c++-gtk-utils
thread.h
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00001 /* Copyright (C) 2005 to 2012 Chris Vine
00002 
00003 The library comprised in this file or of which this file is part is
00004 distributed by Chris Vine under the GNU Lesser General Public
00005 License as follows:
00006 
00007    This library is free software; you can redistribute it and/or
00008    modify it under the terms of the GNU Lesser General Public License
00009    as published by the Free Software Foundation; either version 2.1 of
00010    the License, or (at your option) any later version.
00011 
00012    This library is distributed in the hope that it will be useful, but
00013    WITHOUT ANY WARRANTY; without even the implied warranty of
00014    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00015    Lesser General Public License, version 2.1, for more details.
00016 
00017    You should have received a copy of the GNU Lesser General Public
00018    License, version 2.1, along with this library (see the file LGPL.TXT
00019    which came with this source code package in the c++-gtk-utils
00020    sub-directory); if not, write to the Free Software Foundation, Inc.,
00021    51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
00022 
00023 */
00024 
00025 #ifndef CGU_THREAD_H
00026 #define CGU_THREAD_H
00027 
00028 #include <memory>  // for std::unique_ptr or std::auto_ptr
00029 #include <utility> // for std::move
00030 
00031 #include <pthread.h>
00032 
00033 #include <c++-gtk-utils/callback.h>
00034 #include <c++-gtk-utils/mutex.h>
00035 #include <c++-gtk-utils/cgu_config.h>
00036 
00037 namespace Cgu {
00038 
00039 namespace Thread {
00040 
00041 /**
00042  * @class Cgu::Thread::Thread thread.h c++-gtk-utils/thread.h
00043  * @brief A class representing a pthread thread.
00044  * @sa Thread::Mutex Thread::Mutex::Lock Thread::Cond Thread::Future Thread::JoinableHandle
00045  *
00046  * The Thread class encapsulates a pthread thread.  It can start, join
00047  * and cancel a thread.
00048  *
00049  * The Thread class, and the associated CancelBlock class, can be used
00050  * interchangeably with (and mixed with) GThread objects and
00051  * functions, and GMutex, GStaticMutex, GStaticRecMutex and GCond, as
00052  * they all use pthreads underneath on POSIX and other unix-like OSes.
00053  * In addition it can be used with threads started with the C++11
00054  * threading facilities, as in C++11 on unix-like OSes these
00055  * facilities will be built on top of pthreads (for which purpose
00056  * C++11 provides the std::native_handle_type type and
00057  * std::thread::native_handle() function).  Even where they are not,
00058  * they will use the same threading primitives provided by the kernel.
00059  *
00060  * @anchor ThreadsAnchor
00061  * @b c++-gtk-utils @b library @b and @b C++11 @b threads
00062  *
00063  * As mentioned above, the thread facilities provided by this library
00064  * can be freely interchanged with the threading facilities provided
00065  * by C++11.
00066  *
00067  * The main features available from this library and not C++11 are
00068  * thread cancellation and the associated Cgu::Thread::CancelBlock
00069  * class, and the Cgu::Thread::JoinableHandle class for scoped
00070  * joinable thread handling.
00071  *
00072  * C++11 does not provide thread cancellation or interruption support,
00073  * and C++ will never be able to do so on a complete basis because to
00074  * do so requires support from the underlying OS, which therefore
00075  * makes it platform specific (in this case, POSIX specific):
00076  * cancellation is only of limited use if it cannot reliably interrupt
00077  * blocking system calls.  The POSIX specification sets out the
00078  * interruptible cancellation points in System Interfaces, section
00079  * 2.9.5, Cancellation Points, and in effect specifies all the system
00080  * calls which can block as cancellation points.
00081  *
00082  * Whether, in C++ programs, destructors of local objects in the
00083  * cancelled thread are called is also system specific and is not
00084  * specified by POSIX.  Most modern commercial unixes, and recent
00085  * linux/BSD distributions based on NPTL (in the case of Linux, those
00086  * based on 2.6/3.* kernels), will unwind the stack and call
00087  * destructors on thread cancellation by means of a pseudo-exception,
00088  * but older distributions relying on the former linuxthreads
00089  * implementation will not.  Therefore for maximum portability
00090  * cancellation would only be used where there are plain data
00091  * structures/built-in types in existence in local scope when it
00092  * occurs, and if there is anything in free store to be released some
00093  * clean-ups would be implemented with
00094  * pthread_cleanup_push()/pthread_cleanup_pop().  This should be
00095  * controlled with pthread_setcancelstate() and/or the CancelBlock
00096  * class to choose the cancellation point.
