text: /* GIO - GLib Input, Output and Streaming Library
   * 
   * Copyright (C) 2006-2007 Red Hat, Inc.
   *
   * This library is free software; you can redistribute it and/or
   * modify it under the terms of the GNU Lesser General Public
   * License as published by the Free Software Foundation; either
   * version 2 of the License, or (at your option) any later version.
   *
   * This library 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
   * Lesser General Public License for more details.
   *
   * You should have received a copy of the GNU Lesser General
   * Public License along with this library; if not, write to the
   * Free Software Foundation, Inc., 59 Temple Place, Suite 330,
   * Boston, MA 02111-1307, USA.
   *
   * Author: Alexander Larsson <alexl@redhat.com>
   */
  
  #include "config.h"
  
  #include <sys/types.h>
  #include <sys/stat.h>
  #include <fcntl.h>
  #ifdef HAVE_UNISTD_H
  #include <unistd.h>
  #endif
  #include <errno.h>
  #include <string.h>
  
  #include <glib.h>
  #include <glib/gstdio.h>
  #include "glibintl.h"
  #include "gioerror.h"
  #include "gcancellable.h"
  #include "glocalfileoutputstream.h"
  #include "glocalfileinfo.h"
  
  #ifdef G_OS_WIN32
  #include <io.h>
  #ifndef S_ISDIR
  #define S_ISDIR(m) (((m) & _S_IFMT) == _S_IFDIR)
  #endif
  #ifndef S_ISREG
  #define S_ISREG(m) (((m) & _S_IFMT) == _S_IFREG)
  #endif
  #endif
  
  #ifndef O_BINARY
  #define O_BINARY 0
  #endif
  
  #include "gioalias.h"
  
  #define g_local_file_output_stream_get_type _g_local_file_output_stream_get_type
  G_DEFINE_TYPE (GLocalFileOutputStream, g_local_file_output_stream, G_TYPE_FILE_OUTPUT_STREAM);
  
  /* Some of the file replacement code was based on the code from gedit,
   * relicenced to LGPL with permissions from the authors.
   */
  
  #define BACKUP_EXTENSION "~"
  
  struct _GLocalFileOutputStreamPrivate {
    char *tmp_filename;
    char *original_filename;
    char *backup_filename;
    char *etag;
    gboolean sync_on_close;
    int fd;
  };
  
  static gssize     g_local_file_output_stream_write        (GOutputStream      *stream,
  							   const void         *buffer,
  							   gsize               count,
  							   GCancellable       *cancellable,
  							   GError            **error);
  static gboolean   g_local_file_output_stream_close        (GOutputStream      *stream,
  							   GCancellable       *cancellable,
  							   GError            **error);
  static GFileInfo *g_local_file_output_stream_query_info   (GFileOutputStream  *stream,
  							   const char         *attributes,
  							   GCancellable       *cancellable,
  							   GError            **error);
  static char *     g_local_file_output_stream_get_etag     (GFileOutputStream  *stream);
  static goffset    g_local_file_output_stream_tell         (GFileOutputStream  *stream);
  static gboolean   g_local_file_output_stream_can_seek     (GFileOutputStream  *stream);
  static gboolean   g_local_file_output_stream_seek         (GFileOutputStream  *stream,
  							   goffset             offset,
  							   GSeekType           type,
  							   GCancellable       *cancellable,
  							   GError            **error);
  static gboolean   g_local_file_output_stream_can_truncate (GFileOutputStream  *stream);
  static gboolean   g_local_file_output_stream_truncate     (GFileOutputStream  *stream,
  							   goffset             size,
  							   GCancellable       *cancellable,
  							   GError            **error);
  
  static void
  g_local_file_output_stream_finalize (GObject *object)
  {
    GLocalFileOutputStream *file;
    
    file = G_LOCAL_FILE_OUTPUT_STREAM (object);
    
    g_free (file->priv->tmp_filename);
    g_free (file->priv->original_filename);
    g_free (file->priv->backup_filename);
    g_free (file->priv->etag);
  
