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, see <http://www.gnu.org/licenses/>.
  17  *
  18  * Author: Alexander Larsson <alexl@redhat.com>
  19  */
  20
  21 #include "config.h"
  22
  23 #include <sys/types.h>
  24 #include <sys/stat.h>
  25 #include <fcntl.h>
  26 #include <errno.h>
  27 #include <string.h>
  28
  29 #include <glib.h>
  30 #include <glib/gstdio.h>
  31 #include "glibintl.h"
  32 #include "gioerror.h"
  33 #include "gcancellable.h"
  34 #include "glocalfileoutputstream.h"
  35 #include "gfileinfo.h"
  36 #include "glocalfileinfo.h"
  37
  38 #ifdef G_OS_UNIX
  39 #include <unistd.h>
  40 #include "gfiledescriptorbased.h"
  41 #endif
  42
  43 #ifdef G_OS_WIN32
  44 #include <io.h>
  45 #ifndef S_ISDIR
  46 #define S_ISDIR(m) (((m) & _S_IFMT) == _S_IFDIR)
  47 #endif
  48 #ifndef S_ISREG
  49 #define S_ISREG(m) (((m) & _S_IFMT) == _S_IFREG)
  50 #endif
  51 #endif
  52
  53 #ifndef O_BINARY
  54 #define O_BINARY 0
  55 #endif
  56
  57 struct _GLocalFileOutputStreamPrivate {
  58   char *tmp_filename;
  59   char *original_filename;
  60   char *backup_filename;
  61   char *etag;
  62   guint sync_on_close : 1;
  63   guint do_close : 1;
  64   int fd;
  65 };
  66
  67 #ifdef G_OS_UNIX
  68 static void       g_file_descriptor_based_iface_init   (GFileDescriptorBasedIface *iface);
  69 #endif
  70
  71 #define g_local_file_output_stream_get_type _g_local_file_output_stream_get_type
  72 #ifdef G_OS_UNIX
  73 G_DEFINE_TYPE_WITH_CODE (GLocalFileOutputStream, g_local_file_output_stream, G_TYPE_FILE_OUTPUT_STREAM,
  74                          G_ADD_PRIVATE (GLocalFileOutputStream)
  75                          G_IMPLEMENT_INTERFACE (G_TYPE_FILE_DESCRIPTOR_BASED,
  76                                                 g_file_descriptor_based_iface_init))
  77 #else
  78 G_DEFINE_TYPE_WITH_CODE (GLocalFileOutputStream, g_local_file_output_stream, G_TYPE_FILE_OUTPUT_STREAM,
  79                          G_ADD_PRIVATE (GLocalFileOutputStream))
  80 #endif
  81
  82
  83 /* Some of the file replacement code was based on the code from gedit,
  84  * relicenced to LGPL with permissions from the authors.
  85  */
  86
  87 #define BACKUP_EXTENSION "~"
  88
  89 static gssize     g_local_file_output_stream_write        (GOutputStream      *stream,
  90                                                            const void         *buffer,
  91                                                            gsize               count,
  92                                                            GCancellable       *cancellable,
  93                                                            GError            **error);
  94 static gboolean   g_local_file_output_stream_close        (GOutputStream      *stream,
  95                                                            GCancellable       *cancellable,
  96                                                            GError            **error);
  97 static GFileInfo *g_local_file_output_stream_query_info   (GFileOutputStream  *stream,
  98                                                            const char         *attributes,
  99                                                            GCancellable       *cancellable,
 100                                                            GError            **error);
 101 static char *     g_local_file_output_stream_get_etag     (GFileOutputStream  *stream);
 102 static goffset    g_local_file_output_stream_tell         (GFileOutputStream  *stream);
 103 static gboolean   g_local_file_output_stream_can_seek     (GFileOutputStream  *stream);
 104 static gboolean   g_local_file_output_stream_seek         (GFileOutputStream  *stream,
 105                                                            goffset             offset,
 106                                                            GSeekType           type,
 107                                                            GCancellable       *cancellable,
 108                                                            GError            **error);
 109 static gboolean   g_local_file_output_stream_can_truncate (GFileOutputStream  *stream);
 110 static gboolean   g_local_file_output_stream_truncate     (GFileOutputStream  *stream,
 111                                                            goffset             size,
