/* ptsend.c - ptsend */

#include 

/*------------------------------------------------------------------------
 *  ptsend  -  Send a message to a port by adding it to the queue
 *------------------------------------------------------------------------
 */
syscall ptsend(
          int32         portid,         /* ID of port to use            */
          umsg32        msg             /* Message to send              */
        )
{
        intmask mask;                   /* Saved interrupt mask         */
        struct  ptentry *ptptr;         /* Pointer to table entry       */
        int32   seq;                    /* Local copy of sequence num.  */
        struct  ptnode  *msgnode;       /* Allocated message node       */
        struct  ptnode  *tailnode;      /* Last node in port or NULL    */

        mask = disable();
        if ( isbadport(portid) ||
             (ptptr= &porttab[portid])->ptstate != PT_ALLOC ) {
                restore(mask);
                return SYSERR;
        }

        /* Wait for space and verify port has not been reset */

        seq = ptptr->ptseq;             /* Record original sequence     */
        if (wait(ptptr->ptssem) == SYSERR
            || ptptr->ptstate != PT_ALLOC
            || ptptr->ptseq != seq) {
                restore(mask);
                return SYSERR;
        }
        if (ptfree == NULL) {
                panic("Port system ran out of message nodes");
        }

        /* Obtain node from free list by unlinking */

        msgnode = ptfree;               /* Point to first free node     */
        ptfree  = msgnode->ptnext;      /* Unlink from the free list    */
        msgnode->ptnext = NULL;         /* Set fields in the node       */
        msgnode->ptmsg  = msg;

        /* Link into queue for the specified port */

        tailnode = ptptr->pttail;
        if (tailnode == NULL) {         /* Queue for port was empty     */
                ptptr->pttail = ptptr->pthead = msgnode;
        } else {                        /* Insert new node at tail      */
                tailnode->ptnext = msgnode;
                ptptr->pttail = msgnode;
        }
        signal(ptptr->ptrsem);
        restore(mask);
        return OK;
}