gio/glocalfileoutputstream.c

   1 /* GIO - GLib Input, Output and Streaming Library
   2  *
   3  * Copyright (C) 2006-2007 Red Hat, Inc.
   4  *
   5  * This library is free software; you can redistribute it and/or
   6  * modify it under the terms of the GNU Lesser General Public
   7  * License as published by the Free Software Foundation; either
   8  * version 2 of the License, or (at your option) any later version.
   9  *
  10  * This library is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13  * Lesser General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU Lesser General
  16  * Public License along with this library; if not, write to the
  17  * Free Software Foundation, Inc., 59 Temple Place, Suite 330,
  18  * Boston, MA 02111-1307, USA.
  19  *
  20  * Author: Alexander Larsson <alexl@redhat.com>
  21  */
  22
  23 #include "config.h"
  24
  25 #include <sys/types.h>
  26 #include <sys/stat.h>
  27 #include <fcntl.h>
  28 #ifdef HAVE_UNISTD_H
  29 #include <unistd.h>
  30 #endif
  31 #include <errno.h>
  32 #include <string.h>
  33
  34 #include <glib.h>
  35 #include <glib/gstdio.h>
  36 #include "glibintl.h"
  37 #include "gioerror.h"
  38 #include "gcancellable.h"
  39 #include "glocalfileoutputstream.h"
  40 #include "glocalfileinfo.h"
  41
  42 #ifdef G_OS_UNIX
  43 #include "gfiledescriptorbased.h"
  44 #endif
  45
  46 #ifdef G_OS_WIN32
  47 #include <io.h>
  48 #ifndef S_ISDIR
  49 #define S_ISDIR(m) (((m) & _S_IFMT) == _S_IFDIR)
  50 #endif
  51 #ifndef S_ISREG
  52 #define S_ISREG(m) (((m) & _S_IFMT) == _S_IFREG)
  53 #endif
  54 #endif
  55
  56 #ifndef O_BINARY
  57 #define O_BINARY 0
  58 #endif
  59
  60
  61 #ifdef G_OS_UNIX
  62 static void       g_file_descriptor_based_iface_init   (GFileDescriptorBasedIface *iface);
  63 #endif
  64
  65 #define g_local_file_output_stream_get_type _g_local_file_output_stream_get_type
  66 #ifdef G_OS_UNIX
  67 G_DEFINE_TYPE_WITH_CODE (GLocalFileOutputStream, g_local_file_output_stream, G_TYPE_FILE_OUTPUT_STREAM,
  68                          G_IMPLEMENT_INTERFACE (G_TYPE_FILE_DESCRIPTOR_BASED,
  69                                                 g_file_descriptor_based_iface_init)
  70                            );
  71 #else
  72 G_DEFINE_TYPE_WITH_CODE (GLocalFileOutputStream, g_local_file_output_stream, G_TYPE_FILE_OUTPUT_STREAM,);
  73 #endif
  74
  75
  76 /* Some of the file replacement code was based on the code from gedit,
  77  * relicenced to LGPL with permissions from the authors.
  78  */
  79
  80 #define BACKUP_EXTENSION "~"
  81
  82 struct _GLocalFileOutputStreamPrivate {
  83   char *tmp_filename;
  84   char *original_filename;
  85   char *backup_filename;
  86   char *etag;
  87   guint sync_on_close : 1;
  88   guint do_close : 1;
  89   int fd;
  90 };
  91
  92 static gssize     g_local_file_output_stream_write        (GOutputStream      *stream,
  93                                                            const void         *buffer,
  94                                                            gsize               count,
  95                                                            GCancellable       *cancellable,
  96                                                            GError            **error);
  97 static gboolean   g_local_file_output_stream_close        (GOutputStream      *stream,
  98                                                            GCancellable       *cancellable,
  99                                                            GError            **error);
 100 static GFileInfo *g_local_file_output_stream_query_info   (GFileOutputStream  *stream,
 101                                                            const char         *attributes,
 102                                                            GCancellable       *cancellable,
 103                                                            GError            **error);
 104 static char *     g_local_file_output_stream_get_etag     (GFileOutputStream  *stream);
 105 static goffset    g_local_file_output_stream_tell         (GFileOutputStream  *stream);
 106 static gboolean   g_local_file_output_stream_can_seek     (GFileOutputStream  *stream);
 107 static gboolean   g_local_file_output_stream_seek         (GFileOutputStream  *stream,
 108                                                            goffset             offset,
 109                                                            GSeekType           type,
 110                                                            GCancellable       *cancellable,
 111                                                            GError            **error);
 112 static gboolean   g_local_file_output_stream_can_truncate (GFileOutputStream  *stream);
