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 2.1 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 #include "glib-private.h"
  44
  45 #ifdef G_OS_WIN32
  46 #include <io.h>
  47 #ifndef S_ISDIR
  48 #define S_ISDIR(m) (((m) & _S_IFMT) == _S_IFDIR)
  49 #endif
  50 #ifndef S_ISREG
  51 #define S_ISREG(m) (((m) & _S_IFMT) == _S_IFREG)
  52 #endif
  53 #endif
  54
  55 #ifndef O_BINARY
  56 #define O_BINARY 0
  57 #endif
  58
  59 struct _GLocalFileOutputStreamPrivate {
  60   char *tmp_filename;
  61   char *original_filename;
  62   char *backup_filename;
  63   char *etag;
  64   guint sync_on_close : 1;
  65   guint do_close : 1;
  66   int fd;
  67 };
  68
  69 #ifdef G_OS_UNIX
  70 static void       g_file_descriptor_based_iface_init   (GFileDescriptorBasedIface *iface);
  71 #endif
  72
  73 #define g_local_file_output_stream_get_type _g_local_file_output_stream_get_type
  74 #ifdef G_OS_UNIX
  75 G_DEFINE_TYPE_WITH_CODE (GLocalFileOutputStream, g_local_file_output_stream, G_TYPE_FILE_OUTPUT_STREAM,
  76                          G_ADD_PRIVATE (GLocalFileOutputStream)
  77                          G_IMPLEMENT_INTERFACE (G_TYPE_FILE_DESCRIPTOR_BASED,
  78                                                 g_file_descriptor_based_iface_init))
  79 #else
  80 G_DEFINE_TYPE_WITH_CODE (GLocalFileOutputStream, g_local_file_output_stream, G_TYPE_FILE_OUTPUT_STREAM,
  81                          G_ADD_PRIVATE (GLocalFileOutputStream))
  82 #endif
  83
  84
  85 /* Some of the file replacement code was based on the code from gedit,
  86  * relicenced to LGPL with permissions from the authors.
  87  */
  88
  89 #define BACKUP_EXTENSION "~"
  90
  91 static gssize     g_local_file_output_stream_write        (GOutputStream      *stream,
  92                                                            const void         *buffer,
  93                                                            gsize               count,
  94                                                            GCancellable       *cancellable,
  95                                                            GError            **error);
  96 static gboolean   g_local_file_output_stream_close        (GOutputStream      *stream,
  97                                                            GCancellable       *cancellable,
  98                                                            GError            **error);
  99 static GFileInfo *g_local_file_output_stream_query_info   (GFileOutputStream  *stream,
 100                                                            const char         *attributes,
 101                                                            GCancellable       *cancellable,
 102                                                            GError            **error);
 103 static char *     g_local_file_output_stream_get_etag     (GFileOutputStream  *stream);
 104 static goffset    g_local_file_output_stream_tell         (GFileOutputStream  *stream);
 105 static gboolean   g_local_file_output_stream_can_seek     (GFileOutputStream  *stream);
 106 static gboolean   g_local_file_output_stream_seek         (GFileOutputStream  *stream,
 107                                                            goffset             offset,
 108                                                            GSeekType           type,
 109                                                            GCancellable       *cancellable,
 110                                                            GError            **error);
 111 static gboolean   g_local_file_output_stream_can_truncate (GFileOutputStream  *stream);
 112 static gboolean   g_local_file_output_stream_truncate     (GFileOutputStream  *stream,
 113                                                            goffset             size,
 114                                                            GCancellable       *cancellable,
 115                                                            GError            **error);
 116 #ifdef G_OS_UNIX
 117 static int        g_local_file_output_stream_get_fd       (GFileDescriptorBased *stream);
