copy.c

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/* copy.c -- core functions for copying files and directories
   Copyright (C) 89, 90, 91, 1995-2002 Free Software Foundation.

   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 2, 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, write to the Free Software Foundation,
   Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */

/* Extracted from cp.c and librarified by Jim Meyering.  */

#ifdef _AIX
 #pragma alloca
#endif

#include <config.h>
#include <stdio.h>
#include <assert.h>
#include <sys/types.h>

#if HAVE_HURD_H
# include <hurd.h>
#endif

#include "system.h"
#include "error.h"
#include "backupfile.h"
#include "savedir.h"
#include "copy.h"
#include "cp-hash.h"
#include "hash.h"
#include "hash-pjw.h"
#include "same.h"
#include "dirname.h"
#include "full-write.h"
#include "path-concat.h"
#include "quote.h"
#include "same.h"
#include "xreadlink.h"

#define DO_CHOWN(Chown, File, New_uid, New_gid)				\
  (Chown (File, New_uid, New_gid)					\
   /* If non-root uses -p, it's ok if we can't preserve ownership.	\
      But root probably wants to know, e.g. if NFS disallows it,	\
      or if the target system doesn't support file ownership.  */	\
   && ((errno != EPERM && errno != EINVAL) || x->myeuid == 0))

#define SAME_OWNER(A, B) ((A).st_uid == (B).st_uid)
#define SAME_GROUP(A, B) ((A).st_gid == (B).st_gid)
#define SAME_OWNER_AND_GROUP(A, B) (SAME_OWNER (A, B) && SAME_GROUP (A, B))

#define UNWRITABLE(File_name, File_mode)		\
  ( /* euidaccess is not meaningful for symlinks */	\
    ! S_ISLNK (File_mode)				\
    && euidaccess (File_name, W_OK) != 0)

struct dir_list
{
  struct dir_list *parent;
  ino_t ino;
  dev_t dev;
};

/* Describe a just-created or just-renamed destination file.  */
struct F_triple
{
  char const* name;
  ino_t st_ino;
  dev_t st_dev;
};

/* Initial size of the above hash table.  */
#define DEST_INFO_INITIAL_CAPACITY 61

int euidaccess ();
int yesno ();

static int copy_internal PARAMS ((const char *src_path, const char *dst_path,
				  int new_dst, dev_t device,
				  struct dir_list *ancestors,
				  const struct cp_options *x,
				  int move_mode,
				  int *copy_into_self,
				  int *rename_succeeded));

/* Pointers to the file names:  they're used in the diagnostic that is issued
   when we detect the user is trying to copy a directory into itself.  */
static char const *top_level_src_path;
static char const *top_level_dst_path;

/* The invocation name of this program.  */
extern char *program_name;

/* Encapsulate selection of the file mode to be applied to
   new non-directories.  */

static mode_t
get_dest_mode (const struct cp_options *option, mode_t mode)
{
  /* In some applications (e.g., install), use precisely the
     specified mode.  */
  if (option->set_mode)
    return option->mode;

  /* Honor the umask for `cp', but not for `mv' or `cp -p'.
     In addition, `cp' without -p must clear the set-user-ID and set-group-ID
     bits.  POSIX requires it do that when creating new files.  */
  if (!option->move_mode && !option->preserve_mode)
    mode &= (option->umask_kill & ~(S_ISUID | S_ISGID));

  return mode;
}

/* FIXME: describe */
/* FIXME: rewrite this to use a hash table so we avoid the quadratic
   performance hit that's probably noticeable only on trees deeper
   than a few hundred levels.  See use of active_dir_map in remove.c  */

static int
is_ancestor (const struct stat *sb, const struct dir_list *ancestors)
{
  while (ancestors != 0)
    {
      if (ancestors->ino == sb->st_ino && ancestors->dev == sb->st_dev)
	return 1;
      ancestors = ancestors->parent;
    }
  return 0;
}

