ptsend.c

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#include <xinu.h>

syscall ptsend(int32 portid, umsg32 msg)
{
    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;
}