 118 #endif
 119
 120 static void
 121 g_local_file_output_stream_finalize (GObject *object)
 122 {
 123   GLocalFileOutputStream *file;
 124
 125   file = G_LOCAL_FILE_OUTPUT_STREAM (object);
 126
 127   g_free (file->priv->tmp_filename);
 128   g_free (file->priv->original_filename);
 129   g_free (file->priv->backup_filename);
 130   g_free (file->priv->etag);
 131
 132   G_OBJECT_CLASS (g_local_file_output_stream_parent_class)->finalize (object);
 133 }
 134
 135 static void
 136 g_local_file_output_stream_class_init (GLocalFileOutputStreamClass *klass)
 137 {
 138   GObjectClass *gobject_class = G_OBJECT_CLASS (klass);
 139   GOutputStreamClass *stream_class = G_OUTPUT_STREAM_CLASS (klass);
 140   GFileOutputStreamClass *file_stream_class = G_FILE_OUTPUT_STREAM_CLASS (klass);
 141
 142   gobject_class->finalize = g_local_file_output_stream_finalize;
 143
 144   stream_class->write_fn = g_local_file_output_stream_write;
 145   stream_class->close_fn = g_local_file_output_stream_close;
 146   file_stream_class->query_info = g_local_file_output_stream_query_info;
 147   file_stream_class->get_etag = g_local_file_output_stream_get_etag;
 148   file_stream_class->tell = g_local_file_output_stream_tell;
 149   file_stream_class->can_seek = g_local_file_output_stream_can_seek;
 150   file_stream_class->seek = g_local_file_output_stream_seek;
 151   file_stream_class->can_truncate = g_local_file_output_stream_can_truncate;
 152   file_stream_class->truncate_fn = g_local_file_output_stream_truncate;
 153 }
 154
 155 #ifdef G_OS_UNIX
 156 static void
 157 g_file_descriptor_based_iface_init (GFileDescriptorBasedIface *iface)
 158 {
 159   iface->get_fd = g_local_file_output_stream_get_fd;
 160 }
 161 #endif
 162
 163 static void
 164 g_local_file_output_stream_init (GLocalFileOutputStream *stream)
 165 {
 166   stream->priv = g_local_file_output_stream_get_instance_private (stream);
 167   stream->priv->do_close = TRUE;
 168 }
 169
 170 static gssize
 171 g_local_file_output_stream_write (GOutputStream  *stream,
 172                                   const void     *buffer,
 173                                   gsize           count,
 174                                   GCancellable   *cancellable,
 175                                   GError        **error)
 176 {
 177   GLocalFileOutputStream *file;
 178   gssize res;
 179
 180   file = G_LOCAL_FILE_OUTPUT_STREAM (stream);
 181
 182   while (1)
 183     {
 184       if (g_cancellable_set_error_if_cancelled (cancellable, error))
 185         return -1;
 186       res = write (file->priv->fd, buffer, count);
 187       if (res == -1)
 188         {
 189           int errsv = errno;
 190
 191           if (errsv == EINTR)
 192             continue;
 193
 194           g_set_error (error, G_IO_ERROR,
 195                        g_io_error_from_errno (errsv),
 196                        _("Error writing to file: %s"),
 197                        g_strerror (errsv));
 198         }
 199
 200       break;
 201     }
 202
 203   return res;
 204 }
 205
 206 void
 207 _g_local_file_output_stream_set_do_close (GLocalFileOutputStream *out,
 208                                           gboolean do_close)
 209 {
 210   out->priv->do_close = do_close;
 211 }
 212
 213 gboolean
 214 _g_local_file_output_stream_really_close (GLocalFileOutputStream *file,
 215                                           GCancellable   *cancellable,
 216                                           GError        **error)
 217 {
 218   GLocalFileStat final_stat;
 219
 220 #ifdef HAVE_FSYNC
 221   if (file->priv->sync_on_close &&
 222       fsync (file->priv->fd) != 0)
 223     {
 224       int errsv = errno;
 225
 226       g_set_error (error, G_IO_ERROR,
 227                    g_io_error_from_errno (errsv),
 228                    _("Error writing to file: %s"),
 229                    g_strerror (errsv));
 230       goto err_out;
 231     }
 232 #endif
 233
 234 #ifdef G_OS_WIN32
 235
 236   /* Must close before renaming on Windows, so just do the close first
 237    * in all cases for now.