/* Read the contents of the directory SRC_PATH_IN, and recursively
   copy the contents to DST_PATH_IN.  NEW_DST is nonzero if
   DST_PATH_IN is a directory that was created previously in the
   recursion.   SRC_SB and ANCESTORS describe SRC_PATH_IN.
   Set *COPY_INTO_SELF to nonzero if SRC_PATH_IN is a parent of
   (or the same as) DST_PATH_IN;  otherwise, set it to zero.
   Return 0 if successful, -1 if an error occurs. */

static int
copy_dir (const char *src_path_in, const char *dst_path_in, int new_dst,
	  const struct stat *src_sb, struct dir_list *ancestors,
	  const struct cp_options *x, int *copy_into_self)
{
  char *name_space;
  char *namep;
  struct cp_options non_command_line_options = *x;
  int ret = 0;

  name_space = savedir (src_path_in);
  if (name_space == NULL)
    {
      /* This diagnostic is a bit vague because savedir can fail in
         several different ways.  */
      error (0, errno, _("cannot access %s"), quote (src_path_in));
      return -1;
    }

  /* For cp's -H option, dereference command line arguments, but do not
     dereference symlinks that are found via recursive traversal.  */
  if (x->dereference == DEREF_COMMAND_LINE_ARGUMENTS)
    non_command_line_options.xstat = lstat;

  namep = name_space;
  while (*namep != '\0')
    {
      int local_copy_into_self;
      char *src_path = path_concat (src_path_in, namep, NULL);
      char *dst_path = path_concat (dst_path_in, namep, NULL);

      if (dst_path == NULL || src_path == NULL)
	xalloc_die ();

      ret |= copy_internal (src_path, dst_path, new_dst, src_sb->st_dev,
			    ancestors, &non_command_line_options, 0,
			    &local_copy_into_self, NULL);
      *copy_into_self |= local_copy_into_self;

      free (dst_path);
      free (src_path);

      namep += strlen (namep) + 1;
    }
  free (name_space);
  return -ret;
}

/* Copy a regular file from SRC_PATH to DST_PATH.
   If the source file contains holes, copies holes and blocks of zeros
   in the source file as holes in the destination file.
   (Holes are read as zeroes by the `read' system call.)
   Use DST_MODE as the 3rd argument in the call to open.
   X provides many option settings.
   Return 0 if successful, -1 if an error occurred.
   *NEW_DST is as in copy_internal.  SRC_SB is the result
   of calling xstat (aka stat in this case) on SRC_PATH.  */

static int
copy_reg (const char *src_path, const char *dst_path,
	  const struct cp_options *x, mode_t dst_mode, int *new_dst,
	  struct stat const *src_sb)
{
  char *buf;
  int buf_size;
  int dest_desc;
  int source_desc;
  struct stat sb;
  struct stat src_open_sb;
  char *cp;
  int *ip;
  int return_val = 0;
  off_t n_read_total = 0;
  int last_write_made_hole = 0;
  int make_holes = (x->sparse_mode == SPARSE_ALWAYS);

  source_desc = open (src_path, O_RDONLY);
  if (source_desc < 0)
    {
      error (0, errno, _("cannot open %s for reading"), quote (src_path));
      return -1;
    }

  if (fstat (source_desc, &src_open_sb))
    {
      error (0, errno, _("cannot fstat %s"), quote (src_path));
      return_val = -1;
      goto close_src_desc;
    }

  /* Compare the source dev/ino from the open file to the incoming,
     saved ones obtained via a previous call to stat.  */
  if (! SAME_INODE (*src_sb, src_open_sb))
    {
      error (0, 0,
	     _("skipping file %s, as it was replaced while being copied"),
	     quote (src_path));
      return_val = -1;
      goto close_src_desc;
    }

  /* These semantics are required for cp.
     The if-block will be taken in move_mode.  */
  if (*new_dst)
    {
      dest_desc = open (dst_path, O_WRONLY | O_CREAT, dst_mode);
    }
  else
    {
      dest_desc = open (dst_path, O_WRONLY | O_TRUNC, dst_mode);

      if (dest_desc < 0 && x->unlink_dest_after_failed_open)
	{
	  if (unlink (dst_path))
	    {
	      error (0, errno, _("cannot remove %s"), quote (dst_path));
	      return_val = -1;
	      goto close_src_desc;
	    }