00097  *
00098  * One of the (perhaps odd) features of C++11 threads is that if the
00099  * destructor of a std::thread object is called which represents a
00100  * joinable thread which has not been detach()ed or join()ed, the
00101  * whole program is terminated with a call to std::terminate(), which
00102  * makes it difficult to use in the presence of exceptions.  Often
00103  * what is wanted however is for join() to be called on a joinable
00104  * thread where the associated thread object goes out of scope, or
00105  * (provided it is done carefully and knowingly) for detach() to be
00106  * called.  The Cgu::Thread::JoinableHandle class can be used where
00107  * either of these two is the appropriate response to this situation.
00108  *
00109  * In addition, the c++-gtk-utils library provides the following which
00110  * are not present in C++11: a guaranteed monotonic clock on timed
00111  * condition variable waits where the operating system supports them;
00112  * read-write locks; and a Cgu::Thread::Future object which is more
00113  * intuitive to use than C++11 futures and features a built in
00114  * Cgu::SafeEmitter object which emits when the particular task has
00115  * completed, and (since version 2.0.2) has associated
00116  * Cgu::Thread::Future::when() methods for passing the result to a
00117  * glib main loop.
00118  *
00119  * @b c++-gtk-utils @b library @b and @b gthreads
00120  *
00121  * As mentioned above, the thread facilities provided by this library
00122  * can be freely interchanged with the threading facilities provided
00123  * by glib.
00124  *
00125  * The main features available with this thread implementation and not
00126  * GThreads are thread cancellation, the mutex scoped locking classes
00127  * Cgu::Thread::Mutex::Lock and Cgu::Thread::RecMutex::Lock, the
00128  * joinable thread scoped management class Cgu::Thread::JoinableHandle
00129  * and the Cgu::Thread::Future class (abstracting thread functions
00130  * which provide a result).
00131  *
00132  * There is no need from the perspective of this class to call
00133  * g_thread_init() before Cgu::Thread::Thread::start() is called, but
00134  * but prior to glib version 2.32 glib itself is not thread-safe
00135  * without g_thread_init(), so where this class is used with glib <
00136  * 2.32, g_thread_init() should be called at program initialization.
00137  *
00138  * See @ref Threading for particulars about GTK+ thread safety.
00139  */
00140 
00141 
00142 class Thread {
00143   pthread_t thread;
00144   // private constructor - this class can only be created with Thread::start
00145   Thread() {}
00146 public:
00147 /**
00148  * This class cannot be copied: it is intended to be held by
00149  * std::unique_ptr.  The copy constructor is deleted.
00150  */
00151   Thread(const Thread&) = delete;
00152 
00153 /**
00154  * This class cannot be copied: it is intended to be held by
00155  * std::unique_ptr.  The assignment operator is deleted.
00156  */
00157   Thread& operator=(const Thread&) = delete;
00158 
00159 /**
00160  * Cancels the thread represented by this Thread object.  It can be
00161  * called by any thread.  The effect is undefined if the thread
00162  * represented by this Thread object has both (a) already terminated
00163  * and (b) been detached or had a call to join() made for it.
00164  * Accordingly, if the user is not able to establish from the program
00165  * logic whether the thread has terminated, the thread must be created
00166  * as joinable and cancel() must not be called after a call to
00167  * detach() has been made or a call to join() has returned.  A
00168  * Thread::JoinableHandle object can used to ensure this.  It does not
00169  * throw.
00170  * @note Use this method with care - sometimes its use is unavoidable
00171  * but destructors for local objects may not be called if a thread
00172  * exits by virtue of a call to cancel() (that depends on the
00173  * implementation).  Most modern commercial unixes, and recent
00174  * linux/BSD distributions based on NPTL, will unwind the stack and
00175  * call destructors on thread cancellation by means of a
00176  * pseudo-exception, but older distributions relying on the former
00177  * linuxthreads implementation will not.  Therefore for maximum
00178  * portability only have plain data structures/built-in types in
00179  * existence in local scope when it occurs and if there is anything in
00180  * free store to be released implement some clean-ups with
00181  * pthread_cleanup_push()/pthread_cleanup_pop().  This should be
00182  * controlled with pthread_setcancelstate() and/or the CancelBlock
00183  * class to choose the cancellation point.
00184  * @sa Cgu::Thread::Exit
00185  */
00186   void cancel() {pthread_cancel(thread);}
00187 
00188 /**
00189  * Joins the thread represented by this Thread object (that is, waits
00190  * for it to terminate).  It can be called by any thread other than
00191  * the one represented by this Thread object.  The result is undefined
00192  * if the thread is or was detached or join() has already been called
00193  * for the thread (a Thread::JoinableHandle object will however give a
00194  * defined result in such cases for threads originally started as
00195  * joinable).  It does not throw.