 112                                                            GCancellable       *cancellable,
 113                                                            GError            **error);
 114 #ifdef G_OS_UNIX
 115 static int        g_local_file_output_stream_get_fd       (GFileDescriptorBased *stream);
 116 #endif
 117
 118 static void
 119 g_local_file_output_stream_finalize (GObject *object)
 120 {
 121   GLocalFileOutputStream *file;
 122
 123   file = G_LOCAL_FILE_OUTPUT_STREAM (object);
 124
 125   g_free (file->priv->tmp_filename);
 126   g_free (file->priv->original_filename);
 127   g_free (file->priv->backup_filename);
 128   g_free (file->priv->etag);
 129
 130   G_OBJECT_CLASS (g_local_file_output_stream_parent_class)->finalize (object);
 131 }
 132
 133 static void
 134 g_local_file_output_stream_class_init (GLocalFileOutputStreamClass *klass)
 135 {
 136   GObjectClass *gobject_class = G_OBJECT_CLASS (klass);
 137   GOutputStreamClass *stream_class = G_OUTPUT_STREAM_CLASS (klass);
 138   GFileOutputStreamClass *file_stream_class = G_FILE_OUTPUT_STREAM_CLASS (klass);
 139
 140   gobject_class->finalize = g_local_file_output_stream_finalize;
 141
 142   stream_class->write_fn = g_local_file_output_stream_write;
 143   stream_class->close_fn = g_local_file_output_stream_close;
 144   file_stream_class->query_info = g_local_file_output_stream_query_info;
 145   file_stream_class->get_etag = g_local_file_output_stream_get_etag;
 146   file_stream_class->tell = g_local_file_output_stream_tell;
 147   file_stream_class->can_seek = g_local_file_output_stream_can_seek;
 148   file_stream_class->seek = g_local_file_output_stream_seek;
 149   file_stream_class->can_truncate = g_local_file_output_stream_can_truncate;
 150   file_stream_class->truncate_fn = g_local_file_output_stream_truncate;
 151 }
 152
 153 #ifdef G_OS_UNIX
 154 static void
 155 g_file_descriptor_based_iface_init (GFileDescriptorBasedIface *iface)
 156 {
 157   iface->get_fd = g_local_file_output_stream_get_fd;
 158 }
 159 #endif
 160
 161 static void
 162 g_local_file_output_stream_init (GLocalFileOutputStream *stream)
 163 {
 164   stream->priv = g_local_file_output_stream_get_instance_private (stream);
 165   stream->priv->do_close = TRUE;
 166 }
 167
 168 static gssize
 169 g_local_file_output_stream_write (GOutputStream  *stream,
 170                                   const void     *buffer,
 171                                   gsize           count,
 172                                   GCancellable   *cancellable,
 173                                   GError        **error)
 174 {
 175   GLocalFileOutputStream *file;
 176   gssize res;
 177
 178   file = G_LOCAL_FILE_OUTPUT_STREAM (stream);
 179
 180   while (1)
 181     {
 182       if (g_cancellable_set_error_if_cancelled (cancellable, error))
 183         return -1;
 184       res = write (file->priv->fd, buffer, count);
 185       if (res == -1)
 186         {
 187           int errsv = errno;
 188
 189           if (errsv == EINTR)
 190             continue;
 191
 192           g_set_error (error, G_IO_ERROR,
 193                        g_io_error_from_errno (errsv),
 194                        _("Error writing to file: %s"),
 195                        g_strerror (errsv));
 196         }
 197
 198       break;
 199     }
 200
 201   return res;
 202 }
 203
 204 void
 205 _g_local_file_output_stream_set_do_close (GLocalFileOutputStream *out,
 206                                           gboolean do_close)
 207 {
 208   out->priv->do_close = do_close;
 209 }
 210
 211 gboolean
 212 _g_local_file_output_stream_really_close (GLocalFileOutputStream *file,
 213                                           GCancellable   *cancellable,
 214                                           GError        **error)
 215 {
 216   GLocalFileStat final_stat;
 217
 218 #ifdef HAVE_FSYNC
 219   if (file->priv->sync_on_close &&
 220       fsync (file->priv->fd) != 0)
 221     {
 222       int errsv = errno;
 223
 224       g_set_error (error, G_IO_ERROR,
 225                    g_io_error_from_errno (errsv),
 226                    _("Error writing to file: %s"),
 227                    g_strerror (errsv));
 228       goto err_out;
 229     }
 230 #endif
 231
 232 #ifdef G_OS_WIN32
 233
 234   /* Must close before renaming on Windows, so just do the close first
 235    * in all cases for now.