 113 static gboolean   g_local_file_output_stream_truncate     (GFileOutputStream  *stream,
 114                                                            goffset             size,
 115                                                            GCancellable       *cancellable,
 116                                                            GError            **error);
 117 #ifdef G_OS_UNIX
 118 static int        g_local_file_output_stream_get_fd       (GFileDescriptorBased *stream);
 119 #endif
 120
 121 static void
 122 g_local_file_output_stream_finalize (GObject *object)
 123 {
 124   GLocalFileOutputStream *file;
 125
 126   file = G_LOCAL_FILE_OUTPUT_STREAM (object);
 127
 128   g_free (file->priv->tmp_filename);
 129   g_free (file->priv->original_filename);
 130   g_free (file->priv->backup_filename);
 131   g_free (file->priv->etag);
 132
 133   G_OBJECT_CLASS (g_local_file_output_stream_parent_class)->finalize (object);
 134 }
 135
 136
 137 static void
 138 g_local_file_output_stream_class_init (GLocalFileOutputStreamClass *klass)
 139 {
 140   GObjectClass *gobject_class = G_OBJECT_CLASS (klass);
 141   GOutputStreamClass *stream_class = G_OUTPUT_STREAM_CLASS (klass);
 142   GFileOutputStreamClass *file_stream_class = G_FILE_OUTPUT_STREAM_CLASS (klass);
 143
 144   g_type_class_add_private (klass, sizeof (GLocalFileOutputStreamPrivate));
 145
 146   gobject_class->finalize = g_local_file_output_stream_finalize;
 147
 148   stream_class->write_fn = g_local_file_output_stream_write;
 149   stream_class->close_fn = g_local_file_output_stream_close;
 150   file_stream_class->query_info = g_local_file_output_stream_query_info;
 151   file_stream_class->get_etag = g_local_file_output_stream_get_etag;
 152   file_stream_class->tell = g_local_file_output_stream_tell;
 153   file_stream_class->can_seek = g_local_file_output_stream_can_seek;
 154   file_stream_class->seek = g_local_file_output_stream_seek;
 155   file_stream_class->can_truncate = g_local_file_output_stream_can_truncate;
 156   file_stream_class->truncate_fn = g_local_file_output_stream_truncate;
 157 }
 158
 159 #ifdef G_OS_UNIX
 160 static void
 161 g_file_descriptor_based_iface_init (GFileDescriptorBasedIface *iface)
 162 {
 163   iface->get_fd = g_local_file_output_stream_get_fd;
 164 }
 165 #endif
 166
 167 static void
 168 g_local_file_output_stream_init (GLocalFileOutputStream *stream)
 169 {
 170   stream->priv = G_TYPE_INSTANCE_GET_PRIVATE (stream,
 171                                               G_TYPE_LOCAL_FILE_OUTPUT_STREAM,
 172                                               GLocalFileOutputStreamPrivate);
 173   stream->priv->do_close = TRUE;
 174 }
 175
 176 static gssize
 177 g_local_file_output_stream_write (GOutputStream  *stream,
 178                                   const void     *buffer,
 179                                   gsize           count,
 180                                   GCancellable   *cancellable,
 181                                   GError        **error)
 182 {
 183   GLocalFileOutputStream *file;
 184   gssize res;
 185
 186   file = G_LOCAL_FILE_OUTPUT_STREAM (stream);
 187
 188   while (1)
 189     {
 190       if (g_cancellable_set_error_if_cancelled (cancellable, error))
 191         return -1;
 192       res = write (file->priv->fd, buffer, count);
 193       if (res == -1)
 194         {
 195           int errsv = errno;
 196
 197           if (errsv == EINTR)
 198             continue;
 199
 200           g_set_error (error, G_IO_ERROR,
 201                        g_io_error_from_errno (errsv),
 202                        _("Error writing to file: %s"),
 203                        g_strerror (errsv));
 204         }
 205
 206       break;
 207     }
 208
 209   return res;
 210 }
 211
 212 void
 213 _g_local_file_output_stream_set_do_close (GLocalFileOutputStream *out,
 214                                           gboolean do_close)
 215 {
 216   out->priv->do_close = do_close;
 217 }
 218
 219 gboolean
 220 _g_local_file_output_stream_really_close (GLocalFileOutputStream *file,
 221                                           GCancellable   *cancellable,
 222                                           GError        **error)
 223 {
 224   GLocalFileStat final_stat;
 225   int res;
 226
 227 #ifdef HAVE_FSYNC
 228   if (file->priv->sync_on_close &&
 229       fsync (file->priv->fd) != 0)
 230     {
 231       int errsv = errno;
 232
 233       g_set_error (error, G_IO_ERROR,
 234                    g_io_error_from_errno (errsv),
 235                    _("Error writing to file: %s"),
 236                    g_strerror (errsv));
 237       goto err_out;
 238     }
 239 #endif
 240
 241 #ifdef G_OS_WIN32
 242
 243   /* Must close before renaming on Windows, so just do the close first
 244    * in all cases for now.
