emitter_error() is definitive. This method
* is thread safe and may be called by any thread. It will not throw.
* @note This method will return true automatically if is_error() and
* is_done() return true, because if the function represented by this
* Cgu::Thread::Future object was cancelled or exited with an uncaught
* exception, done_emitter is never emitted. In addition, if this
* method returns true, then is_done() must also return true.
*
* Since 2.0.2
*/
bool is_emitter_done() const;
/**
* @return true if (a) a Cgu::Thread::Exit exception has been thrown
* by the function represented by this Cgu::Thread::Future object
* (which will have been consumed by this Cgu::Thread::Future object),
* (b) an exception derived from std::exception has been thrown by
* that function which was not caught in that function (and which will
* also have been consumed by this Cgu::Thread::Future object), (c)
* the worker thread in which that function runs was cancelled in
* mid-course with a call to cancel() or (d) the thread wrapper
* implementing the worker thread in this Cgu::Thread::Future object
* threw and then consumed std::bad_alloc (this is different from the
* run() method throwing std::bad_alloc). In these cases the value
* obtained by get() or move_get() will not be valid (it will be a
* default constructed object of the return type of the function
* represented by this Cgu::Thread::Future object). Otherwise this
* method returns false. The result of this method is definitive once
* get() or move_get() has unblocked or is_done() returns true. This
* method is thread safe and may be called by any thread. It will not
* throw.
*/
bool is_error() const;
/**
* @return true if an uncaught exception arose in emitting @ref
* DoneEmitterAnchor "done_emitter" when executing callbacks connected
* to it. Otherwise this method returns false. The result of this
* method is definitive once is_emitter_done() returns true. This
* method is thread safe and may be called by any thread. It will not
* throw.
* @note This method will return false automatically if is_error()
* returns true, because if the function represented by this
* Cgu::Thread::Future object was cancelled or exited with an uncaught
* exception, done_emitter is never emitted. It follows that if this
* method returns true, is_error() must return false.
*/
bool is_emitter_error() const;
/**
* A Cgu::SafeEmitter object which is emitted when the function
* represented by this Cgu::Thread::Future object finishes correctly
* (that is, the function is not cancelled and does not throw any
* uncaught exceptions). By itself it does not do too much as it is
* emitted (and connected callbacks execute in) the same worker thread
* immediately after the Future function has completed. However, any
* thread can connect a Callback object to this Cgu::SafeEmitter
* object and a connected callback can, say, cause another Callback to
* be executed in a thread's main loop using Cgu::Callback::post(),
* and from version 2.0.2 when() methods are provided which will do
* this for users automatically. Once the run() method has been
* called, this Cgu::Thread::Future object (and so done_emitter) will
* always stay in existence until the function represented by it has
* completed (whether correctly, by cancellation or by a thrown
* exception) and any callbacks connected to the done_emitter object
* have completed, irrespective of whether the intrusive pointer
* returned by the make() methods has gone out of scope.
* @note 1. Cancellation is blocked while the Cgu::SafeEmitter object
* emits and any connected callback executes.
* @note 2. A connected callback can however terminate the worker
* thread by throwing Cgu::Thread::Exit (in which case no subsequent
* callbacks to be executed on that emission will execute either: the
* worker thread will safely terminate and unwind the stack in so
* doing). In that event, the emitter_error flag will be set.
* @note 3. All other uncaught exceptions which might be thrown by the
* Cgu::SafeEmitter object emitting, or by a connected callback
* function executing, are consumed to retain the integrity of the
* Thread::Future object. In the event of such an exception being
* thrown, the emitter_error flag will be set. In summary, the
* emitter_error flag will be set if (a) a callback function throws
* Cgu::Thread::Exit, (b) some other uncaught exception escapes from a
* callback function or (c) Cgu::SafeEmitter::emit() throws
* std::bad_alloc or the copy constructor of a bound argument which is
* not a reference argument has thrown. If the user knows that the
* callback function does not throw Cgu::Thread::Exit and does not
* allow any other exception to escape, then the cause must be a
* std::bad_alloc memory exception in Cgu::SafeEmitter::emit() or the
* copy constructor of a non-reference bound argument throwing.
* @note 4. An emission is thread safe if the connected callback
* functions are thread safe.