 236    */
 237   if (_fstati64 (file->priv->fd, &final_stat) == 0)
 238     file->priv->etag = _g_local_file_info_create_etag (&final_stat);
 239
 240   if (!g_close (file->priv->fd, NULL))
 241     {
 242       int errsv = errno;
 243
 244       g_set_error (error, G_IO_ERROR,
 245                    g_io_error_from_errno (errsv),
 246                    _("Error closing file: %s"),
 247                    g_strerror (errsv));
 248       return FALSE;
 249     }
 250
 251 #endif
 252
 253   if (file->priv->tmp_filename)
 254     {
 255       /* We need to move the temp file to its final place,
 256        * and possibly create the backup file
 257        */
 258
 259       if (file->priv->backup_filename)
 260         {
 261           if (g_cancellable_set_error_if_cancelled (cancellable, error))
 262             goto err_out;
 263
 264 #ifdef G_OS_UNIX
 265           /* create original -> backup link, the original is then renamed over */
 266           if (g_unlink (file->priv->backup_filename) != 0 &&
 267               errno != ENOENT)
 268             {
 269               int errsv = errno;
 270
 271               g_set_error (error, G_IO_ERROR,
 272                            G_IO_ERROR_CANT_CREATE_BACKUP,
 273                            _("Error removing old backup link: %s"),
 274                            g_strerror (errsv));
 275               goto err_out;
 276             }
 277
 278           if (link (file->priv->original_filename, file->priv->backup_filename) != 0)
 279             {
 280               /*  link failed or is not supported, try rename  */
 281               if (g_rename (file->priv->original_filename, file->priv->backup_filename) != 0)
 282                 {
 283                   int errsv = errno;
 284
 285                   g_set_error (error, G_IO_ERROR,
 286                                G_IO_ERROR_CANT_CREATE_BACKUP,
 287                                _("Error creating backup copy: %s"),
 288                                g_strerror (errsv));
 289                   goto err_out;
 290                 }
 291             }
 292 #else
 293             /* If link not supported, just rename... */
 294           if (g_rename (file->priv->original_filename, file->priv->backup_filename) != 0)
 295             {
 296               int errsv = errno;
 297
 298               g_set_error (error, G_IO_ERROR,
 299                            G_IO_ERROR_CANT_CREATE_BACKUP,
 300                            _("Error creating backup copy: %s"),
 301                            g_strerror (errsv));
 302               goto err_out;
 303             }
 304 #endif
 305         }
 306
 307
 308       if (g_cancellable_set_error_if_cancelled (cancellable, error))
 309         goto err_out;
 310
 311       /* tmp -> original */
 312       if (g_rename (file->priv->tmp_filename, file->priv->original_filename) != 0)
 313         {
 314           int errsv = errno;
 315
 316           g_set_error (error, G_IO_ERROR,
 317                        g_io_error_from_errno (errsv),
 318                        _("Error renaming temporary file: %s"),
 319                        g_strerror (errsv));
 320           goto err_out;
 321         }
 322
 323       g_clear_pointer (&file->priv->tmp_filename, g_free);
 324     }
 325
 326   if (g_cancellable_set_error_if_cancelled (cancellable, error))
 327     goto err_out;
 328
 329 #ifndef G_OS_WIN32              /* Already did the fstat() and close() above on Win32 */
 330
 331   if (fstat (file->priv->fd, &final_stat) == 0)
 332     file->priv->etag = _g_local_file_info_create_etag (&final_stat);
 333
 334   if (!g_close (file->priv->fd, NULL))
 335     {
 336       int errsv = errno;
 337
 338       g_set_error (error, G_IO_ERROR,
 339                    g_io_error_from_errno (errsv),
 340                    _("Error closing file: %s"),
 341                    g_strerror (errsv));
 342       goto err_out;
 343     }
 344
 345 #endif
 346
 347   return TRUE;
 348  err_out:
 349
 350 #ifndef G_OS_WIN32
 351   /* A simple try to close the fd in case we fail before the actual close */
 352   g_close (file->priv->fd, NULL);
 353 #endif
 354   if (file->priv->tmp_filename)
 355     g_unlink (file->priv->tmp_filename);
 356
 357   return FALSE;
 358 }
 359
 360
 361 static gboolean
 362 g_local_file_output_stream_close (GOutputStream  *stream,
 363                                   GCancellable   *cancellable,
 364                                   GError        **error)
 365 {
 366   GLocalFileOutputStream *file;
 367
 368   file = G_LOCAL_FILE_OUTPUT_STREAM (stream);
 369
 370   if (file->priv->do_close)
 371     return _g_local_file_output_stream_really_close (file,
 372                                                      cancellable,
 373                                                      error);
 374   return TRUE;
 375 }
 376
 377 static char *
 378 g_local_file_output_stream_get_etag (GFileOutputStream *stream)
 379 {
 380   GLocalFileOutputStream *file;
 381
 382   file = G_LOCAL_FILE_OUTPUT_STREAM (stream);
 383
 384   return g_strdup (file->priv->etag);
 385 }
 386
 387 static goffset
 388 g_local_file_output_stream_tell (GFileOutputStream *stream)
 389 {
 390   GLocalFileOutputStream *file;
 391   off_t pos;
 392
 393   file = G_LOCAL_FILE_OUTPUT_STREAM (stream);
 394
 395   pos = lseek (file->priv->fd, 0, SEEK_CUR);
 396
 397   if (pos == (off_t)-1)
 398     return 0;
 399
 400   return pos;
 401 }
 402
 403 static gboolean