 245    */
 246   if (_fstati64 (file->priv->fd, &final_stat) == 0)
 247     file->priv->etag = _g_local_file_info_create_etag (&final_stat);
 248
 249   res = close (file->priv->fd);
 250   if (res == -1)
 251     {
 252       int errsv = errno;
 253
 254       g_set_error (error, G_IO_ERROR,
 255                    g_io_error_from_errno (errsv),
 256                    _("Error closing file: %s"),
 257                    g_strerror (errsv));
 258       return FALSE;
 259     }
 260
 261 #endif
 262
 263   if (file->priv->tmp_filename)
 264     {
 265       /* We need to move the temp file to its final place,
 266        * and possibly create the backup file
 267        */
 268
 269       if (file->priv->backup_filename)
 270         {
 271           if (g_cancellable_set_error_if_cancelled (cancellable, error))
 272             goto err_out;
 273
 274 #ifdef HAVE_LINK
 275           /* create original -> backup link, the original is then renamed over */
 276           if (g_unlink (file->priv->backup_filename) != 0 &&
 277               errno != ENOENT)
 278             {
 279               int errsv = errno;
 280
 281               g_set_error (error, G_IO_ERROR,
 282                            G_IO_ERROR_CANT_CREATE_BACKUP,
 283                            _("Error removing old backup link: %s"),
 284                            g_strerror (errsv));
 285               goto err_out;
 286             }
 287
 288           if (link (file->priv->original_filename, file->priv->backup_filename) != 0)
 289             {
 290               /*  link failed or is not supported, try rename  */
 291               if (g_rename (file->priv->original_filename, file->priv->backup_filename) != 0)
 292                 {
 293                   int errsv = errno;
 294
 295                   g_set_error (error, G_IO_ERROR,
 296                                G_IO_ERROR_CANT_CREATE_BACKUP,
 297                                _("Error creating backup copy: %s"),
 298                                g_strerror (errsv));
 299                   goto err_out;
 300                 }
 301             }
 302 #else
 303             /* If link not supported, just rename... */
 304           if (g_rename (file->priv->original_filename, file->priv->backup_filename) != 0)
 305             {
 306               int errsv = errno;
 307
 308               g_set_error (error, G_IO_ERROR,
 309                            G_IO_ERROR_CANT_CREATE_BACKUP,
 310                            _("Error creating backup copy: %s"),
 311                            g_strerror (errsv));
 312               goto err_out;
 313             }
 314 #endif
 315         }
 316
 317
 318       if (g_cancellable_set_error_if_cancelled (cancellable, error))
 319         goto err_out;
 320
 321       /* tmp -> original */
 322       if (g_rename (file->priv->tmp_filename, file->priv->original_filename) != 0)
 323         {
 324           int errsv = errno;
 325
 326           g_set_error (error, G_IO_ERROR,
 327                        g_io_error_from_errno (errsv),
 328                        _("Error renaming temporary file: %s"),
 329                        g_strerror (errsv));
 330           goto err_out;
 331         }
 332     }
 333
 334   if (g_cancellable_set_error_if_cancelled (cancellable, error))
 335     goto err_out;
 336
 337 #ifndef G_OS_WIN32              /* Already did the fstat() and close() above on Win32 */
 338
 339   if (fstat (file->priv->fd, &final_stat) == 0)
 340     file->priv->etag = _g_local_file_info_create_etag (&final_stat);
 341
 342   while (1)
 343     {
 344       res = close (file->priv->fd);
 345       if (res == -1)
 346         {
 347           int errsv = errno;
 348
 349           g_set_error (error, G_IO_ERROR,
 350                        g_io_error_from_errno (errsv),
 351                        _("Error closing file: %s"),
 352                        g_strerror (errsv));
 353         }
 354       break;
 355     }
 356
 357   return res != -1;
 358
 359 #else
 360
 361   return TRUE;
 362
 363 #endif
 364
 365  err_out:
 366
 367 #ifndef G_OS_WIN32
 368   /* A simple try to close the fd in case we fail before the actual close */
 369   close (file->priv->fd);
 370 #endif
 371   return FALSE;
 372 }
 373
 374
 375 static gboolean
 376 g_local_file_output_stream_close (GOutputStream  *stream,
 377                                   GCancellable   *cancellable,
 378                                   GError        **error)
 379 {
 380   GLocalFileOutputStream *file;
 381
 382   file = G_LOCAL_FILE_OUTPUT_STREAM (stream);
 383
 384   if (file->priv->do_close)
 385     return _g_local_file_output_stream_really_close (file,
 386                                                      cancellable,
 387                                                      error);
 388   return TRUE;
 389 }
 390
 391 static char *
 392 g_local_file_output_stream_get_etag (GFileOutputStream *stream)
 393 {
 394   GLocalFileOutputStream *file;
 395
 396   file = G_LOCAL_FILE_OUTPUT_STREAM (stream);
 397
 398   return g_strdup (file->priv->etag);
 399 }
 400
 401 static goffset
 402 g_local_file_output_stream_tell (GFileOutputStream *stream)
 403 {
 404   GLocalFileOutputStream *file;
 405   off_t pos;
 406
 407   file = G_LOCAL_FILE_OUTPUT_STREAM (stream);
 408
 409   pos = lseek (file->priv->fd, 0, SEEK_CUR);
 410
 411   if (pos == (off_t)-1)
 412     return 0;
 413
 414   return pos;
 415 }
 416
 417 static gboolean
 418 g_local_file_output_stream_can_seek (GFileOutputStream *stream)
 419 {
 420   GLocalFileOutputStream *file;
 421   off_t pos;
 422
 423   file = G_LOCAL_FILE_OUTPUT_STREAM (stream);