    G_OBJECT_CLASS (g_local_file_output_stream_parent_class)->finalize (object);
  }
  
  static void
  g_local_file_output_stream_class_init (GLocalFileOutputStreamClass *klass)
  {
    GObjectClass *gobject_class = G_OBJECT_CLASS (klass);
    GOutputStreamClass *stream_class = G_OUTPUT_STREAM_CLASS (klass);
    GFileOutputStreamClass *file_stream_class = G_FILE_OUTPUT_STREAM_CLASS (klass);
    
    g_type_class_add_private (klass, sizeof (GLocalFileOutputStreamPrivate));
    
    gobject_class->finalize = g_local_file_output_stream_finalize;
  
    stream_class->write_fn = g_local_file_output_stream_write;
    stream_class->close_fn = g_local_file_output_stream_close;
    file_stream_class->query_info = g_local_file_output_stream_query_info;
    file_stream_class->get_etag = g_local_file_output_stream_get_etag;
    file_stream_class->tell = g_local_file_output_stream_tell;
    file_stream_class->can_seek = g_local_file_output_stream_can_seek;
    file_stream_class->seek = g_local_file_output_stream_seek;
    file_stream_class->can_truncate = g_local_file_output_stream_can_truncate;
    file_stream_class->truncate_fn = g_local_file_output_stream_truncate;
  }
  
  static void
  g_local_file_output_stream_init (GLocalFileOutputStream *stream)
  {
    stream->priv = G_TYPE_INSTANCE_GET_PRIVATE (stream,
  					      G_TYPE_LOCAL_FILE_OUTPUT_STREAM,
  					      GLocalFileOutputStreamPrivate);
  }
  
  static gssize
  g_local_file_output_stream_write (GOutputStream  *stream,
  				  const void     *buffer,
  				  gsize           count,
  				  GCancellable   *cancellable,
  				  GError        **error)
  {
    GLocalFileOutputStream *file;
    gssize res;
  
    file = G_LOCAL_FILE_OUTPUT_STREAM (stream);
  
    while (1)
      {
        if (g_cancellable_set_error_if_cancelled (cancellable, error))
  	return -1;
        res = write (file->priv->fd, buffer, count);
        if (res == -1)
  	{
            int errsv = errno;
  
  	  if (errsv == EINTR)
  	    continue;
  	  
  	  g_set_error (error, G_IO_ERROR,
  		       g_io_error_from_errno (errsv),
  		       _("Error writing to file: %s"),
  		       g_strerror (errsv));
  	}
        
        break;
      }
    
    return res;
  }
  
  static gboolean
  g_local_file_output_stream_close (GOutputStream  *stream,
  				  GCancellable   *cancellable,
  				  GError        **error)
  {
    GLocalFileOutputStream *file;
    GLocalFileStat final_stat;
    int res;
  
    file = G_LOCAL_FILE_OUTPUT_STREAM (stream);
  
  #ifdef HAVE_FSYNC
    if (file->priv->sync_on_close &&
        fsync (file->priv->fd) != 0)
      {
        int errsv = errno;
        
        g_set_error (error, G_IO_ERROR,
  		   g_io_error_from_errno (errno),
  		   _("Error writing to file: %s"),
  		   g_strerror (errsv));
        goto err_out;
      }
  #endif
   
  #ifdef G_OS_WIN32
  
    /* Must close before renaming on Windows, so just do the close first
     * in all cases for now.
     */
    if (_fstati64 (file->priv->fd, &final_stat) == 0)
      file->priv->etag = _g_local_file_info_create_etag (&final_stat);
  
    res = close (file->priv->fd);
    if (res == -1)
      {
        int errsv = errno;
        
        g_set_error (error, G_IO_ERROR,
  		   g_io_error_from_errno (errsv),
  		   _("Error closing file: %s"),
  		   g_strerror (errsv));
        return FALSE;
      }
  
  #endif
  
    if (file->priv->tmp_filename)
      {
        /* We need to move the temp file to its final place,
         * and possibly create the backup file
         */
  
        if (file->priv->backup_filename)
  	{
  	  if (g_cancellable_set_error_if_cancelled (cancellable, error))
  	    goto err_out;
  	  
