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reinstate NULL cast by request, where the NULL was being passed as a vararg

/*	$NetBSD: hack.pager.c,v 1.21 2011/09/01 07:18:50 plunky Exp $	*/

/*
 * Copyright (c) 1985, Stichting Centrum voor Wiskunde en Informatica,
 * Amsterdam
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 * - Redistributions of source code must retain the above copyright notice,
 * this list of conditions and the following disclaimer.
 *
 * - Redistributions in binary form must reproduce the above copyright
 * notice, this list of conditions and the following disclaimer in the
 * documentation and/or other materials provided with the distribution.
 *
 * - Neither the name of the Stichting Centrum voor Wiskunde en
 * Informatica, nor the names of its contributors may be used to endorse or
 * promote products derived from this software without specific prior
 * written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
 * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
 * OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/*
 * Copyright (c) 1982 Jay Fenlason <hack@gnu.org>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL
 * THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
 * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include <sys/cdefs.h>
#ifndef lint
__RCSID("$NetBSD: hack.pager.c,v 1.21 2011/09/01 07:18:50 plunky Exp $");
#endif				/* not lint */

/* This file contains the command routine dowhatis() and a pager. */
/*
 * Also readmail() and doshell(), and generally the things that contact the
 * outside world.
 */

#include <sys/types.h>
#include <sys/wait.h>
#include <signal.h>
#include <stdlib.h>
#include <unistd.h>
#include "hack.h"
#include "extern.h"

static void intruph(int);
static void page_more(FILE *, int);
static int page_file(const char *, boolean);
static int child(int);

int
dowhatis(void)
{
	FILE           *fp;
	char            bufr[BUFSZ + 6];
	char           *buf = &bufr[6], *ep, q;

	if (!(fp = fopen(DATAFILE, "r")))
		pline("Cannot open data file!");
	else {
		pline("Specify what? ");
		q = readchar();
		if (q != '\t')
			while (fgets(buf, BUFSZ, fp))
				if (*buf == q) {
					ep = strchr(buf, '\n');
					if (ep)
						*ep = 0;
					/* else: bad data file */
					else {
						pline("Bad data file!");
						(void) fclose(fp);
						return(0);
					}
					/* Expand tab 'by hand' */
					if (buf[1] == '\t') {
						buf = bufr;
						buf[0] = q;
						(void) strncpy(buf + 1, "       ", 7);
					}
					pline("%s", buf);
					if (ep[-1] == ';') {
						pline("More info? ");
						if (readchar() == 'y') {
							page_more(fp, 1);	/* does fclose() */
							return (0);
						}
					}
					(void) fclose(fp);	/* kopper@psuvax1 */
					return (0);
				}
		pline("I've never heard of such things.");
		(void) fclose(fp);
	}
	return (0);
}

/* make the paging of a file interruptible */
static int      got_intrup;

static void
intruph(int n __unused)
{
	got_intrup++;
}

/* simple pager, also used from dohelp() */
/* strip: nr of chars to be stripped from each line (0 or 1) */
static void
page_more(FILE *fp, int strip)
{
	char           *bufr, *ep;
	sig_t           prevsig = signal(SIGINT, intruph);

	set_pager(0);
	bufr = alloc(CO);
	bufr[CO - 1] = 0;
	while (fgets(bufr, CO - 1, fp) && (!strip || *bufr == '\t') && !got_intrup) {
		ep = strchr(bufr, '\n');
		if (ep)
			*ep = 0;
		if (page_line(bufr + strip)) {
			set_pager(2);
			goto ret;
		}
	}
	set_pager(1);
ret:
	free(bufr);
	(void) fclose(fp);
	(void) signal(SIGINT, prevsig);
	got_intrup = 0;
}

static boolean  whole_screen = TRUE;
#define	PAGMIN	12		/* minimum # of lines for page below level
				 * map */

void
set_whole_screen(void)
{				/* called in termcap as soon as LI is known */
	whole_screen = (LI - ROWNO - 2 <= PAGMIN || !CD);
}

#ifdef NEWS
int
readnews(void)
{
	int             ret;

	whole_screen = TRUE;	/* force a docrt(), our first */
	ret = page_file(NEWS, TRUE);
	set_whole_screen();
	return (ret);		/* report whether we did docrt() */
}
#endif	/* NEWS */

/* mode:  0: open  1: wait+close  2: close */
void
set_pager(int mode)
{
	static boolean  so;
	if (mode == 0) {
		if (!whole_screen) {
			/* clear topline */
			clrlin();
			/* use part of screen below level map */
			curs(1, ROWNO + 4);
		} else {
			cls();
		}
		so = flags.standout;
		flags.standout = 1;
	} else {
		if (mode == 1) {
			curs(1, LI);
			more();
		}
		flags.standout = so;
		if (whole_screen)
			docrt();
		else {
			curs(1, ROWNO + 4);
			cl_eos();
		}
	}
}

int
page_line(const char *s)	/* returns 1 if we should quit */
{
	if (cury == LI - 1) {
		if (!*s)
			return (0);	/* suppress blank lines at top */
		putchar('\n');
		cury++;
		cmore("q\033");
		if (morc) {
			morc = 0;
			return (1);
		}
		if (whole_screen)
			cls();
		else {
			curs(1, ROWNO + 4);
			cl_eos();
		}
	}
	puts(s);
	cury++;
	return (0);
}