 404 g_local_file_output_stream_can_seek (GFileOutputStream *stream)
 405 {
 406   GLocalFileOutputStream *file;
 407   off_t pos;
 408
 409   file = G_LOCAL_FILE_OUTPUT_STREAM (stream);
 410
 411   pos = lseek (file->priv->fd, 0, SEEK_CUR);
 412
 413   if (pos == (off_t)-1 && errno == ESPIPE)
 414     return FALSE;
 415
 416   return TRUE;
 417 }
 418
 419 static int
 420 seek_type_to_lseek (GSeekType type)
 421 {
 422   switch (type)
 423     {
 424     default:
 425     case G_SEEK_CUR:
 426       return SEEK_CUR;
 427
 428     case G_SEEK_SET:
 429       return SEEK_SET;
 430
 431     case G_SEEK_END:
 432       return SEEK_END;
 433     }
 434 }
 435
 436 static gboolean
 437 g_local_file_output_stream_seek (GFileOutputStream  *stream,
 438                                  goffset             offset,
 439                                  GSeekType           type,
 440                                  GCancellable       *cancellable,
 441                                  GError            **error)
 442 {
 443   GLocalFileOutputStream *file;
 444   off_t pos;
 445
 446   file = G_LOCAL_FILE_OUTPUT_STREAM (stream);
 447
 448   pos = lseek (file->priv->fd, offset, seek_type_to_lseek (type));
 449
 450   if (pos == (off_t)-1)
 451     {
 452       int errsv = errno;
 453
 454       g_set_error (error, G_IO_ERROR,
 455                    g_io_error_from_errno (errsv),
 456                    _("Error seeking in file: %s"),
 457                    g_strerror (errsv));
 458       return FALSE;
 459     }
 460
 461   return TRUE;
 462 }
 463
 464 static gboolean
 465 g_local_file_output_stream_can_truncate (GFileOutputStream *stream)
 466 {
 467   /* We can't truncate pipes and stuff where we can't seek */
 468   return g_local_file_output_stream_can_seek (stream);
 469 }
 470
 471 static gboolean
 472 g_local_file_output_stream_truncate (GFileOutputStream  *stream,
 473                                      goffset             size,
 474                                      GCancellable       *cancellable,
 475                                      GError            **error)
 476 {
 477   GLocalFileOutputStream *file;
 478   int res;
 479
 480   file = G_LOCAL_FILE_OUTPUT_STREAM (stream);
 481
 482  restart:
 483 #ifdef G_OS_WIN32
 484   res = g_win32_ftruncate (file->priv->fd, size);
 485 #else
 486   res = ftruncate (file->priv->fd, size);
 487 #endif
 488
 489   if (res == -1)
 490     {
 491       int errsv = errno;
 492
 493       if (errsv == EINTR)
 494         {
 495           if (g_cancellable_set_error_if_cancelled (cancellable, error))
 496             return FALSE;
 497           goto restart;
 498         }
 499
 500       g_set_error (error, G_IO_ERROR,
 501                    g_io_error_from_errno (errsv),
 502                    _("Error truncating file: %s"),
 503                    g_strerror (errsv));
 504       return FALSE;
 505     }
 506
 507   return TRUE;
 508 }
 509
 510
 511 static GFileInfo *
 512 g_local_file_output_stream_query_info (GFileOutputStream  *stream,
 513                                        const char         *attributes,
 514                                        GCancellable       *cancellable,
 515                                        GError            **error)
 516 {
 517   GLocalFileOutputStream *file;
 518
 519   file = G_LOCAL_FILE_OUTPUT_STREAM (stream);
 520
 521   if (g_cancellable_set_error_if_cancelled (cancellable, error))
 522     return NULL;
 523
 524   return _g_local_file_info_get_from_fd (file->priv->fd,
 525                                          attributes,
 526                                          error);
 527 }
 528
 529 GFileOutputStream *
 530 _g_local_file_output_stream_new (int fd)
 531 {
 532   GLocalFileOutputStream *stream;
 533
 534   stream = g_object_new (G_TYPE_LOCAL_FILE_OUTPUT_STREAM, NULL);
 535   stream->priv->fd = fd;
 536   return G_FILE_OUTPUT_STREAM (stream);
 537 }
 538
 539 static void
 540 set_error_from_open_errno (const char *filename,
 541                            GError    **error)
 542 {
 543   int errsv = errno;
 544
 545   if (errsv == EINVAL)
 546     /* This must be an invalid filename, on e.g. FAT */
 547     g_set_error_literal (error, G_IO_ERROR,
 548                          G_IO_ERROR_INVALID_FILENAME,
 549                          _("Invalid filename"));
 550   else
 551     {
 552       char *display_name = g_filename_display_name (filename);
 553       g_set_error (error, G_IO_ERROR,
 554                    g_io_error_from_errno (errsv),
 555                    _("Error opening file “%s”: %s"),
 556                        display_name, g_strerror (errsv));
 557       g_free (display_name);
 558     }
 559 }
 560
 561 static GFileOutputStream *
 562 output_stream_open (const char    *filename,
 563                     gint           open_flags,
 564                     guint          mode,
 565                     GCancellable  *cancellable,
 566                     GError       **error)
 567 {
 568   GLocalFileOutputStream *stream;
 569   gint fd;
 570
 571   fd = g_open (filename, open_flags, mode);
 572   if (fd == -1)
 573     {
 574       set_error_from_open_errno (filename, error);
 575       return NULL;
 576     }
 577
 578   stream = g_object_new (G_TYPE_LOCAL_FILE_OUTPUT_STREAM, NULL);
 579   stream->priv->fd = fd;
 580   return G_FILE_OUTPUT_STREAM (stream);
 581 }
 582
 583 GFileOutputStream *
 584 _g_local_file_output_stream_open  (const char        *filename,
