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 #include <linux/decompress/unlz4.h>
  15
  16 #include <linux/types.h>
  17 #include <linux/string.h>
  18 #include <linux/init.h>
  19
  20 #ifndef CONFIG_DECOMPRESS_GZIP
  21 # define gunzip NULL
  22 #endif
  23 #ifndef CONFIG_DECOMPRESS_BZIP2
  24 # define bunzip2 NULL
  25 #endif
  26 #ifndef CONFIG_DECOMPRESS_LZMA
  27 # define unlzma NULL
  28 #endif
  29 #ifndef CONFIG_DECOMPRESS_XZ
  30 # define unxz NULL
  31 #endif
  32 #ifndef CONFIG_DECOMPRESS_LZO
  33 # define unlzo NULL
  34 #endif
  35 #ifndef CONFIG_DECOMPRESS_LZ4
  36 # define unlz4 NULL
  37 #endif
  38
  39 struct compress_format {
  40         unsigned char magic[2];
  41         const char *name;
  42         decompress_fn decompressor;
  43 };
  44
  45 static const struct compress_format compressed_formats[] __initconst = {
  46         { {037, 0213}, "gzip", gunzip },
  47         { {037, 0236}, "gzip", gunzip },
  48         { {0x42, 0x5a}, "bzip2", bunzip2 },
  49         { {0x5d, 0x00}, "lzma", unlzma },
  50         { {0xfd, 0x37}, "xz", unxz },
  51         { {0x89, 0x4c}, "lzo", unlzo },
  52         { {0x02, 0x21}, "lz4", unlz4 },
  53         { {0, 0}, NULL, NULL }
  54 };
  55
  56 decompress_fn __init decompress_method(const unsigned char *inbuf, int len,
  57                                 const char **name)
  58 {
  59         const struct compress_format *cf;
  60
  61         if (len < 2)
  62                 return NULL;    /* Need at least this much... */
  63
  64         for (cf = compressed_formats; cf->name; cf++) {
  65                 if (!memcmp(inbuf, cf->magic, 2))
  66                         break;
  67
  68         }
  69         if (name)
  70                 *name = cf->name;
  71         return cf->decompressor;
  72 }