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