00196  */
00197   void join() {pthread_join(thread, 0);}
00198 
00199 /**
00200  * Detaches the thread represented by this Thread object where it is
00201  * joinable, so as to make it unjoinable.  The effect is unspecified
00202  * if the thread is already unjoinable (a Thread::JoinableHandle
00203  * object will however give a defined result in such cases for threads
00204  * originally started as joinable).  It does not throw.
00205  */
00206   void detach() {pthread_detach(thread);}
00207 
00208 /**
00209  * Specifies whether the calling thread is the same thread as is
00210  * represented by this Thread object.  The effect is undefined if the
00211  * thread represented by this Thread object has both (a) already
00212  * terminated and (b) been detached or had a call to join() made for
00213  * it.  Accordingly, if the user is not able to establish from the
00214  * program logic whether the thread has terminated, the thread must be
00215  * created as joinable and is_caller() must not be called after a call
00216  * to detach() has been made or a call to join() has returned.  A
00217  * Thread::JoinableHandle object can used to ensure this.  This method
00218  * does not throw.
00219  * @return Returns true if the caller is in the thread represented by
00220  * this Thread object.
00221  */
00222   bool is_caller() {return pthread_equal(thread, pthread_self());}
00223 
00224 /**
00225  * Starts a new thread.  It can be called by any thread.
00226  * @param cb A callback object (created by Callback::make())
00227  * encapsulating the function to be executed by the new thread.  The
00228  * Thread object returned by this function will take ownership of the
00229  * callback: it will automatically be deleted either by the new thread
00230  * when it has finished with it, or by this method in the calling
00231  * thread if the attempt to start a new thread fails (including if
00232  * std::bad_alloc is thrown).
00233  * @param joinable Whether the join() method may be called in relation
00234  * to the new thread.
00235  * @return A Thread object representing the new thread which has been
00236  * started, held by a std::unique_ptr object as it has single
00237  * ownership semantics.  The std::unique_ptr object will be empty
00238  * (that is std::unique_ptr<Cgu::Thread::Thread>::get() will return 0)
00239  * if the thread did not start correctly, which would mean that memory
00240  * is exhausted, the pthread thread limit has been reached or pthread
00241  * has run out of other resources to start new threads.
00242  * @exception std::bad_alloc This method might throw std::bad_alloc if
00243  * memory is exhausted and the system throws in that case.  (This
00244  * exception will not be thrown if the library has been installed
00245  * using the --with-glib-memory-slices-no-compat configuration option:
00246  * instead glib will terminate the program if it is unable to obtain
00247  * memory from the operating system.)
00248  * @note 1. The thread will keep running even if the return value of
00249  * start() goes out of scope (but it will no longer be possible to
00250  * call any of the methods in this class for it, which is fine if the
00251  * thread is not started as joinable and it is not intended to cancel
00252  * it).
00253  * @note 2. If the thread is started with the joinable attribute, the
00254  * user must subsequently either call the join() or the detach()
00255  * method, as otherwise a resource leak may occur (the destructor of
00256  * this class does not call detach() automatically).  Alternatively,
00257  * the return value of this method can be passed to a
00258  * Thread::JoinableHandle object which will do this automatically in
00259  * the Thread::JoinableHandle object's destructor.
00260  * @note 3. Any Thread::Exit exception thrown from the function
00261  * executed by the new thread will be caught and consumed.  The thread
00262  * will safely terminate and unwind the stack in so doing.
00263  * @note 4. If any uncaught exception other than Thread::Exit is
00264  * allowed to propagate from the initial function executed by the new
00265  * thread, the exception is not consumed (NPTL's forced stack
00266  * unwinding on cancellation does not permit catching with an ellipsis
00267  * argument without rethrowing, and even if it did permit it, the
00268  * result would be an unreported error).  The C++11 standard requires
00269  * std::terminate() to be called in such a case and so the entire
00270  * program terminated.  Accordingly, a user must make sure that no
00271  * exceptions, other than Thread::Exit or any cancellation
00272  * pseudo-exception, can propagate from the initial function executed
00273  * by the new thread.
00274  * @note 5. If the library is compiled using the --with-auto-ptr
00275  * configuration option, then this function will return a
00276  * Thread::Thread object by std::auto_ptr instead of std::unique_ptr
00277  * in order to retain compatibility with the 1.2 series of the
00278  * library.