  #ifdef HAVE_LINK
  	  /* create original -> backup link, the original is then renamed over */
  	  if (g_unlink (file->priv->backup_filename) != 0 &&
  	      errno != ENOENT)
  	    {
                int errsv = errno;
  
  	      g_set_error (error, G_IO_ERROR,
  			   G_IO_ERROR_CANT_CREATE_BACKUP,
  			   _("Error removing old backup link: %s"),
  			   g_strerror (errsv));
  	      goto err_out;
  	    }
  
  	  if (link (file->priv->original_filename, file->priv->backup_filename) != 0)
  	    {
  	      /*  link failed or is not supported, try rename  */
  	      if (g_rename (file->priv->original_filename, file->priv->backup_filename) != 0)
  		{
                    int errsv = errno;
  
  	    	  g_set_error (error, G_IO_ERROR,
  		    	       G_IO_ERROR_CANT_CREATE_BACKUP,
  			       _("Error creating backup copy: %s"),
  			       g_strerror (errsv));
  	          goto err_out;
  		}
  	    }
  #else
  	    /* If link not supported, just rename... */
  	  if (g_rename (file->priv->original_filename, file->priv->backup_filename) != 0)
  	    {
                int errsv = errno;
  
  	      g_set_error (error, G_IO_ERROR,
  			   G_IO_ERROR_CANT_CREATE_BACKUP,
  			   _("Error creating backup copy: %s"),
  			   g_strerror (errsv));
  	      goto err_out;
  	    }
  #endif
  	}
        
  
        if (g_cancellable_set_error_if_cancelled (cancellable, error))
  	goto err_out;
  
        /* tmp -> original */
        if (g_rename (file->priv->tmp_filename, file->priv->original_filename) != 0)
  	{
            int errsv = errno;
  
  	  g_set_error (error, G_IO_ERROR,
  		       g_io_error_from_errno (errsv),
  		       _("Error renaming temporary file: %s"),
  		       g_strerror (errsv));
  	  goto err_out;
  	}
      }
    
    if (g_cancellable_set_error_if_cancelled (cancellable, error))
      goto err_out;
        
  #ifndef G_OS_WIN32		/* Already did the fstat() and close() above on Win32 */
  
    if (fstat (file->priv->fd, &final_stat) == 0)
      file->priv->etag = _g_local_file_info_create_etag (&final_stat);
  
    while (1)
      {
        res = close (file->priv->fd);
        if (res == -1)
  	{
            int errsv = errno;
  
  	  g_set_error (error, G_IO_ERROR,
  		       g_io_error_from_errno (errsv),
  		       _("Error closing file: %s"),
  		       g_strerror (errsv));
  	}
        break;
      }
    
    return res != -1;
  
  #else
  
    return TRUE;
  
  #endif
  
   err_out:
  
  #ifndef G_OS_WIN32
    /* A simple try to close the fd in case we fail before the actual close */
    close (file->priv->fd);
  #endif
    return FALSE;
  }
  
  static char *
  g_local_file_output_stream_get_etag (GFileOutputStream *stream)
  {
    GLocalFileOutputStream *file;
  
    file = G_LOCAL_FILE_OUTPUT_STREAM (stream);
    
    return g_strdup (file->priv->etag);
  }
  
  static goffset
  g_local_file_output_stream_tell (GFileOutputStream *stream)
  {
    GLocalFileOutputStream *file;
    off_t pos;
  
    file = G_LOCAL_FILE_OUTPUT_STREAM (stream);
    
    pos = lseek (file->priv->fd, 0, SEEK_CUR);
  
    if (pos == (off_t)-1)
      return 0;
    
    return pos;
  }
  
  static gboolean
  g_local_file_output_stream_can_seek (GFileOutputStream *stream)
  {
    GLocalFileOutputStream *file;
    off_t pos;
  
    file = G_LOCAL_FILE_OUTPUT_STREAM (stream);
    
    pos = lseek (file->priv->fd, 0, SEEK_CUR);
  
    if (pos == (off_t)-1 && errno == ESPIPE)
      return FALSE;
    
    return TRUE;
  }
  
  static int
  seek_type_to_lseek (GSeekType type)
  {
    switch (type)
      {
      default:
      case G_SEEK_CUR:
        return SEEK_CUR;
        
