tar-1.29HEADtar-1.29master

1 files changed, 1295 insertions, 0 deletions

diff --git a/src/sparse.c b/src/sparse.c
new file mode 100644
index 0000000..4e78401
--- /dev/null
+++ b/src/sparse.c
@@ -0,0 +1,1295 @@
+/* Functions for dealing with sparse files
+
+   Copyright 2003-2007, 2010, 2013-2016 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify it
+   under the terms of the GNU General Public License as published by the
+   Free Software Foundation; either version 3, or (at your option) any later
+   version.
+
+   This program is distributed in the hope that it will be useful, but
+   WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General
+   Public License for more details.
+
+   You should have received a copy of the GNU General Public License along
+   with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#include <system.h>
+#include <inttostr.h>
+#include <quotearg.h>
+#include "common.h"
+
+struct tar_sparse_file;
+static bool sparse_select_optab (struct tar_sparse_file *file);
+
+enum sparse_scan_state
+  {
+    scan_begin,
+    scan_block,
+    scan_end
+  };
+
+struct tar_sparse_optab
+{
+  bool (*init) (struct tar_sparse_file *);
+  bool (*done) (struct tar_sparse_file *);
+  bool (*sparse_member_p) (struct tar_sparse_file *);
+  bool (*dump_header) (struct tar_sparse_file *);
+  bool (*fixup_header) (struct tar_sparse_file *);
+  bool (*decode_header) (struct tar_sparse_file *);
+  bool (*scan_block) (struct tar_sparse_file *, enum sparse_scan_state,
+		      void *);
+  bool (*dump_region) (struct tar_sparse_file *, size_t);
+  bool (*extract_region) (struct tar_sparse_file *, size_t);
+};
+
+struct tar_sparse_file
+{
+  int fd;                           /* File descriptor */
+  bool seekable;                    /* Is fd seekable? */
+  off_t offset;                     /* Current offset in fd if seekable==false.
+				       Otherwise unused */
+  off_t dumped_size;                /* Number of bytes actually written
+				       to the archive */
+  struct tar_stat_info *stat_info;  /* Information about the file */
+  struct tar_sparse_optab const *optab; /* Operation table */
+  void *closure;                    /* Any additional data optab calls might
+				       require */
+};
+
+/* Dump zeros to file->fd until offset is reached. It is used instead of
+   lseek if the output file is not seekable */
+static bool
+dump_zeros (struct tar_sparse_file *file, off_t offset)
+{
+  static char const zero_buf[BLOCKSIZE];
+
+  if (offset < file->offset)
+    {
+      errno = EINVAL;
+      return false;
+    }
+
+  while (file->offset < offset)
+    {
+      size_t size = (BLOCKSIZE < offset - file->offset
+		     ? BLOCKSIZE
+		     : offset - file->offset);
+      ssize_t wrbytes;
+
+      wrbytes = write (file->fd, zero_buf, size);
+      if (wrbytes <= 0)
+	{
+	  if (wrbytes == 0)
+	    errno = EINVAL;
+	  return false;
+	}
+      file->offset += wrbytes;
+    }
+
+  return true;
+}
+
+static bool
+tar_sparse_member_p (struct tar_sparse_file *file)
+{
+  if (file->optab->sparse_member_p)
+    return file->optab->sparse_member_p (file);
+  return false;
+}
+
+static bool
+tar_sparse_init (struct tar_sparse_file *file)
+{
+  memset (file, 0, sizeof *file);
+
+  if (!sparse_select_optab (file))
+    return false;
+
+  if (file->optab->init)
+    return file->optab->init (file);
+
+  return true;
+}
+
+static bool
+tar_sparse_done (struct tar_sparse_file *file)
+{
+  if (file->optab->done)
+    return file->optab->done (file);
+  return true;
+}
+
+static bool
+tar_sparse_scan (struct tar_sparse_file *file, enum sparse_scan_state state,
+		 void *block)
+{
+  if (file->optab->scan_block)
+    return file->optab->scan_block (file, state, block);
