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prevent file races by obtaining an fd for the RCS file and
do our operations on that, this is safe and guarantees we
can operate on the file until we close(2) it.

a fix is coming for the remaining races in our diff code.
okay niallo@ and ray@

/*	$OpenBSD: rcsdiff.c,v 1.58 2006/04/26 21:55:22 joris Exp $	*/
/*
 * Copyright (c) 2005 Joris Vink <joris@openbsd.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. 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 "includes.h"

#include "rcsprog.h"
#include "diff.h"

static int rcsdiff_file(RCSFILE *, RCSNUM *, const char *);
static int rcsdiff_rev(RCSFILE *, RCSNUM *, RCSNUM *);

static int flags = 0;
static int kflag = RCS_KWEXP_ERR;

int
rcsdiff_main(int argc, char **argv)
{
	int fd, i, ch, status;
	RCSNUM *rev1, *rev2;
	RCSFILE *file;
	char fpath[MAXPATHLEN], *rev_str1, *rev_str2;

	rev1 = rev2 = NULL;
	rev_str1 = rev_str2 = NULL;
	status = 0;

	strlcpy(diffargs, "diff", sizeof(diffargs));

	while ((ch = rcs_getopt(argc, argv, "ck:nqr:TuVx::z::")) != -1) {
		switch (ch) {
		case 'c':
			strlcat(diffargs, " -c", sizeof(diffargs));
			diff_format = D_CONTEXT;
			break;
		case 'k':
			kflag = rcs_kflag_get(rcs_optarg);
			if (RCS_KWEXP_INVAL(kflag)) {
				warnx("invalid RCS keyword substitution mode");
				(usage)();
				exit(1);
			}
			break;
		case 'n':
			strlcat(diffargs, " -n", sizeof(diffargs));
			diff_format = D_RCSDIFF;
			break;
		case 'q':
			flags |= QUIET;
			break;
		case 'u':
			strlcat(diffargs, " -u", sizeof(diffargs));
			diff_format = D_UNIFIED;
			break;
		case 'r':
			rcs_setrevstr2(&rev_str1, &rev_str2, rcs_optarg);
			break;
		case 'T':
			/*
			 * kept for compatibility
			 */
			break;
		case 'V':
			printf("%s\n", rcs_version);
			exit(0);
			/* NOTREACHED */
		case 'x':
			/* Use blank extension if none given. */
			rcs_suffixes = rcs_optarg ? rcs_optarg : "";
			break;
		case 'z':
			timezone_flag = rcs_optarg;
			break;
		default:
			(usage)();
			exit (1);
		}
	}

	argc -= rcs_optind;
	argv += rcs_optind;

	if (argc == 0) {
		warnx("no input file");
		(usage)();
		exit(1);
	}

	for (i = 0; i < argc; i++) {
		fd = rcs_statfile(argv[i], fpath, sizeof(fpath), flags);
		if (fd < 0)
			continue;

		if ((file = rcs_open(fpath, fd,
		    RCS_READ|RCS_PARSE_FULLY)) == NULL)
			continue;

		rcs_kwexp_set(file, kflag);

		if (rev_str1 != NULL) {
			if ((rev1 = rcs_getrevnum(rev_str1, file)) == NULL)
				errx(1, "bad revision number");
		}
		if (rev_str2 != NULL) {
			if ((rev2 = rcs_getrevnum(rev_str2, file)) == NULL)
				errx(1, "bad revision number");
		}

		if (!(flags & QUIET)) {
			fprintf(stderr, "%s\n", RCS_DIFF_DIV);
			fprintf(stderr, "RCS file: %s\n", fpath);
		}

		diff_file = argv[i];

		/* No revisions given. */
		if (rev_str1 == NULL) {
			if (rcsdiff_file(file, file->rf_head, argv[i]) < 0)
				status = 2;
		/* One revision given. */
		} else if (rev_str2 == NULL) {
			if (rcsdiff_file(file, rev1, argv[i]) < 0)
				status = 2;
		/* Two revisions given. */
		} else {
			if (rcsdiff_rev(file, rev1, rev2) < 0)
				status = 2;
		}

		rcs_close(file);

		if (rev1 != NULL) {
			rcsnum_free(rev1);
			rev1 = NULL;
		}
		if (rev2 != NULL) {
			rcsnum_free(rev2);
			rev2 = NULL;
		}
	}

	return (status);
}

void
rcsdiff_usage(void)
{
	fprintf(stderr,
	    "usage: rcsdiff [-cnquV] [-kmode] [-rrev] "
	    "[-xsuffixes] [-ztz] file ...\n");
}

static int
rcsdiff_file(RCSFILE *file, RCSNUM *rev, const char *filename)
{
	int ret, fd;
	time_t t;
	struct stat st;
	char path1[MAXPATHLEN], path2[MAXPATHLEN];
	BUF *b1, *b2;
	char rbuf[64];
	struct tm *tb;
	struct timeval tv[2], tv2[2];

	memset(&tv, 0, sizeof(tv));
	memset(&tv2, 0, sizeof(tv2));

	ret = -1;
	b1 = b2 = NULL;

