1/*
2 * make-sparse.c --- make a sparse file from stdin
3 *
4 * Copyright 2004 by Theodore Ts'o.
5 *
6 * %Begin-Header%
7 * This file may be redistributed under the terms of the GNU Public
8 * License.
9 * %End-Header%
10 */
11
12#define _LARGEFILE_SOURCE
13#define _LARGEFILE64_SOURCE
14
15#include <stdio.h>
16#include <unistd.h>
17#include <stdlib.h>
18#include <sys/types.h>
19#include <sys/stat.h>
20#include <fcntl.h>
21#include <errno.h>
22
23int full_read(int fd, char *buf, size_t count)
24{
25	int got, total = 0;
26	int pass = 0;
27
28	while (count > 0) {
29		got = read(fd, buf, count);
30		if (got == -1) {
31			if ((errno == EINTR) || (errno == EAGAIN))
32				continue;
33			return total ? total : -1;
34		}
35		if (got == 0) {
36			if (pass++ >= 3)
37				return total;
38			continue;
39		}
40		pass = 0;
41		buf += got;
42		total += got;
43		count -= got;
44	}
45	return total;
46}
47
48int main(int argc, char **argv)
49{
50	int fd, got, i;
51	int zflag = 0;
52	char buf[1024];
53
54	if (argc != 2) {
55		fprintf(stderr, "Usage: make-sparse out-file\n");
56		exit(1);
57	}
58	fd = open(argv[1], O_WRONLY|O_CREAT|O_TRUNC|O_LARGEFILE, 0777);
59	if (fd < 0) {
60		perror(argv[1]);
61		exit(1);
62	}
63	while (1) {
64		got = full_read(0, buf, sizeof(buf));
65		if (got == 0)
66			break;
67		if (got == sizeof(buf)) {
68			for (i=0; i < sizeof(buf); i++)
69				if (buf[i])
70					break;
71			if (i == sizeof(buf)) {
72				lseek(fd, sizeof(buf), SEEK_CUR);
73				zflag = 1;
74				continue;
75			}
76		}
77		zflag = 0;
78		write(fd, buf, got);
79	}
80	if (zflag) {
81		lseek(fd, -1, SEEK_CUR);
82		buf[0] = 0;
83		write(fd, buf, 1);
84	}
85	return 0;
86}
87
88