00279  */
00280 #ifdef CGU_USE_AUTO_PTR
00281   static std::auto_ptr<Cgu::Thread::Thread> start(const Cgu::Callback::Callback* cb,
00282                                                   bool joinable);
00283 #else
00284   static std::unique_ptr<Cgu::Thread::Thread> start(const Cgu::Callback::Callback* cb,
00285                                                     bool joinable);
00286 #endif
00287 
00288 #ifdef CGU_USE_GLIB_MEMORY_SLICES_NO_COMPAT
00289   CGU_GLIB_MEMORY_SLICES_FUNCS
00290 #endif
00291 };
00292 
00293 /**
00294  * @class Cgu::Thread::JoinableHandle thread.h c++-gtk-utils/thread.h
00295  * @brief A class wrapping a Thread::Thread object representing a
00296  * joinable thread.
00297  * @sa Thread::Thread Thread::Future
00298  *
00299  * This class enables a joinable thread to be made more easily
00300  * exception safe.  It can also be used to provide that a joinable
00301  * thread is not detached or joined while other methods dependent on
00302  * that might still be called, and to provide a defined result where
00303  * there are multiple calls to join() and/or detach().  When it is
00304  * destroyed, it will either detach or join the thread represented by
00305  * the wrapped Thread::Thread object unless it has previously been
00306  * detached or joined using the detach() or join() methods, so
00307  * avoiding thread resource leaks.  Whether it will detach() or join()
00308  * on destruction depends on the Thread::JoinableHandle::Action
00309  * argument passed to the
00310  * Thread::JoinableHandle::JoinableHandle(std::unique_ptr<Thread::Thread>,
00311  * Action) constructor.
00312  * 
00313  * Passing Thread::JoinableHandle::detach_on_exit to that argument is
00314  * not always the correct choice where the thread callback has been
00315  * bound to a reference argument in local scope and an exception might
00316  * be thrown, because the thread will keep running after the
00317  * Thread::JoinableHandle object and other local variables have
00318  * (because of the exception) gone out of scope.  Consider the
00319  * following trivial parallelized calculation example:
00320  *
00321  * @code
00322  * std::vector<int> get_readings();
00323  * void get_mean(const std::vector<int>& v, int& result);
00324  * void get_std_deviation(const std::vector<int>& v, int& result); // might throw
00325  * void show_result(int mean, int deviation);
00326  *
00327  * using namespace Cgu;
00328  * void do_calc() {
00329  *   int i, j;
00330  *   std::vector<int> v = get_readings();
00331  *   // with bound reference arguments, Callback::make() requires explicit type instantation
00332  *   std::unique_ptr<Thread::Thread> t =
00333  *     Thread::Thread::start(Callback::make<const std::vector<int>&, int&>(&get_mean, v, i), true);
00334  *   if (t.get()) {  // checks whether thread started correctly
00335  *     get_std_deviation(v, j);
00336  *     t->join();
00337  *     show_result(i, j);
00338  *   }
00339  * }
00340  * @endcode
00341  *
00342  * If get_std_deviation() throws, as well as there being a potential
00343  * thread resource leak by virtue of no join being made, the thread
00344  * executing get_mean() will continue running and attempt to access
00345  * variable v, and put its result in variable i, which may by then
00346  * both be out of scope.  To deal with such a case, the thread could
00347  * be wrapped in a Thread::JoinableHandle object which joins on exit
00348  * rather than detaches, for example:
00349  *
00350  * @code
00351  * ...
00352  * using namespace Cgu;
00353  * void do_calc() {
00354  *   int i, j;
00355  *   std::vector<int> v = get_readings();
00356  *   // with reference arguments, Callback::make() requires explicit type instantation
00357  *   Thread::JoinableHandle t(Thread::Thread::start(Callback::make<const std::vector<int>&, int&>(&get_mean, v, i), true),
00358  *                            Thread::JoinableHandle::join_on_exit);
00359  *   if (t.is_managing()) {  // checks whether thread started correctly
00360  *     get_std_deviation(v, j);
00361  *     t.join();
00362  *     show_result(i, j);
00363  *   }
00364  * }
00365  * @endcode
00366  *
00367  * Better still, however, would be to use Cgu::Thread::Future in this
00368  * kind of usage, namely a usage where a worker thread is intended to
00369  * provide a result for inspection.
00370  *
00371  * @note These examples assume that the std::vector library
00372  * implementation permits concurrent reads of a vector object by
00373  * different threads.  Whether that is the case depends on the
00374  * documentation of the library concerned (if designed for a
00375  * multi-threaded environment, most will permit this).