      case G_SEEK_SET:
        return SEEK_SET;
        
      case G_SEEK_END:
        return SEEK_END;
      }
  }
  
  static gboolean
  g_local_file_output_stream_seek (GFileOutputStream  *stream,
  				 goffset             offset,
  				 GSeekType           type,
  				 GCancellable       *cancellable,
  				 GError            **error)
  {
    GLocalFileOutputStream *file;
    off_t pos;
  
    file = G_LOCAL_FILE_OUTPUT_STREAM (stream);
  
    pos = lseek (file->priv->fd, offset, seek_type_to_lseek (type));
  
    if (pos == (off_t)-1)
      {
        int errsv = errno;
  
        g_set_error (error, G_IO_ERROR,
  		   g_io_error_from_errno (errsv),
  		   _("Error seeking in file: %s"),
  		   g_strerror (errsv));
        return FALSE;
      }
    
    return TRUE;
  }
  
  static gboolean
  g_local_file_output_stream_can_truncate (GFileOutputStream *stream)
  {
    /* We can't truncate pipes and stuff where we can't seek */
    return g_local_file_output_stream_can_seek (stream);
  }
  
  static gboolean
  g_local_file_output_stream_truncate (GFileOutputStream  *stream,
  				     goffset             size,
  				     GCancellable       *cancellable,
  				     GError            **error)
  {
    GLocalFileOutputStream *file;
    int res;
  
    file = G_LOCAL_FILE_OUTPUT_STREAM (stream);
  
   restart:
  #ifdef G_OS_WIN32
    res = g_win32_ftruncate (file->priv->fd, size);
  #else
    res = ftruncate (file->priv->fd, size);
  #endif
    
    if (res == -1)
      {
        int errsv = errno;
  
        if (errsv == EINTR)
  	{
  	  if (g_cancellable_set_error_if_cancelled (cancellable, error))
  	    return FALSE;
  	  goto restart;
  	}
  
        g_set_error (error, G_IO_ERROR,
  		   g_io_error_from_errno (errsv),
  		   _("Error truncating file: %s"),
  		   g_strerror (errsv));
        return FALSE;
      }
    
    return TRUE;
  }
  
  
  static GFileInfo *
  g_local_file_output_stream_query_info (GFileOutputStream  *stream,
  				       const char         *attributes,
  				       GCancellable       *cancellable,
  				       GError            **error)
  {
    GLocalFileOutputStream *file;
  
    file = G_LOCAL_FILE_OUTPUT_STREAM (stream);
  
    if (g_cancellable_set_error_if_cancelled (cancellable, error))
      return NULL;
    
    return _g_local_file_info_get_from_fd (file->priv->fd,
  					 attributes,
  					 error);
  }
  
  GFileOutputStream *
  _g_local_file_output_stream_create  (const char        *filename,
  				     GFileCreateFlags   flags,
  				     GCancellable      *cancellable,
  				     GError           **error)
  {
    GLocalFileOutputStream *stream;
    int mode;
    int fd;
  
    if (g_cancellable_set_error_if_cancelled (cancellable, error))
      return NULL;
  
    if (flags & G_FILE_CREATE_PRIVATE)
      mode = 0600;
    else
      mode = 0666;
    
    fd = g_open (filename, O_CREAT | O_EXCL | O_WRONLY | O_BINARY, mode);
    if (fd == -1)
      {
        int errsv = errno;
  
        if (errsv == EINVAL)
  	/* This must be an invalid filename, on e.g. FAT */
  	g_set_error_literal (error, G_IO_ERROR,
                               G_IO_ERROR_INVALID_FILENAME,
                               _("Invalid filename"));
        else
  	{
  	  char *display_name = g_filename_display_name (filename);
  	  g_set_error (error, G_IO_ERROR,
  		       g_io_error_from_errno (errsv),
  		       _("Error opening file '%s': %s"),
  		       display_name, g_strerror (errsv));
  	  g_free (display_name);
  	}
        return NULL;
      }
    
    stream = g_object_new (G_TYPE_LOCAL_FILE_OUTPUT_STREAM, NULL);
    stream->priv->fd = fd;
    return G_FILE_OUTPUT_STREAM (stream);
  }
  