 424
 425   pos = lseek (file->priv->fd, 0, SEEK_CUR);
 426
 427   if (pos == (off_t)-1 && errno == ESPIPE)
 428     return FALSE;
 429
 430   return TRUE;
 431 }
 432
 433 static int
 434 seek_type_to_lseek (GSeekType type)
 435 {
 436   switch (type)
 437     {
 438     default:
 439     case G_SEEK_CUR:
 440       return SEEK_CUR;
 441
 442     case G_SEEK_SET:
 443       return SEEK_SET;
 444
 445     case G_SEEK_END:
 446       return SEEK_END;
 447     }
 448 }
 449
 450 static gboolean
 451 g_local_file_output_stream_seek (GFileOutputStream  *stream,
 452                                  goffset             offset,
 453                                  GSeekType           type,
 454                                  GCancellable       *cancellable,
 455                                  GError            **error)
 456 {
 457   GLocalFileOutputStream *file;
 458   off_t pos;
 459
 460   file = G_LOCAL_FILE_OUTPUT_STREAM (stream);
 461
 462   pos = lseek (file->priv->fd, offset, seek_type_to_lseek (type));
 463
 464   if (pos == (off_t)-1)
 465     {
 466       int errsv = errno;
 467
 468       g_set_error (error, G_IO_ERROR,
 469                    g_io_error_from_errno (errsv),
 470                    _("Error seeking in file: %s"),
 471                    g_strerror (errsv));
 472       return FALSE;
 473     }
 474
 475   return TRUE;
 476 }
 477
 478 static gboolean
 479 g_local_file_output_stream_can_truncate (GFileOutputStream *stream)
 480 {
 481   /* We can't truncate pipes and stuff where we can't seek */
 482   return g_local_file_output_stream_can_seek (stream);
 483 }
 484
 485 static gboolean
 486 g_local_file_output_stream_truncate (GFileOutputStream  *stream,
 487                                      goffset             size,
 488                                      GCancellable       *cancellable,
 489                                      GError            **error)
 490 {
 491   GLocalFileOutputStream *file;
 492   int res;
 493
 494   file = G_LOCAL_FILE_OUTPUT_STREAM (stream);
 495
 496  restart:
 497 #ifdef G_OS_WIN32
 498   res = g_win32_ftruncate (file->priv->fd, size);
 499 #else
 500   res = ftruncate (file->priv->fd, size);
 501 #endif
 502
 503   if (res == -1)
 504     {
 505       int errsv = errno;
 506
 507       if (errsv == EINTR)
 508         {
 509           if (g_cancellable_set_error_if_cancelled (cancellable, error))
 510             return FALSE;
 511           goto restart;
 512         }
 513
 514       g_set_error (error, G_IO_ERROR,
 515                    g_io_error_from_errno (errsv),
 516                    _("Error truncating file: %s"),
 517                    g_strerror (errsv));
 518       return FALSE;
 519     }
 520
 521   return TRUE;
 522 }
 523
 524
 525 static GFileInfo *
 526 g_local_file_output_stream_query_info (GFileOutputStream  *stream,
 527                                        const char         *attributes,
 528                                        GCancellable       *cancellable,
 529                                        GError            **error)
 530 {
 531   GLocalFileOutputStream *file;
 532
 533   file = G_LOCAL_FILE_OUTPUT_STREAM (stream);
 534
 535   if (g_cancellable_set_error_if_cancelled (cancellable, error))
 536     return NULL;
 537
 538   return _g_local_file_info_get_from_fd (file->priv->fd,
 539                                          attributes,
 540                                          error);
 541 }
 542
 543 GFileOutputStream *
 544 _g_local_file_output_stream_open  (const char        *filename,
 545                                    gboolean          readable,
 546                                    GCancellable      *cancellable,
 547                                    GError           **error)
 548 {
 549   GLocalFileOutputStream *stream;
 550   int fd;
 551   int open_flags;
 552
 553   if (g_cancellable_set_error_if_cancelled (cancellable, error))
 554     return NULL;
 555
 556   open_flags = O_BINARY;
 557   if (readable)
 558     open_flags |= O_RDWR;
 559   else
 560     open_flags |= O_WRONLY;
 561
 562   fd = g_open (filename, open_flags, 0666);
 563   if (fd == -1)
 564     {
 565       int errsv = errno;
 566
 567       if (errsv == EINVAL)
 568         /* This must be an invalid filename, on e.g. FAT */
 569         g_set_error_literal (error, G_IO_ERROR,
 570                              G_IO_ERROR_INVALID_FILENAME,
 571                              _("Invalid filename"));
 572       else
 573         {
 574           char *display_name = g_filename_display_name (filename);
 575           g_set_error (error, G_IO_ERROR,
 576                        g_io_error_from_errno (errsv),
 577                        _("Error opening file '%s': %s"),
 578                        display_name, g_strerror (errsv));
 579           g_free (display_name);
 580         }
 581       return NULL;
 582     }
 583
 584   stream = g_object_new (G_TYPE_LOCAL_FILE_OUTPUT_STREAM, NULL);
 585   stream->priv->fd = fd;
 586   return G_FILE_OUTPUT_STREAM (stream);
 587 }
 588
 589 GFileOutputStream *
 590 _g_local_file_output_stream_create  (const char        *filename,
 591                                      gboolean          readable,
 592                                      GFileCreateFlags   flags,
 593                                      GCancellable      *cancellable,
 594                                      GError           **error)
 595 {
 596   GLocalFileOutputStream *stream;
 597   int mode;
 598   int fd;
 599   int open_flags;
 600
 601   if (g_cancellable_set_error_if_cancelled (cancellable, error))
 602     return NULL;
 603