 585                                    gboolean          readable,
 586                                    GCancellable      *cancellable,
 587                                    GError           **error)
 588 {
 589   int open_flags;
 590
 591   if (g_cancellable_set_error_if_cancelled (cancellable, error))
 592     return NULL;
 593
 594   open_flags = O_BINARY;
 595   if (readable)
 596     open_flags |= O_RDWR;
 597   else
 598     open_flags |= O_WRONLY;
 599
 600   return output_stream_open (filename, open_flags, 0666, cancellable, error);
 601 }
 602
 603 static gint
 604 mode_from_flags_or_info (GFileCreateFlags   flags,
 605                          GFileInfo         *reference_info)
 606 {
 607   if (flags & G_FILE_CREATE_PRIVATE)
 608     return 0600;
 609   else if (reference_info && g_file_info_has_attribute (reference_info, "unix::mode"))
 610     return g_file_info_get_attribute_uint32 (reference_info, "unix::mode") & (~S_IFMT);
 611   else
 612     return 0666;
 613 }
 614
 615 GFileOutputStream *
 616 _g_local_file_output_stream_create  (const char        *filename,
 617                                      gboolean          readable,
 618                                      GFileCreateFlags   flags,
 619                                      GFileInfo         *reference_info,
 620                                      GCancellable      *cancellable,
 621                                      GError           **error)
 622 {
 623   int mode;
 624   int open_flags;
 625
 626   if (g_cancellable_set_error_if_cancelled (cancellable, error))
 627     return NULL;
 628
 629   mode = mode_from_flags_or_info (flags, reference_info);
 630
 631   open_flags = O_CREAT | O_EXCL | O_BINARY;
 632   if (readable)
 633     open_flags |= O_RDWR;
 634   else
 635     open_flags |= O_WRONLY;
 636
 637   return output_stream_open (filename, open_flags, mode, cancellable, error);
 638 }
 639
 640 GFileOutputStream *
 641 _g_local_file_output_stream_append  (const char        *filename,
 642                                      GFileCreateFlags   flags,
 643                                      GCancellable      *cancellable,
 644                                      GError           **error)
 645 {
 646   int mode;
 647
 648   if (g_cancellable_set_error_if_cancelled (cancellable, error))
 649     return NULL;
 650
 651   if (flags & G_FILE_CREATE_PRIVATE)
 652     mode = 0600;
 653   else
 654     mode = 0666;
 655
 656   return output_stream_open (filename, O_CREAT | O_APPEND | O_WRONLY | O_BINARY, mode,
 657                              cancellable, error);
 658 }
 659
 660 static char *
 661 create_backup_filename (const char *filename)
 662 {
 663   return g_strconcat (filename, BACKUP_EXTENSION, NULL);
 664 }
 665
 666 #define BUFSIZE 8192 /* size of normal write buffer */
 667
 668 static gboolean
 669 copy_file_data (gint     sfd,
 670                 gint     dfd,
 671                 GError **error)
 672 {
 673   gboolean ret = TRUE;
 674   gpointer buffer;
 675   const gchar *write_buffer;
 676   gssize bytes_read;
 677   gssize bytes_to_write;
 678   gssize bytes_written;
 679
 680   buffer = g_malloc (BUFSIZE);
 681
 682   do
 683     {
 684       bytes_read = read (sfd, buffer, BUFSIZE);
 685       if (bytes_read == -1)
 686         {
 687           int errsv = errno;
 688
 689           if (errsv == EINTR)
 690             continue;
 691
 692           g_set_error (error, G_IO_ERROR,
 693                        g_io_error_from_errno (errsv),
 694                        _("Error reading from file: %s"),
 695                        g_strerror (errsv));
 696           ret = FALSE;
 697           break;
 698         }
 699
 700       bytes_to_write = bytes_read;
 701       write_buffer = buffer;
 702
 703       do
 704         {
 705           bytes_written = write (dfd, write_buffer, bytes_to_write);
 706           if (bytes_written == -1)
 707             {
 708               int errsv = errno;
 709
 710               if (errsv == EINTR)
 711                 continue;
 712
 713               g_set_error (error, G_IO_ERROR,
 714                            g_io_error_from_errno (errsv),
 715                            _("Error writing to file: %s"),
 716                            g_strerror (errsv));
 717               ret = FALSE;
 718               break;
 719             }
 720
 721           bytes_to_write -= bytes_written;
 722           write_buffer += bytes_written;
 723         }
 724       while (bytes_to_write > 0);
 725
 726     } while ((bytes_read != 0) && (ret == TRUE));
 727
 728   g_free (buffer);
 729
 730   return ret;
 731 }
 732
 733 static int
 734 handle_overwrite_open (const char    *filename,
 735                        gboolean       readable,
 736                        const char    *etag,
 737                        gboolean       create_backup,
 738                        char         **temp_filename,
 739                        GFileCreateFlags flags,
 740                        GFileInfo       *reference_info,
 741                        GCancellable  *cancellable,
 742                        GError       **error)
 743 {
 744   int fd = -1;
 745   GLocalFileStat original_stat;
 746   char *current_etag;
 747   gboolean is_symlink;
 748   int open_flags;
 749   int res;
 750   int mode;
 751
 752   mode = mode_from_flags_or_info (flags, reference_info);
 753
 754   /* We only need read access to the original file if we are creating a backup.
