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lib/decompress.c 1.7 KB
81f7e3824   Eric Lee   Initial Release, ...
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  // SPDX-License-Identifier: GPL-2.0
  /*
   * decompress.c
   *
   * Detect the decompression method based on magic number
   */
  
  #include <linux/decompress/generic.h>
  
  #include <linux/decompress/bunzip2.h>
  #include <linux/decompress/unlzma.h>
  #include <linux/decompress/unxz.h>
  #include <linux/decompress/inflate.h>
  #include <linux/decompress/unlzo.h>
  #include <linux/decompress/unlz4.h>
  
  #include <linux/types.h>
  #include <linux/string.h>
  #include <linux/init.h>
  #include <linux/printk.h>
  
  #ifndef CONFIG_DECOMPRESS_GZIP
  # define gunzip NULL
  #endif
  #ifndef CONFIG_DECOMPRESS_BZIP2
  # define bunzip2 NULL
  #endif
  #ifndef CONFIG_DECOMPRESS_LZMA
  # define unlzma NULL
  #endif
  #ifndef CONFIG_DECOMPRESS_XZ
  # define unxz NULL
  #endif
  #ifndef CONFIG_DECOMPRESS_LZO
  # define unlzo NULL
  #endif
  #ifndef CONFIG_DECOMPRESS_LZ4
  # define unlz4 NULL
  #endif
  
  struct compress_format {
  	unsigned char magic[2];
  	const char *name;
  	decompress_fn decompressor;
  };
  
  static const struct compress_format compressed_formats[] __initconst = {
  	{ {0x1f, 0x8b}, "gzip", gunzip },
  	{ {0x1f, 0x9e}, "gzip", gunzip },
  	{ {0x42, 0x5a}, "bzip2", bunzip2 },
  	{ {0x5d, 0x00}, "lzma", unlzma },
  	{ {0xfd, 0x37}, "xz", unxz },
  	{ {0x89, 0x4c}, "lzo", unlzo },
  	{ {0x02, 0x21}, "lz4", unlz4 },
  	{ {0, 0}, NULL, NULL }
  };
  
  decompress_fn __init decompress_method(const unsigned char *inbuf, long len,
  				const char **name)
  {
  	const struct compress_format *cf;
  
  	if (len < 2) {
  		if (name)
  			*name = NULL;
  		return NULL;	/* Need at least this much... */
  	}
  
  	pr_debug("Compressed data magic: %#.2x %#.2x
  ", inbuf[0], inbuf[1]);
  
  	for (cf = compressed_formats; cf->name; cf++) {
  		if (!memcmp(inbuf, cf->magic, 2))
  			break;
  
  	}
  	if (name)
  		*name = cf->name;
  	return cf->decompressor;
  }