 604   if (flags & G_FILE_CREATE_PRIVATE)
 605     mode = 0600;
 606   else
 607     mode = 0666;
 608
 609   open_flags = O_CREAT | O_EXCL | O_BINARY;
 610   if (readable)
 611     open_flags |= O_RDWR;
 612   else
 613     open_flags |= O_WRONLY;
 614
 615   fd = g_open (filename, open_flags, mode);
 616   if (fd == -1)
 617     {
 618       int errsv = errno;
 619
 620       if (errsv == EINVAL)
 621         /* This must be an invalid filename, on e.g. FAT */
 622         g_set_error_literal (error, G_IO_ERROR,
 623                              G_IO_ERROR_INVALID_FILENAME,
 624                              _("Invalid filename"));
 625       else
 626         {
 627           char *display_name = g_filename_display_name (filename);
 628           g_set_error (error, G_IO_ERROR,
 629                        g_io_error_from_errno (errsv),
 630                        _("Error opening file '%s': %s"),
 631                        display_name, g_strerror (errsv));
 632           g_free (display_name);
 633         }
 634       return NULL;
 635     }
 636
 637   stream = g_object_new (G_TYPE_LOCAL_FILE_OUTPUT_STREAM, NULL);
 638   stream->priv->fd = fd;
 639   return G_FILE_OUTPUT_STREAM (stream);
 640 }
 641
 642 GFileOutputStream *
 643 _g_local_file_output_stream_append  (const char        *filename,
 644                                      GFileCreateFlags   flags,
 645                                      GCancellable      *cancellable,
 646                                      GError           **error)
 647 {
 648   GLocalFileOutputStream *stream;
 649   int mode;
 650   int fd;
 651
 652   if (g_cancellable_set_error_if_cancelled (cancellable, error))
 653     return NULL;
 654
 655   if (flags & G_FILE_CREATE_PRIVATE)
 656     mode = 0600;
 657   else
 658     mode = 0666;
 659
 660   fd = g_open (filename, O_CREAT | O_APPEND | O_WRONLY | O_BINARY, mode);
 661   if (fd == -1)
 662     {
 663       int errsv = errno;
 664
 665       if (errsv == EINVAL)
 666         /* This must be an invalid filename, on e.g. FAT */
 667         g_set_error_literal (error, G_IO_ERROR,
 668                              G_IO_ERROR_INVALID_FILENAME,
 669                              _("Invalid filename"));
 670       else
 671         {
 672           char *display_name = g_filename_display_name (filename);
 673           g_set_error (error, G_IO_ERROR,
 674                        g_io_error_from_errno (errsv),
 675                        _("Error opening file '%s': %s"),
 676                        display_name, g_strerror (errsv));
 677           g_free (display_name);
 678         }
 679       return NULL;
 680     }
 681
 682   stream = g_object_new (G_TYPE_LOCAL_FILE_OUTPUT_STREAM, NULL);
 683   stream->priv->fd = fd;
 684
 685   return G_FILE_OUTPUT_STREAM (stream);
 686 }
 687
 688 static char *
 689 create_backup_filename (const char *filename)
 690 {
 691   return g_strconcat (filename, BACKUP_EXTENSION, NULL);
 692 }
 693
 694 #define BUFSIZE 8192 /* size of normal write buffer */
 695
 696 static gboolean
 697 copy_file_data (gint     sfd,
 698                 gint     dfd,
 699                 GError **error)
 700 {
 701   gboolean ret = TRUE;
 702   gpointer buffer;
 703   const gchar *write_buffer;
 704   gssize bytes_read;
 705   gssize bytes_to_write;
 706   gssize bytes_written;
 707
 708   buffer = g_malloc (BUFSIZE);
 709
 710   do
 711     {
 712       bytes_read = read (sfd, buffer, BUFSIZE);
 713       if (bytes_read == -1)
 714         {
 715           int errsv = errno;
 716
 717           if (errsv == EINTR)
 718             continue;
 719
 720           g_set_error (error, G_IO_ERROR,
 721                        g_io_error_from_errno (errsv),
 722                        _("Error reading from file: %s"),
 723                        g_strerror (errsv));
 724           ret = FALSE;
 725           break;
 726         }
 727
 728       bytes_to_write = bytes_read;
 729       write_buffer = buffer;
 730
 731       do
 732         {
 733           bytes_written = write (dfd, write_buffer, bytes_to_write);
 734           if (bytes_written == -1)
 735             {
 736               int errsv = errno;
 737
 738               if (errsv == EINTR)
 739                 continue;
 740
 741               g_set_error (error, G_IO_ERROR,
 742                            g_io_error_from_errno (errsv),
 743                            _("Error writing to file: %s"),
 744                            g_strerror (errsv));
 745               ret = FALSE;
 746               break;
 747             }
 748
 749           bytes_to_write -= bytes_written;
 750           write_buffer += bytes_written;
 751         }
 752       while (bytes_to_write > 0);
 753
 754     } while ((bytes_read != 0) && (ret == TRUE));
 755
 756   g_free (buffer);
 757
 758   return ret;
 759 }
 760
 761 static int
 762 handle_overwrite_open (const char    *filename,
 763                        gboolean       readable,
 764                        const char    *etag,
 765                        gboolean       create_backup,
 766                        char         **temp_filename,
 767                        GFileCreateFlags flags,
 768                        GCancellable  *cancellable,
 769                        GError       **error)
 770 {
 771   int fd = -1;
 772   GLocalFileStat original_stat;
 773   char *current_etag;
 774   gboolean is_symlink;
 775   int open_flags;
 776   int res;
 777   int mode;
 778
 779   if (flags & G_FILE_CREATE_PRIVATE)
 780     mode = 0600;
 781   else
 782     mode = 0666;
 783
 784   /* We only need read access to the original file if we are creating a backup.