 755    * We also add O_CREATE to avoid a race if the file was just removed */
 756   if (create_backup || readable)
 757     open_flags = O_RDWR | O_CREAT | O_BINARY;
 758   else
 759     open_flags = O_WRONLY | O_CREAT | O_BINARY;
 760
 761   /* Some systems have O_NOFOLLOW, which lets us avoid some races
 762    * when finding out if the file we opened was a symlink */
 763 #ifdef O_NOFOLLOW
 764   is_symlink = FALSE;
 765   fd = g_open (filename, open_flags | O_NOFOLLOW, mode);
 766   if (fd == -1 && errno == ELOOP)
 767     {
 768       /* Could be a symlink, or it could be a regular ELOOP error,
 769        * but then the next open will fail too. */
 770       is_symlink = TRUE;
 771       fd = g_open (filename, open_flags, mode);
 772     }
 773 #else
 774   fd = g_open (filename, open_flags, mode);
 775   /* This is racy, but we do it as soon as possible to minimize the race */
 776   is_symlink = g_file_test (filename, G_FILE_TEST_IS_SYMLINK);
 777 #endif
 778
 779   if (fd == -1)
 780     {
 781       int errsv = errno;
 782       char *display_name = g_filename_display_name (filename);
 783       g_set_error (error, G_IO_ERROR,
 784                    g_io_error_from_errno (errsv),
 785                    _("Error opening file “%s”: %s"),
 786                    display_name, g_strerror (errsv));
 787       g_free (display_name);
 788       return -1;
 789     }
 790
 791 #ifdef G_OS_WIN32
 792   res = _fstati64 (fd, &original_stat);
 793 #else
 794   res = fstat (fd, &original_stat);
 795 #endif
 796
 797   if (res != 0)
 798     {
 799       int errsv = errno;
 800       char *display_name = g_filename_display_name (filename);
 801       g_set_error (error, G_IO_ERROR,
 802                    g_io_error_from_errno (errsv),
 803                    _("Error when getting information for file “%s”: %s"),
 804                    display_name, g_strerror (errsv));
 805       g_free (display_name);
 806       goto err_out;
 807     }
 808
 809   /* not a regular file */
 810   if (!S_ISREG (original_stat.st_mode))
 811     {
 812       if (S_ISDIR (original_stat.st_mode))
 813         g_set_error_literal (error,
 814                              G_IO_ERROR,
 815                              G_IO_ERROR_IS_DIRECTORY,
 816                              _("Target file is a directory"));
 817       else
 818         g_set_error_literal (error,
 819                              G_IO_ERROR,
 820                              G_IO_ERROR_NOT_REGULAR_FILE,
 821                              _("Target file is not a regular file"));
 822       goto err_out;
 823     }
 824
 825   if (etag != NULL)
 826     {
 827       current_etag = _g_local_file_info_create_etag (&original_stat);
 828       if (strcmp (etag, current_etag) != 0)
 829         {
 830           g_set_error_literal (error,
 831                                G_IO_ERROR,
 832                                G_IO_ERROR_WRONG_ETAG,
 833                                _("The file was externally modified"));
 834           g_free (current_etag);
 835           goto err_out;
 836         }
 837       g_free (current_etag);
 838     }
 839
 840   /* We use two backup strategies.
 841    * The first one (which is faster) consist in saving to a
 842    * tmp file then rename the original file to the backup and the
 843    * tmp file to the original name. This is fast but doesn't work
 844    * when the file is a link (hard or symbolic) or when we can't
 845    * write to the current dir or can't set the permissions on the
 846    * new file.
 847    * The second strategy consist simply in copying the old file
 848    * to a backup file and rewrite the contents of the file.
