freebuf.c

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#include <xinu.h>

syscall freebuf(char *bufaddr)
{
    intmask mask;          /* Saved interrupt mask      */
    struct bpentry *bpptr; /* Pointer to entry in buftab    */
    bpid32 poolid;         /* ID of buffer's pool       */

    mask = disable();

    /* Extract pool ID from integer prior to buffer address */

    bufaddr -= sizeof(bpid32);
    poolid = *(bpid32 *)bufaddr;
    if (poolid < 0 || poolid >= nbpools)
    {
        restore(mask);
        return SYSERR;
    }

    /* Get address of correct pool entry in table */

    bpptr = &buftab[poolid];

    /* Insert buffer into list and signal semaphore */

    ((struct bpentry *)bufaddr)->bpnext = bpptr->bpnext;
    bpptr->bpnext = (struct bpentry *)bufaddr;
    signal(bpptr->bpsem);
    restore(mask);
    return OK;
}