00376  */
00377 class JoinableHandle {
00378 public:
00379   enum Action {detach_on_exit, join_on_exit};
00380 
00381 private:
00382   Mutex mutex; // make this the first member so the constructors are strongly exception safe
00383   Action action;
00384   bool detached;
00385   std::unique_ptr<Cgu::Thread::Thread> thread;
00386 
00387 public:
00388 /**
00389  * Cancels the thread represented by the wrapped Thread::Thread
00390  * object.  It can be called by any thread.  The effect is undefined
00391  * if when called the thread represented by the wrapped Thread::Thread
00392  * object has both (a) already terminated and (b) had a call to join()
00393  * or detach() made for it.  Accordingly, if the user is not able to
00394  * establish from the program logic whether the thread has terminated,
00395  * cancel() must not be called after a call to detach() has been made
00396  * or a call to join() has returned: this can be ensured by only
00397  * detaching or joining via this object's destructor (that is, by not
00398  * using the explicit detach() and join() methods).  This method does
00399  * not throw.
00400  * @note Use this method with care - see Thread::cancel() for further
00401  * information.
00402  */
00403   void cancel();
00404 
00405 /**
00406  * Joins the thread represented by the wrapped Thread::Thread object
00407  * (that is, waits for it to terminate), unless the detach() or join()
00408  * method has previously been called in which case this call does
00409  * nothing.  It can be called by any thread other than the one
00410  * represented by the wrapped Thread::Thread object, but only one
00411  * thread can wait on it: if one thread (thread A) calls it while
00412  * another thread (thread B) is already blocking on it, thread A's
00413  * call to this method will return immediately and return false.  It
00414  * does not throw.
00415  * @return true if a successful join() has been accomplished (that is,
00416  * detach() or join() have not previously been called), otherwise
00417  * false.
00418  */
00419   bool join();
00420 
00421 /**
00422  * Detaches the thread represented by this Thread::Thread object, so
00423  * as to make it unjoinable, unless the detach() or join() method has
00424  * previously been called in which case this call does nothing.  It
00425  * does not throw.
00426  */
00427   void detach();
00428 
00429 /**
00430  * Specifies whether the calling thread is the same thread as is
00431  * represented by the wrapped Thread::Thread object.  It can be called
00432  * by any thread.  The effect is undefined if the thread represented
00433  * by the wrapped Thread::Thread object has both (a) already
00434  * terminated and (b) had a call to join() or detach() made for it.
00435  * Accordingly, if the user is not able to establish from the program
00436  * logic whether the thread has terminated, is_caller() must not be
00437  * called after a call to detach() has been made or a call to join()
00438  * has returned: this can be ensured by only detaching or joining via
00439  * this object's destructor (that is, by not using the explicit
00440  * detach() and join() methods).  This method does not throw.
00441  * @return Returns true if the caller is in the thread represented by
00442  * the wrapped Thread::Thread object.  If not, or this JoinableHandle
00443  * does not wrap any Thread object, then returns false.
00444  */
00445   bool is_caller();
00446 
00447 /**
00448  * Specifies whether this JoinableHandle object has been initialized
00449  * with a Thread::Thread object representing a correctly started
00450  * thread in respect of which neither JoinableHandle::detach() nor
00451  * JoinableHandle::join() has been called.  It can be called by any
00452  * thread.  It is principally intended to enable the constructor
00453  * taking a std::unique_ptr<Cgu::Thread::Thread> object to be directly
00454  * initialized by a call to Thread::Thread::start(), by providing a
00455  * means for the thread calling Thread::Thread::start() to check
00456  * afterwards that the new thread did, in fact, start correctly.  Note
00457  * that this method will return true even after the thread has
00458  * finished, provided neither the join() nor detach() method has been
00459  * called.
00460  * @return Returns true if this object has been initialized by a
00461  * Thread::Thread object representing a correctly started thread in
00462  * respect of which neither JoinableHandle::detach() nor
00463  * JoinableHandle::join() has been called, otherwise false.
00464  */
00465   bool is_managing();
00466 
00467 /**
00468  * Moves one JoinableHandle object to another JoinableHandle object.
00469  * This is a move operation which transfers ownership to the assignee,
00470  * as the handles store their Thread::Thread object by
00471  * std::unique_ptr<>.  Any existing thread managed by the assignee
00472  * prior to the move will be detached if it has not already been
00473  * detached or joined. This method will not throw.
00474  * @param h The assignor/movant, which will cease to hold a valid
00475  * Thread::Thread object after the move has taken place.
