usr/src/cmd/sh/stak.c

#
/*
 * UNIX shell
 *
 * S. R. Bourne
 * Bell Telephone Laboratories
 *
 */

#include        "defs.h"

STKPTR          stakbot=nullstr;


/* ========     storage allocation      ======== */

STKPTR  getstak(asize)
        INT             asize;
{       /* allocate requested stack */
        REG STKPTR      oldstak;
        REG INT         size;

        size=round(asize,BYTESPERWORD);
        oldstak=stakbot;
        staktop = stakbot += size;
        return(oldstak);
}

STKPTR  locstak()
{       /* set up stack for local use
         * should be followed by `endstak'
         */
        IF brkend-stakbot<BRKINCR
        THEN    setbrk(brkincr);
                IF brkincr < BRKMAX
                THEN    brkincr += 256;
                FI
        FI
        return(stakbot);
}

STKPTR  savstak()
{
        assert(staktop==stakbot);
        return(stakbot);
}

STKPTR  endstak(argp)
        REG STRING      argp;
{       /* tidy up after `locstak' */
        REG STKPTR      oldstak;
        *argp++=0;
        oldstak=stakbot; stakbot=staktop=round(argp,BYTESPERWORD);
        return(oldstak);
}

VOID    tdystak(x)
        REG STKPTR      x;
{
        /* try to bring stack back to x */
        WHILE ADR(stakbsy)>ADR(x)
        DO free(stakbsy);
           stakbsy = stakbsy->word;
        OD
        staktop=stakbot=max(ADR(x),ADR(stakbas));
        rmtemp(x);
}

stakchk()
{
        IF (brkend-stakbas)>BRKINCR+BRKINCR
        THEN    setbrk(-BRKINCR);
        FI
}

STKPTR  cpystak(x)
        STKPTR          x;
{
        return(endstak(movstr(x,locstak())));
}