1/* vi: set sw=4 ts=4: */
2/*
3 * Utility routines.
4 *
5 * Copyright (C) 2010 Denys Vlasenko
6 *
7 * Licensed under GPLv2, see file LICENSE in this tarball for details.
8 */
9#include "libbb.h"
10
11uoff_t FAST_FUNC get_volume_size_in_bytes(int fd,
12		const char *override,
13		unsigned override_units,
14		int extend)
15{
16	uoff_t result;
17
18	if (override) {
19		result = XATOOFF(override);
20		if (result >= (uoff_t)(MAXINT(off_t)) / override_units)
21			bb_error_msg_and_die("image size is too big");
22		result *= override_units;
23		/* seek past end fails on block devices but works on files */
24		if (lseek(fd, result - 1, SEEK_SET) != (off_t)-1) {
25			if (extend)
26				xwrite(fd, "", 1); /* file grows if needed */
27		}
28		//else {
29		//	bb_error_msg("warning, block device is smaller");
30		//}
31	} else {
32		/* more portable than BLKGETSIZE[64] */
33		result = xlseek(fd, 0, SEEK_END);
34	}
35
36	xlseek(fd, 0, SEEK_SET);
37
38	/* Prevent things like this:
39	 * $ dd if=/dev/zero of=foo count=1 bs=1024
40	 * $ mkswap foo
41	 * Setting up swapspace version 1, size = 18446744073709548544 bytes
42	 *
43	 * Picked 16k arbitrarily: */
44	if (result < 16*1024)
45		bb_error_msg_and_die("image is too small");
46
47	return result;
48}
49