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✏️ Editing: my_symlink2.c

/* Copyright (c) 2000, 2001, 2003, 2005-2007 MySQL AB
   Use is subject to license terms

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; version 2 of the License.

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., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1335  USA */

/*
  Advanced symlink handling.
  This is used in MyISAM to let users symlinks tables to different disk.
  The main idea with these functions is to automatically create, delete and
  rename files and symlinks like they would be one unit.
*/

#include "mysys_priv.h"
#include "mysys_err.h"
#include <m_string.h>

File my_create_with_symlink(const char *linkname, const char *filename,
			    mode_t createflags, int access_flags, myf MyFlags)
{
  File file;
  int tmp_errno;
  /* Test if we should create a link */
  int create_link;
  char abs_linkname[FN_REFLEN];
  DBUG_ENTER("my_create_with_symlink");
  DBUG_PRINT("enter", ("linkname: %s  filename: %s",
                       linkname ? linkname : "(NULL)",
                       filename ? filename : "(NULL)"));

if (my_disable_symlinks)
  {
    DBUG_PRINT("info", ("Symlinks disabled"));
    /* Create only the file, not the link and file */
    create_link= 0;
    if (linkname)
      filename= linkname;
  }
  else
  {
    if (linkname)
      my_realpath(abs_linkname, linkname, MYF(0));
    create_link= (linkname && strcmp(abs_linkname,filename));
  }

if (!(MyFlags & MY_DELETE_OLD))
  {
    if (!access(filename,F_OK))
    {
      my_errno= errno= EEXIST;
      my_error(EE_CANTCREATEFILE, MYF(0), filename, EEXIST);
      DBUG_RETURN(-1);
    }
    if (create_link && !access(linkname,F_OK))
    {
      my_errno= errno= EEXIST;
      my_error(EE_CANTCREATEFILE, MYF(0), linkname, EEXIST);
      DBUG_RETURN(-1);
    }
  }

if ((file=my_create(filename, createflags, access_flags, MyFlags)) >= 0)
  {
    if (create_link)
    {
      /* Delete old link/file */
      if (MyFlags & MY_DELETE_OLD)
	my_delete(linkname, MYF(0));
      /* Create link */
      if (my_symlink(filename, linkname, MyFlags))
      {
	/* Fail, remove everything we have done */
	tmp_errno=my_errno;
	my_close(file,MYF(0));
	my_delete(filename, MYF(0));
	file= -1;
	my_errno=tmp_errno;
      }
    }
  }
  DBUG_RETURN(file);
}

/*
  If the file is a normal file, just rename it.
  If the file is a symlink:
   - Create a new file with the name 'to' that points at
     symlink_dir/basename(to)
   - Rename the symlinked file to symlink_dir/basename(to)
   - Delete 'from'
   If something goes wrong, restore everything.
*/

int my_rename_with_symlink(const char *from, const char *to, myf MyFlags)
{
#ifndef HAVE_READLINK
  return my_rename(from, to, MyFlags);
#else
  char link_name[FN_REFLEN], tmp_name[FN_REFLEN];
  int was_symlink= (!my_disable_symlinks &&
		    !my_readlink(link_name, from, MYF(0)));
  int result=0;
  int name_is_different;
  DBUG_ENTER("my_rename_with_symlink");

if (!was_symlink)
    DBUG_RETURN(my_rename(from, to, MyFlags));

/* Change filename that symlink pointed to */
  strmov(tmp_name, to);
  fn_same(tmp_name,link_name,1);		/* Copy dir */
  name_is_different= strcmp(link_name, tmp_name);
  if (name_is_different && !access(tmp_name, F_OK))
  {
    my_errno= EEXIST;
    if (MyFlags & MY_WME)
      my_error(EE_CANTCREATEFILE, MYF(0), tmp_name, EEXIST);
    DBUG_RETURN(1);
  }

/* Create new symlink */
  if (my_symlink(tmp_name, to, MyFlags))
    DBUG_RETURN(1);

/*
    Rename symlinked file if the base name didn't change.
    This can happen if you use this function where 'from' and 'to' has
    the same basename and different directories.
   */

if (name_is_different && my_rename(link_name, tmp_name, MyFlags))
  {
    int save_errno=my_errno;
    my_delete(to, MyFlags);			/* Remove created symlink */
    my_errno=save_errno;
    DBUG_RETURN(1);
  }

/* Remove original symlink */
  if (my_delete(from, MyFlags))
  {
    int save_errno=my_errno;
    /* Remove created link */
    my_delete(to, MyFlags);
    /* Rename file back */
    if (strcmp(link_name, tmp_name))
      (void) my_rename(tmp_name, link_name, MyFlags);
    my_errno=save_errno;
    result= 1;
  }
  DBUG_RETURN(result);
#endif /* HAVE_READLINK */
}

/** delete a - possibly symlinked - table file

This is used to delete a file that is part of a table (e.g. MYI or MYD
  file of MyISAM) when dropping a table. A file might be a symlink -
  if the table was created with DATA DIRECTORY or INDEX DIRECTORY -
  in this case both the symlink and the symlinked file are deleted,
  but only if the symlinked file is not in the datadir.
*/

int my_handler_delete_with_symlink(const char *filename, myf sync_dir)
{
  char real[FN_REFLEN];
  int res= 0;
  DBUG_ENTER("my_handler_delete_with_symlink");

if (my_is_symlink(filename))
  {
    /*
      Delete the symlinked file only if the symlink is not
      pointing into datadir.
    */
    if (!(my_realpath(real, filename, MYF(0)) ||
          mysys_test_invalid_symlink(real)))
      res= my_delete(real, MYF(MY_NOSYMLINKS | sync_dir));
  }
  DBUG_RETURN(my_delete(filename, sync_dir) || res);
}

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