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xrevstack.c

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/*
 *      Copyright (c) 1989 by the Massachusetts Institute of Technology.
 *      For copying and distribution information, see the file
 *      "mit-copyright.h".
 *
 *      Modified for jwgc by Daniel Henninger.
 */

#include "mit-copyright.h"

#ifndef X_DISPLAY_MISSING

#ifndef TRUEREVSTACK
#include "X_gram.h"

x_gram *bottom_gram = NULL;
x_gram *unlinked = NULL;
int reverse_stack = 0;

void 
add_to_bottom(gram)
        x_gram *gram;
{
        if (bottom_gram) {
                bottom_gram->below = gram;
                gram->below = NULL;
                gram->above = bottom_gram;
                bottom_gram = gram;
        }
        else {
                gram->above = NULL;
                gram->below = NULL;
                bottom_gram = gram;
        }
}

/* ARGSUSED */
void 
pull_to_top(gram)
        x_gram *gram;
{
}

/* ARGSUSED */
void 
push_to_bottom(gram)
        x_gram *gram;
{
}

void 
delete_gram(gram)
        x_gram *gram;
{
        if (gram == bottom_gram) {
                if (gram->above) {
                        bottom_gram = gram->above;
                        bottom_gram->below = NULL;
                }
                else {
                        bottom_gram = NULL;
                }
        }
        else if (gram == unlinked) {
                if (gram->above) {
                        unlinked = gram->above;
                        unlinked->below = NULL;
                }
                else {
                        unlinked = NULL;
                }
        }
        else {
                if (gram->above)
                        gram->above->below = gram->below;
                gram->below->above = gram->above;
        }

        /*
         * fix up above & below pointers so that calling delete_gram again is
         * safe
         */
        gram->below = gram;
        gram->above = gram;
}

void 
unlink_gram(gram)
        x_gram *gram;
{
        delete_gram(gram);

        if (unlinked) {
                unlinked->below = gram;
                gram->below = NULL;
                gram->above = unlinked;
                unlinked = gram;
        }
        else {
                gram->above = NULL;
                gram->below = NULL;
                unlinked = gram;
        }
}

#endif

#ifdef TRUEREVSTACK

#include "X_gram.h"
#include "main.h"
#include <stdio.h>

x_gram *bottom_gram = NULL;
static x_gram *top_gram = NULL;

void 
pull_to_top(gram)
        x_gram *gram;
{
        if (gram == top_gram) {
                /* already here */
                return;
        }
        else if (top_gram == NULL) {
                /* no grams at all.  Make gram both top and bottom */
                top_gram = gram;
                bottom_gram = gram;
        }
        else if (gram == bottom_gram) {
                /* bottom gram is special case */
                bottom_gram = bottom_gram->above;
                bottom_gram->below = NULL;
                top_gram->above = gram;
                gram->below = top_gram;
                top_gram = gram;
        }
        else {
                /* normal case of a gram in the middle */
                gram->above->below = gram->below;
                gram->below->above = gram->above;
                top_gram->above = gram;
                gram->below = top_gram;
                gram->above = NULL;
                top_gram = gram;
        }
}

void 
push_to_bottom(gram)
        x_gram *gram;
{
        if (gram == bottom_gram) {
                /* already here */
                return;
        }
        else if (bottom_gram == NULL) {
                /* no grams at all.  Make gram both top and bottom */
                gram->above = NULL;
                gram->below = NULL;
                top_gram = gram;
                bottom_gram = gram;
        }
        else if (gram == top_gram) {
                /* top gram is special case */
                top_gram = top_gram->below;
                top_gram->above = NULL;
                bottom_gram->below = gram;
                gram->above = bottom_gram;
                bottom_gram = gram;
        }
        else {
                /* normal case of a gram in the middle */
                gram->above->below = gram->below;
                gram->below->above = gram->above;
                bottom_gram->below = gram;
                gram->above = bottom_gram;
                gram->below = NULL;
                bottom_gram = gram;
        }
}

void 
unlink_gram(gram)
        x_gram *gram;
{
        if (top_gram == bottom_gram) {
                /* the only gram in the stack */
                top_gram = NULL;
                bottom_gram = NULL;
        }
        else if (gram == top_gram) {
                top_gram = gram->below;
                top_gram->above = NULL;
        }
        else if (gram == bottom_gram) {
                bottom_gram = gram->above;
                bottom_gram->below = NULL;
        }
        else {
                gram->above->below = gram->below;
                gram->below->above = gram->above;
        }
}

void 
add_to_bottom(gram)
        x_gram *gram;
{
        if (bottom_gram == NULL) {
                gram->above = NULL;
                gram->below = NULL;
                top_gram = gram;
                bottom_gram = gram;
        }
        else {
                bottom_gram->below = gram;
                gram->above = bottom_gram;
                gram->below = NULL;
                bottom_gram = gram;
        }
}

#endif                          /* TRUEREVSTACK */

#endif                          /* X_DISPLAY_MISSING */

Last updated at Tue Dec 18 21:07:42 PST 2007.

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