* @note 5. This Cgu::Thread::Future object's mutex is released while
* the Cgu::SafeEmitter object emits. This means that any connected
* callbacks can safely call, say, the Future object's get() or
* is_error() methods. However, a connected callback should not have
* a bound argument comprising a copy of this Cgu::Thread::Future
* object held by intrusive pointer as returned by the make() methods
* (that would result in this Cgu::Thread::Future object owning, via
* done_emitter, a reference to itself and so become incapable of
* being freed). The callback may, however, take a pointer to this
* Cgu::Thread::Future object as a bound argument, as obtained by the
* Cgu::IntrusivePtr::get() method, because this Cgu::Thread::Future
* object is guaranteed to remain in existence until all callbacks
* connected to done_emitter have completed executing.
* @anchor DoneEmitterAnchor
*/
SafeEmitter done_emitter;
/* Only has effect if --with-glib-memory-slices-compat or
* --with-glib-memory-slices-no-compat option picked */
CGU_GLIB_MEMORY_SLICES_FUNCS
};
/**
* A convenience helper function which calls
* Cgu::Thread::Future::make() to obtain a Future object without the
* need to specify the return value of the function represented by the
* new object: that is deduced from the signature of that function.
* This is useful shorthand when also employed with the C++11 'auto'
* keyword.
* @exception std::bad_alloc It might throw std::bad_alloc if memory
* is exhausted and the system throws in that case. (This exception
* will not be thrown if the library has been installed using the
* \--with-glib-memory-slices-no-compat configuration option: instead
* glib will terminate the program if it is unable to obtain memory
* from the operating system.)
* @exception Cgu::Thread::MutexError It might throw
* Cgu::Thread::MutexError if initialisation of the contained mutex
* fails. (It is often not worth checking for this, as it means
* either memory is exhausted or pthread has run out of other
* resources to create new mutexes.)
* @exception Cgu::Thread::CondError It might throw
* Cgu::Thread::CondError if initialisation of the contained condition
* variable fails. (It is often not worth checking for this, as it
* means either memory is exhausted or pthread has run out of other
* resources to create new condition variables.)
* @note This method will also throw if the copy or move constructor
* of a bound argument throws, or the default constructor of the
* return value type of the function represented by the new object
* throws.
*
* Since 2.0.4
*/
template <class Obj, class Ret, class... Params, class... Args>
Cgu::IntrusivePtr<Cgu::Thread::Future<Ret>> make_future(Obj& obj,
Ret (Obj::*func)(Params...),
Args&&... args) {
return Cgu::Thread::Future<Ret>::make(obj, func, std::forward<Args>(args)...);
}
/**
* A convenience helper function which calls
* Cgu::Thread::Future::make() to obtain a Future object without the
* need to specify the return value of the function represented by the
* new object: that is deduced from the signature of that function.
* This is useful shorthand when also employed with the C++11 'auto'
* keyword.
* @exception std::bad_alloc It might throw std::bad_alloc if memory
* is exhausted and the system throws in that case. (This exception
* will not be thrown if the library has been installed using the
* \--with-glib-memory-slices-no-compat configuration option: instead
* glib will terminate the program if it is unable to obtain memory
* from the operating system.)
* @exception Cgu::Thread::MutexError It might throw
* Cgu::Thread::MutexError if initialisation of the contained mutex
* fails. (It is often not worth checking for this, as it means
* either memory is exhausted or pthread has run out of other
* resources to create new mutexes.)
* @exception Cgu::Thread::CondError It might throw
* Cgu::Thread::CondError if initialisation of the contained condition
* variable fails. (It is often not worth checking for this, as it
* means either memory is exhausted or pthread has run out of other
* resources to create new condition variables.)
* @note This method will also throw if the copy or move constructor
* of a bound argument throws, or the default constructor of the
* return value type of the function represented by the new object
* throws.
*
* Since 2.0.4
*/
template <class Obj, class Ret, class... Params, class... Args>
Cgu::IntrusivePtr<Cgu::Thread::Future<Ret>> make_future(const Obj& obj,
Ret (Obj::*func)(Params...) const,
Args&&... args) {
return Cgu::Thread::Future<Ret>::make(obj, func, std::forward<Args>(args)...);
}
/**
* A convenience helper function which calls
* Cgu::Thread::Future::make() to obtain a Future object without the
* need to specify the return value of the function represented by the
* new object: that is deduced from the signature of that function.
* This is useful shorthand when also employed with the C++11 'auto'
* keyword.
* @exception std::bad_alloc It might throw std::bad_alloc if memory
* is exhausted and the system throws in that case. (This exception
* will not be thrown if the library has been installed using the
* \--with-glib-memory-slices-no-compat configuration option: instead
* glib will terminate the program if it is unable to obtain memory
* from the operating system.)
