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 #ifndef _LARGEFILE_SOURCE
13 #define _LARGEFILE_SOURCE
14 #endif
15 #ifndef _LARGEFILE64_SOURCE
16 #define _LARGEFILE64_SOURCE
17 #endif
18
19 #include <stdio.h>
20 #include <unistd.h>
21 #include <stdlib.h>
22 #include <sys/types.h>
23 #include <sys/stat.h>
24 #include <fcntl.h>
25 #include <errno.h>
26
full_read(int fd,char * buf,size_t count)27 int full_read(int fd, char *buf, size_t count)
28 {
29 int got, total = 0;
30 int pass = 0;
31
32 while (count > 0) {
33 got = read(fd, buf, count);
34 if (got == -1) {
35 if ((errno == EINTR) || (errno == EAGAIN))
36 continue;
37 return total ? total : -1;
38 }
39 if (got == 0) {
40 if (pass++ >= 3)
41 return total;
42 continue;
43 }
44 pass = 0;
45 buf += got;
46 total += got;
47 count -= got;
48 }
49 return total;
50 }
51
main(int argc,char ** argv)52 int main(int argc, char **argv)
53 {
54 int fd, got, i;
55 int zflag = 0;
56 char buf[1024];
57
58 if (argc != 2) {
59 fprintf(stderr, "Usage: make-sparse out-file\n");
60 exit(1);
61 }
62 fd = open(argv[1], O_WRONLY|O_CREAT|O_TRUNC|O_LARGEFILE, 0777);
63 if (fd < 0) {
64 perror(argv[1]);
65 exit(1);
66 }
67 while (1) {
68 got = full_read(0, buf, sizeof(buf));
69 if (got == 0)
70 break;
71 if (got == sizeof(buf)) {
72 for (i=0; i < sizeof(buf); i++)
73 if (buf[i])
74 break;
75 if (i == sizeof(buf)) {
76 lseek(fd, sizeof(buf), SEEK_CUR);
77 zflag = 1;
78 continue;
79 }
80 }
81 zflag = 0;
82 write(fd, buf, got);
83 }
84 if (zflag) {
85 lseek(fd, -1, SEEK_CUR);
86 buf[0] = 0;
87 write(fd, buf, 1);
88 }
89 return 0;
90 }
91
92