 238    */
 239   if (GLIB_PRIVATE_CALL (g_win32_fstat) (file->priv->fd, &final_stat) == 0)
 240     file->priv->etag = _g_local_file_info_create_etag (&final_stat);
 241
 242   if (!g_close (file->priv->fd, NULL))
 243     {
 244       int errsv = errno;
 245
 246       g_set_error (error, G_IO_ERROR,
 247                    g_io_error_from_errno (errsv),
 248                    _("Error closing file: %s"),
 249                    g_strerror (errsv));
 250       return FALSE;
 251     }
 252
 253 #endif
 254
 255   if (file->priv->tmp_filename)
 256     {
 257       /* We need to move the temp file to its final place,
 258        * and possibly create the backup file
 259        */
 260
 261       if (file->priv->backup_filename)
 262         {
 263           if (g_cancellable_set_error_if_cancelled (cancellable, error))
 264             goto err_out;
 265
 266 #ifdef G_OS_UNIX
 267           /* create original -> backup link, the original is then renamed over */
 268           if (g_unlink (file->priv->backup_filename) != 0 &&
 269               errno != ENOENT)
 270             {
 271               int errsv = errno;
 272
 273               g_set_error (error, G_IO_ERROR,
 274                            G_IO_ERROR_CANT_CREATE_BACKUP,
 275                            _("Error removing old backup link: %s"),
 276                            g_strerror (errsv));
 277               goto err_out;
 278             }
 279
 280           if (link (file->priv->original_filename, file->priv->backup_filename) != 0)
 281             {
 282               /*  link failed or is not supported, try rename  */
 283               if (g_rename (file->priv->original_filename, file->priv->backup_filename) != 0)
 284                 {
 285                   int errsv = errno;
 286
 287                   g_set_error (error, G_IO_ERROR,
 288                                G_IO_ERROR_CANT_CREATE_BACKUP,
 289                                _("Error creating backup copy: %s"),
 290                                g_strerror (errsv));
 291                   goto err_out;
 292                 }
 293             }
 294 #else
 295             /* If link not supported, just rename... */
 296           if (g_rename (file->priv->original_filename, file->priv->backup_filename) != 0)
 297             {
 298               int errsv = errno;
 299
 300               g_set_error (error, G_IO_ERROR,
 301                            G_IO_ERROR_CANT_CREATE_BACKUP,
 302                            _("Error creating backup copy: %s"),
 303                            g_strerror (errsv));
 304               goto err_out;
 305             }
 306 #endif
 307         }
 308
 309
 310       if (g_cancellable_set_error_if_cancelled (cancellable, error))
 311         goto err_out;
 312
 313       /* tmp -> original */
 314       if (g_rename (file->priv->tmp_filename, file->priv->original_filename) != 0)
 315         {
 316           int errsv = errno;
 317
 318           g_set_error (error, G_IO_ERROR,
 319                        g_io_error_from_errno (errsv),
 320                        _("Error renaming temporary file: %s"),
 321                        g_strerror (errsv));
 322           goto err_out;
 323         }
 324
 325       g_clear_pointer (&file->priv->tmp_filename, g_free);
 326     }
 327
 328   if (g_cancellable_set_error_if_cancelled (cancellable, error))
 329     goto err_out;
 330
 331 #ifndef G_OS_WIN32              /* Already did the fstat() and close() above on Win32 */
 332
 333   if (fstat (file->priv->fd, &final_stat) == 0)
 334     file->priv->etag = _g_local_file_info_create_etag (&final_stat);
 335
 336   if (!g_close (file->priv->fd, NULL))
 337     {
 338       int errsv = errno;
 339
 340       g_set_error (error, G_IO_ERROR,
 341                    g_io_error_from_errno (errsv),
 342                    _("Error closing file: %s"),
 343                    g_strerror (errsv));
 344       goto err_out;
 345     }
 346
 347 #endif
 348
 349   return TRUE;
 350  err_out:
 351
 352 #ifndef G_OS_WIN32
 353   /* A simple try to close the fd in case we fail before the actual close */
 354   g_close (file->priv->fd, NULL);
 355 #endif
 356   if (file->priv->tmp_filename)
 357     g_unlink (file->priv->tmp_filename);
 358
 359   return FALSE;
 360 }
 361
 362
 363 static gboolean
