/* create.c - create, newpid */

#include 

local   int newpid();

/*------------------------------------------------------------------------
 *  create  -  create a process to start running a procedure
 *------------------------------------------------------------------------
 */
pid32   create(
          void          *procaddr,      /* procedure address            */
          uint32        ssize,          /* stack size in bytes          */
          pri16         priority,       /* process priority > 0         */
          char          *name,          /* name (for debugging)         */
          uint32        nargs,          /* number of args that follow   */
          ...
        )
{
        intmask         mask;           /* interrupt mask               */
        pid32           pid;            /* stores new process id        */
        struct  procent *prptr;         /* pointer to proc. table entry */
        int32           i;
        uint32          *a;             /* points to list of args       */
        uint32          *saddr;         /* stack address                */

        mask = disable();
        if (ssize < MINSTK) {
                ssize = MINSTK;
        }
        if  ((priority < 1) || ((pid=newpid()) == SYSERR) ||
             ((saddr = (uint32 *)getstk(ssize)) == (uint32 *)SYSERR) ) {
                restore(mask);
                return SYSERR;
        }

        prcount++;
        prptr = &proctab[pid];

        /* initialize process table entry for new process */

        prptr->prstate = PR_SUSP;       /* initial state is suspended   */
        prptr->prprio = priority;
        prptr->prstkbase = (char *)saddr;
        prptr->prstklen = ssize;
        prptr->prname[PNMLEN-1] = NULLCH;
        for (i=0 ; iprname[i]=name[i])!=NULLCH; i++)
                ;
        prptr->prsem = -1;
        prptr->prparent = (pid32)getpid();
        prptr->prhasmsg = FALSE;

        /* set up initial device descriptors for the shell              */
        prptr->prdesc[0] = CONSOLE;     /* stdin  is CONSOLE device     */
        prptr->prdesc[1] = CONSOLE;     /* stdout is CONSOLE device     */
        prptr->prdesc[2] = CONSOLE;     /* stderr is CONSOLE device     */

        /* Initialize stack as if the process was called                */

        *saddr = STACKMAGIC;

        /* push arguments */
        a = (uint32 *)(&nargs + 1);     /* start of args                */
        a += nargs -1;                  /* last argument                */
        for ( ; nargs > 4 ; nargs--)    /* machine dependent; copy args */
                *--saddr = *a--;        /* onto created process's stack */
        *--saddr = (long)procaddr;
        for(i = 11; i >= 4; i--)
                *--saddr = 0;
        for(i = 4; i > 0; i--) {
                if(i <= nargs)
                        *--saddr = *a--;
                else
                        *--saddr = 0;
        }
        *--saddr = (long)INITRET;       /* push on return address       */
        *--saddr = (long)0x00000053;    /* CPSR F bit set,              */
                                        /* Supervisor mode              */
        prptr->prstkptr = (char *)saddr;
        restore(mask);
        return pid;
}

/*------------------------------------------------------------------------
 *  newpid  -  Obtain a new (free) process ID
 *------------------------------------------------------------------------
 */
local   pid32   newpid(void)
{
        uint32  i;                      /* iterate through all processes*/
        static  pid32 nextpid = 1;      /* position in table to try or  */
                                        /*  one beyond end of table     */

        /* check all NPROC slots */

        for (i = 0; i < NPROC; i++) {
                nextpid %= NPROC;       /* wrap around to beginning */
                if (proctab[nextpid].prstate == PR_FREE) {
                        return nextpid++;
                } else {
                        nextpid++;
                }
        }
        return (pid32) SYSERR;
}