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] == '0' && buf[1] == '7' && buf[2] == '0' && buf[3] == '7' && buf[4] == '0' && buf[5] == '1') {
  64                 long pos = 0;
  65
  66                 /* Search for CPIO_END */
  67                 do {
  68                         char *h;
  69                         fseek(f, pos, SEEK_SET);
  70                         buf[sizeof(buf) - 1] = 0;
  71                         s = fread(buf, CPIO_ENDLEN, 2, f);
  72                         if (s <= 0)
  73                                 break;
  74
  75                         h = strstr(buf, CPIO_END);
  76                         if (h) {
  77                                 pos = (h - buf) + pos + CPIO_ENDLEN;
  78                                 fseek(f, pos, SEEK_SET);
  79                                 break;
  80                         }
  81                         pos += CPIO_ENDLEN;
  82                 } while (!feof(f));
  83
  84                 if (feof(f)) {
  85                         /* CPIO_END not found, just cat the whole file */
  86                         fseek(f, 0, SEEK_SET);
  87                 } else {
  88                         /* skip zeros */
  89                         while (!feof(f)) {
  90                                 size_t i;
  91
  92                                 buf[sizeof(buf) - 1] = 0;
  93                                 s = fread(buf, 1, sizeof(buf) - 1, f);
  94                                 if (s <= 0)
  95                                         break;
  96
  97                                 for (i = 0; (i < s) && (buf[i] == 0); i++) ;
  98
  99                                 if (buf[i] != 0) {
 100                                         pos += i;
 101                                         fseek(f, pos, SEEK_SET);
 102                                         break;
 103                                 }
 104
 105                                 pos += s;
 106                         }
 107                 }
 108         }
 109         /* cat out the rest */
 110         while (!feof(f)) {
 111                 s = fread(buf, 1, sizeof(buf), f);
 112                 if (s <= 0)
 113                         break;
 114
 115                 s = fwrite(buf, 1, s, stdout);
 116                 if (s <= 0)
 117                         break;
 118         }
 119         fclose(f);
 120
 121         return EXIT_SUCCESS;
 122 }