usr/src/cmd/sh/stak.h

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

/* To use stack as temporary workspace across
 * possible storage allocation (eg name lookup)
 * a) get ptr from `relstak'
 * b) can now use `pushstak'
 * c) then reset with `setstak'
 * d) `absstak' gives real address if needed
 */
#define         relstak()       (staktop-stakbot)
#define         absstak(x)      (stakbot+Rcheat(x))
#define         setstak(x)      (staktop=absstak(x))
#define         pushstak(c)     (*staktop++=(c))
#define         zerostak()      (*staktop=0)

/* Used to address an item left on the top of
 * the stack (very temporary)
 */
#define         curstak()       (staktop)

/* `usestak' before `pushstak' then `fixstak'
 * These routines are safe against heap
 * being allocated.
 */
#define         usestak()       {locstak();}

/* for local use only since it hands
 * out a real address for the stack top
 */
STKPTR          locstak();

/* Will allocate the item being used and return its
 * address (safe now).
 */
#define         fixstak()       endstak(staktop)

/* For use after `locstak' to hand back
 * new stack top and then allocate item
 */
STKPTR          endstak();

/* Copy a string onto the stack and
 * allocate the space.
 */
STKPTR          cpystak();

/* Allocate given ammount of stack space */
STKPTR          getstak();

/* A chain of ptrs of stack blocks that
 * have become covered by heap allocation.
 * `tdystak' will return them to the heap.
 */
BLKPTR          stakbsy;

/* Base of the entire stack */
STKPTR          stakbas;

/* Top of entire stack */
STKPTR          brkend;

/* Base of current item */
STKPTR          stakbot;

/* Top of current item */
STKPTR          staktop;

/* Used with tdystak */
STKPTR          savstak();