+  return true;
+}
+
+static bool
+tar_sparse_dump_region (struct tar_sparse_file *file, size_t i)
+{
+  if (file->optab->dump_region)
+    return file->optab->dump_region (file, i);
+  return false;
+}
+
+static bool
+tar_sparse_extract_region (struct tar_sparse_file *file, size_t i)
+{
+  if (file->optab->extract_region)
+    return file->optab->extract_region (file, i);
+  return false;
+}
+
+static bool
+tar_sparse_dump_header (struct tar_sparse_file *file)
+{
+  if (file->optab->dump_header)
+    return file->optab->dump_header (file);
+  return false;
+}
+
+static bool
+tar_sparse_decode_header (struct tar_sparse_file *file)
+{
+  if (file->optab->decode_header)
+    return file->optab->decode_header (file);
+  return true;
+}
+
+static bool
+tar_sparse_fixup_header (struct tar_sparse_file *file)
+{
+  if (file->optab->fixup_header)
+    return file->optab->fixup_header (file);
+  return true;
+}
+
+
+static bool
+lseek_or_error (struct tar_sparse_file *file, off_t offset)
+{
+  if (file->seekable
+      ? lseek (file->fd, offset, SEEK_SET) < 0
+      : ! dump_zeros (file, offset))
+    {
+      seek_diag_details (file->stat_info->orig_file_name, offset);
+      return false;
+    }
+  return true;
+}
+
+/* Takes a blockful of data and basically cruises through it to see if
+   it's made *entirely* of zeros, returning a 0 the instant it finds
+   something that is a nonzero, i.e., useful data.  */
+static bool
+zero_block_p (char const *buffer, size_t size)
+{
+  while (size--)
+    if (*buffer++)
+      return false;
+  return true;
+}
+
+static void
+sparse_add_map (struct tar_stat_info *st, struct sp_array const *sp)
+{
+  struct sp_array *sparse_map = st->sparse_map;
+  size_t avail = st->sparse_map_avail;
+  if (avail == st->sparse_map_size)
+    st->sparse_map = sparse_map =
+      x2nrealloc (sparse_map, &st->sparse_map_size, sizeof *sparse_map);
+  sparse_map[avail] = *sp;
+  st->sparse_map_avail = avail + 1;
+}
+
+/* Scan the sparse file byte-by-byte and create its map. */
+static bool
+sparse_scan_file_raw (struct tar_sparse_file *file)
+{
+  struct tar_stat_info *st = file->stat_info;
+  int fd = file->fd;
+  char buffer[BLOCKSIZE];
+  size_t count = 0;
+  off_t offset = 0;
+  struct sp_array sp = {0, 0};
+
+  st->archive_file_size = 0;
+
+  if (!tar_sparse_scan (file, scan_begin, NULL))
+    return false;
+
+  while ((count = blocking_read (fd, buffer, sizeof buffer)) != 0
+         && count != SAFE_READ_ERROR)
+    {
+      /* Analyze the block.  */
+      if (zero_block_p (buffer, count))
+        {
+          if (sp.numbytes)
+            {
+              sparse_add_map (st, &sp);
+              sp.numbytes = 0;
+              if (!tar_sparse_scan (file, scan_block, NULL))
+                return false;
+            }
+        }
+      else
+        {
+          if (sp.numbytes == 0)
+            sp.offset = offset;
+          sp.numbytes += count;
+          st->archive_file_size += count;
+          if (!tar_sparse_scan (file, scan_block, buffer))
+            return false;
+        }
+
+      offset += count;
+    }
+
+  /* save one more sparse segment of length 0 to indicate that
+     the file ends with a hole */
+  if (sp.numbytes == 0)
+    sp.offset = offset;
+
+  sparse_add_map (st, &sp);
+  st->archive_file_size += count;
+  return tar_sparse_scan (file, scan_end, NULL);
+}
+
+static bool
+sparse_scan_file_wholesparse (struct tar_sparse_file *file)
+{
+  struct tar_stat_info *st = file->stat_info;
+  struct sp_array sp = {0, 0};
+
+  /* Note that this function is called only for truly sparse files of size >= 1
+     block size (checked via ST_IS_SPARSE before).  See the thread
+     http://www.mail-archive.com/bug-tar@gnu.org/msg04209.html for more info */
