extra/scanlzma/scanlzma.c

   1 /*
   2     scanlzma, scan for lzma compressed data in stdin and echo it to stdout.
   3     Copyright (C) 2006 Timo Lindfors
   4
   5     This program is free software; you can redistribute it and/or modify
   6     it under the terms of the GNU General Public License as published by
   7     the Free Software Foundation; either version 2 of the License, or
   8     (at your option) any later version.
   9
  10     This program is distributed in the hope that it will be useful,
  11     but WITHOUT ANY WARRANTY; without even the implied warranty of
  12     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13     GNU General Public License for more details.
  14 */
  15
  16 /* Usage example:
  17
  18    $ wget http://www.wifi-shop.cz/Files/produkty/wa2204/wa2204av1.4.1.zip
  19    $ unzip wa2204av1.4.1.zip
  20    $ gcc scanlzma.c -o scanlzma -Wall
  21    $ ./scanlzma 0 < WA2204-FW1.4.1/linux-1.4.bin | lzma -c -d | strings | grep -i "copyright"
  22    UpdateDD version 2.5, Copyright (C) 2005 Philipp Benner.
  23    Copyright (C) 2005 Philipp Benner.
  24    Copyright (C) 2005 Philipp Benner.
  25    mawk 1.3%s%s %s, Copyright (C) Michael D. Brennan
  26    # Copyright (C) 1998, 1999, 2001  Henry Spencer.
  27    ...
  28
  29 */
  30
  31
  32 /* LZMA compressed file format */
  33 /* --------------------------- */
  34 /* Offset Size Description */
  35 /*   0     1   Special LZMA properties for compressed data */
  36 /*   1     4   Dictionary size (little endian) */
  37 /*   5     8   Uncompressed size (little endian). -1 means unknown size */
  38 /*  13         Compressed data */
  39
  40 #include <stdlib.h>
  41 #include <stdio.h>
  42 #include <string.h>
  43
  44 #define BUFSIZE 4096
  45
  46 int find_lzma_header(unsigned char *buf) {
  47         return (buf[0] < 0xE1
  48                 && buf[0] == 0x5d
  49                 && buf[4] < 0x20
  50                 && (memcmp (buf + 10 , "\x00\x00\x00", 3) == 0
  51                     || (memcmp (buf + 5, "\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF", 8) == 0)));
  52 }
  53
  54 int main(int argc, char *argv[]) {
  55         unsigned char buf[BUFSIZE];
  56         int ret, i, numlzma, blocks=0;
  57
  58         if (argc != 2) {
  59                 printf("usage: %s numlzma < infile | lzma -c -d > outfile\n"
  60                        "where numlzma is index of lzma file to extract, starting from zero.\n",
  61                        argv[0]);
  62                 exit(1);
  63         }
  64         numlzma = atoi(argv[1]);
  65
  66         for (;;) {
  67                 /* Read data. */
  68                 ret = fread(buf, BUFSIZE, 1, stdin);
  69                 if (ret != 1)
  70                         break;
  71
  72                 /* Scan for signature. */
  73                 for (i = 0; i<BUFSIZE-23; i++) {
  74                         if (find_lzma_header(buf+i) && numlzma-- <= 0) {
  75                                 fwrite(buf+i, (BUFSIZE-i), 1, stdout);
  76                                 for (;;) {
  77                                         int ch;
  78                                         ch = getchar();
  79                                         if (ch == EOF)
  80                                                 exit(0);
  81                                         putchar(ch);
  82                                 }
  83                         }
  84                 }
  85                 blocks++;
  86         }
  87         return 1;
  88 }