skipcpio/skipcpio.c

   1 /* dracut-install.c  -- install files and executables
   2
   3    Copyright (C) 2012 Harald Hoyer
   4    Copyright (C) 2012 Red Hat, Inc.  All rights reserved.
   5
   6    This program is free software: you can redistribute it and/or modify
   7    under the terms of the GNU Lesser General Public License as published by
   8    the Free Software Foundation; either version 2.1 of the License, or
   9    (at your option) any later version.
  10
  11    This program is distributed in the hope that it will be useful, but
  12    WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public License
  17    along with this program; If not, see <http://www.gnu.org/licenses/>.
  18 */
  19
  20 #define PROGRAM_VERSION_STRING "1"
  21
  22 #ifndef _GNU_SOURCE
  23 #define _GNU_SOURCE
  24 #endif
  25
  26 #include <stdbool.h>
  27 #include <stdio.h>
  28 #include <stdlib.h>
  29 #include <unistd.h>
  30 #include <string.h>
  31
  32 #define CPIO_END "TRAILER!!!"
  33 #define CPIO_ENDLEN (sizeof(CPIO_END)-1)
  34
  35 static char buf[CPIO_ENDLEN * 2 + 1];
  36
  37 int main(int argc, char **argv)
  38 {
  39         FILE *f;
  40         size_t s;
  41
  42         if (argc != 2) {
  43                 fprintf(stderr, "Usage: %s <file>\n", argv[0]);
  44                 exit(1);
  45         }
  46
  47         f = fopen(argv[1], "r");
  48
  49         if (f == NULL) {
  50                 fprintf(stderr, "Cannot open file '%s'\n", argv[1]);
  51                 exit(1);
  52         }
  53
  54         s = fread(buf, 6, 1, f);
  55         if (s <= 0) {
  56                 fprintf(stderr, "Read error from file '%s'\n", argv[1]);
  57                 fclose(f);
  58                 exit(1);
  59         }
  60         fseek(f, 0, SEEK_SET);
  61
  62         /* check, if this is a cpio archive */
  63         if ((buf[0] == 0x71 && buf[1] == 0xc7)
  64             || (buf[0] == '0' && buf[1] == '7' && buf[2] == '0' && buf[3] == '7' && buf[4] == '0' && buf[5] == '1')) {
  65                 long pos = 0;
  66
  67                 /* Search for CPIO_END */
  68                 do {
  69                         char *h;
  70                         fseek(f, pos, SEEK_SET);
  71                         buf[sizeof(buf) - 1] = 0;
  72                         s = fread(buf, CPIO_ENDLEN, 2, f);
  73                         if (s <= 0)
  74                                 break;
  75
  76                         h = strstr(buf, CPIO_END);
  77                         if (h) {
  78                                 pos = (h - buf) + pos + CPIO_ENDLEN;
  79                                 fseek(f, pos, SEEK_SET);
  80                                 break;
  81                         }
  82                         pos += CPIO_ENDLEN;
  83                 } while (!feof(f));
  84
  85                 if (feof(f)) {
  86                         /* CPIO_END not found, just cat the whole file */
  87                         fseek(f, 0, SEEK_SET);
  88                 } else {
  89                         /* skip zeros */
  90                         while (!feof(f)) {
  91                                 size_t i;
  92
  93                                 buf[sizeof(buf) - 1] = 0;
  94                                 s = fread(buf, 1, sizeof(buf) - 1, f);
  95                                 if (s <= 0)
  96                                         break;
  97
  98                                 for (i = 0; (i < s) && (buf[i] == 0); i++) ;
  99
 100                                 if (buf[i] != 0) {
 101                                         pos += i;
 102                                         fseek(f, pos, SEEK_SET);
 103                                         break;
 104                                 }
 105
 106                                 pos += s;
 107                         }
 108                 }
 109         }
 110         /* cat out the rest */
 111         while (!feof(f)) {
 112                 s = fread(buf, 1, sizeof(buf), f);
 113                 if (s <= 0)
 114                         break;
 115
 116                 s = fwrite(buf, 1, s, stdout);
 117                 if (s <= 0)
 118                         break;
 119         }
 120         fclose(f);
 121
 122         return EXIT_SUCCESS;
 123 }