+  if (ST_NBLOCKS (st->stat) == 0)
+    {
+      st->archive_file_size = 0;
+      sp.offset = st->stat.st_size;
+      sparse_add_map (st, &sp);
+      return true;
+    }
+
+  return false;
+}
+
+#ifdef SEEK_HOLE
+/* Try to engage SEEK_HOLE/SEEK_DATA feature. */
+static bool
+sparse_scan_file_seek (struct tar_sparse_file *file)
+{
+  struct tar_stat_info *st = file->stat_info;
+  int fd = file->fd;
+  struct sp_array sp = {0, 0};
+  off_t offset = 0;
+  off_t data_offset;
+  off_t hole_offset;
+
+  st->archive_file_size = 0;
+
+  for (;;)
+    {
+      /* locate first chunk of data */
+      data_offset = lseek (fd, offset, SEEK_DATA);
+
+      if (data_offset == (off_t)-1)
+        /* ENXIO == EOF; error otherwise */
+        {
+          if (errno == ENXIO)
+            {
+              /* file ends with hole, add one more empty chunk of data */
+              sp.numbytes = 0;
+              sp.offset = st->stat.st_size;
+              sparse_add_map (st, &sp);
+              return true;
+            }
+          return false;
+        }
+
+      hole_offset = lseek (fd, data_offset, SEEK_HOLE);
+
+      /* according to specs, if FS does not fully support
+	 SEEK_DATA/SEEK_HOLE it may just implement kind of "wrapper" around
+	 classic lseek() call.  We must detect it here and try to use other
+	 hole-detection methods. */
+      if (offset == 0 /* first loop */
+          && data_offset == 0
+          && hole_offset == st->stat.st_size)
+        {
+          lseek (fd, 0, SEEK_SET);
+          return false;
+        }
+
+      sp.offset = data_offset;
+      sp.numbytes = hole_offset - data_offset;
+      sparse_add_map (st, &sp);
+
+      st->archive_file_size += sp.numbytes;
+      offset = hole_offset;
+    }
+
+  return true;
+}
+#endif
+
+static bool
+sparse_scan_file (struct tar_sparse_file *file)
+{
+  /* always check for completely sparse files */
+  if (sparse_scan_file_wholesparse (file))
+    return true;
+
+  switch (hole_detection)
+    {
+    case HOLE_DETECTION_DEFAULT:
+    case HOLE_DETECTION_SEEK:
+#ifdef SEEK_HOLE
+      if (sparse_scan_file_seek (file))
+        return true;
+#else
+      if (hole_detection == HOLE_DETECTION_SEEK)
+	WARN((0, 0,
+	      _("\"seek\" hole detection is not supported, using \"raw\".")));
+      /* fall back to "raw" for this and all other files */
+      hole_detection = HOLE_DETECTION_RAW;
+#endif
+    case HOLE_DETECTION_RAW:
+      if (sparse_scan_file_raw (file))
+	return true;
+    }
+  
+  return false;
+}
+
+static struct tar_sparse_optab const oldgnu_optab;
+static struct tar_sparse_optab const star_optab;
+static struct tar_sparse_optab const pax_optab;
+
+static bool
+sparse_select_optab (struct tar_sparse_file *file)
+{
+  switch (current_format == DEFAULT_FORMAT ? archive_format : current_format)
+    {
+    case V7_FORMAT:
+    case USTAR_FORMAT:
+      return false;
+
+    case OLDGNU_FORMAT:
+    case GNU_FORMAT: /*FIXME: This one should disappear? */
+      file->optab = &oldgnu_optab;
+      break;
+
+    case POSIX_FORMAT:
+      file->optab = &pax_optab;
+      break;
+
+    case STAR_FORMAT:
+      file->optab = &star_optab;
+      break;
+
+    default:
+      return false;
+    }
+  return true;
+}
+
+static bool
+sparse_dump_region (struct tar_sparse_file *file, size_t i)
+{
+  union block *blk;
+  off_t bytes_left = file->stat_info->sparse_map[i].numbytes;
+
+  if (!lseek_or_error (file, file->stat_info->sparse_map[i].offset))
+    return false;
+
+  while (bytes_left > 0)
+    {
+      size_t bufsize = (bytes_left > BLOCKSIZE) ? BLOCKSIZE : bytes_left;
+      size_t bytes_read;
+
+      blk = find_next_block ();
+      bytes_read = safe_read (file->fd, blk->buffer, bufsize);
+      if (bytes_read == SAFE_READ_ERROR)
+	{
+          read_diag_details (file->stat_info->orig_file_name,
+	                     (file->stat_info->sparse_map[i].offset
+			      + file->stat_info->sparse_map[i].numbytes
+			      - bytes_left),
+			     bufsize);
+	  return false;
+	}
+
+      memset (blk->buffer + bytes_read, 0, BLOCKSIZE - bytes_read);
+      bytes_left -= bytes_read;
+      file->dumped_size += bytes_read;
+      set_next_block_after (blk);
+    }
+
+  return true;
+}
+
+static bool
+sparse_extract_region (struct tar_sparse_file *file, size_t i)
+{
+  off_t write_size;
+
+  if (!lseek_or_error (file, file->stat_info->sparse_map[i].offset))
+    return false;
+
+  write_size = file->stat_info->sparse_map[i].numbytes;
+
+  if (write_size == 0)
+    {
+      /* Last block of the file is a hole */
+      if (file->seekable && sys_truncate (file->fd))
+	truncate_warn (file->stat_info->orig_file_name);
+    }
+  else while (write_size > 0)
+    {
+      size_t count;
+      size_t wrbytes = (write_size > BLOCKSIZE) ? BLOCKSIZE : write_size;
+      union block *blk = find_next_block ();
+      if (!blk)
+	{
+	  ERROR ((0, 0, _("Unexpected EOF in archive")));
+	  return false;
+	}
+      set_next_block_after (blk);
+      count = blocking_write (file->fd, blk->buffer, wrbytes);
+      write_size -= count;
+      file->dumped_size += count;
+      mv_size_left (file->stat_info->archive_file_size - file->dumped_size);
+      file->offset += count;
+      if (count != wrbytes)
+	{
+	  write_error_details (file->stat_info->orig_file_name,
+			       count, wrbytes);
+	  return false;
+	}
+    }
+  return true;
+}
+
+
+
+/* Interface functions */
+enum dump_status
+sparse_dump_file (int fd, struct tar_stat_info *st)
+{
+  bool rc;
+  struct tar_sparse_file file;
+
+  if (!tar_sparse_init (&file))
+    return dump_status_not_implemented;
+
+  file.stat_info = st;
+  file.fd = fd;
+  file.seekable = true; /* File *must* be seekable for dump to work */
+
+  rc = sparse_scan_file (&file);
+  if (rc && file.optab->dump_region)
+    {
+      tar_sparse_dump_header (&file);
+
+      if (fd >= 0)
+	{
+	  size_t i;
+
+	  mv_begin_write (file.stat_info->file_name,
+		          file.stat_info->stat.st_size,
+		          file.stat_info->archive_file_size - file.dumped_size);
+	  for (i = 0; rc && i < file.stat_info->sparse_map_avail; i++)
+	    rc = tar_sparse_dump_region (&file, i);
+	}
+    }
+
+  pad_archive (file.stat_info->archive_file_size - file.dumped_size);
+  return (tar_sparse_done (&file) && rc) ? dump_status_ok : dump_status_short;
+}
+
+bool
+sparse_member_p (struct tar_stat_info *st)
+{
+  struct tar_sparse_file file;
+
+  if (!tar_sparse_init (&file))
+    return false;
+  file.stat_info = st;
+  return tar_sparse_member_p (&file);
+}
+
+bool
+sparse_fixup_header (struct tar_stat_info *st)
+{
+  struct tar_sparse_file file;
+
+  if (!tar_sparse_init (&file))
+    return false;
+  file.stat_info = st;
+  return tar_sparse_fixup_header (&file);
+}
+
+enum dump_status
+sparse_extract_file (int fd, struct tar_stat_info *st, off_t *size)
+{
+  bool rc = true;
+  struct tar_sparse_file file;
+  size_t i;
+
+  if (!tar_sparse_init (&file))
+    return dump_status_not_implemented;
+
+  file.stat_info = st;
+  file.fd = fd;
+  file.seekable = lseek (fd, 0, SEEK_SET) == 0;
+  file.offset = 0;
+
+  rc = tar_sparse_decode_header (&file);
+  for (i = 0; rc && i < file.stat_info->sparse_map_avail; i++)
+    rc = tar_sparse_extract_region (&file, i);
+  *size = file.stat_info->archive_file_size - file.dumped_size;
+  return (tar_sparse_done (&file) && rc) ? dump_status_ok : dump_status_short;
+}
+
+enum dump_status
+sparse_skip_file (struct tar_stat_info *st)
+{
+  bool rc = true;
+  struct tar_sparse_file file;
+
+  if (!tar_sparse_init (&file))
+    return dump_status_not_implemented;
+
+  file.stat_info = st;
+  file.fd = -1;
+
+  rc = tar_sparse_decode_header (&file);
+  skip_file (file.stat_info->archive_file_size - file.dumped_size);
+  return (tar_sparse_done (&file) && rc) ? dump_status_ok : dump_status_short;
+}
+
+
+static bool
+check_sparse_region (struct tar_sparse_file *file, off_t beg, off_t end)
+{
+  if (!lseek_or_error (file, beg))
+    return false;
+
+  while (beg < end)
+    {
+      size_t bytes_read;
+      size_t rdsize = BLOCKSIZE < end - beg ? BLOCKSIZE : end - beg;
+      char diff_buffer[BLOCKSIZE];
+
+      bytes_read = safe_read (file->fd, diff_buffer, rdsize);
+      if (bytes_read == SAFE_READ_ERROR)
+	{
+          read_diag_details (file->stat_info->orig_file_name,
+	                     beg,
+			     rdsize);
+	  return false;
+	}
+      if (!zero_block_p (diff_buffer, bytes_read))
+	{
+	  char begbuf[INT_BUFSIZE_BOUND (off_t)];
+ 	  report_difference (file->stat_info,
+			     _("File fragment at %s is not a hole"),
+			     offtostr (beg, begbuf));
+	  return false;
+	}
+
+      beg += bytes_read;
+    }
+  return true;
+}
+
+static bool
+check_data_region (struct tar_sparse_file *file, size_t i)
+{
+  off_t size_left;
+
+  if (!lseek_or_error (file, file->stat_info->sparse_map[i].offset))
+    return false;
+  size_left = file->stat_info->sparse_map[i].numbytes;
+  mv_size_left (file->stat_info->archive_file_size - file->dumped_size);
+
+  while (size_left > 0)
+    {
+      size_t bytes_read;
+      size_t rdsize = (size_left > BLOCKSIZE) ? BLOCKSIZE : size_left;
+      char diff_buffer[BLOCKSIZE];
+
+      union block *blk = find_next_block ();
+      if (!blk)
+	{
+	  ERROR ((0, 0, _("Unexpected EOF in archive")));
+	  return false;
+	}
+      set_next_block_after (blk);
+      bytes_read = safe_read (file->fd, diff_buffer, rdsize);
+      if (bytes_read == SAFE_READ_ERROR)
+	{
+          read_diag_details (file->stat_info->orig_file_name,
+			     (file->stat_info->sparse_map[i].offset
+			      + file->stat_info->sparse_map[i].numbytes
+			      - size_left),
+			     rdsize);
+	  return false;
+	}
+      file->dumped_size += bytes_read;
+      size_left -= bytes_read;
+      mv_size_left (file->stat_info->archive_file_size - file->dumped_size);
+      if (memcmp (blk->buffer, diff_buffer, rdsize))
+	{
+	  report_difference (file->stat_info, _("Contents differ"));
+	  return false;
+	}
+    }
+  return true;
+}
+
+bool
+sparse_diff_file (int fd, struct tar_stat_info *st)
+{
+  bool rc = true;
+  struct tar_sparse_file file;
+  size_t i;
+  off_t offset = 0;
+
+  if (!tar_sparse_init (&file))
+    return dump_status_not_implemented;
+
+  file.stat_info = st;
+  file.fd = fd;
+  file.seekable = true; /* File *must* be seekable for compare to work */
+
+  rc = tar_sparse_decode_header (&file);
+  mv_begin_read (st);
+  for (i = 0; rc && i < file.stat_info->sparse_map_avail; i++)
+    {
+      rc = check_sparse_region (&file,
+				offset, file.stat_info->sparse_map[i].offset)
+	    && check_data_region (&file, i);
+      offset = file.stat_info->sparse_map[i].offset
+	        + file.stat_info->sparse_map[i].numbytes;
+    }
+
+  if (!rc)
+    skip_file (file.stat_info->archive_file_size - file.dumped_size);
+  mv_end ();
+
+  tar_sparse_done (&file);
+  return rc;
+}
+
+
+/* Old GNU Format. The sparse file information is stored in the
+   oldgnu_header in the following manner:
+
+   The header is marked with type 'S'. Its 'size' field contains
+   the cumulative size of all non-empty blocks of the file. The
+   actual file size is stored in 'realsize' member of oldgnu_header.
+
+   The map of the file is stored in a list of 'struct sparse'.
+   Each struct contains offset to the block of data and its
+   size (both as octal numbers). The first file header contains
+   at most 4 such structs (SPARSES_IN_OLDGNU_HEADER). If the map
+   contains more structs, then the field 'isextended' of the main
+   header is set to 1 (binary) and the 'struct sparse_header'
+   header follows, containing at most 21 following structs
+   (SPARSES_IN_SPARSE_HEADER). If more structs follow, 'isextended'
+   field of the extended header is set and next  next extension header
+   follows, etc... */
+
+enum oldgnu_add_status
+  {
+    add_ok,
+    add_finish,
+    add_fail
+  };
+
+static bool
+oldgnu_sparse_member_p (struct tar_sparse_file *file __attribute__ ((unused)))
+{
+  return current_header->header.typeflag == GNUTYPE_SPARSE;
+}
+
+/* Add a sparse item to the sparse file and its obstack */
+static enum oldgnu_add_status
+oldgnu_add_sparse (struct tar_sparse_file *file, struct sparse *s)
+{
+  struct sp_array sp;
+
+  if (s->numbytes[0] == '\0')
+    return add_finish;
+  sp.offset = OFF_FROM_HEADER (s->offset);
+  sp.numbytes = OFF_FROM_HEADER (s->numbytes);
+  if (sp.offset < 0 || sp.numbytes < 0
+      || INT_ADD_OVERFLOW (sp.offset, sp.numbytes)
+      || file->stat_info->stat.st_size < sp.offset + sp.numbytes
+      || file->stat_info->archive_file_size < 0)
+    return add_fail;
+
+  sparse_add_map (file->stat_info, &sp);
+  return add_ok;
+}
+
+static bool
+oldgnu_fixup_header (struct tar_sparse_file *file)
+{
+  /* NOTE! st_size was initialized from the header
+     which actually contains archived size. The following fixes it */
+  off_t realsize = OFF_FROM_HEADER (current_header->oldgnu_header.realsize);
+  file->stat_info->archive_file_size = file->stat_info->stat.st_size;
+  file->stat_info->stat.st_size = max (0, realsize);
+  return 0 <= realsize;
+}
+
+/* Convert old GNU format sparse data to internal representation */
+static bool
+oldgnu_get_sparse_info (struct tar_sparse_file *file)
+{
+  size_t i;
+  union block *h = current_header;
+  int ext_p;
+  enum oldgnu_add_status rc;
+
+  file->stat_info->sparse_map_avail = 0;
+  for (i = 0; i < SPARSES_IN_OLDGNU_HEADER; i++)
+    {
+      rc = oldgnu_add_sparse (file, &h->oldgnu_header.sp[i]);
+      if (rc != add_ok)
+	break;
+    }
+
+  for (ext_p = h->oldgnu_header.isextended;
+       rc == add_ok && ext_p; ext_p = h->sparse_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_SPARSE_HEADER && rc == add_ok; i++)
+	rc = oldgnu_add_sparse (file, &h->sparse_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 void
+oldgnu_store_sparse_info (struct tar_sparse_file *file, size_t *pindex,
+			  struct sparse *sp, size_t sparse_size)
+{
+  for (; *pindex < file->stat_info->sparse_map_avail
+	 && sparse_size > 0; sparse_size--, sp++, ++*pindex)
+    {
+      OFF_TO_CHARS (file->stat_info->sparse_map[*pindex].offset,
+		    sp->offset);
+      OFF_TO_CHARS (file->stat_info->sparse_map[*pindex].numbytes,
+		    sp->numbytes);
+    }
+}
+
+static bool
+oldgnu_dump_header (struct tar_sparse_file *file)
+{
+  off_t block_ordinal = current_block_ordinal ();
+  union block *blk;
+  size_t i;
+
+  blk = start_header (file->stat_info);
+  blk->header.typeflag = GNUTYPE_SPARSE;
+  if (file->stat_info->sparse_map_avail > SPARSES_IN_OLDGNU_HEADER)
+    blk->oldgnu_header.isextended = 1;
+
+  /* Store the real file size */
+  OFF_TO_CHARS (file->stat_info->stat.st_size, blk->oldgnu_header.realsize);
+  /* Store the effective (shrunken) file size */
+  OFF_TO_CHARS (file->stat_info->archive_file_size, blk->header.size);
+
+  i = 0;
+  oldgnu_store_sparse_info (file, &i,
+			    blk->oldgnu_header.sp,
+			    SPARSES_IN_OLDGNU_HEADER);
+  blk->oldgnu_header.isextended = i < file->stat_info->sparse_map_avail;
+  finish_header (file->stat_info, blk, block_ordinal);
+
+  while (i < file->stat_info->sparse_map_avail)
+    {
+      blk = find_next_block ();
+      memset (blk->buffer, 0, BLOCKSIZE);
+      oldgnu_store_sparse_info (file, &i,
+				blk->sparse_header.sp,
+				SPARSES_IN_SPARSE_HEADER);
+      if (i < file->stat_info->sparse_map_avail)
+	blk->sparse_header.isextended = 1;
+      set_next_block_after (blk);
+    }
+  return true;
+}
+
+static struct tar_sparse_optab const oldgnu_optab = {
+  NULL,  /* No init function */
+  NULL,  /* No done function */
+  oldgnu_sparse_member_p,
+  oldgnu_dump_header,
+  oldgnu_fixup_header,
+  oldgnu_get_sparse_info,
+  NULL,  /* No scan_block function */
+  sparse_dump_region,
+  sparse_extract_region,
+};
+
+
+/* Star */
+
+static bool
+star_sparse_member_p (struct tar_sparse_file *file __attribute__ ((unused)))
+{
+  return current_header->header.typeflag == GNUTYPE_SPARSE;
+}
+
+static bool
+star_fixup_header (struct tar_sparse_file *file)
+{
+  /* NOTE! st_size was initialized from the header
+     which actually contains archived size. The following fixes it */
+  off_t realsize = OFF_FROM_HEADER (current_header->star_in_header.realsize);
+  file->stat_info->archive_file_size = file->stat_info->stat.st_size;
+  file->stat_info->stat.st_size = max (0, realsize);
+  return 0 <= realsize;
+}
+
+/* Convert STAR format sparse data to internal representation */
+static bool
+star_get_sparse_info (struct tar_sparse_file *file)
+{
+  size_t i;
+  union block *h = current_header;
+  int ext_p;
+  enum oldgnu_add_status rc = add_ok;
+
+  file->stat_info->sparse_map_avail = 0;
+
+  if (h->star_in_header.prefix[0] == '\0'
+      && 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]);
+      file->dumped_size += BLOCKSIZE;
+    }
+
+  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;
+}
+
+/* Start a header that uses the effective (shrunken) file size.  */
+static union block *
+pax_start_header (struct tar_stat_info *st)
+{
+  off_t realsize = st->stat.st_size;
+  union block *blk;
+  st->stat.st_size = st->archive_file_size;
+  blk = start_header (st);
+  st->stat.st_size = realsize;
+  return blk;
+}
+
+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 = pax_start_header (file->stat_info);
+  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 const *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);
+  /* Make sure the created header name is shorter than NAME_FIELD_SIZE: */
+  if (strlen (file->stat_info->file_name) > NAME_FIELD_SIZE)
+    file->stat_info->file_name[NAME_FIELD_SIZE] = 0;
+
+  blk = pax_start_header (file->stat_info);
+  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;
+
+  errno = 0;
+  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 (off_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,
+};