 364 g_local_file_output_stream_close (GOutputStream  *stream,
 365                                   GCancellable   *cancellable,
 366                                   GError        **error)
 367 {
 368   GLocalFileOutputStream *file;
 369
 370   file = G_LOCAL_FILE_OUTPUT_STREAM (stream);
 371
 372   if (file->priv->do_close)
 373     return _g_local_file_output_stream_really_close (file,
 374                                                      cancellable,
 375                                                      error);
 376   return TRUE;
 377 }
 378
 379 static char *
 380 g_local_file_output_stream_get_etag (GFileOutputStream *stream)
 381 {
 382   GLocalFileOutputStream *file;
 383
 384   file = G_LOCAL_FILE_OUTPUT_STREAM (stream);
 385
 386   return g_strdup (file->priv->etag);
 387 }
 388
 389 static goffset
 390 g_local_file_output_stream_tell (GFileOutputStream *stream)
 391 {
 392   GLocalFileOutputStream *file;
 393   off_t pos;
 394
 395   file = G_LOCAL_FILE_OUTPUT_STREAM (stream);
 396
 397   pos = lseek (file->priv->fd, 0, SEEK_CUR);
 398
 399   if (pos == (off_t)-1)
 400     return 0;
 401
 402   return pos;
 403 }
 404
 405 static gboolean
 406 g_local_file_output_stream_can_seek (GFileOutputStream *stream)
 407 {
 408   GLocalFileOutputStream *file;
 409   off_t pos;
 410
 411   file = G_LOCAL_FILE_OUTPUT_STREAM (stream);
 412
 413   pos = lseek (file->priv->fd, 0, SEEK_CUR);
 414
 415   if (pos == (off_t)-1 && errno == ESPIPE)
 416     return FALSE;
 417
 418   return TRUE;
 419 }
 420
 421 static int
 422 seek_type_to_lseek (GSeekType type)
 423 {
 424   switch (type)
 425     {
 426     default:
 427     case G_SEEK_CUR:
 428       return SEEK_CUR;
 429
 430     case G_SEEK_SET:
 431       return SEEK_SET;
 432
 433     case G_SEEK_END:
 434       return SEEK_END;
 435     }
 436 }
 437
 438 static gboolean
 439 g_local_file_output_stream_seek (GFileOutputStream  *stream,
 440                                  goffset             offset,
 441                                  GSeekType           type,
 442                                  GCancellable       *cancellable,
 443                                  GError            **error)
 444 {
 445   GLocalFileOutputStream *file;
 446   off_t pos;
 447
 448   file = G_LOCAL_FILE_OUTPUT_STREAM (stream);
 449
 450   pos = lseek (file->priv->fd, offset, seek_type_to_lseek (type));
 451
 452   if (pos == (off_t)-1)
 453     {
 454       int errsv = errno;
 455
 456       g_set_error (error, G_IO_ERROR,
 457                    g_io_error_from_errno (errsv),
 458                    _("Error seeking in file: %s"),
 459                    g_strerror (errsv));
 460       return FALSE;
 461     }
 462
 463   return TRUE;
 464 }
 465
 466 static gboolean
 467 g_local_file_output_stream_can_truncate (GFileOutputStream *stream)
 468 {
 469   /* We can't truncate pipes and stuff where we can't seek */
 470   return g_local_file_output_stream_can_seek (stream);
 471 }
 472
 473 static gboolean
 474 g_local_file_output_stream_truncate (GFileOutputStream  *stream,
 475                                      goffset             size,
 476                                      GCancellable       *cancellable,
 477                                      GError            **error)
 478 {
 479   GLocalFileOutputStream *file;
 480   int res;
 481
 482   file = G_LOCAL_FILE_OUTPUT_STREAM (stream);
 483
 484  restart:
 485 #ifdef G_OS_WIN32
 486   res = g_win32_ftruncate (file->priv->fd, size);
 487 #else
 488   res = ftruncate (file->priv->fd, size);
 489 #endif
 490
 491   if (res == -1)
 492     {
 493       int errsv = errno;
 494
 495       if (errsv == EINTR)
 496         {
 497           if (g_cancellable_set_error_if_cancelled (cancellable, error))
 498             return FALSE;
 499           goto restart;
 500         }
 501
 502       g_set_error (error, G_IO_ERROR,
 503                    g_io_error_from_errno (errsv),
 504                    _("Error truncating file: %s"),
 505                    g_strerror (errsv));
 506       return FALSE;
 507     }
 508
 509   return TRUE;
 510 }
 511
 512
 513 static GFileInfo *
 514 g_local_file_output_stream_query_info (GFileOutputStream  *stream,
 515                                        const char         *attributes,
 516                                        GCancellable       *cancellable,