  GFileOutputStream *
  _g_local_file_output_stream_append  (const char        *filename,
  				     GFileCreateFlags   flags,
  				     GCancellable      *cancellable,
  				     GError           **error)
  {
    GLocalFileOutputStream *stream;
    int mode;
    int fd;
  
    if (g_cancellable_set_error_if_cancelled (cancellable, error))
      return NULL;
  
    if (flags & G_FILE_CREATE_PRIVATE)
      mode = 0600;
    else
      mode = 0666;
  
    fd = g_open (filename, O_CREAT | O_APPEND | O_WRONLY | O_BINARY, mode);
    if (fd == -1)
      {
        int errsv = errno;
  
        if (errsv == EINVAL)
  	/* This must be an invalid filename, on e.g. FAT */
  	g_set_error_literal (error, G_IO_ERROR,
                               G_IO_ERROR_INVALID_FILENAME,
                               _("Invalid filename"));
        else
  	{
  	  char *display_name = g_filename_display_name (filename);
  	  g_set_error (error, G_IO_ERROR,
  		       g_io_error_from_errno (errsv),
  		       _("Error opening file '%s': %s"),
  		       display_name, g_strerror (errsv));
  	  g_free (display_name);
  	}
        return NULL;
      }
    
    stream = g_object_new (G_TYPE_LOCAL_FILE_OUTPUT_STREAM, NULL);
    stream->priv->fd = fd;
    
    return G_FILE_OUTPUT_STREAM (stream);
  }
  
  static char *
  create_backup_filename (const char *filename)
  {
    return g_strconcat (filename, BACKUP_EXTENSION, NULL);
  }
  
  #define BUFSIZE	8192 /* size of normal write buffer */
  
  static gboolean
  copy_file_data (gint     sfd,
  		gint     dfd,
  		GError **error)
  {
    gboolean ret = TRUE;
    gpointer buffer;
    const gchar *write_buffer;
    gssize bytes_read;
    gssize bytes_to_write;
    gssize bytes_written;
    
    buffer = g_malloc (BUFSIZE);
    
    do
      {
        bytes_read = read (sfd, buffer, BUFSIZE);
        if (bytes_read == -1)
  	{
            int errsv = errno;
  
  	  if (errsv == EINTR)
  	    continue;
  	  
  	  g_set_error (error, G_IO_ERROR,
  		       g_io_error_from_errno (errsv),
  		       _("Error reading from file: %s"),
  		       g_strerror (errsv));
  	  ret = FALSE;
  	  break;
  	}
        
        bytes_to_write = bytes_read;
        write_buffer = buffer;
        
        do
  	{
  	  bytes_written = write (dfd, write_buffer, bytes_to_write);
  	  if (bytes_written == -1)
  	    {
                int errsv = errno;
  
  	      if (errsv == EINTR)
  		continue;
  	      
  	      g_set_error (error, G_IO_ERROR,
  			   g_io_error_from_errno (errsv),
  			   _("Error writing to file: %s"),
  			   g_strerror (errsv));
  	      ret = FALSE;
  	      break;
  	    }
  	  
  	  bytes_to_write -= bytes_written;
  	  write_buffer += bytes_written;
  	}
        while (bytes_to_write > 0);
        
      } while ((bytes_read != 0) && (ret == TRUE));
  
    g_free (buffer);
    
    return ret;
  }
  
  static int
  handle_overwrite_open (const char    *filename,
  		       const char    *etag,
  		       gboolean       create_backup,
  		       char         **temp_filename,
  		       GFileCreateFlags flags,
  		       GCancellable  *cancellable,
  		       GError       **error)
  {
    int fd = -1;
    GLocalFileStat original_stat;
    char *current_etag;
    gboolean is_symlink;
    int open_flags;
    int res;
    int mode;
  
    if (flags & G_FILE_CREATE_PRIVATE)
      mode = 0600;
    else
      mode = 0666;
  
