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 #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
  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
  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