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Linux/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 #include <linux/printk.h>
 20 
 21 #ifndef CONFIG_DECOMPRESS_GZIP
 22 # define gunzip NULL
 23 #endif
 24 #ifndef CONFIG_DECOMPRESS_BZIP2
 25 # define bunzip2 NULL
 26 #endif
 27 #ifndef CONFIG_DECOMPRESS_LZMA
 28 # define unlzma NULL
 29 #endif
 30 #ifndef CONFIG_DECOMPRESS_XZ
 31 # define unxz NULL
 32 #endif
 33 #ifndef CONFIG_DECOMPRESS_LZO
 34 # define unlzo NULL
 35 #endif
 36 #ifndef CONFIG_DECOMPRESS_LZ4
 37 # define unlz4 NULL
 38 #endif
 39 
 40 struct compress_format {
 41         unsigned char magic[2];
 42         const char *name;
 43         decompress_fn decompressor;
 44 };
 45 
 46 static const struct compress_format compressed_formats[] __initconst = {
 47         { {0x1f, 0x8b}, "gzip", gunzip },
 48         { {0x1f, 0x9e}, "gzip", gunzip },
 49         { {0x42, 0x5a}, "bzip2", bunzip2 },
 50         { {0x5d, 0x00}, "lzma", unlzma },
 51         { {0xfd, 0x37}, "xz", unxz },
 52         { {0x89, 0x4c}, "lzo", unlzo },
 53         { {0x02, 0x21}, "lz4", unlz4 },
 54         { {0, 0}, NULL, NULL }
 55 };
 56 
 57 decompress_fn __init decompress_method(const unsigned char *inbuf, long len,
 58                                 const char **name)
 59 {
 60         const struct compress_format *cf;
 61 
 62         if (len < 2) {
 63                 if (name)
 64                         *name = NULL;
 65                 return NULL;    /* Need at least this much... */
 66         }
 67 
 68         pr_debug("Compressed data magic: %#.2x %#.2x\n", inbuf[0], inbuf[1]);
 69 
 70         for (cf = compressed_formats; cf->name; cf++) {
 71                 if (!memcmp(inbuf, cf->magic, 2))
 72                         break;
 73 
 74         }
 75         if (name)
 76                 *name = cf->name;
 77         return cf->decompressor;
 78 }
 79 

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