contrib/make-sparse.c

   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
  23 int 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
  48 int main(int argc, char **argv)
  49 {
  50         int fd, got, i;
  51         char buf[1024];
  52
  53         if (argc != 2) {
  54                 fprintf(stderr, "Usage: make-sparse out-file\n");
  55                 exit(1);
  56         }
  57         fd = open(argv[1], O_WRONLY|O_CREAT|O_TRUNC|O_LARGEFILE, 0777);
  58         if (fd < 0) {
  59                 perror(argv[1]);
  60                 exit(1);
  61         }
  62         while (1) {
  63                 got = full_read(0, buf, sizeof(buf));
  64                 if (got == 0)
  65                         break;
  66                 if (got == sizeof(buf)) {
  67                         for (i=0; i < sizeof(buf); i++)
  68                                 if (buf[i])
  69                                         break;
  70                         if (i == sizeof(buf)) {
  71                                 lseek(fd, sizeof(buf), SEEK_CUR);
  72                                 continue;
  73                         }
  74                 }
  75                 write(fd, buf, got);
  76         }
  77         return 0;
  78 }
  79