/*
 * Flexible pager: feed it with a number of lines and it will decide
 * whether these should be fed to the pager above, or displayed in a
 * corner.
 * Call:
 *	cornline(0, title or 0)	: initialize
 *	cornline(1, text)	: add text to the chain of texts
 *	cornline(2, morcs)	: output everything and cleanup
 *	cornline(3, 0)		: cleanup
 */

void
cornline(int mode, const char *text)
{
	static struct line {
		struct line    *next_line;
		char           *line_text;
	}              *texthead, *texttail;
	static int      maxlen;
	static int      linect;
	struct line    *tl;

	if (mode == 0) {
		texthead = 0;
		maxlen = 0;
		linect = 0;
		if (text) {
			cornline(1, text);	/* title */
			cornline(1, "");	/* blank line */
		}
		return;
	}
	if (mode == 1) {
		int             len;

		if (!text)
			return;	/* superfluous, just to be sure */
		linect++;
		len = strlen(text);
		if (len > maxlen)
			maxlen = len;
		tl = alloc(len + sizeof(*tl) + 1);
		tl->next_line = 0;
		tl->line_text = (char *) (tl + 1);
		(void) strcpy(tl->line_text, text);
		if (!texthead)
			texthead = tl;
		else
			texttail->next_line = tl;
		texttail = tl;
		return;
	}
	/* --- now we really do it --- */
	if (mode == 2 && linect == 1)	/* topline only */
		pline("%s", texthead->line_text);
	else if (mode == 2) {
		int             curline, lth;

		if (flags.toplin == 1)
			more();	/* ab@unido */
		remember_topl();

		lth = CO - maxlen - 2;	/* Use full screen width */
		if (linect < LI && lth >= 10) {	/* in a corner */
			home();
			cl_end();
			flags.toplin = 0;
			curline = 1;
			for (tl = texthead; tl; tl = tl->next_line) {
				curs(lth, curline);
				if (curline > 1)
					cl_end();
				putsym(' ');
				putstr(tl->line_text);
				curline++;
			}
			curs(lth, curline);
			cl_end();
			cmore(text);
			home();
			cl_end();
			docorner(lth, curline - 1);
		} else {	/* feed to pager */
			set_pager(0);
			for (tl = texthead; tl; tl = tl->next_line) {
				if (page_line(tl->line_text)) {
					set_pager(2);
					goto cleanup;
				}
			}
			if (text) {
				cgetret(text);
				set_pager(2);
			} else
				set_pager(1);
		}
	}
cleanup:
	while ((tl = texthead) != NULL) {
		texthead = tl->next_line;
		free(tl);
	}
}

int
dohelp(void)
{
	char            c;

	pline("Long or short help? ");
	while (((c = readchar()) != 'l') && (c != 's') && !strchr(quitchars, c))
		sound_bell();
	if (!strchr(quitchars, c))
		(void) page_file((c == 'l') ? HELP : SHELP, FALSE);
	return (0);
}

/* return: 0 - cannot open fnam; 1 - otherwise */
static int
page_file(const char *fnam, boolean silent)
{
#ifdef DEF_PAGER		/* this implies that UNIX is defined */
	{
		/* use external pager; this may give security problems */

		int             fd = open(fnam, O_RDONLY);

		if (fd < 0) {
			if (!silent)
				pline("Cannot open %s.", fnam);
			return (0);
		}
		if (child(1)) {

			/*
			 * Now that child() does a setuid(getuid()) and a
			 * chdir(), we may not be able to open file fnam
			 * anymore, so make it stdin.
			 */
			(void) close(0);
			if (dup(fd)) {
				if (!silent)
					printf("Cannot open %s as stdin.\n", fnam);
			} else {
				execl(catmore, "page", (char *)NULL);
				if (!silent)
					printf("Cannot exec %s.\n", catmore);
			}
			exit(1);
		}
		(void) close(fd);
	}
#else	/* DEF_PAGER */
	{
		FILE           *f;	/* free after Robert Viduya */

		if ((f = fopen(fnam, "r")) == (FILE *) 0) {
			if (!silent) {
				home();
				perror(fnam);
				flags.toplin = 1;
				pline("Cannot open %s.", fnam);
			}
			return (0);
		}
		page_more(f, 0);
	}
#endif	/* DEF_PAGER */

	return (1);
}

#ifdef UNIX
#ifdef SHELL
int
dosh(void)
{
	char           *str;
	if (child(0)) {
		if ((str = getenv("SHELL")) != NULL)
			execl(str, str, (char *)NULL);
		else
			execl("/bin/sh", "sh", (char *)NULL);
		pline("sh: cannot execute.");
		exit(1);
	}
	return (0);
}
#endif	/* SHELL */

static int
child(int wt)
{
	int             status;
	int             f;

	f = fork();
	if (f == 0) {		/* child */
		settty(NULL);	/* also calls end_screen() */
		(void) setuid(getuid());
		(void) setgid(getgid());
#ifdef CHDIR
		(void) chdir(getenv("HOME"));
#endif	/* CHDIR */
		return (1);
	}
	if (f == -1) {		/* cannot fork */
		pline("Fork failed. Try again.");
		return (0);
	}
	/* fork succeeded; wait for child to exit */
	(void) signal(SIGINT, SIG_IGN);
	(void) signal(SIGQUIT, SIG_IGN);
	(void) wait(&status);
	gettty();
	setftty();
	(void) signal(SIGINT, done1);
#ifdef WIZARD
	if (wizard)
		(void) signal(SIGQUIT, SIG_DFL);
#endif	/* WIZARD */
	if (wt)
		getret();
	docrt();
	return (0);
}
#endif	/* UNIX */