 517                                        GError            **error)
 518 {
 519   GLocalFileOutputStream *file;
 520
 521   file = G_LOCAL_FILE_OUTPUT_STREAM (stream);
 522
 523   if (g_cancellable_set_error_if_cancelled (cancellable, error))
 524     return NULL;
 525
 526   return _g_local_file_info_get_from_fd (file->priv->fd,
 527                                          attributes,
 528                                          error);
 529 }
 530
 531 GFileOutputStream *
 532 _g_local_file_output_stream_new (int fd)
 533 {
 534   GLocalFileOutputStream *stream;
 535
 536   stream = g_object_new (G_TYPE_LOCAL_FILE_OUTPUT_STREAM, NULL);
 537   stream->priv->fd = fd;
 538   return G_FILE_OUTPUT_STREAM (stream);
 539 }
 540
 541 static void
 542 set_error_from_open_errno (const char *filename,
 543                            GError    **error)
 544 {
 545   int errsv = errno;
 546
 547   if (errsv == EINVAL)
 548     /* This must be an invalid filename, on e.g. FAT */
 549     g_set_error_literal (error, G_IO_ERROR,
 550                          G_IO_ERROR_INVALID_FILENAME,
 551                          _("Invalid filename"));
 552   else
 553     {
 554       char *display_name = g_filename_display_name (filename);
 555       g_set_error (error, G_IO_ERROR,
 556                    g_io_error_from_errno (errsv),
 557                    _("Error opening file “%s”: %s"),
 558                        display_name, g_strerror (errsv));
 559       g_free (display_name);
 560     }
 561 }
 562
 563 static GFileOutputStream *
 564 output_stream_open (const char    *filename,
 565                     gint           open_flags,
 566                     guint          mode,
 567                     GCancellable  *cancellable,
 568                     GError       **error)
 569 {
 570   GLocalFileOutputStream *stream;
 571   gint fd;
 572
 573   fd = g_open (filename, open_flags, mode);
 574   if (fd == -1)
 575     {
 576       set_error_from_open_errno (filename, error);
 577       return NULL;
 578     }
 579
 580   stream = g_object_new (G_TYPE_LOCAL_FILE_OUTPUT_STREAM, NULL);
 581   stream->priv->fd = fd;
 582   return G_FILE_OUTPUT_STREAM (stream);
 583 }
 584
 585 GFileOutputStream *
 586 _g_local_file_output_stream_open  (const char        *filename,
 587                                    gboolean          readable,
 588                                    GCancellable      *cancellable,
 589                                    GError           **error)
 590 {
 591   int open_flags;
 592
 593   if (g_cancellable_set_error_if_cancelled (cancellable, error))
 594     return NULL;
 595
 596   open_flags = O_BINARY;
 597   if (readable)
 598     open_flags |= O_RDWR;
 599   else
 600     open_flags |= O_WRONLY;
 601
 602   return output_stream_open (filename, open_flags, 0666, cancellable, error);
 603 }
 604
 605 static gint
 606 mode_from_flags_or_info (GFileCreateFlags   flags,
 607                          GFileInfo         *reference_info)
 608 {
 609   if (flags & G_FILE_CREATE_PRIVATE)
 610     return 0600;
 611   else if (reference_info && g_file_info_has_attribute (reference_info, "unix::mode"))
 612     return g_file_info_get_attribute_uint32 (reference_info, "unix::mode") & (~S_IFMT);
 613   else
 614     return 0666;
 615 }
 616
 617 GFileOutputStream *
 618 _g_local_file_output_stream_create  (const char        *filename,
 619                                      gboolean          readable,
 620                                      GFileCreateFlags   flags,
 621                                      GFileInfo         *reference_info,
 622                                      GCancellable      *cancellable,
 623                                      GError           **error)
 624 {
 625   int mode;
 626   int open_flags;
 627
 628   if (g_cancellable_set_error_if_cancelled (cancellable, error))
 629     return NULL;
 630
 631   mode = mode_from_flags_or_info (flags, reference_info);
 632
 633   open_flags = O_CREAT | O_EXCL | O_BINARY;
 634   if (readable)
 635     open_flags |= O_RDWR;
 636   else
 637     open_flags |= O_WRONLY;
 638
 639   return output_stream_open (filename, open_flags, mode, cancellable, error);
 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   int mode;
 649
 650   if (g_cancellable_set_error_if_cancelled (cancellable, error))