00476  * @return A reference to the assignee JoinableHandle object after
00477  * assignment.
00478  * @note 1. This method is thread safe as regards the assignee (the
00479  * object assigned to), but no synchronization is carried out with
00480  * respect to the rvalue assignor/movant.  This is because temporaries
00481  * are only visible and accessible in the thread carrying out the move
00482  * operation and synchronization for them would represent pointless
00483  * overhead.  In a case where the user uses std::move to force a move
00484  * from a named object, and that named object's lifetime is managed by
00485  * (or the object is otherwise accessed by) a different thread than
00486  * the one making the move, the user must carry out her own
00487  * synchronization with respect to that different thread, as the named
00488  * object will be mutated by the move.
00489  * @note 2. If the library is compiled using the --with-auto-ptr
00490  * configuration option, then this operator's signature is
00491  * JoinableHandle& operator=(JoinableHandle& h) in order to retain
00492  * compatibility with the 1.2 series of the library.
00493  */
00494 #ifdef CGU_USE_AUTO_PTR
00495   JoinableHandle& operator=(JoinableHandle& h);
00496 #else
00497   JoinableHandle& operator=(JoinableHandle&& h);
00498 #endif
00499 
00500 /**
00501  * This constructor initializes a new JoinableHandle object with a
00502  * std::unique_ptr<Thread::Thread> object, as provided by
00503  * Thread::Thread::start().  This is a move operation which transfers
00504  * ownership to the new object.
00505  * @param thr The initializing Thread::Thread object (which must have
00506  * been created as joinable) passed by a std::unique_ptr smart
00507  * pointer.  This is a move operation.
00508  * @param act Either Thread::JoinableHandle::detach_on_exit (which
00509  * will cause the destructor to detach the thread if it has not
00510  * previously been detached or joined) or
00511  * Thread::JoinableHandle::join_on_exit (which will cause the
00512  * destructor to join the thread if it has not previously been
00513  * detached or joined).
00514  * @exception Cgu::Thread::MutexError Throws this exception if
00515  * initialization of the internal mutex fails.  The constructor is
00516  * strongly exception safe: if Cgu::Thread::MutexError is thrown, the
00517  * initializing std::unique_ptr<Cgu::Thread::Thread> object will be
00518  * left unchanged.  (It is often not worth checking for this
00519  * exception, as it means either memory is exhausted or pthread has
00520  * run out of other resources to create new mutexes.)
00521  * @note 1. It is not necessary to check that the thread parameter
00522  * represents a correctly started thread (that is, that thr.get() does
00523  * not return 0) before this constructor is invoked, because that can
00524  * be done after construction by calling JoinableHandle::is_managing()
00525  * (a JoinableHangle object can safely handle a case where thr.get()
00526  * does return 0).  This enables a JoinableHandle object to be
00527  * directly initialized by this constructor from a call to
00528  * Thread::Thread::start().
00529  * @note 2. No synchronization is carried out with respect to the
00530  * initializing std::unique_ptr object.  This is because such an
00531  * object is usually passed to this constructor as a temporary, which
00532  * is only visible and accessible in the thread carrying out the move
00533  * operation, in which case synchronization would represent pointless
00534  * overhead.  In a case where the user uses std::move to force a move
00535  * from a named std::unique_ptr object, and that named object's
00536  * lifetime is managed by (or the object is otherwise accessed by) a
00537  * different thread than the one making the move, the user must carry
00538  * out her own synchronization with respect to that different thread,
00539  * as the initializing std::unique_ptr object will be mutated by the
00540  * move.
00541  * @note 3. If the library is compiled using the --with-auto-ptr
00542  * configuration option, then this constructor's signature is
00543  * JoinableHandle(std::auto_ptr<Cgu::Thread::Thread> thr, Action act)
00544  * in order to retain compatibility with the 1.2 series of the library
00545  * @sa JoinableHandle::is_managing().
00546  */
00547 #ifdef CGU_USE_AUTO_PTR
00548   JoinableHandle(std::auto_ptr<Cgu::Thread::Thread> thr, Action act): action(act), detached(false), thread(thr.release()) {}
00549 #else
00550   JoinableHandle(std::unique_ptr<Cgu::Thread::Thread> thr, Action act): action(act), detached(false), thread(std::move(thr)) {}
00551 #endif
00552   
00553 /**
00554  * This constructor initializes a new JoinableHandle object with an
00555  * existing JoinableHandle object.  This is a move operation which
00556  * transfers ownership to the new object.
00557  * @param h The initializing JoinableHandle object, which will cease
00558  * to hold a valid Thread::Thread object after the initialization has
00559  * taken place.