 785    * We also add O_CREATE to avoid a race if the file was just removed */
 786   if (create_backup || readable)
 787     open_flags = O_RDWR | O_CREAT | O_BINARY;
 788   else
 789     open_flags = O_WRONLY | O_CREAT | O_BINARY;
 790
 791   /* Some systems have O_NOFOLLOW, which lets us avoid some races
 792    * when finding out if the file we opened was a symlink */
 793 #ifdef O_NOFOLLOW
 794   is_symlink = FALSE;
 795   fd = g_open (filename, open_flags | O_NOFOLLOW, mode);
 796   if (fd == -1 && errno == ELOOP)
 797     {
 798       /* Could be a symlink, or it could be a regular ELOOP error,
 799        * but then the next open will fail too. */
 800       is_symlink = TRUE;
 801       fd = g_open (filename, open_flags, mode);
 802     }
 803 #else
 804   fd = g_open (filename, open_flags, mode);
 805   /* This is racy, but we do it as soon as possible to minimize the race */
 806   is_symlink = g_file_test (filename, G_FILE_TEST_IS_SYMLINK);
 807 #endif
 808
 809   if (fd == -1)
 810     {
 811       int errsv = errno;
 812       char *display_name = g_filename_display_name (filename);
 813       g_set_error (error, G_IO_ERROR,
 814                    g_io_error_from_errno (errsv),
 815                    _("Error opening file '%s': %s"),
 816                    display_name, g_strerror (errsv));
 817       g_free (display_name);
 818       return -1;
 819     }
 820
 821 #ifdef G_OS_WIN32
 822   res = _fstati64 (fd, &original_stat);
 823 #else
 824   res = fstat (fd, &original_stat);
 825 #endif
 826
 827   if (res != 0)
 828     {
 829       int errsv = errno;
 830       char *display_name = g_filename_display_name (filename);
 831       g_set_error (error, G_IO_ERROR,
 832                    g_io_error_from_errno (errsv),
 833                    _("Error when getting information for file '%s': %s"),
 834                    display_name, g_strerror (errsv));
 835       g_free (display_name);
 836       goto err_out;
 837     }
 838
 839   /* not a regular file */
 840   if (!S_ISREG (original_stat.st_mode))
 841     {
 842       if (S_ISDIR (original_stat.st_mode))
 843         g_set_error_literal (error,
 844                              G_IO_ERROR,
 845                              G_IO_ERROR_IS_DIRECTORY,
 846                              _("Target file is a directory"));
 847       else
 848         g_set_error_literal (error,
 849                              G_IO_ERROR,
 850                              G_IO_ERROR_NOT_REGULAR_FILE,
 851                              _("Target file is not a regular file"));
 852       goto err_out;
 853     }
 854
 855   if (etag != NULL)
 856     {
 857       current_etag = _g_local_file_info_create_etag (&original_stat);
 858       if (strcmp (etag, current_etag) != 0)
 859         {
 860           g_set_error_literal (error,
 861                                G_IO_ERROR,
 862                                G_IO_ERROR_WRONG_ETAG,
 863                                _("The file was externally modified"));
 864           g_free (current_etag);
 865           goto err_out;
 866         }
 867       g_free (current_etag);
 868     }
 869
 870   /* We use two backup strategies.
 871    * The first one (which is faster) consist in saving to a
 872    * tmp file then rename the original file to the backup and the
 873    * tmp file to the original name. This is fast but doesn't work
 874    * when the file is a link (hard or symbolic) or when we can't
 875    * write to the current dir or can't set the permissions on the
 876    * new file.
 877    * The second strategy consist simply in copying the old file
 878    * to a backup file and rewrite the contents of the file.
