omnithread.h

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    void wait(void);
	// wait for the condition variable to be signalled.  The mutex is
	// implicitly released before waiting and locked again after waking up.
	// If wait() is called by multiple threads, a signal may wake up more
	// than one thread.  See POSIX threads documentation for details.

    int timedwait(unsigned long secs, unsigned long nanosecs = 0);
	// timedwait() is given an absolute time to wait until.  To wait for a
	// relative time from now, use omni_thread::get_time. See POSIX threads
	// documentation for why absolute times are better than relative.
	// Returns 1 (true) if successfully signalled, 0 (false) if time
	// expired.

    void signal(void);
	// if one or more threads have called wait(), signal wakes up at least
	// one of them, possibly more.  See POSIX threads documentation for
	// details.

    void broadcast(void);
	// broadcast is like signal but wakes all threads which have called
	// wait().

private:
    // dummy copy constructor and operator= to prevent copying
    omni_condition(const omni_condition&);
    omni_condition& operator=(const omni_condition&);

OMNI_THREAD_EXPOSE:
    OMNI_CONDITION_IMPLEMENTATION
};


///////////////////////////////////////////////////////////////////////////
//
// Counting semaphore
//
///////////////////////////////////////////////////////////////////////////

class _OMNITHREAD_NTDLL_ omni_semaphore {

public:
    omni_semaphore(unsigned int initial = 1);
    ~omni_semaphore(void);

    void wait(void);
	// if semaphore value is > 0 then decrement it and carry on. If it's
	// already 0 then block.

    int trywait(void);
	// if semaphore value is > 0 then decrement it and return 1 (true).
	// If it's already 0 then return 0 (false).

    void post(void);
	// if any threads are blocked in wait(), wake one of them up. Otherwise
	// increment the value of the semaphore.

private:
    // dummy copy constructor and operator= to prevent copying
    omni_semaphore(const omni_semaphore&);
    omni_semaphore& operator=(const omni_semaphore&);

OMNI_THREAD_EXPOSE:
    OMNI_SEMAPHORE_IMPLEMENTATION
};

//
// A helper class for semaphores, similar to omni_mutex_lock above.
//

class _OMNITHREAD_NTDLL_ omni_semaphore_lock {
    omni_semaphore& sem;
public:
    omni_semaphore_lock(omni_semaphore& s) : sem(s) { sem.wait(); }
    ~omni_semaphore_lock(void) { sem.post(); }
private:
    // dummy copy constructor and operator= to prevent copying
    omni_semaphore_lock(const omni_semaphore_lock&);
    omni_semaphore_lock& operator=(const omni_semaphore_lock&);
};


///////////////////////////////////////////////////////////////////////////
//
// Thread
//
///////////////////////////////////////////////////////////////////////////

class _OMNITHREAD_NTDLL_ omni_thread {

public:

    enum priority_t {
	PRIORITY_LOW,
	PRIORITY_NORMAL,
	PRIORITY_HIGH
    };

    enum state_t {
	STATE_NEW,		// thread object exists but thread hasn't
				// started yet.
	STATE_RUNNING,		// thread is running.
	STATE_TERMINATED	// thread has terminated but storage has not
				// been reclaimed (i.e. waiting to be joined).
    };

    //
    // Constructors set up the thread object but the thread won't start until
    // start() is called. The create method can be used to construct and start
    // a thread in a single call.
    //

    omni_thread(void (*fn)(void*), void* arg = NULL,
		priority_t pri = PRIORITY_NORMAL);
    omni_thread(void* (*fn)(void*), void* arg = NULL,
		priority_t pri = PRIORITY_NORMAL);
	// these constructors create a thread which will run the given function
	// when start() is called.  The thread will be detached if given a
	// function with void return type, undetached if given a function
	// returning void*. If a thread is detached, storage for the thread is
	// reclaimed automatically on termination. Only an undetached thread
	// can be joined.

    void start(void);
	// start() causes a thread created with one of the constructors to
	// start executing the appropriate function.

