/* $Header: /nw/tony/src/stevie/src/RCS/linefunc.c,v 1.2 89/03/11 22:42:32 tony Exp $
 *
 * Basic line-oriented motions.
 */

#include "stevie.h"

/*
 * nextline(curr)
 *
 * Return a pointer to the beginning of the next line after the one
 * referenced by 'curr'. Return NULL if there is no next line (at EOF).
 */

LNPTR *
nextline(curr)
LNPTR    *curr;
{
    static  LNPTR    next;

        if (curr->linep && curr->linep->next != Fileend->linep) {
                next.index = 0;
                next.linep = curr->linep->next;
                return &next;
        }
    return (LNPTR *) NULL;
}

/*
 * prevline(curr)
 *
 * Return a pointer to the beginning of the line before the one
 * referenced by 'curr'. Return NULL if there is no prior line.
 */

LNPTR *
prevline(curr)
LNPTR    *curr;
{
    static  LNPTR    prev;

        if (curr->linep->prev != Filetop->linep) {
                prev.index = 0;
                prev.linep = curr->linep->prev;
                return &prev;
        }
    return (LNPTR *) NULL;
}

/*
 * coladvance(p,col)
 *
 * Try to advance to the specified column, starting at p.
 */

LNPTR *
coladvance(p, col)
LNPTR    *p;
register int    col;
{
        static  LNPTR    lp;
        register int    c, in;

        lp.linep = p->linep;
        lp.index = p->index;

        /* If we're on a blank ('\n' only) line, we can't do anything */
        if (lp.linep->s[lp.index] == '\0')
                return &lp;
        /* try to advance to the specified column */
        for ( c=0; col-- > 0; c++ ) {
                /* Count a tab for what it's worth (if list mode not on) */
                if ( gchar(&lp) == TAB && !P(P_LS) ) {
                        in = ((P(P_TS)-1) - c%P(P_TS));
                        col -= in;
                        c += in;
                }
                /* Don't go past the end of */
                /* the file or the line. */
                if (inc(&lp)) {
                        dec(&lp);
                        break;
                }
        }
        return &lp;
}