sparse.c

gnu tar 源码包。 tar 软件是 Unix 系统下的一个打包软件

      && h->star_in_header.sp[0].offset[10] != '\0')
    {
      /* Old star format */
      for (i = 0; i < SPARSES_IN_STAR_HEADER; i++)
	{
	  rc = oldgnu_add_sparse (file, &h->star_in_header.sp[i]);
	  if (rc != add_ok)
	    break;
	}
      ext_p = h->star_in_header.isextended;
    }
  else
    ext_p = 1;

  for (; rc == add_ok && ext_p; ext_p = h->star_ext_header.isextended)
    {
      h = find_next_block ();
      if (!h)
	{
	  ERROR ((0, 0, _("Unexpected EOF in archive")));
	  return false;
	}
      set_next_block_after (h);
      for (i = 0; i < SPARSES_IN_STAR_EXT_HEADER && rc == add_ok; i++)
	rc = oldgnu_add_sparse (file, &h->star_ext_header.sp[i]);
    }

  if (rc == add_fail)
    {
      ERROR ((0, 0, _("%s: invalid sparse archive member"),
	      file->stat_info->orig_file_name));
      return false;
    }
  return true;
}


static struct tar_sparse_optab const star_optab = {
  NULL,  /* No init function */
  NULL,  /* No done function */
  star_sparse_member_p,
  NULL,
  star_fixup_header,
  star_get_sparse_info,
  NULL,  /* No scan_block function */
  NULL, /* No dump region function */
  sparse_extract_region,
};


/* GNU PAX sparse file format. There are several versions:

   * 0.0

   The initial version of sparse format used by tar 1.14-1.15.1.
   The sparse file map is stored in x header:

   GNU.sparse.size      Real size of the stored file
   GNU.sparse.numblocks Number of blocks in the sparse map
   repeat numblocks time
     GNU.sparse.offset    Offset of the next data block
     GNU.sparse.numbytes  Size of the next data block
   end repeat

   This has been reported as conflicting with the POSIX specs. The reason is
   that offsets and sizes of non-zero data blocks were stored in multiple
   instances of GNU.sparse.offset/GNU.sparse.numbytes variables, whereas
   POSIX requires the latest occurrence of the variable to override all
   previous occurrences.
   
   To avoid this incompatibility two following versions were introduced.

   * 0.1

   Used by tar 1.15.2 -- 1.15.91 (alpha releases).
   
   The sparse file map is stored in
   x header:

   GNU.sparse.size      Real size of the stored file
   GNU.sparse.numblocks Number of blocks in the sparse map
   GNU.sparse.map       Map of non-null data chunks. A string consisting
                       of comma-separated values "offset,size[,offset,size]..."

   The resulting GNU.sparse.map string can be *very* long. While POSIX does not
   impose any limit on the length of a x header variable, this can confuse some
   tars.

   * 1.0

   Starting from this version, the exact sparse format version is specified
   explicitely in the header using the following variables:

   GNU.sparse.major     Major version 
   GNU.sparse.minor     Minor version

   X header keeps the following variables:
   
   GNU.sparse.name      Real file name of the sparse file
   GNU.sparse.realsize  Real size of the stored file (corresponds to the old
                        GNU.sparse.size variable)

   The name field of the ustar header is constructed using the pattern
   "%d/GNUSparseFile.%p/%f".
   
   The sparse map itself is stored in the file data block, preceding the actual
   file data. It consists of a series of octal numbers of arbitrary length,
   delimited by newlines. The map is padded with nulls to the nearest block
   boundary.

   The first number gives the number of entries in the map. Following are map
   entries, each one consisting of two numbers giving the offset and size of
   the data block it describes.

   The format is designed in such a way that non-posix aware tars and tars not
   supporting GNU.sparse.* keywords will extract each sparse file in its
   condensed form with the file map attached and will place it into a separate
   directory. Then, using a simple program it would be possible to expand the
   file to its original form even without GNU tar.

