mqueue.inl

ecos实时嵌入式操作系统

// put() copies len bytes of *buf into the queue at priority prio
CYGPRI_KERNEL_SYNCH_MQUEUE_INLINE Cyg_Mqueue::qerr_t
Cyg_Mqueue::put( const char *buf, size_t len, unsigned int prio, bool block
#ifdef CYGFUN_KERNEL_THREADS_TIMER
                 , cyg_tick_count timeout
#endif
               )
{
    CYG_REPORT_FUNCTYPE( "err=%d");
    CYG_REPORT_FUNCARG4( "buf=%08x, len=%ld, prio=%ud, block=%d",
                         buf, len, prio, block==true );
    CYG_CHECK_DATA_PTRC( buf );
    CYG_ASSERT_THISC();
    CYG_PRECONDITIONC( len <= (size_t)msgsize );

    qerr_t err;
    struct qentry *qtmp, *qent;

    // wait till a freelist entry is available
    if ( true == block ) {
#ifdef CYGFUN_KERNEL_THREADS_TIMER
        if ( timeout != 0) {
	    if ( false == putsem.wait(timeout) ) {
                err = TIMEOUT;
                goto exit;
            }
        }
        else
#endif
        if ( false == putsem.wait() ) {
            err = INTR;
            goto exit;
        }
    } else { 
        if ( false == putsem.trywait() ) {
            err = WOULDBLOCK;
            goto exit;
        }
    }

    // prevent preemption when fiddling with important members
    Cyg_Scheduler::lock();

    CYG_ASSERT_THISC();

    // get a queue entry from the freelist
    // don't need to check the freelist - the semaphore tells us there's
    // definitely a usable non-busy one there. It's just a question of
    // locating it.

    if (!freelist->busy) { // fast-track common case
        qent     = freelist;
        freelist = freelist->next;
    } else {
        for ( qtmp=freelist; !qtmp->next->busy; qtmp=qtmp->next )
            CYG_EMPTY_STATEMENT; // skip through
        qent       = qtmp->next;
        qtmp->next = qent->next;
    }
            
    // now put it in place in q

    if ( NULL == q ) {
        q = qent;
        q->next = NULL;
    } else {
        struct qentry **qentp;

        // insert into queue according to prio
        for ( qentp=&q; NULL != *qentp; qentp = &((*qentp)->next) ) {
            if ((*qentp)->priority < prio)
                break;
        } // for

        qent->next = *qentp;
        *qentp = qent;
    } // else
    
    qent->priority = prio; // have to set this now so when the sched is
                           // unlocked, other qent's can be added in the
                           // right place
    qent->busy = true; // let things know this entry should be ignored until
                       // it's finished having its data copied

    // unlock the scheduler, and potentially switch threads, but
    // that's okay now. We don't want it locked for the expensive memcpy
    Cyg_Scheduler::unlock();

    qent->buflen   = len;
    memcpy( qent->buf(), buf, len );

    // make available now - setting non-atomically is alright if you think
    // about it - the only thing that matters is that it's completed before
    // the post()
    qent->busy = false;

    // if we have to notify someone, we only do it if no-one's already
    // sitting waiting for a message to appear, AND if it's a transition
    // from empty to non-empty

    if ( callback != NULL && !getsem.waiting() && (0 == getsem.peek()) ) {
        getsem.post();        
        callback( *this, callback_data );
    } else
        getsem.post();        

    err = OK;

 exit:
    CYG_ASSERT_THISC();
    CYG_REPORT_RETVAL(err);
    return err;
} // Cyg_Mqueue::put()

//------------------------------------------------------------------------


// get() returns the oldest highest priority message in the queue in *buf
// and sets *prio to the priority (if prio is non-NULL) and *len to the
// actual message size

CYGPRI_KERNEL_SYNCH_MQUEUE_INLINE Cyg_Mqueue::qerr_t
Cyg_Mqueue::get( char *buf, size_t *len, unsigned int *prio, bool block
#ifdef CYGFUN_KERNEL_THREADS_TIMER
                 , cyg_tick_count timeout
#endif
               )
{
    CYG_REPORT_FUNCTYPE( "err=%d");
    CYG_REPORT_FUNCARG4( "buf=%08x, len=%08x, prio=%08x, block=%d",
                         buf, len, prio, block==true );
    CYG_CHECK_DATA_PTRC( buf );
    CYG_CHECK_DATA_PTRC( len );
    if ( NULL != prio )
        CYG_CHECK_DATA_PTRC( prio );
    CYG_ASSERT_THISC();

    qerr_t err;
    struct qentry *qent;