 849    */
 850
 851   if ((flags & G_FILE_CREATE_REPLACE_DESTINATION) ||
 852       (!(original_stat.st_nlink > 1) && !is_symlink))
 853     {
 854       char *dirname, *tmp_filename;
 855       int tmpfd;
 856
 857       dirname = g_path_get_dirname (filename);
 858       tmp_filename = g_build_filename (dirname, ".goutputstream-XXXXXX", NULL);
 859       g_free (dirname);
 860
 861       tmpfd = g_mkstemp_full (tmp_filename, (readable ? O_RDWR : O_WRONLY) | O_BINARY, mode);
 862       if (tmpfd == -1)
 863         {
 864           g_free (tmp_filename);
 865           goto fallback_strategy;
 866         }
 867
 868       /* try to keep permissions (unless replacing) */
 869
 870       if ( ! (flags & G_FILE_CREATE_REPLACE_DESTINATION) &&
 871            (
 872 #ifdef HAVE_FCHOWN
 873             fchown (tmpfd, original_stat.st_uid, original_stat.st_gid) == -1 ||
 874 #endif
 875 #ifdef HAVE_FCHMOD
 876             fchmod (tmpfd, original_stat.st_mode) == -1 ||
 877 #endif
 878             0
 879             )
 880           )
 881         {
 882           GLocalFileStat tmp_statbuf;
 883           int tres;
 884
 885 #ifdef G_OS_WIN32
 886           tres = _fstati64 (tmpfd, &tmp_statbuf);
 887 #else
 888           tres = fstat (tmpfd, &tmp_statbuf);
 889 #endif
 890           /* Check that we really needed to change something */
 891           if (tres != 0 ||
 892               original_stat.st_uid != tmp_statbuf.st_uid ||
 893               original_stat.st_gid != tmp_statbuf.st_gid ||
 894               original_stat.st_mode != tmp_statbuf.st_mode)
 895             {
 896               g_close (tmpfd, NULL);
 897               g_unlink (tmp_filename);
 898               g_free (tmp_filename);
 899               goto fallback_strategy;
 900             }
 901         }
 902
 903       g_close (fd, NULL);
 904       *temp_filename = tmp_filename;
 905       return tmpfd;
 906     }
 907
 908  fallback_strategy:
 909
 910   if (create_backup)
 911     {
 912 #if defined(HAVE_FCHOWN) && defined(HAVE_FCHMOD)
 913       struct stat tmp_statbuf;
 914 #endif
 915       char *backup_filename;
 916       int bfd;
 917
 918       backup_filename = create_backup_filename (filename);
 919
 920       if (g_unlink (backup_filename) == -1 && errno != ENOENT)
 921         {
 922           g_set_error_literal (error,
 923                                G_IO_ERROR,
 924                                G_IO_ERROR_CANT_CREATE_BACKUP,
 925                                _("Backup file creation failed"));
 926           g_free (backup_filename);
 927           goto err_out;
 928         }
 929
 930       bfd = g_open (backup_filename,
 931                     O_WRONLY | O_CREAT | O_EXCL | O_BINARY,
 932                     original_stat.st_mode & 0777);
 933
 934       if (bfd == -1)
 935         {
 936           g_set_error_literal (error,
 937                                G_IO_ERROR,
 938                                G_IO_ERROR_CANT_CREATE_BACKUP,
 939                                _("Backup file creation failed"));
 940           g_free (backup_filename);
 941           goto err_out;
 942         }
 943
 944       /* If needed, Try to set the group of the backup same as the
 945        * original file. If this fails, set the protection
 946        * bits for the group same as the protection bits for
 947        * others. */
 948 #if defined(HAVE_FCHOWN) && defined(HAVE_FCHMOD)
 949       if (fstat (bfd, &tmp_statbuf) != 0)
 950         {
 951           g_set_error_literal (error,
 952                                G_IO_ERROR,
 953                                G_IO_ERROR_CANT_CREATE_BACKUP,
 954                                _("Backup file creation failed"));
 955           g_unlink (backup_filename);
 956           g_close (bfd, NULL);
 957           g_free (backup_filename);
 958           goto err_out;
 959         }
 960
 961       if ((original_stat.st_gid != tmp_statbuf.st_gid)  &&
 962           fchown (bfd, (uid_t) -1, original_stat.st_gid) != 0)
 963         {
 964           if (fchmod (bfd,
 965                       (original_stat.st_mode & 0707) |
 966                       ((original_stat.st_mode & 07) << 3)) != 0)
 967             {
 968               g_set_error_literal (error,
 969                                    G_IO_ERROR,
 970                                    G_IO_ERROR_CANT_CREATE_BACKUP,
 971                                    _("Backup file creation failed"));
 972               g_unlink (backup_filename);
 973               g_close (bfd, NULL);
 974               g_free (backup_filename);
 975               goto err_out;
 976             }
 977         }
 978 #endif
 979
 980       if (!copy_file_data (fd, bfd, NULL))
 981         {
 982           g_set_error_literal (error,
 983                                G_IO_ERROR,
 984                                G_IO_ERROR_CANT_CREATE_BACKUP,
 985                                _("Backup file creation failed"));
 986           g_unlink (backup_filename);
 987           g_close (bfd, NULL);
 988           g_free (backup_filename);
 989
 990           goto err_out;
 991         }
 992
 993       g_close (bfd, NULL);
 994       g_free (backup_filename);
 995
 996       /* Seek back to the start of the file after the backup copy */
