Dr. Dobb's Journal - November 2008 - (Page 41)

the “current thread.” In old versions of Boost, a default-constructed boost::thread object was special, in that it represented the current thread. Now, a default-constructed boost::thread object doesn’t represent any thread at all. The only use for such an object was for identifying a thread, and comparison with other boost::thread objects: This role is now taken by the boost::thread::id class. Thread IDs sport the full range of comparison operators, and can be freely copied. If two thread IDs represent the same thread they compare equal, and if they represent different threads then they are not equal. Also, the thread IDs for distinct threads form a total order, so they can be used as keys in associative containers such as std::map . boost::mutex map_mutex; std::map data_map; void f() { boost::mutex::scoped_lock lk(map_mutex); some_data& my_data= data_map[boost::this_thread ::get_id()]; lk.unlock(); do_stuff(my_data); } A default-constructed boost::thread::id represents “not any thread,” and will not compare equal to any boost::thread::id that holds the ID of a thread of execution. ordinary C++ exception, and can be caught and handled just like any other exception. In this case, it is perfectly acceptable for the thread to be interrupted again. This can be useful if the thread is performing a series of tasks: If a task is interrupted, the thread can catch the interruption exception and move on to the next task. The interruption points are: • boost::thread::join() • boost::thread::timed_join() • boost::condition_variable::wait() • boost::condition_variable::timed_wait() • boost::condition_variable_any::wait() • boost::condition_variable_any::timed_wait() • boost::this_thread::sleep() • boost::this_thread::interruption_point() The last one (boost::this_thread::interruption_point()) lets you place interruption points at carefully chosen places in your code, when the code would not otherwise execute an interruption point. It can be used as part of a processing loop; for example, if you are Interrupting Threads The final new aspect of thread management introduced with Boost 1.35.0 is the ability to interrupt a running thread. This is done by calling the interrupt() member function of the boost::thread object associated with the thread you wish to interrupt. Interruption is an asynchronous request, and is nonbinding—it merely sets a flag in the data structure associated with the thread being interrupted. When that thread reaches an interruption point, it then throws a boost::thread_interrupted exception if interruption is enabled, and clears the flag. If interruption is disabled, the exception is not thrown and the flag remains set. This is an Solutions for every world. Visual Modeling for Business, IT and Systems Enterprise Architect from Sparx Systems redefines visual modeling with a huge set of built-in tools, technologies and capabilities, coupled with a lightweight footprint and great agility. With deep support for UML 2.1 and its related standards, Enterprise Architect 7.1 is the ideal tool to analyze, design, build and manage your next software project. November 2008 l www.ddj.com l Dr. Dobb’s Journal 41 http://sparxsystems.com http://sparxsystems.com http://www.ddj.com

Table of Contents Feed for the Digital Edition of Dr. Dobb's Journal - November 2008

Dr. Dobb's Journal - November 2008 Contents Friday Night Fish Fry Alia Vox Developer Diaries Developer's Notebook Saving Open Source Conversations iPhone Building Your Own Web Server Green Telnet What's New In Boost Threads? Testing Service Oriented Architectures Test Case Generation, UML, and Eclipse Unit Testing Web Services C3 Programming The Agile Edge Swaine's Flames Effective Concurrency

Dr. Dobb's Journal - November 2008

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