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 #include <linux/init.h>
  18
  19 #ifndef CONFIG_DECOMPRESS_GZIP
  20 # define gunzip NULL
  21 #endif
  22 #ifndef CONFIG_DECOMPRESS_BZIP2
  23 # define bunzip2 NULL
  24 #endif
  25 #ifndef CONFIG_DECOMPRESS_LZMA
  26 # define unlzma NULL
  27 #endif
  28 #ifndef CONFIG_DECOMPRESS_XZ
  29 # define unxz NULL
  30 #endif
  31 #ifndef CONFIG_DECOMPRESS_LZO
  32 # define unlzo NULL
  33 #endif
  34
  35 struct compress_format {
  36         unsigned char magic[2];
  37         const char *name;
  38         decompress_fn decompressor;
  39 };
  40
  41 static const struct compress_format compressed_formats[] __initconst = {
  42         { {037, 0213}, "gzip", gunzip },
  43         { {037, 0236}, "gzip", gunzip },
  44         { {0x42, 0x5a}, "bzip2", bunzip2 },
  45         { {0x5d, 0x00}, "lzma", unlzma },
  46         { {0xfd, 0x37}, "xz", unxz },
  47         { {0x89, 0x4c}, "lzo", unlzo },
  48         { {0, 0}, NULL, NULL }
  49 };
  50
  51 decompress_fn __init decompress_method(const unsigned char *inbuf, int len,
  52                                 const char **name)
  53 {
  54         const struct compress_format *cf;
  55
  56         if (len < 2)
  57                 return NULL;    /* Need at least this much... */
  58
  59         for (cf = compressed_formats; cf->name; cf++) {
  60                 if (!memcmp(inbuf, cf->magic, 2))
  61                         break;
  62
  63         }
  64         if (name)
  65                 *name = cf->name;
  66         return cf->decompressor;
  67 }