my_symlink2.cc

/* Copyright (C) 2000 MySQL AB

   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 St, Fifth Floor, Boston, MA  02110-1301  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 automaticly create, delete and
  rename files and symlinks like they would be one unit.
*/

#include <config.h>

#include <drizzled/internal/my_sys.h>
#include <drizzled/error.h>
#include <drizzled/internal/m_string.h>

namespace drizzled {
namespace internal {

int my_create_with_symlink(const char *linkname, const char *filename,
                           int createflags, int access_flags, myf MyFlags)
{
  /* Test if we should create a link */
  bool create_link= false;
  char rp_buff[PATH_MAX];

  if (my_disable_symlinks)
  {
    /* Create only the file, not the link and file */
    if (linkname)
      filename= linkname;
  }
  else if (linkname)
  {
    if (!realpath(linkname,rp_buff))
      my_load_path(rp_buff, linkname, NULL);
    rp_buff[FN_REFLEN-1]= '\0';
    char abs_linkname[FN_REFLEN];
    strcpy(abs_linkname, rp_buff);
    create_link= strcmp(abs_linkname, filename);
  }

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

  int file= my_create(filename, createflags, access_flags, MyFlags);
  if (file >= 0 && create_link)
  {
    /* Delete old link/file */
    if (MyFlags & MY_DELETE_OLD)
      my_delete(linkname, MYF(0));
    /* Create link */
    if (symlink(filename,linkname))
    {
      /* Fail, remove everything we have done */
      int tmp_errno= errno;
      my_close(file, MYF(0));
      my_delete(filename, MYF(0));
      file= -1;
      errno= tmp_errno;
    }
    else if (MyFlags & MY_SYNC_DIR)
      my_sync_dir_by_file(linkname, MyFlags);
  }
  return file;
}

/*
  If the file was a symlink, delete both symlink and the file which the
  symlink pointed to.
*/

int my_delete_with_symlink(const char *name, myf MyFlags)
{
  char link_name[FN_REFLEN];
  ssize_t sym_link_size= readlink(name,link_name,FN_REFLEN-1);
  int was_symlink= (!my_disable_symlinks && sym_link_size != -1);
  int result;

  if (!(result=my_delete(name, MyFlags)))
  {
    if (was_symlink)
    {
      link_name[sym_link_size]= '\0';
      result= my_delete(link_name, MyFlags);
    }
  }
  return(result);
}

/*
  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)
{
  char link_name[FN_REFLEN], tmp_name[FN_REFLEN];
  int sym_link_size= -1;
  int was_symlink= (!my_disable_symlinks &&
                   (sym_link_size= static_cast<int>(readlink(from,link_name,
                                                    FN_REFLEN-1))) != -1); 
  int result=0;
  int name_is_different;

  if (!was_symlink)
    return(my_rename(from, to, MyFlags));
  else
    link_name[sym_link_size]= '\0';

  /* Change filename that symlink pointed to */
  strcpy(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))
  {
    errno= EEXIST;
    if (MyFlags & MY_WME)
      my_error(EE_CANTCREATEFILE, MYF(0), tmp_name, EEXIST);
    return 1;
  }

  /* Create new symlink */
  if (symlink(tmp_name, to))
    return 1;
  else if (MyFlags & MY_SYNC_DIR)
    my_sync_dir_by_file(to, MyFlags);

  /*
    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=errno;
    my_delete(to, MyFlags);     /* Remove created symlink */
    errno=save_errno;
    return 1;
  }

  /* Remove original symlink */
  if (my_delete(from, MyFlags))
  {
    int save_errno=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);
    errno=save_errno;
    result= 1;
  }
  return(result);
}

} /* namespace internal */
} /* namespace drizzled */