   Bu default, v.1.0 archives are created. To use other formats,
   --sparse-version option is provided. Additionally, v.0.0 can be obtained
   by deleting GNU.sparse.map from 0.1 format: --sparse-version 0.1
   --pax-option delete=GNU.sparse.map
*/

static bool
pax_sparse_member_p (struct tar_sparse_file *file)
{
  return file->stat_info->sparse_map_avail > 0
          || file->stat_info->sparse_major > 0;
}

static bool
pax_dump_header_0 (struct tar_sparse_file *file)
{
  off_t block_ordinal = current_block_ordinal ();
  union block *blk;
  size_t i;
  char nbuf[UINTMAX_STRSIZE_BOUND];
  struct sp_array *map = file->stat_info->sparse_map;
  char *save_file_name = NULL;
  
  /* Store the real file size */
  xheader_store ("GNU.sparse.size", file->stat_info, NULL);
  xheader_store ("GNU.sparse.numblocks", file->stat_info, NULL);
  
  if (xheader_keyword_deleted_p ("GNU.sparse.map")
      || tar_sparse_minor == 0)
    {
      for (i = 0; i < file->stat_info->sparse_map_avail; i++)
	{
	  xheader_store ("GNU.sparse.offset", file->stat_info, &i);
	  xheader_store ("GNU.sparse.numbytes", file->stat_info, &i);
	}
    }
  else
    {
      xheader_store ("GNU.sparse.name", file->stat_info, NULL);
      save_file_name = file->stat_info->file_name;
      file->stat_info->file_name = xheader_format_name (file->stat_info,
					       "%d/GNUSparseFile.%p/%f", 0);

      xheader_string_begin (&file->stat_info->xhdr);
      for (i = 0; i < file->stat_info->sparse_map_avail; i++)
	{
	  if (i)
	    xheader_string_add (&file->stat_info->xhdr, ",");
	  xheader_string_add (&file->stat_info->xhdr,
			      umaxtostr (map[i].offset, nbuf));
	  xheader_string_add (&file->stat_info->xhdr, ",");
	  xheader_string_add (&file->stat_info->xhdr,
			      umaxtostr (map[i].numbytes, nbuf));
	}
      if (!xheader_string_end (&file->stat_info->xhdr,
			       "GNU.sparse.map"))
	{
	  free (file->stat_info->file_name);
	  file->stat_info->file_name = save_file_name;
	  return false;
	}
    }
  blk = start_header (file->stat_info);
  /* Store the effective (shrunken) file size */
  OFF_TO_CHARS (file->stat_info->archive_file_size, blk->header.size);
  finish_header (file->stat_info, blk, block_ordinal);
  if (save_file_name)
    {
      free (file->stat_info->file_name);
      file->stat_info->file_name = save_file_name;
    }
  return true;
}

static bool
pax_dump_header_1 (struct tar_sparse_file *file)
{
  off_t block_ordinal = current_block_ordinal ();
  union block *blk;
  char *p, *q;
  size_t i;
  char nbuf[UINTMAX_STRSIZE_BOUND];
  off_t size = 0;
  struct sp_array *map = file->stat_info->sparse_map;
  char *save_file_name = file->stat_info->file_name;

#define COPY_STRING(b,dst,src) do                \
 {                                               \
   char *endp = b->buffer + BLOCKSIZE;           \
   char *srcp = src;                             \
   while (*srcp)                                 \
     {                                           \
       if (dst == endp)                          \
	 {                                       \
	   set_next_block_after (b);             \
	   b = find_next_block ();               \
           dst = b->buffer;                      \
	   endp = b->buffer + BLOCKSIZE;         \
	 }                                       \
       *dst++ = *srcp++;                         \
     }                                           \
   } while (0)                       

  /* Compute stored file size */
  p = umaxtostr (file->stat_info->sparse_map_avail, nbuf);
  size += strlen (p) + 1;
  for (i = 0; i < file->stat_info->sparse_map_avail; i++)
    {
      p = umaxtostr (map[i].offset, nbuf);
      size += strlen (p) + 1;
      p = umaxtostr (map[i].numbytes, nbuf);
      size += strlen (p) + 1;
    }
  size = (size + BLOCKSIZE - 1) / BLOCKSIZE;
  file->stat_info->archive_file_size += size * BLOCKSIZE;
  file->dumped_size += size * BLOCKSIZE;
  
  /* Store sparse file identification */
  xheader_store ("GNU.sparse.major", file->stat_info, NULL);
  xheader_store ("GNU.sparse.minor", file->stat_info, NULL);
  xheader_store ("GNU.sparse.name", file->stat_info, NULL);
  xheader_store ("GNU.sparse.realsize", file->stat_info, NULL);
  
  file->stat_info->file_name = xheader_format_name (file->stat_info,
					    "%d/GNUSparseFile.%p/%f", 0);

  blk = start_header (file->stat_info);
  /* Store the effective (shrunken) file size */
  OFF_TO_CHARS (file->stat_info->archive_file_size, blk->header.size);
  finish_header (file->stat_info, blk, block_ordinal);
  free (file->stat_info->file_name);
  file->stat_info->file_name = save_file_name;

