commandqueue.h

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/******************************************************************************
 Copyright (c) 2012-2016 Institut für Nachrichtentechnik, Universität Rostock
 Copyright (c) 2006-2012 Quality & Usability Lab
                         Deutsche Telekom Laboratories, TU Berlin
 
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// https://AudioProcessingFramework.github.io/
 
 
#ifndef APF_COMMANDQUEUE_H
#define APF_COMMANDQUEUE_H
 
#include <thread>   // std::this_thread::sleep_for
#include <chrono>   // std::chrono::microseconds
#include <cassert>  // for assert()
 
#include "apf/lockfreefifo.h"
 
namespace apf
{
 
class CommandQueue : NonCopyable
{
  public:
    struct Command : NonCopyable
    {
      virtual ~Command() {}
 
      virtual void execute() = 0;
 
      virtual void cleanup() = 0;
    };
 
    class WaitCommand : public Command
    {
      public:
        WaitCommand(bool& done) : _done(done) {}
 
      private:
        virtual void execute() { }
        virtual void cleanup() { _done = true; }
 
        bool& _done;
    };
 
 
 
    explicit CommandQueue(size_t size)
      : _in_fifo(size)
      , _out_fifo(size)
      , _active(true)
    {}
 
    ~CommandQueue()
    {
      this->cleanup_commands();
      // TODO: warning if process queue is not empty?
      // TODO: if inactive -> process commands (if active -> ???)
    }
 
    inline void push(Command* cmd);
 
    inline void wait();
 
    void cleanup_commands()
    {
      Command* cmd;
      while ((cmd = _out_fifo.pop()) != nullptr) { _cleanup(cmd); }
    }
 
    // TODO: avoid return value?
    inline bool deactivate()
    {
      this->cleanup_commands();
      if (_in_fifo.empty()) _active = false;
      return !_active;
    }
 
    inline void reactivate()
    {
      this->cleanup_commands();
      assert(_in_fifo.empty());
      _active = true;
    }
 
 
 
 
    void process_commands()
    {
      Command* cmd;
      while ((cmd = _in_fifo.pop()) != nullptr)
      {
        cmd->execute();
        bool result = _out_fifo.push(cmd);
        // If _out_fifo is full, cmd is not cleaned up!
        // This is very unlikely to happen (if not impossible).
        assert(result && "Error in _out_fifo.push()!");
        (void)result;  // avoid "unused-but-set-variable" warning
      }
    }
 
    bool commands_available() const
    {
      return !_in_fifo.empty();
    }
 
 
  private:
    void _cleanup(Command* cmd)
    {
      assert(cmd != nullptr);
      cmd->cleanup();
      delete cmd;
    }
 
    LockFreeFifo<Command*> _in_fifo;
    LockFreeFifo<Command*> _out_fifo;
 
    bool _active;  
};
 
void CommandQueue::push(Command* cmd)
{
  if (!_active)
  {
    cmd->execute();
    _cleanup(cmd);
    return;
  }
 
  // First remove all commands from _out_fifo.
  // This ensures that it's not going to be full which would block
  // process_commands() and its calling realtime thread.
  this->cleanup_commands();
 
  // Now push the command on _in_fifo; if the FIFO is full: retry, retry, ...
  while (!_in_fifo.push(cmd))
  {
    // We don't really know if that ever happens, so we abort in debug-mode:
    assert(false && "Error in _in_fifo.push()!");
    // TODO: avoid this sleep?
    std::this_thread::sleep_for(std::chrono::microseconds(50));
  }
}
 
void CommandQueue::wait()
{
  bool done = false;
  this->push(new WaitCommand(done));
 
  this->cleanup_commands();
  while (!done)
  {
    // TODO: avoid this sleep?
    std::this_thread::sleep_for(std::chrono::microseconds(50));
    this->cleanup_commands();
  }
}
 
}  // namespace apf
 
#endif