lib/decompress.c

   1 /*
   2  * decompress.c
   3  *
   4  * Detect the decompression method based on magic number
   5  */
   6
   7 #include <linux/decompress/generic.h>
   8
   9 #include <linux/decompress/bunzip2.h>
  10 #include <linux/decompress/unlzma.h>
  11 #include <linux/decompress/unxz.h>
  12 #include <linux/decompress/inflate.h>
  13 #include <linux/decompress/unlzo.h>
  14
  15 #include <linux/types.h>
  16 #include <linux/string.h>
  17
  18 #ifndef CONFIG_DECOMPRESS_GZIP
  19 # define gunzip NULL
  20 #endif
  21 #ifndef CONFIG_DECOMPRESS_BZIP2
  22 # define bunzip2 NULL
  23 #endif
  24 #ifndef CONFIG_DECOMPRESS_LZMA
  25 # define unlzma NULL
  26 #endif
  27 #ifndef CONFIG_DECOMPRESS_XZ
  28 # define unxz NULL
  29 #endif
  30 #ifndef CONFIG_DECOMPRESS_LZO
  31 # define unlzo NULL
  32 #endif
  33
  34 static const struct compress_format {
  35         unsigned char magic[2];
  36         const char *name;
  37         decompress_fn decompressor;
  38 } compressed_formats[] = {
  39         { {037, 0213}, "gzip", gunzip },
  40         { {037, 0236}, "gzip", gunzip },
  41         { {0x42, 0x5a}, "bzip2", bunzip2 },
  42         { {0x5d, 0x00}, "lzma", unlzma },
  43         { {0xfd, 0x37}, "xz", unxz },
  44         { {0x89, 0x4c}, "lzo", unlzo },
  45         { {0, 0}, NULL, NULL }
  46 };
  47
  48 decompress_fn decompress_method(const unsigned char *inbuf, int len,
  49                                 const char **name)
  50 {
  51         const struct compress_format *cf;
  52
  53         if (len < 2)
  54                 return NULL;    /* Need at least this much... */
  55
  56         for (cf = compressed_formats; cf->name; cf++) {
  57                 if (!memcmp(inbuf, cf->magic, 2))
  58                         break;
  59
  60         }
  61         if (name)
  62                 *name = cf->name;
  63         return cf->decompressor;
  64 }