    /* We only need read access to the original file if we are creating a backup.
     * We also add O_CREATE to avoid a race if the file was just removed */
    if (create_backup)
      open_flags = O_RDWR | O_CREAT | O_BINARY;
    else
      open_flags = O_WRONLY | O_CREAT | O_BINARY;
    
    /* Some systems have O_NOFOLLOW, which lets us avoid some races
     * when finding out if the file we opened was a symlink */
  #ifdef O_NOFOLLOW
    is_symlink = FALSE;
    fd = g_open (filename, open_flags | O_NOFOLLOW, mode);
    if (fd == -1 && errno == ELOOP)
      {
        /* Could be a symlink, or it could be a regular ELOOP error,
         * but then the next open will fail too. */
        is_symlink = TRUE;
        fd = g_open (filename, open_flags, mode);
      }
  #else
    fd = g_open (filename, open_flags, mode);
    /* This is racy, but we do it as soon as possible to minimize the race */
    is_symlink = g_file_test (filename, G_FILE_TEST_IS_SYMLINK);
  #endif
      
    if (fd == -1)
      {
        int errsv = errno;
        char *display_name = g_filename_display_name (filename);
        g_set_error (error, G_IO_ERROR,
  		   g_io_error_from_errno (errsv),
  		   _("Error opening file '%s': %s"),
  		   display_name, g_strerror (errsv));
        g_free (display_name);
        return -1;
      }
    
  #ifdef G_OS_WIN32
    res = _fstati64 (fd, &original_stat);
  #else
    res = fstat (fd, &original_stat);
  #endif
  
    if (res != 0) 
      {
        int errsv = errno;
        char *display_name = g_filename_display_name (filename);
        g_set_error (error, G_IO_ERROR,
  		   g_io_error_from_errno (errsv),
  		   _("Error stating file '%s': %s"),
  		   display_name, g_strerror (errsv));
        g_free (display_name);
        goto err_out;
      }
    
    /* not a regular file */
    if (!S_ISREG (original_stat.st_mode))
      {
        if (S_ISDIR (original_stat.st_mode))
  	g_set_error_literal (error,
                               G_IO_ERROR,
                               G_IO_ERROR_IS_DIRECTORY,
                               _("Target file is a directory"));
        else
  	g_set_error_literal (error,
                               G_IO_ERROR,
                               G_IO_ERROR_NOT_REGULAR_FILE,
                               _("Target file is not a regular file"));
        goto err_out;
      }
    
    if (etag != NULL)
      {
        current_etag = _g_local_file_info_create_etag (&original_stat);
        if (strcmp (etag, current_etag) != 0)
  	{
  	  g_set_error_literal (error,
                                 G_IO_ERROR,
                                 G_IO_ERROR_WRONG_ETAG,
                                 _("The file was externally modified"));
  	  g_free (current_etag);
  	  goto err_out;
  	}
        g_free (current_etag);
      }
  
    /* We use two backup strategies.
     * The first one (which is faster) consist in saving to a
     * tmp file then rename the original file to the backup and the
     * tmp file to the original name. This is fast but doesn't work
     * when the file is a link (hard or symbolic) or when we can't
     * write to the current dir or can't set the permissions on the
     * new file. 
     * The second strategy consist simply in copying the old file
     * to a backup file and rewrite the contents of the file.
     */
    
    if ((flags & G_FILE_CREATE_REPLACE_DESTINATION) ||
        (!(original_stat.st_nlink > 1) && !is_symlink))
      {
        char *dirname, *tmp_filename;
        int tmpfd;
        
        dirname = g_path_get_dirname (filename);
        tmp_filename = g_build_filename (dirname, ".goutputstream-XXXXXX", NULL);
        g_free (dirname);
  
        tmpfd = g_mkstemp (tmp_filename);
        if (tmpfd == -1)
  	{
  	  g_free (tmp_filename);
  	  goto fallback_strategy;
  	}
        
        /* try to keep permissions (unless replacing) */
  
        if ( ! (flags & G_FILE_CREATE_REPLACE_DESTINATION) &&
  	   (
  #ifdef HAVE_FCHOWN
  	    fchown (tmpfd, original_stat.st_uid, original_stat.st_gid) == -1 ||
  #endif
  #ifdef HAVE_FCHMOD
  	    fchmod (tmpfd, original_stat.st_mode) == -1 ||
  #endif
  	    0
  	    )
  	  )
  	{
  	  struct stat tmp_statbuf;
  	  