 997       if (lseek (fd, 0, SEEK_SET) == -1)
 998         {
 999           int errsv = errno;
1000
1001           g_set_error (error, G_IO_ERROR,
1002                        g_io_error_from_errno (errsv),
1003                        _("Error seeking in file: %s"),
1004                        g_strerror (errsv));
1005           goto err_out;
1006         }
1007     }
1008
1009   if (flags & G_FILE_CREATE_REPLACE_DESTINATION)
1010     {
1011       g_close (fd, NULL);
1012
1013       if (g_unlink (filename) != 0)
1014         {
1015           int errsv = errno;
1016
1017           g_set_error (error, G_IO_ERROR,
1018                        g_io_error_from_errno (errsv),
1019                        _("Error removing old file: %s"),
1020                        g_strerror (errsv));
1021           goto err_out2;
1022         }
1023
1024       if (readable)
1025         open_flags = O_RDWR | O_CREAT | O_BINARY;
1026       else
1027         open_flags = O_WRONLY | O_CREAT | O_BINARY;
1028       fd = g_open (filename, open_flags, mode);
1029       if (fd == -1)
1030         {
1031           int errsv = errno;
1032           char *display_name = g_filename_display_name (filename);
1033           g_set_error (error, G_IO_ERROR,
1034                        g_io_error_from_errno (errsv),
1035                        _("Error opening file “%s”: %s"),
1036                        display_name, g_strerror (errsv));
1037           g_free (display_name);
1038           goto err_out2;
1039         }
1040     }
1041   else
1042     {
1043       /* Truncate the file at the start */
1044 #ifdef G_OS_WIN32
1045       if (g_win32_ftruncate (fd, 0) == -1)
1046 #else
1047         if (ftruncate (fd, 0) == -1)
1048 #endif
1049           {
1050             int errsv = errno;
1051
1052             g_set_error (error, G_IO_ERROR,
1053                          g_io_error_from_errno (errsv),
1054                          _("Error truncating file: %s"),
1055                          g_strerror (errsv));
1056             goto err_out;
1057           }
1058     }
1059
1060   return fd;
1061
1062  err_out:
1063   g_close (fd, NULL);
1064  err_out2:
1065   return -1;
1066 }
1067
1068 GFileOutputStream *
1069 _g_local_file_output_stream_replace (const char        *filename,
1070                                      gboolean          readable,
1071                                      const char        *etag,
1072                                      gboolean           create_backup,
1073                                      GFileCreateFlags   flags,
1074                                      GFileInfo         *reference_info,
1075                                      GCancellable      *cancellable,
1076                                      GError           **error)
1077 {
1078   GLocalFileOutputStream *stream;
1079   int mode;
1080   int fd;
1081   char *temp_file;
1082   gboolean sync_on_close;
1083   int open_flags;
1084
1085   if (g_cancellable_set_error_if_cancelled (cancellable, error))
1086     return NULL;
1087
1088   temp_file = NULL;
1089
1090   mode = mode_from_flags_or_info (flags, reference_info);
1091   sync_on_close = FALSE;
1092
1093   /* If the file doesn't exist, create it */
1094   open_flags = O_CREAT | O_EXCL | O_BINARY;
1095   if (readable)
1096     open_flags |= O_RDWR;
1097   else
1098     open_flags |= O_WRONLY;
1099   fd = g_open (filename, open_flags, mode);
1100
1101   if (fd == -1 && errno == EEXIST)
1102     {
1103       /* The file already exists */
1104       fd = handle_overwrite_open (filename, readable, etag,
1105                                   create_backup, &temp_file,
1106                                   flags, reference_info,
1107                                   cancellable, error);
1108       if (fd == -1)
1109         return NULL;
1110
1111       /* If the final destination exists, we want to sync the newly written
1112        * file to ensure the data is on disk when we rename over the destination.
1113        * otherwise if we get a system crash we can lose both the new and the
1114        * old file on some filesystems. (I.E. those that don't guarantee the
1115        * data is written to the disk before the metadata.)
1116        */
1117       sync_on_close = TRUE;
1118     }
1119   else if (fd == -1)
1120     {
1121       set_error_from_open_errno (filename, error);
1122       return NULL;
1123     }
1124
1125
1126   stream = g_object_new (G_TYPE_LOCAL_FILE_OUTPUT_STREAM, NULL);
1127   stream->priv->fd = fd;
1128   stream->priv->sync_on_close = sync_on_close;
1129   stream->priv->tmp_filename = temp_file;
1130   if (create_backup)
1131     stream->priv->backup_filename = create_backup_filename (filename);
1132   stream->priv->original_filename =  g_strdup (filename);
1133
1134   return G_FILE_OUTPUT_STREAM (stream);
1135 }
1136
1137 gint
1138 _g_local_file_output_stream_get_fd (GLocalFileOutputStream *stream)
1139 {
1140   g_return_val_if_fail (G_IS_LOCAL_FILE_OUTPUT_STREAM (stream), -1);
1141   return stream->priv->fd;
1142 }
1143
1144 #ifdef G_OS_UNIX
1145 static int
1146 g_local_file_output_stream_get_fd (GFileDescriptorBased *fd_based)
1147 {
1148   GLocalFileOutputStream *stream = G_LOCAL_FILE_OUTPUT_STREAM (fd_based);
1149   return _g_local_file_output_stream_get_fd (stream);
1150 }
1151 #endif