include/comphelper/threadpool.hxx

   1 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
   2 /*
   3  * This file is part of the LibreOffice project.
   4  *
   5  * This Source Code Form is subject to the terms of the Mozilla Public
   6  * License, v. 2.0. If a copy of the MPL was not distributed with this
   7  * file, You can obtain one at http://mozilla.org/MPL/2.0/.
   8  */
   9
  10 #ifndef INCLUDED_COMPHELPER_THREADPOOL_HXX
  11 #define INCLUDED_COMPHELPER_THREADPOOL_HXX
  12
  13 #include <sal/config.h>
  14 #include <rtl/ref.hxx>
  15 #include <comphelper/comphelperdllapi.h>
  16 #include <mutex>
  17 #include <condition_variable>
  18 #include <cstddef>
  19 #include <vector>
  20 #include <memory>
  21
  22 namespace comphelper
  23 {
  24 class ThreadTaskTag;
  25
  26 class COMPHELPER_DLLPUBLIC ThreadTask
  27 {
  28 friend class ThreadPool;
  29 friend struct std::default_delete<ThreadTask>;
  30     std::shared_ptr<ThreadTaskTag>  mpTag;
  31
  32     /// execute this task
  33     void      exec();
  34 protected:
  35     /// override to get your task performed by the pool
  36     virtual void doWork() = 0;
  37     /// once pushed ThreadTasks are destroyed by the pool
  38     virtual   ~ThreadTask() {}
  39 public:
  40     ThreadTask(std::shared_ptr<ThreadTaskTag> pTag);
  41 };
  42
  43 /// A very basic thread-safe thread pool implementation
  44 class COMPHELPER_DLLPUBLIC ThreadPool final
  45 {
  46 public:
  47     /// returns a pointer to a shared pool with optimal thread
  48     /// count for the CPU
  49     static      ThreadPool& getSharedOptimalPool();
  50
  51     static std::shared_ptr<ThreadTaskTag> createThreadTaskTag();
  52
  53     static bool isTaskTagDone(const std::shared_ptr<ThreadTaskTag>&);
  54
  55     /// returns a configurable max-concurrency
  56     /// limit to avoid spawning an unnecessarily
  57     /// large number of threads on high-core boxes.
  58     /// MAX_CONCURRENCY env. var. controls the cap.
  59     static      std::size_t getPreferredConcurrency();
  60
  61     ThreadPool( std::size_t nWorkers );
  62     ~ThreadPool();
  63
  64     /// push a new task onto the work queue
  65     void        pushTask( std::unique_ptr<ThreadTask> pTask);
  66
  67     /** Wait until all queued tasks associated with the tag are completed
  68         @param  bJoin - if set call joinThreadsIfIdle() at the end
  69     */
  70     void        waitUntilDone(const std::shared_ptr<ThreadTaskTag>&, bool bJoin = true);
  71
  72     /// join all threads if there are no tasks presently.
  73     void        joinThreadsIfIdle();
  74
  75     /// return true if there are no queued or worked-on tasks
  76     bool        isIdle() const { return maTasks.empty() && mnBusyWorkers == 0; };
  77
  78     /// return the number of live worker threads
  79     sal_Int32   getWorkerCount() const { return mnMaxWorkers; }
  80
  81     /// wait until all work is completed, then join all threads
  82     void        shutdown();
  83
  84 private:
  85     ThreadPool(const ThreadPool&) = delete;
  86     ThreadPool& operator=(const ThreadPool&) = delete;
  87
  88     class ThreadWorker;
  89     friend class ThreadWorker;
  90
  91     /** Pop a work task
  92         @param  bWait - if set wait until task present or termination
  93         @return a new task to perform, or NULL if list empty or terminated
  94     */
  95     std::unique_ptr<ThreadTask> popWorkLocked( std::unique_lock< std::mutex > & rGuard, bool bWait );
  96     void shutdownLocked(std::unique_lock<std::mutex>&);
  97     void incBusyWorker();
  98     void decBusyWorker();
  99
 100     /// signalled when all in-progress tasks are complete
 101     std::mutex              maMutex;
 102     std::condition_variable maTasksChanged;
 103     bool                    mbTerminate;
 104     std::size_t const       mnMaxWorkers;
 105     std::size_t             mnBusyWorkers;
 106     std::vector< std::unique_ptr<ThreadTask> >   maTasks;
 107     std::vector< rtl::Reference< ThreadWorker > > maWorkers;
 108 };
 109
 110 } // namespace comphelper
 111
 112 #endif // INCLUDED_COMPHELPER_THREADPOOL_HXX
 113
 114 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */