/* xsparse - expands compressed sparse file images extracted from GNU tar
   archives.

   Copyright 2006, 2007, 2010, 2013 Free Software Foundation, Inc.

   This file is part of GNU tar.

   GNU tar 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 of the License, or
   (at your option) any later version.

   GNU tar 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/>.

   Written by Sergey Poznyakoff  */

#include <stdlib.h>
#include <stdint.h>
#include <stdio.h>
#include <stdarg.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <limits.h>
#include <errno.h>

/* Bound on length of the string representing an off_t.
   See INT_STRLEN_BOUND in intprops.h for explanation */
#define OFF_T_STRLEN_BOUND ((sizeof (off_t) * CHAR_BIT) * 146 / 485 + 1)
#define OFF_T_STRSIZE_BOUND (OFF_T_STRLEN_BOUND+1)

#define BLOCKSIZE 512

struct sp_array
{
  off_t offset;
  off_t numbytes;
};

char *progname;
int verbose;

void
die (int code, char *fmt, ...)
{
  va_list ap;

  fprintf (stderr, "%s: ", progname);
  va_start (ap, fmt);
  vfprintf (stderr, fmt, ap);
  va_end (ap);
  fprintf (stderr, "\n");
  exit (code);
}

void *
emalloc (size_t size)
{
  char *p = malloc (size);
  if (!p)
    die (1, "not enough memory");
  return p;
}

off_t
string_to_off (char *p, char **endp)
{
  off_t v = 0;

  for (; *p; p++)
    {
      int digit = *p - '0';
      off_t x = v * 10;
      if (9 < (unsigned) digit)
	{
	  if (endp)
	    {
	      *endp = p;
	      break;
	    }
	  die (1, "number parse error near %s", p);
	}
      else if (x / 10 != v)
	die (1, "number out of allowed range, near %s", p);
      v = x + digit;
      if (v < 0)
	die (1, "negative number");
    }
  if (endp)
    *endp = p;
  return v;
}

size_t
string_to_size (char *p, char **endp)
{
  off_t v = string_to_off (p, endp);
  size_t ret = v;
  if (ret != v)
    die (1, "number too big");
  return ret;
}

size_t sparse_map_size;
struct sp_array *sparse_map;

void
get_line (char *s, int size, FILE *stream)
{
  char *p = fgets (s, size, stream);
  size_t len;

  if (!p)
    die (1, "unexpected end of file");
  len = strlen (p);
  if (s[len - 1] != '\n')
    die (1, "buffer overflow");
  s[len - 1] = 0;
}

int
get_var (FILE *fp, char **name, char **value)
{
  static char *buffer;
  static size_t bufsize = OFF_T_STRSIZE_BOUND;
  char *p, *q;

  buffer = emalloc (bufsize);
  do
    {
      size_t len, s;

      if (!fgets (buffer, bufsize, fp))
	return 0;
      len = strlen (buffer);
      if (len == 0)
	return 0;

      s = string_to_size (buffer, &p);
      if (*p != ' ')
	die (1, "malformed header: expected space but found %s", p);
      if (buffer[len-1] != '\n')
	{
	  if (bufsize < s + 1)
	    {
	      bufsize = s + 1;
	      buffer = realloc (buffer, bufsize);
	      if (!buffer)
		die (1, "not enough memory");
	    }
	  if (!fgets (buffer + len, s - len + 1, fp))
	    die (1, "unexpected end of file or read error");
	}
      p++;
    }
  while (memcmp (p, "GNU.sparse.", 11));

  p += 11;
  q = strchr (p, '=');
  if (!q)
    die (1, "malformed header: expected '=' not found");
  *q++ = 0;
  q[strlen (q) - 1] = 0;
  *name = p;
  *value = q;
  return 1;
}

char *outname;
off_t outsize;
unsigned version_major;
unsigned version_minor;

void
read_xheader (char *name)
{
  char *kw, *val;
  FILE *fp = fopen (name, "r");
  char *expect = NULL;
  size_t i = 0;

  if (verbose)
    printf ("Reading extended header file\n");

  while (get_var (fp, &kw, &val))
    {
      if (verbose)
	printf ("Found variable GNU.sparse.%s = %s\n", kw, val);

      if (expect && strcmp (kw, expect))
	die (1, "bad keyword sequence: expected '%s' but found '%s'",
	     expect, kw);
      expect = NULL;
      if (strcmp (kw, "name") == 0)
	{
	  outname = emalloc (strlen (val) + 1);
	  strcpy (outname, val);
	}
      else if (strcmp (kw, "major") == 0)
	{
	  version_major = string_to_size (val, NULL);
	}
      else if (strcmp (kw, "minor") == 0)
	{
	  version_minor = string_to_size (val, NULL);
	}
      else if (strcmp (kw, "realsize") == 0
	       || strcmp (kw, "size") == 0)
	{
	  outsize = string_to_off (val, NULL);
	}
      else if (strcmp (kw, "numblocks") == 0)
	{
	  sparse_map_size = string_to_size (val, NULL);
	  sparse_map = emalloc (sparse_map_size * sizeof *sparse_map);
	}
      else if (strcmp (kw, "offset") == 0)
	{
	  sparse_map[i].offset = string_to_off (val, NULL);
	  expect = "numbytes";
	}
      else if (strcmp (kw, "numbytes") == 0)
	{
	  sparse_map[i++].numbytes = string_to_off (val, NULL);
	}
      else if (strcmp (kw, "map") == 0)
	{
	  for (i = 0; i < sparse_map_size; i++)
	    {
	      sparse_map[i].offset = string_to_off (val, &val);
	      if (*val != ',')
		die (1, "bad GNU.sparse.map: expected ',' but found '%c'",
		     *val);
	      sparse_map[i].numbytes = string_to_off (val+1, &val);
	      if (*val != ',')
		{
		  if (!(*val == 0 && i == sparse_map_size-1))
		    die (1, "bad GNU.sparse.map: expected ',' but found '%c'",
			 *val);
		}
	      else
		val++;
	    }
	  if (*val)
	    die (1, "bad GNU.sparse.map: garbage at the end");
	}
    }
  if (expect)
    die (1, "bad keyword sequence: expected '%s' not found", expect);
  if (version_major == 0 && sparse_map_size == 0)
    die (1, "size of the sparse map unknown");
  if (i != sparse_map_size)
    die (1, "not all sparse entries supplied");
  fclose (fp);
}

void
read_map (FILE *ifp)
{
  size_t i;
  char nbuf[OFF_T_STRSIZE_BOUND];

  if (verbose)
    printf ("Reading v.1.0 sparse map\n");

  get_line (nbuf, sizeof nbuf, ifp);
  sparse_map_size = string_to_size (nbuf, NULL);
  sparse_map = emalloc (sparse_map_size * sizeof *sparse_map);

  for (i = 0; i < sparse_map_size; i++)
    {
      get_line (nbuf, sizeof nbuf, ifp);
      sparse_map[i].offset = string_to_off (nbuf, NULL);
      get_line (nbuf, sizeof nbuf, ifp);
      sparse_map[i].numbytes = string_to_off (nbuf, NULL);
    }

  fseeko (ifp, ((ftell (ifp) + BLOCKSIZE - 1) / BLOCKSIZE) * BLOCKSIZE,
	  SEEK_SET);
}

void
expand_sparse (FILE *sfp, int ofd)
{
  size_t i;
  off_t max_numbytes = 0;
  size_t maxbytes;
  char *buffer;

  for (i = 0; i < sparse_map_size; i++)
    if (max_numbytes < sparse_map[i].numbytes)
      max_numbytes = sparse_map[i].numbytes;

  maxbytes = max_numbytes < SIZE_MAX ? max_numbytes : SIZE_MAX;

  for (buffer = malloc (maxbytes); !buffer; maxbytes /= 2)
    if (maxbytes == 0)
      die (1, "not enough memory");

  for (i = 0; i < sparse_map_size; i++)
    {
      off_t size = sparse_map[i].numbytes;

      if (size == 0)
	ftruncate (ofd, sparse_map[i].offset);
      else
	{
	  lseek (ofd, sparse_map[i].offset, SEEK_SET);
	  while (size)
	    {
	      size_t rdsize = (size < maxbytes) ? size : maxbytes;
	      if (rdsize != fread (buffer, 1, rdsize, sfp))
		die (1, "read error (%d)", errno);
	      if (rdsize != write (ofd, buffer, rdsize))
		die (1, "write error (%d)", errno);
	      size -= rdsize;
	    }
	}
    }
  free (buffer);
}

void
usage (int code)
{
  printf ("Usage: %s [OPTIONS] infile [outfile]\n", progname);
  printf ("%s: expand sparse files extracted from GNU archives\n",
	  progname);
  printf ("\nOPTIONS are:\n\n");
  printf ("  -h           Display this help list\n");
  printf ("  -n           Dry run: do nothing, print what would have been done\n");
  printf ("  -v           Increase verbosity level\n");
  printf ("  -x FILE      Parse extended header FILE\n\n");

  exit (code);
}

void
guess_outname (char *name)
{
  char *p;
  char *s;

  if (name[0] == '.' && name[1] == '/')
    name += 2;

  p = name + strlen (name) - 1;
  s = NULL;

  for (; p > name && *p != '/'; p--)
    ;
  if (*p == '/')
    s = p + 1;
  if (p != name)
    {
      for (p--; p > name && *p != '/'; p--)
	;
    }

  if (*p != '/')
    {
      if (s)
	outname = s;
      else
	{
	  outname = emalloc (4 + strlen (name));
	  strcpy (outname, "../");
	  strcpy (outname + 3, name);
	}
    }
  else
    {
      size_t len = p - name + 1;
      outname = emalloc (len + strlen (s) + 1);
      memcpy (outname, name, len);
      strcpy (outname + len, s);
    }
}

int
main (int argc, char **argv)
{
  int c;
  int dry_run = 0;
  char *xheader_file = NULL;
  char *inname;
  FILE *ifp;
  struct stat st;
  int ofd;

  progname = argv[0];
  while ((c = getopt (argc, argv, "hnvx:")) != EOF)
    {
      switch (c)
	{
	case 'h':
	  usage (0);
	  break;

	case 'x':
	  xheader_file = optarg;
	  break;

	case 'n':
	  dry_run = 1;
	case 'v':
	  verbose++;
	  break;

	default:
	  exit (1);
	}
    }

  argc -= optind;
  argv += optind;

  if (argc == 0 || argc > 2)
    usage (1);

  if (xheader_file)
    read_xheader (xheader_file);

  inname = argv[0];
  if (argv[1])
    outname = argv[1];

  if (stat (inname, &st))
    die (1, "cannot stat %s (%d)", inname, errno);

  ifp = fopen (inname, "r");
  if (ifp == NULL)
    die (1, "cannot open file %s (%d)", inname, errno);

  if (!xheader_file || version_major == 1)
    read_map (ifp);

  if (!outname)
    guess_outname (inname);

  ofd = open (outname, O_RDWR|O_CREAT|O_TRUNC, st.st_mode);
  if (ofd == -1)
    die (1, "cannot open file %s (%d)", outname, errno);

  if (verbose)
    printf ("Expanding file '%s' to '%s'\n", inname, outname);

  if (dry_run)
    {
      printf ("Finished dry run\n");
      return 0;
    }

  expand_sparse (ifp, ofd);

  fclose (ifp);
  close (ofd);

  if (verbose)
    printf ("Done\n");

  if (outsize)
    {
      if (stat (outname, &st))
	die (1, "cannot stat output file %s (%d)", outname, errno);
      if (st.st_size != outsize)
	die (1, "expanded file has wrong size");
    }

  return 0;
}