  blk = find_next_block ();
  q = blk->buffer;
  p = umaxtostr (file->stat_info->sparse_map_avail, nbuf);
  COPY_STRING (blk, q, p);
  COPY_STRING (blk, q, "\n");
  for (i = 0; i < file->stat_info->sparse_map_avail; i++)
    {
      p = umaxtostr (map[i].offset, nbuf);
      COPY_STRING (blk, q, p);
      COPY_STRING (blk, q, "\n");
      p = umaxtostr (map[i].numbytes, nbuf);
      COPY_STRING (blk, q, p);
      COPY_STRING (blk, q, "\n");
    }
  memset (q, 0, BLOCKSIZE - (q - blk->buffer));
  set_next_block_after (blk);
  return true;
}

static bool
pax_dump_header (struct tar_sparse_file *file)
{
  file->stat_info->sparse_major = tar_sparse_major;
  file->stat_info->sparse_minor = tar_sparse_minor;

  return (file->stat_info->sparse_major == 0) ?
           pax_dump_header_0 (file) : pax_dump_header_1 (file);
}

static bool
decode_num (uintmax_t *num, char const *arg, uintmax_t maxval)
{
  uintmax_t u;
  char *arg_lim;

  if (!ISDIGIT (*arg))
    return false;
  
  u = strtoumax (arg, &arg_lim, 10);

  if (! (u <= maxval && errno != ERANGE) || *arg_lim)
    return false;
  
  *num = u;
  return true;
}

static bool
pax_decode_header (struct tar_sparse_file *file)
{
  if (file->stat_info->sparse_major > 0)
    {
      uintmax_t u;
      char nbuf[UINTMAX_STRSIZE_BOUND];
      union block *blk;
      char *p;
      size_t i;

#define COPY_BUF(b,buf,src) do                                     \
 {                                                                 \
   char *endp = b->buffer + BLOCKSIZE;                             \
   char *dst = buf;                                                \
   do                                                              \
     {                                                             \
       if (dst == buf + UINTMAX_STRSIZE_BOUND -1)                  \
         {                                                         \
           ERROR ((0, 0, _("%s: numeric overflow in sparse archive member"), \
	          file->stat_info->orig_file_name));               \
           return false;                                           \
         }                                                         \
       if (src == endp)                                            \
	 {                                                         \
	   set_next_block_after (b);                               \
           file->dumped_size += BLOCKSIZE;                         \
           b = find_next_block ();                                 \
           src = b->buffer;                                        \
	   endp = b->buffer + BLOCKSIZE;                           \
	 }                                                         \
       *dst = *src++;                                              \
     }                                                             \
   while (*dst++ != '\n');                                         \
   dst[-1] = 0;                                                    \
 } while (0)                       

      set_next_block_after (current_header);
      file->dumped_size += BLOCKSIZE;
      blk = find_next_block ();
      p = blk->buffer;
      COPY_BUF (blk,nbuf,p);
      if (!decode_num (&u, nbuf, TYPE_MAXIMUM (size_t)))
	{
	  ERROR ((0, 0, _("%s: malformed sparse archive member"), 
		  file->stat_info->orig_file_name));
	  return false;
	}
      file->stat_info->sparse_map_size = u;
      file->stat_info->sparse_map = xcalloc (file->stat_info->sparse_map_size,
					     sizeof (*file->stat_info->sparse_map));
      file->stat_info->sparse_map_avail = 0;
      for (i = 0; i < file->stat_info->sparse_map_size; i++)
	{
	  struct sp_array sp;
	  
	  COPY_BUF (blk,nbuf,p);
	  if (!decode_num (&u, nbuf, TYPE_MAXIMUM (off_t)))
	    {
	      ERROR ((0, 0, _("%s: malformed sparse archive member"), 
		      file->stat_info->orig_file_name));
	      return false;
	    }
	  sp.offset = u;
	  COPY_BUF (blk,nbuf,p);
	  if (!decode_num (&u, nbuf, TYPE_MAXIMUM (size_t)))
	    {
	      ERROR ((0, 0, _("%s: malformed sparse archive member"), 
		      file->stat_info->orig_file_name));
	      return false;
	    }
	  sp.numbytes = u;
	  sparse_add_map (file->stat_info, &sp);
	}
      set_next_block_after (blk);
    }
  
  return true;
}

static struct tar_sparse_optab const pax_optab = {
  NULL,  /* No init function */
  NULL,  /* No done function */
  pax_sparse_member_p,
  pax_dump_header,
  NULL,
  pax_decode_header,  
  NULL,  /* No scan_block function */
  sparse_dump_region,
  sparse_extract_region,
};