  	  /* Check that we really needed to change something */
  	  if (fstat (tmpfd, &tmp_statbuf) != 0 ||
  	      original_stat.st_uid != tmp_statbuf.st_uid ||
  	      original_stat.st_gid != tmp_statbuf.st_gid ||
  	      original_stat.st_mode != tmp_statbuf.st_mode)
  	    {
  	      close (tmpfd);
  	      g_unlink (tmp_filename);
  	      g_free (tmp_filename);
  	      goto fallback_strategy;
  	    }
  	}
  
        close (fd);
        *temp_filename = tmp_filename;
        return tmpfd;
      }
  
   fallback_strategy:
  
    if (create_backup)
      {
  #if defined(HAVE_FCHOWN) && defined(HAVE_FCHMOD)
        struct stat tmp_statbuf;      
  #endif
        char *backup_filename;
        int bfd;
        
        backup_filename = create_backup_filename (filename);
  
        if (g_unlink (backup_filename) == -1 && errno != ENOENT)
  	{
  	  g_set_error_literal (error,
                                 G_IO_ERROR,
                                 G_IO_ERROR_CANT_CREATE_BACKUP,
                                 _("Backup file creation failed"));
  	  g_free (backup_filename);
  	  goto err_out;
  	}
  
        bfd = g_open (backup_filename,
  		    O_WRONLY | O_CREAT | O_EXCL | O_BINARY,
  		    original_stat.st_mode & 0777);
  
        if (bfd == -1)
  	{
  	  g_set_error_literal (error,
                                 G_IO_ERROR,
                                 G_IO_ERROR_CANT_CREATE_BACKUP,
                                 _("Backup file creation failed"));
  	  g_free (backup_filename);
  	  goto err_out;
  	}
  
        /* If needed, Try to set the group of the backup same as the
         * original file. If this fails, set the protection
         * bits for the group same as the protection bits for
         * others. */
  #if defined(HAVE_FCHOWN) && defined(HAVE_FCHMOD)
        if (fstat (bfd, &tmp_statbuf) != 0)
  	{
  	  g_set_error_literal (error,
                                 G_IO_ERROR,
                                 G_IO_ERROR_CANT_CREATE_BACKUP,
                                 _("Backup file creation failed"));
  	  g_unlink (backup_filename);
  	  g_free (backup_filename);
  	  goto err_out;
  	}
        
        if ((original_stat.st_gid != tmp_statbuf.st_gid)  &&
  	  fchown (bfd, (uid_t) -1, original_stat.st_gid) != 0)
  	{
  	  if (fchmod (bfd,
  		      (original_stat.st_mode & 0707) |
  		      ((original_stat.st_mode & 07) << 3)) != 0)
  	    {
  	      g_set_error_literal (error,
                                     G_IO_ERROR,
                                     G_IO_ERROR_CANT_CREATE_BACKUP,
                                     _("Backup file creation failed"));
  	      g_unlink (backup_filename);
  	      close (bfd);
  	      g_free (backup_filename);
  	      goto err_out;
  	    }
  	}
  #endif
  
        if (!copy_file_data (fd, bfd, NULL))
  	{
  	  g_set_error_literal (error,
                                 G_IO_ERROR,
                                 G_IO_ERROR_CANT_CREATE_BACKUP,
                                 _("Backup file creation failed"));
  	  g_unlink (backup_filename);
  	  close (bfd);
  	  g_free (backup_filename);
  	  
  	  goto err_out;
  	}
        
        close (bfd);
        g_free (backup_filename);
  