	diff_rev1 = rev;
	diff_rev2 = NULL;

	if ((fd = open(filename, O_RDONLY)) == -1) {
		warn("%s", filename);
		goto out;
	}

	rcsnum_tostr(rev, rbuf, sizeof(rbuf));
	if (!(flags & QUIET)) {
		fprintf(stderr, "retrieving revision %s\n", rbuf);
		fprintf(stderr, "%s -r%s %s\n", diffargs, rbuf, filename);
	}

	if ((b1 = rcs_getrev(file, rev)) == NULL) {
		warnx("failed to retrieve revision %s", rbuf);
		goto out;
	}

	b1 = rcs_kwexp_buf(b1, file, rev);
	tv[0].tv_sec = (long)rcs_rev_getdate(file, rev);
	tv[1].tv_sec = tv[0].tv_sec;

	if ((b2 = rcs_buf_load(filename, BUF_AUTOEXT)) == NULL) {
		warnx("failed to load file: `%s'", filename);
		goto out;
	}

	/* XXX - GNU uses GMT */
	if (fstat(fd, &st) == -1)
		err(1, "%s", filename);

	tb = gmtime(&st.st_mtime);
	t = mktime(tb);

	tv2[0].tv_sec = t;
	tv2[1].tv_sec = t;

	strlcpy(path1, rcs_tmpdir, sizeof(path1));
	strlcat(path1, "/diff1.XXXXXXXXXX", sizeof(path1));
	rcs_buf_write_stmp(b1, path1, 0600);

	rcs_buf_free(b1);
	b1 = NULL;

	if (utimes(path1, (const struct timeval *)&tv) < 0)
		warn("utimes");

	strlcpy(path2, rcs_tmpdir, sizeof(path2));
	strlcat(path2, "/diff2.XXXXXXXXXX", sizeof(path2));
	rcs_buf_write_stmp(b2, path2, 0600);

	rcs_buf_free(b2);
	b2 = NULL;

	if (utimes(path2, (const struct timeval *)&tv2) < 0)
		warn("utimes");

	rcs_diffreg(path1, path2, NULL);
	ret = 0;

out:
	if (fd != -1)
		(void)close(fd);
	if (b1 != NULL)
		rcs_buf_free(b1);
	if (b2 != NULL)
		rcs_buf_free(b2);

	return (ret);
}

static int
rcsdiff_rev(RCSFILE *file, RCSNUM *rev1, RCSNUM *rev2)
{
	int ret;
	char path1[MAXPATHLEN], path2[MAXPATHLEN];
	BUF *b1, *b2;
	char rbuf1[64], rbuf2[64];
	struct timeval tv[2], tv2[2];

	ret = -1;
	b1 = b2 = NULL;
	memset(&tv, 0, sizeof(tv));
	memset(&tv2, 0, sizeof(tv2));

	diff_rev1 = rev1;
	diff_rev2 = rev2;

	rcsnum_tostr(rev1, rbuf1, sizeof(rbuf1));
	if (!(flags & QUIET))
		fprintf(stderr, "retrieving revision %s\n", rbuf1);

	if ((b1 = rcs_getrev(file, rev1)) == NULL) {
		warnx("failed to retrieve revision %s", rbuf1);
		goto out;
	}

	b1 = rcs_kwexp_buf(b1, file, rev1);
	tv[0].tv_sec = (long)rcs_rev_getdate(file, rev1);
	tv[1].tv_sec = tv[0].tv_sec;

	rcsnum_tostr(rev2, rbuf2, sizeof(rbuf2));
	if (!(flags & QUIET))
		fprintf(stderr, "retrieving revision %s\n", rbuf2);

	if ((b2 = rcs_getrev(file, rev2)) == NULL) {
		warnx("failed to retrieve revision %s", rbuf2);
		goto out;
	}

	b2 = rcs_kwexp_buf(b2, file, rev2);
	tv2[0].tv_sec = (long)rcs_rev_getdate(file, rev2);
	tv2[1].tv_sec = tv2[0].tv_sec;

	if (!(flags & QUIET))
		fprintf(stderr, "%s -r%s -r%s\n", diffargs, rbuf1, rbuf2);

	strlcpy(path1, rcs_tmpdir, sizeof(path1));
	strlcat(path1, "/diff1.XXXXXXXXXX", sizeof(path1));
	rcs_buf_write_stmp(b1, path1, 0600);

	rcs_buf_free(b1);
	b1 = NULL;

	if (utimes(path1, (const struct timeval *)&tv) < 0)
		warn("utimes");

	strlcpy(path2, rcs_tmpdir, sizeof(path2));
	strlcat(path2, "/diff2.XXXXXXXXXX", sizeof(path2));
	rcs_buf_write_stmp(b2, path2, 0600);

	rcs_buf_free(b2);
	b2 = NULL;

	if (utimes(path2, (const struct timeval *)&tv2) < 0)
		warn("utimes");

	rcs_diffreg(path1, path2, NULL);
	ret = 0;

out:
	if (b1 != NULL)
		rcs_buf_free(b1);
	if (b2 != NULL)
		rcs_buf_free(b2);

	return (ret);
}