protected:

    omni_thread(void* arg = NULL, priority_t pri = PRIORITY_NORMAL);
	// this constructor is used in a derived class.  The thread will
	// execute the run() or run_undetached() member functions depending on
	// whether start() or start_undetached() is called respectively.

    void start_undetached(void);
	// can be used with the above constructor in a derived class to cause
	// the thread to be undetached.  In this case the thread executes the
	// run_undetached member function.

    virtual ~omni_thread(void);
	// destructor cannot be called by user (except via a derived class).
	// Use exit() or cancel() instead. This also means a thread object must
	// be allocated with new - it cannot be statically or automatically
	// allocated. The destructor of a class that inherits from omni_thread
	// shouldn't be public either (otherwise the thread object can be
	// destroyed while the underlying thread is still running).

public:

    void join(void**);
	// join causes the calling thread to wait for another's completion,
	// putting the return value in the variable of type void* whose address
	// is given (unless passed a null pointer). Only undetached threads
	// may be joined. Storage for the thread will be reclaimed.

    void set_priority(priority_t);
	// set the priority of the thread.

    static omni_thread* create(void (*fn)(void*), void* arg = NULL,
			       priority_t pri = PRIORITY_NORMAL);
    static omni_thread* create(void* (*fn)(void*), void* arg = NULL,
			       priority_t pri = PRIORITY_NORMAL);
	// create spawns a new thread executing the given function with the
	// given argument at the given priority. Returns a pointer to the
	// thread object. It simply constructs a new thread object then calls
	// start.

    static void exit(void* return_value = NULL);
	// causes the calling thread to terminate.

    static omni_thread* self(void);
	// returns the calling thread's omni_thread object.
	// If the calling thread is not the main thread and
	// is not created using this library, returns 0.

    static void yield(void);
	// allows another thread to run.

    static void sleep(unsigned long secs, unsigned long nanosecs = 0);
	// sleeps for the given time.

    static void get_time(unsigned long* abs_sec, unsigned long* abs_nsec,
			 unsigned long rel_sec = 0, unsigned long rel_nsec=0);
	// calculates an absolute time in seconds and nanoseconds, suitable for
	// use in timed_waits on condition variables, which is the current time
	// plus the given relative offset.


    static void stacksize(unsigned long sz);
    static unsigned long stacksize();
        // Use this value as the stack size when spawning a new thread.
        // The default value (0) means that the thread library default is
        // to be used.

private:

    virtual void run(void* arg) {}
    virtual void* run_undetached(void* arg) { return NULL; }
	// can be overridden in a derived class.  When constructed using the
	// the constructor omni_thread(void*, priority_t), these functions are
	// called by start() and start_undetached() respectively.

    void common_constructor(void* arg, priority_t pri, int det);
	// implements the common parts of the constructors.

    omni_mutex mutex;
	// used to protect any members which can change after construction,
	// i.e. the following 2 members:

    state_t _state;
    priority_t _priority;

    static omni_mutex* next_id_mutex;
    static int next_id;
    int _id;

    void (*fn_void)(void*);
    void* (*fn_ret)(void*);
    void* thread_arg;
    int detached;

public:

    priority_t priority(void) {

	// return this thread's priority.

	omni_mutex_lock l(mutex);
	return _priority;
    }

    state_t state(void) {

	// return thread state (invalid, new, running or terminated).

	omni_mutex_lock l(mutex);
	return _state;
    }

    int id(void) { return _id; }
	// return unique thread id within the current process.


    // This class plus the instance of it declared below allows us to execute
    // some initialisation code before main() is called.

    class _OMNITHREAD_NTDLL_ init_t {
	static int count;
    public:
	init_t(void);
    };

    friend class init_t;

OMNI_THREAD_EXPOSE:
    OMNI_THREAD_IMPLEMENTATION
};

#ifndef __rtems__
static omni_thread::init_t omni_thread_init;
#else
// RTEMS calls global Ctor/Dtor in a context that is not
// a posix thread. Calls to functions to pthread_self() in
// that context returns NULL. 
// So, for RTEMS we will make the thread initialization at the
// beginning of the Init task that has a posix context.
#endif

#endif