 879    */
 880
 881   if ((flags & G_FILE_CREATE_REPLACE_DESTINATION) ||
 882       (!(original_stat.st_nlink > 1) && !is_symlink))
 883     {
 884       char *dirname, *tmp_filename;
 885       int tmpfd;
 886
 887       dirname = g_path_get_dirname (filename);
 888       tmp_filename = g_build_filename (dirname, ".goutputstream-XXXXXX", NULL);
 889       g_free (dirname);
 890
 891       tmpfd = g_mkstemp_full (tmp_filename, (readable ? O_RDWR : O_WRONLY) | O_BINARY, mode);
 892       if (tmpfd == -1)
 893         {
 894           g_free (tmp_filename);
 895           goto fallback_strategy;
 896         }
 897
 898       /* try to keep permissions (unless replacing) */
 899
 900       if ( ! (flags & G_FILE_CREATE_REPLACE_DESTINATION) &&
 901            (
 902 #ifdef HAVE_FCHOWN
 903             fchown (tmpfd, original_stat.st_uid, original_stat.st_gid) == -1 ||
 904 #endif
 905 #ifdef HAVE_FCHMOD
 906             fchmod (tmpfd, original_stat.st_mode) == -1 ||
 907 #endif
 908             0
 909             )
 910           )
 911         {
 912           GLocalFileStat tmp_statbuf;
 913           int tres;
 914
 915 #ifdef G_OS_WIN32
 916           tres = _fstati64 (tmpfd, &tmp_statbuf);
 917 #else
 918           tres = fstat (tmpfd, &tmp_statbuf);
 919 #endif
 920           /* Check that we really needed to change something */
 921           if (tres != 0 ||
 922               original_stat.st_uid != tmp_statbuf.st_uid ||
 923               original_stat.st_gid != tmp_statbuf.st_gid ||
 924               original_stat.st_mode != tmp_statbuf.st_mode)
 925             {
 926               close (tmpfd);
 927               g_unlink (tmp_filename);
 928               g_free (tmp_filename);
 929               goto fallback_strategy;
 930             }
 931         }
 932
 933       close (fd);
 934       *temp_filename = tmp_filename;
 935       return tmpfd;
 936     }
 937
 938  fallback_strategy:
 939
 940   if (create_backup)
 941     {
 942 #if defined(HAVE_FCHOWN) && defined(HAVE_FCHMOD)
 943       struct stat tmp_statbuf;
 944 #endif
 945       char *backup_filename;
 946       int bfd;
 947
 948       backup_filename = create_backup_filename (filename);
 949
 950       if (g_unlink (backup_filename) == -1 && errno != ENOENT)
 951         {
 952           g_set_error_literal (error,
 953                                G_IO_ERROR,
 954                                G_IO_ERROR_CANT_CREATE_BACKUP,
 955                                _("Backup file creation failed"));
 956           g_free (backup_filename);
 957           goto err_out;
 958         }
 959
 960       bfd = g_open (backup_filename,
 961                     O_WRONLY | O_CREAT | O_EXCL | O_BINARY,
 962                     original_stat.st_mode & 0777);
 963
 964       if (bfd == -1)
 965         {
 966           g_set_error_literal (error,
 967                                G_IO_ERROR,
 968                                G_IO_ERROR_CANT_CREATE_BACKUP,
 969                                _("Backup file creation failed"));
 970           g_free (backup_filename);
 971           goto err_out;
 972         }
 973
 974       /* If needed, Try to set the group of the backup same as the
 975        * original file. If this fails, set the protection
 976        * bits for the group same as the protection bits for
 977        * others. */
 978 #if defined(HAVE_FCHOWN) && defined(HAVE_FCHMOD)
 979       if (fstat (bfd, &tmp_statbuf) != 0)
 980         {
 981           g_set_error_literal (error,
 982                                G_IO_ERROR,
 983                                G_IO_ERROR_CANT_CREATE_BACKUP,
 984                                _("Backup file creation failed"));
 985           g_unlink (backup_filename);
 986           g_free (backup_filename);
 987           goto err_out;
 988         }
 989
 990       if ((original_stat.st_gid != tmp_statbuf.st_gid)  &&
 991           fchown (bfd, (uid_t) -1, original_stat.st_gid) != 0)
 992         {
 993           if (fchmod (bfd,
 994                       (original_stat.st_mode & 0707) |
 995                       ((original_stat.st_mode & 07) << 3)) != 0)
 996             {
 997               g_set_error_literal (error,
 998                                    G_IO_ERROR,
 999                                    G_IO_ERROR_CANT_CREATE_BACKUP,
1000                                    _("Backup file creation failed"));
1001               g_unlink (backup_filename);
1002               close (bfd);
1003               g_free (backup_filename);
1004               goto err_out;
1005             }
1006         }
1007 #endif
1008
1009       if (!copy_file_data (fd, bfd, NULL))
1010         {
1011           g_set_error_literal (error,
1012                                G_IO_ERROR,
1013                                G_IO_ERROR_CANT_CREATE_BACKUP,
1014                                _("Backup file creation failed"));
1015           g_unlink (backup_filename);
1016           close (bfd);
1017           g_free (backup_filename);
1018
1019           goto err_out;
1020         }
1021
1022       close (bfd);
1023       g_free (backup_filename);
1024
1025       /* Seek back to the start of the file after the backup copy */
1026       if (lseek (fd, 0, SEEK_SET) == -1)
1027         {
1028           int errsv = errno;
1029
1030           g_set_error (error, G_IO_ERROR,
1031                        g_io_error_from_errno (errsv),
1032                        _("Error seeking in file: %s"),
1033                        g_strerror (errsv));