        /* Seek back to the start of the file after the backup copy */
        if (lseek (fd, 0, SEEK_SET) == -1)
  	{
            int errsv = errno;
  
  	  g_set_error (error, G_IO_ERROR,
  		       g_io_error_from_errno (errsv),
  		       _("Error seeking in file: %s"),
  		       g_strerror (errsv));
  	  goto err_out;
  	}
      }
  
    if (flags & G_FILE_CREATE_REPLACE_DESTINATION)
      {
        close (fd);
        
        if (g_unlink (filename) != 0)
  	{
  	  int errsv = errno;
  	  
  	  g_set_error (error, G_IO_ERROR,
  		       g_io_error_from_errno (errsv),
  		       _("Error removing old file: %s"),
  		       g_strerror (errsv));
  	  goto err_out2;
  	}
        
        fd = g_open (filename, O_WRONLY | O_CREAT | O_BINARY, mode);
        if (fd == -1)
  	{
  	  int errsv = errno;
  	  char *display_name = g_filename_display_name (filename);
  	  g_set_error (error, G_IO_ERROR,
  		       g_io_error_from_errno (errsv),
  		       _("Error opening file '%s': %s"),
  		       display_name, g_strerror (errsv));
  	  g_free (display_name);
  	  goto err_out2;
  	}
      }
    else
      {
        /* Truncate the file at the start */
  #ifdef G_OS_WIN32
        if (g_win32_ftruncate (fd, 0) == -1)
  #else
  	if (ftruncate (fd, 0) == -1)
  #endif
  	  {
  	    int errsv = errno;
  	    
  	    g_set_error (error, G_IO_ERROR,
  			 g_io_error_from_errno (errsv),
  			 _("Error truncating file: %s"),
  			 g_strerror (errsv));
  	    goto err_out;
  	  }
      }
      
    return fd;
  
   err_out:
    close (fd);
   err_out2:
    return -1;
  }
  
  GFileOutputStream *
  _g_local_file_output_stream_replace (const char        *filename,
  				     const char        *etag,
  				     gboolean           create_backup,
  				     GFileCreateFlags   flags,
  				     GCancellable      *cancellable,
  				     GError           **error)
  {
    GLocalFileOutputStream *stream;
    int mode;
    int fd;
    char *temp_file;
    gboolean sync_on_close;
  
    if (g_cancellable_set_error_if_cancelled (cancellable, error))
      return NULL;
  
    temp_file = NULL;
  
    if (flags & G_FILE_CREATE_PRIVATE)
      mode = 0600;
    else
      mode = 0666;
    sync_on_close = FALSE;
  
    /* If the file doesn't exist, create it */
    fd = g_open (filename, O_CREAT | O_EXCL | O_WRONLY | O_BINARY, mode);
  
    if (fd == -1 && errno == EEXIST)
      {
        /* The file already exists */
        fd = handle_overwrite_open (filename, etag, create_backup, &temp_file,
  				  flags, cancellable, error);
        if (fd == -1)
  	return NULL;
  
        /* If the final destination exists, we want to sync the newly written
         * file to ensure the data is on disk when we rename over the destination.
         * otherwise if we get a system crash we can lose both the new and the
         * old file on some filesystems. (I.E. those that don't guarantee the
         * data is written to the disk before the metadata.)
         */
        sync_on_close = TRUE;
      }
    else if (fd == -1)
      {
        int errsv = errno;
  
        if (errsv == EINVAL)
  	/* This must be an invalid filename, on e.g. FAT */
  	g_set_error_literal (error, G_IO_ERROR,
                               G_IO_ERROR_INVALID_FILENAME,
                               _("Invalid filename"));
        else
  	{
  	  char *display_name = g_filename_display_name (filename);
  	  g_set_error (error, G_IO_ERROR,
  		       g_io_error_from_errno (errsv),
  		       _("Error opening file '%s': %s"),
  		       display_name, g_strerror (errsv));
  	  g_free (display_name);
  	}
        return NULL;
      }
    
   
    stream = g_object_new (G_TYPE_LOCAL_FILE_OUTPUT_STREAM, NULL);
    stream->priv->fd = fd;
    stream->priv->sync_on_close = sync_on_close;
    stream->priv->tmp_filename = temp_file;
    if (create_backup)
      stream->priv->backup_filename = create_backup_filename (filename);
    stream->priv->original_filename =  g_strdup (filename);
    
    return G_FILE_OUTPUT_STREAM (stream);
  }
  