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