* @exception Cgu::Thread::MutexError It might throw
* Cgu::Thread::MutexError if initialisation of the contained mutex
* fails. (It is often not worth checking for this, as it means
* either memory is exhausted or pthread has run out of other
* resources to create new mutexes.)
* @exception Cgu::Thread::CondError It might throw
* Cgu::Thread::CondError if initialisation of the contained condition
* variable fails. (It is often not worth checking for this, as it
* means either memory is exhausted or pthread has run out of other
* resources to create new condition variables.)
* @note This method will also throw if the copy or move constructor
* of a bound argument throws, or the default constructor of the
* return value type of the function represented by the new object
* throws.
*
* Since 2.0.4
*/
template <class Ret, class... Params, class... Args>
Cgu::IntrusivePtr<Cgu::Thread::Future<Ret>> make_future(Ret (*func)(Params...),
Args&&... args) {
return Cgu::Thread::Future<Ret>::make(func, std::forward<Args>(args)...);
}
/**
* A convenience helper function which calls
* Cgu::Thread::Future::make() to obtain a Future object without the
* need to specify the return value of the function represented by the
* new object: that is deduced from the signature of that function.
* This is useful shorthand when also employed with the C++11 'auto'
* keyword.
*
* From version 2.0.14, this method takes the callable object as a
* template parameter, and in prior versions it took it as a
* std::function object. Before version 2.0.14 it was necessary to
* specify the return value of any callable object which was not a
* std::function object as a specific template parameter: this is not
* necessary in version 2.0.14, as it is deduced automatically.
*
* @exception std::bad_alloc It might throw std::bad_alloc if memory
* is exhausted and the system throws in that case. (This exception
* will not be thrown if the library has been installed using the
* \--with-glib-memory-slices-no-compat configuration option: instead
* glib will terminate the program if it is unable to obtain memory
* from the operating system.)
* @exception Cgu::Thread::MutexError It might throw
* Cgu::Thread::MutexError if initialisation of the contained mutex
* fails. (It is often not worth checking for this, as it means
* either memory is exhausted or pthread has run out of other
* resources to create new mutexes.)
* @exception Cgu::Thread::CondError It might throw
* Cgu::Thread::CondError if initialisation of the contained condition
* variable fails. (It is often not worth checking for this, as it
* means either memory is exhausted or pthread has run out of other
* resources to create new condition variables.)
* @note 1. This method will also throw if the copy or move
* constructor of the callable object passed as an argument throws, or
* the default constructor of the return value type of the function
* represented by the new object throws.
* @note 2. If the callable object passed as an argument has both
* const and non-const operator()() methods, the non-const version
* will be called even if the callable object passed is a const
* object.
*
* Since 2.0.4
*/
// we don't need this version of make_future() for syntactic reasons -
// the version taking a single template parameter will do by itself
// syntactically because it can use decltype. However, we include
// this version in order to be API compatible with c++-gtk-utils <
// 2.0.14, which required the return type to be specified when this
// method is passed something other than a std::function object.
// SFINAE will take care of the rest, except with a corner case where
// all of the following apply: (i) a function object is passed whose
// operator()() method returns a copy of the function object (or
// another function object of the same type), (ii) the function object
// is passed to this method as a rvalue and not a lvalue, and (iii)
// the user specifically states the return type when instantiating
// this template function. This would give rise to an ambiguity, but
// its happening is extremely unlikely, and cannot happen with a
// lambda or the return value of std::bind, because those types are
// only known to the compiler, and cannot happen with other objects if
// the user lets template deduction take its course.
template <class Ret, class Func>
Cgu::IntrusivePtr<Cgu::Thread::Future<Ret>> make_future(Func&& functor) {
return Cgu::Thread::Future<Ret>::make(std::forward<Func>(functor));
}
// we don't want to document this function: it provides the type
// deduction of the return value of the passed functor (it deals with
// cases where this is not specified expressly).
#ifndef DOXYGEN_PARSING
template <class Func>
auto make_future(Func&& functor) -> Cgu::IntrusivePtr<Cgu::Thread::Future<decltype(functor())>> {
return Cgu::Thread::Future<decltype(functor())>::make(std::forward<Func>(functor));
}
#endif
} // namespace Thread
} // namespace Cgu
#include <c++-gtk-utils/future.tpp>
#endif