1034           goto err_out;
1035         }
1036     }
1037
1038   if (flags & G_FILE_CREATE_REPLACE_DESTINATION)
1039     {
1040       close (fd);
1041
1042       if (g_unlink (filename) != 0)
1043         {
1044           int errsv = errno;
1045
1046           g_set_error (error, G_IO_ERROR,
1047                        g_io_error_from_errno (errsv),
1048                        _("Error removing old file: %s"),
1049                        g_strerror (errsv));
1050           goto err_out2;
1051         }
1052
1053       if (readable)
1054         open_flags = O_RDWR | O_CREAT | O_BINARY;
1055       else
1056         open_flags = O_WRONLY | O_CREAT | O_BINARY;
1057       fd = g_open (filename, open_flags, mode);
1058       if (fd == -1)
1059         {
1060           int errsv = errno;
1061           char *display_name = g_filename_display_name (filename);
1062           g_set_error (error, G_IO_ERROR,
1063                        g_io_error_from_errno (errsv),
1064                        _("Error opening file '%s': %s"),
1065                        display_name, g_strerror (errsv));
1066           g_free (display_name);
1067           goto err_out2;
1068         }
1069     }
1070   else
1071     {
1072       /* Truncate the file at the start */
1073 #ifdef G_OS_WIN32
1074       if (g_win32_ftruncate (fd, 0) == -1)
1075 #else
1076         if (ftruncate (fd, 0) == -1)
1077 #endif
1078           {
1079             int errsv = errno;
1080
1081             g_set_error (error, G_IO_ERROR,
1082                          g_io_error_from_errno (errsv),
1083                          _("Error truncating file: %s"),
1084                          g_strerror (errsv));
1085             goto err_out;
1086           }
1087     }
1088
1089   return fd;
1090
1091  err_out:
1092   close (fd);
1093  err_out2:
1094   return -1;
1095 }
1096
1097 GFileOutputStream *
1098 _g_local_file_output_stream_replace (const char        *filename,
1099                                      gboolean          readable,
1100                                      const char        *etag,
1101                                      gboolean           create_backup,
1102                                      GFileCreateFlags   flags,
1103                                      GCancellable      *cancellable,
1104                                      GError           **error)
1105 {
1106   GLocalFileOutputStream *stream;
1107   int mode;
1108   int fd;
1109   char *temp_file;
1110   gboolean sync_on_close;
1111   int open_flags;
1112
1113   if (g_cancellable_set_error_if_cancelled (cancellable, error))
1114     return NULL;
1115
1116   temp_file = NULL;
1117
1118   if (flags & G_FILE_CREATE_PRIVATE)
1119     mode = 0600;
1120   else
1121     mode = 0666;
1122   sync_on_close = FALSE;
1123
1124   /* If the file doesn't exist, create it */
1125   open_flags = O_CREAT | O_EXCL | O_BINARY;
1126   if (readable)
1127     open_flags |= O_RDWR;
1128   else
1129     open_flags |= O_WRONLY;
1130   fd = g_open (filename, open_flags, mode);
1131
1132   if (fd == -1 && errno == EEXIST)
1133     {
1134       /* The file already exists */
1135       fd = handle_overwrite_open (filename, readable, etag,
1136                                   create_backup, &temp_file,
1137                                   flags, cancellable, error);
1138       if (fd == -1)
1139         return NULL;
1140
1141       /* If the final destination exists, we want to sync the newly written
1142        * file to ensure the data is on disk when we rename over the destination.
1143        * otherwise if we get a system crash we can lose both the new and the
1144        * old file on some filesystems. (I.E. those that don't guarantee the
1145        * data is written to the disk before the metadata.)
1146        */
1147       sync_on_close = TRUE;
1148     }
1149   else if (fd == -1)
1150     {
1151       int errsv = errno;
1152
1153       if (errsv == EINVAL)
1154         /* This must be an invalid filename, on e.g. FAT */
1155         g_set_error_literal (error, G_IO_ERROR,
1156                              G_IO_ERROR_INVALID_FILENAME,
1157                              _("Invalid filename"));
1158       else
1159         {
1160           char *display_name = g_filename_display_name (filename);
1161           g_set_error (error, G_IO_ERROR,
1162                        g_io_error_from_errno (errsv),
1163                        _("Error opening file '%s': %s"),
1164                        display_name, g_strerror (errsv));
1165           g_free (display_name);
1166         }
1167       return NULL;
1168     }
1169
1170
1171   stream = g_object_new (G_TYPE_LOCAL_FILE_OUTPUT_STREAM, NULL);
1172   stream->priv->fd = fd;
1173   stream->priv->sync_on_close = sync_on_close;
1174   stream->priv->tmp_filename = temp_file;
1175   if (create_backup)
1176     stream->priv->backup_filename = create_backup_filename (filename);
1177   stream->priv->original_filename =  g_strdup (filename);
1178
1179   return G_FILE_OUTPUT_STREAM (stream);
1180 }
1181
1182 gint
1183 _g_local_file_output_stream_get_fd (GLocalFileOutputStream *stream)
1184 {
1185   g_return_val_if_fail (G_IS_LOCAL_FILE_OUTPUT_STREAM (stream), -1);
1186   return stream->priv->fd;
1187 }
1188
1189 #ifdef G_OS_UNIX
1190 static int
1191 g_local_file_output_stream_get_fd (GFileDescriptorBased *fd_based)
1192 {
1193   GLocalFileOutputStream *stream = G_LOCAL_FILE_OUTPUT_STREAM (fd_based);
1194   return _g_local_file_output_stream_get_fd (stream);
1195 }
1196 #endif