	  /* Tell caller that the destination file was unlinked.  */
	  *new_dst = 1;

	  /* Try the open again, but this time with different flags.  */
	  dest_desc = open (dst_path, O_WRONLY | O_CREAT, dst_mode);
	}
    }

  if (dest_desc < 0)
    {
      error (0, errno, _("cannot create regular file %s"), quote (dst_path));
      return_val = -1;
      goto close_src_desc;
    }

  /* Determine the optimal buffer size.  */

  if (fstat (dest_desc, &sb))
    {
      error (0, errno, _("cannot fstat %s"), quote (dst_path));
      return_val = -1;
      goto close_src_and_dst_desc;
    }

  buf_size = ST_BLKSIZE (sb);

#if HAVE_STRUCT_STAT_ST_BLOCKS
  if (x->sparse_mode == SPARSE_AUTO && S_ISREG (sb.st_mode))
    {
      /* Use a heuristic to determine whether SRC_PATH contains any
	 sparse blocks. */

      if (fstat (source_desc, &sb))
	{
	  error (0, errno, _("cannot fstat %s"), quote (src_path));
	  return_val = -1;
	  goto close_src_and_dst_desc;
	}

      /* If the file has fewer blocks than would normally
	 be needed for a file of its size, then
	 at least one of the blocks in the file is a hole. */
      if (S_ISREG (sb.st_mode)
	  && sb.st_size / ST_NBLOCKSIZE > ST_NBLOCKS (sb))
	make_holes = 1;
    }
#endif

  /* Make a buffer with space for a sentinel at the end.  */

  buf = (char *) alloca (buf_size + sizeof (int));

  for (;;)
    {
      ssize_t n_read = read (source_desc, buf, buf_size);
      if (n_read < 0)
	{
#ifdef EINTR
	  if (errno == EINTR)
	    continue;
#endif
	  error (0, errno, _("reading %s"), quote (src_path));
	  return_val = -1;
	  goto close_src_and_dst_desc;
	}
      if (n_read == 0)
	break;

      n_read_total += n_read;

      ip = 0;
      if (make_holes)
	{
	  buf[n_read] = 1;	/* Sentinel to stop loop.  */

	  /* Find first nonzero *word*, or the word with the sentinel.  */

	  ip = (int *) buf;
	  while (*ip++ == 0)
	    ;

	  /* Find the first nonzero *byte*, or the sentinel.  */

	  cp = (char *) (ip - 1);
	  while (*cp++ == 0)
	    ;

	  /* If we found the sentinel, the whole input block was zero,
	     and we can make a hole.  */

	  if (cp > buf + n_read)
	    {
	      /* Make a hole.  */
	      if (lseek (dest_desc, (off_t) n_read, SEEK_CUR) < 0L)
		{
		  error (0, errno, _("cannot lseek %s"), quote (dst_path));
		  return_val = -1;
		  goto close_src_and_dst_desc;
		}
	      last_write_made_hole = 1;
	    }
	  else
	    /* Clear to indicate that a normal write is needed. */
	    ip = 0;
	}
      if (ip == 0)
	{
	  size_t n = n_read;
	  if (full_write (dest_desc, buf, n) != n)
	    {
	      error (0, errno, _("writing %s"), quote (dst_path));
	      return_val = -1;
	      goto close_src_and_dst_desc;
	    }
	  last_write_made_hole = 0;
	}
    }

  /* If the file ends with a `hole', something needs to be written at
     the end.  Otherwise the kernel would truncate the file at the end
     of the last write operation.  */

  if (last_write_made_hole)
    {
#if HAVE_FTRUNCATE
      /* Write a null character and truncate it again.  */
      if (full_write (dest_desc, "", 1) != 1
	  || ftruncate (dest_desc, n_read_total) < 0)
#else
      /* Seek backwards one character and write a null.  */
      if (lseek (dest_desc, (off_t) -1, SEEK_CUR) < 0L
	  || full_write (dest_desc, "", 1) != 1)
#endif
	{
	  error (0, errno, _("writing %s"), quote (dst_path));
	  return_val = -1;
	}
    }