    // wait till a q entry is available
    if ( true == block ) {
#ifdef CYGFUN_KERNEL_THREADS_TIMER
        if ( timeout != 0) {
            if ( false == getsem.wait(timeout) ) {
                err = TIMEOUT;
                goto exit;
            }
        }
        else
#endif
        if ( false == getsem.wait() ) {
            err = INTR;
            goto exit;
        }
    } else { 
        if ( false == getsem.trywait() ) {
            err = WOULDBLOCK;
            goto exit;
        }
    }

    // prevent preemption when fiddling with important members
    
    Cyg_Scheduler::lock();
    
    // don't need to check the q - the semaphore tells us there's
    // definitely a usable non-busy one there. It's just a question of
    // locating it.
    
    if ( !q->busy ) {   // fast-track the common case
        qent       = q;
        q          = qent->next;
    } else {
        struct qentry *qtmp;

        for ( qtmp=q; !qtmp->next->busy; qtmp=qtmp->next )
            CYG_EMPTY_STATEMENT; // skip through

        qent = qtmp->next;
        qtmp->next = qent->next;
    } // else

    // now stick at front of freelist, but marked busy
    qent->next = freelist;
    freelist   = qent;

    qent->busy = true; // don't let it truly be part of the freelist just yet
                       // till the data is copied out

    // unlock the scheduler, and potentially switch threads, but
    // that's okay now. We don't want it locked for the expensive memcpy
    Cyg_Scheduler::unlock();

    *len  = qent->buflen;
    if ( NULL != prio )
        *prio = qent->priority;
    memcpy( buf, qent->buf(), *len );

    // make available now - setting non-atomically is alright if you think
    // about it - the only thing that matters is that it's completed before
    // the post()
    qent->busy = false;

    putsem.post();

    err = OK;

 exit:
    CYG_ASSERT_THISC();
    CYG_REPORT_RETVAL(err);
    return err;
    
} // Cyg_Mqueue::get()

//------------------------------------------------------------------------

// count() returns the number of messages in the queue
inline long
Cyg_Mqueue::count()
{
    CYG_REPORT_FUNCTYPE("curmsgs=%d");
    
    long curmsgs = (long)getsem.peek();

    CYG_REPORT_RETVAL(curmsgs);
    return curmsgs;    
} // Cyg_Mqueue::count()

//------------------------------------------------------------------------


// Supply a callback function to call (with the supplied data argument)
// when the queue goes from empty to non-empty (unless someone's already
// doing a get()). This returns the old callback_fn, and if olddata is
// non-NULL sets it to the old data (yes, really!)
CYGPRI_KERNEL_SYNCH_MQUEUE_INLINE Cyg_Mqueue::callback_fn_t
Cyg_Mqueue::setnotify( callback_fn_t callback_fn, CYG_ADDRWORD data,
                       CYG_ADDRWORD *olddata)
{
    CYG_REPORT_FUNCTYPE("old callback=%08x");
    CYG_REPORT_FUNCARG3XV( callback_fn, data, olddata );
    if ( NULL != callback_fn )
        CYG_CHECK_FUNC_PTRC( callback_fn );
    if (NULL != olddata)
        CYG_CHECK_DATA_PTRC( olddata );

    callback_fn_t oldfn;

    // Need to prevent preemption for accessing common structures
    // Just locking the scheduler has the least overhead
    Cyg_Scheduler::lock();

    oldfn = callback;
    if (NULL != olddata)
        *olddata = callback_data;

    callback_data = data;
    callback      = callback_fn;

    Cyg_Scheduler::unlock();

    CYG_REPORT_RETVAL(oldfn);
    return oldfn;
}

//------------------------------------------------------------------------

#endif /* CYGONCE_KERNEL_MQUEUE_INL multiple inclusion protection */

/* EOF mqueue.inl */