00560  * @exception Cgu::Thread::MutexError Throws this exception if
00561  * initialization of the internal mutex fails.  The constructor is
00562  * strongly exception safe: if Cgu::Thread::MutexError is thrown, the
00563  * initializing Cgu::Thread::JoinableHandle object will be left
00564  * unchanged.  (It is often not worth checking for this exception, as
00565  * it means either memory is exhausted or pthread has run out of other
00566  * resources to create new mutexes.)
00567  * @note 1. No synchronization is carried out with respect to the
00568  * initializing rvalue.  This is because temporaries are only visible
00569  * and accessible in the thread carrying out the move operation and
00570  * synchronization for them would represent pointless overhead.  In a
00571  * case where a user uses std::move to force a move from a named
00572  * object, and that named object's lifetime is managed by (or the
00573  * object is otherwise accessed by) a different thread than the one
00574  * making the move, the user must carry out her own synchronization
00575  * with respect to that different thread, as the named object will be
00576  * mutated by the move.
00577  * @note 2. If the library is compiled using the --with-auto-ptr
00578  * configuration option, then this constructor's signature is
00579  * JoinableHandle(JoinableHandle& h) in order to retain compatibility
00580  * with the 1.2 series of the library.
00581  */
00582 #ifdef CGU_USE_AUTO_PTR
00583   JoinableHandle(JoinableHandle& h): action(h.action), detached(h.detached), thread(std::move(h.thread)) {}
00584 #else
00585   JoinableHandle(JoinableHandle&& h): action(h.action), detached(h.detached), thread(std::move(h.thread)) {}
00586 #endif
00587 
00588 /**
00589  * The default constructor.  Nothing is managed until the move
00590  * assignment operator has been called.
00591  * @exception Cgu::Thread::MutexError Throws this exception if
00592  * initialization of the internal mutex fails.  (It is often not worth
00593  * checking for this exception, as it means either memory is exhausted
00594  * or pthread has run out of other resources to create new mutexes.)
00595  *
00596  * Since 2.0.8
00597  */
00598   JoinableHandle(): action(detach_on_exit), detached(true) {}
00599 
00600 /**
00601  * The destructor will detach a managed thread (if the
00602  * Thread::JoinableHandle::detach_on_exit flag is set) or join it (if
00603  * the Thread::JoinableHandle::join_on_exit flag is set), unless it
00604  * has previously been detached or joined with the detach() or join()
00605  * methods.  The destructor is thread safe (any thread may destroy the
00606  * JoinableHandle object).  The destructor will not throw.
00607  */
00608   ~JoinableHandle();
00609 
00610 /* Only has effect if --with-glib-memory-slices-compat or
00611  * --with-glib-memory-slices-no-compat option picked */
00612   CGU_GLIB_MEMORY_SLICES_FUNCS
00613 };
00614 
00615 /**
00616  * @class CancelBlock thread.h c++-gtk-utils/thread.h
00617  * @brief A class enabling the cancellation state of a thread to be
00618  * controlled.
00619  *
00620  * A class enabling the cancellation state of a thread to be
00621  * controlled, so as to provide exception safe cancellation state
00622  * changes.  When the object goes out of scope, cancellation state is
00623  * returned to the state it was in prior to its construction.
00624  */
00625 
00626 class CancelBlock {
00627   int starting_state;
00628 public:
00629 /**
00630  * This class cannot be copied.  The copy constructor is deleted.
00631  */
00632   CancelBlock(const CancelBlock&) = delete;
00633 
00634 /**
00635  * This class cannot be copied.  The assignment operator is deleted.
00636  */
00637   CancelBlock& operator=(const CancelBlock&) = delete;
00638 
00639 /**
00640  * Makes the thread uncancellable, even if the code passes through a
00641  * cancellation point, while the CancelBlock object exists (when the
00642  * CancelBlock object ceases to exist, cancellation state is returned
00643  * to the state prior to it being constructed).  It should only be
00644  * called by the thread which created the CancelBlock object.  This
00645  * method will not throw.
00646  * @param old_state Indicates the cancellation state of the calling
00647  * thread immediately before this call to block() was made, either
00648  * PTHREAD_CANCEL_ENABLE (if the thread was previously cancellable) or
00649  * PTHREAD_CANCEL_DISABLE (if this call did nothing because the thread
00650  * was already uncancellable).
00651  * @return 0 if successful, else a value other than 0.
00652  */
00653   static int block(int& old_state) {return pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &old_state);}
00654 
00655 /**
00656  * Makes the thread uncancellable, even if the code passes through a
00657  * cancellation point, while the CancelBlock object exists (when the
00658  * CancelBlock object ceases to exist, cancellation state is returned
00659  * to the state prior to it being constructed).  It should only be
00660  * called by the thread which created the CancelBlock object.  This
00661  * method will not throw.
00662  * @return 0 if successful, else a value other than 0.
00663  */
00664   static int block() {int old_state; return block(old_state);}
00665 
00666 /**
00667  * Makes the thread cancellable while the CancelBlock object exists
00668  * (when the CancelBlock object ceases to exist, cancellation state is
00669  * returned to the state prior to it being constructed).  It should
00670  * only be called by the thread which created the CancelBlock object.
00671  * This method will not throw.
00672  * @param old_state Indicates the cancellation state of the calling
00673  * thread immediately before this call to unblock() was made, either
00674  * PTHREAD_CANCEL_DISABLE (if the thread was previously uncancellable)
00675  * or PTHREAD_CANCEL_ENABLE (if this call did nothing because the
00676  * thread was already cancellable).
00677  * @return 0 if successful, else a value other than 0.
00678  */
00679   static int unblock(int& old_state) {return pthread_setcancelstate(PTHREAD_CANCEL_ENABLE, &old_state);}
00680 
00681 /**
00682  * Makes the thread cancellable while the CancelBlock object exists
00683  * (when the CancelBlock object ceases to exist, cancellation state is
00684  * returned to the state prior to it being constructed).  It should
00685  * only be called by the thread which created the CancelBlock object.
00686  * This method will not throw.
00687  * @return 0 if successful, else a value other than 0.
00688  */
00689   static int unblock() {int old_state; return unblock(old_state);}
00690 
00691 /**
00692  * Restores cancallation state to the state it was in immediately
00693  * before this CancelBlock object was constructed.  It should only be
00694  * called by the thread which created the CancelBlock object.  This
00695  * method will not throw.
00696  * @param old_state Indicates the cancellation state of the calling
00697  * thread immediately before this call to restore() was made, either
00698  * PTHREAD_CANCEL_DISABLE (if the thread was previously uncancellable)
00699  * or PTHREAD_CANCEL_ENABLE (if this thread was previously
00700  * cancellable).
00701  * @return 0 if successful, else a value other than 0.
00702  */
00703   int restore(int& old_state) {return pthread_setcancelstate(starting_state, &old_state);}
00704 
00705 /**
00706  * Restores cancallation state to the state it was in immediately
00707  * before this CancelBlock object was constructed.  It should only be
00708  * called by the thread which created the CancelBlock object.  This
00709  * method will not throw.
00710  * @return 0 if successful, else a value other than 0.
00711  */
00712   int restore() {int old_state; return restore(old_state);}
00713 
00714 /**
00715  * The constructor will not throw.
00716  * @param blocking Whether the CancelBlock object should start
00717  * in blocking mode.
00718  */
00719   CancelBlock(bool blocking = true);
00720 
00721 /**
00722  * The destructor will put the thread in the cancellation state that
00723  * it was in immediately before the CancelBlock object was constructed
00724  * (which might be blocking).  It will not throw.
00725  */
00726   ~CancelBlock() {restore();}
00727 
00728 /* Only has effect if --with-glib-memory-slices-compat or
00729  * --with-glib-memory-slices-no-compat option picked */
00730   CGU_GLIB_MEMORY_SLICES_FUNCS
00731 };
00732 
00733 /**
00734  * @class Exit thread.h c++-gtk-utils/thread.h
00735  * @brief A class which can be thrown to terminate the throwing
00736  * thread.
00737  *
00738  * This class can be thrown (instead of calling pthread_exit()) when a
00739  * thread wishes to terminate itself and also ensure stack unwinding,
00740  * so that destructors of local objects are called.  It is caught
00741  * automatically by the implementation of Cgu::Thread::Thread::start()
00742  * so that it will only terminate the thread throwing it and not the
00743  * whole process.  See the Cgu::Thread::Thread::cancel() method above,
00744  * for use when a thread wishes to terminate another one, and the
00745  * caveats on the use of Cgu::Thread::Thread::cancel().
00746  *
00747  * Do not throw a Cgu::Thread::Exit object in a program with more than
00748  * one main loop in order to terminate one of the threads which has
00749  * its own main loop.  Instead, just cause its main loop to terminate
00750  * by, say, calling g_main_loop_quit() on it.
00751  */
00752 class Exit {};
00753 
00754 } // namespace Thread
00755 
00756 } // namespace Cgu
00757 
00758 #endif