 651     return NULL;
 652
 653   if (flags & G_FILE_CREATE_PRIVATE)
 654     mode = 0600;
 655   else
 656     mode = 0666;
 657
 658   return output_stream_open (filename, O_CREAT | O_APPEND | O_WRONLY | O_BINARY, mode,
 659                              cancellable, error);
 660 }
 661
 662 static char *
 663 create_backup_filename (const char *filename)
 664 {
 665   return g_strconcat (filename, BACKUP_EXTENSION, NULL);
 666 }
 667
 668 #define BUFSIZE 8192 /* size of normal write buffer */
 669
 670 static gboolean
 671 copy_file_data (gint     sfd,
 672                 gint     dfd,
 673                 GError **error)
 674 {
 675   gboolean ret = TRUE;
 676   gpointer buffer;
 677   const gchar *write_buffer;
 678   gssize bytes_read;
 679   gssize bytes_to_write;
 680   gssize bytes_written;
 681
 682   buffer = g_malloc (BUFSIZE);
 683
 684   do
 685     {
 686       bytes_read = read (sfd, buffer, BUFSIZE);
 687       if (bytes_read == -1)
 688         {
 689           int errsv = errno;
 690
 691           if (errsv == EINTR)
 692             continue;
 693
 694           g_set_error (error, G_IO_ERROR,
 695                        g_io_error_from_errno (errsv),
 696                        _("Error reading from file: %s"),
 697                        g_strerror (errsv));
 698           ret = FALSE;
 699           break;
 700         }
 701
 702       bytes_to_write = bytes_read;
 703       write_buffer = buffer;
 704
 705       do
 706         {
 707           bytes_written = write (dfd, write_buffer, bytes_to_write);
 708           if (bytes_written == -1)
 709             {
 710               int errsv = errno;
 711
 712               if (errsv == EINTR)
 713                 continue;
 714
 715               g_set_error (error, G_IO_ERROR,
 716                            g_io_error_from_errno (errsv),
 717                            _("Error writing to file: %s"),
 718                            g_strerror (errsv));
 719               ret = FALSE;
 720               break;
 721             }
 722
 723           bytes_to_write -= bytes_written;
 724           write_buffer += bytes_written;
 725         }
 726       while (bytes_to_write > 0);
 727
 728     } while ((bytes_read != 0) && (ret == TRUE));
 729
 730   g_free (buffer);
 731
 732   return ret;
 733 }
 734
 735 static int
 736 handle_overwrite_open (const char    *filename,
 737                        gboolean       readable,
 738                        const char    *etag,
 739                        gboolean       create_backup,
 740                        char         **temp_filename,
 741                        GFileCreateFlags flags,
 742                        GFileInfo       *reference_info,
 743                        GCancellable  *cancellable,
 744                        GError       **error)
 745 {
 746   int fd = -1;
 747   GLocalFileStat original_stat;
 748   char *current_etag;
 749   gboolean is_symlink;
 750   int open_flags;
 751   int res;
 752   int mode;
 753   int errsv;
 754
 755   mode = mode_from_flags_or_info (flags, reference_info);
 756
 757   /* We only need read access to the original file if we are creating a backup.
 758    * We also add O_CREATE to avoid a race if the file was just removed */
 759   if (create_backup || readable)
 760     open_flags = O_RDWR | O_CREAT | O_BINARY;
 761   else
 762     open_flags = O_WRONLY | O_CREAT | O_BINARY;
 763
 764   /* Some systems have O_NOFOLLOW, which lets us avoid some races
 765    * when finding out if the file we opened was a symlink */
 766 #ifdef O_NOFOLLOW
 767   is_symlink = FALSE;
 768   fd = g_open (filename, open_flags | O_NOFOLLOW, mode);
 769   errsv = errno;
 770 #if defined(__FreeBSD__) || defined(__FreeBSD_kernel__) || defined(__DragonFly__)
 771   if (fd == -1 && errsv == EMLINK)
 772 #elif defined(__NetBSD__)
 773   if (fd == -1 && errsv == EFTYPE)
 774 #else
 775   if (fd == -1 && errsv == ELOOP)
 776 #endif
 777     {
 778       /* Could be a symlink, or it could be a regular ELOOP error,
 779        * but then the next open will fail too. */
 780       is_symlink = TRUE;
 781       fd = g_open (filename, open_flags, mode);
 782     }
 783 #else
 784   fd = g_open (filename, open_flags, mode);
 785   errsv = errno;
 786   /* This is racy, but we do it as soon as possible to minimize the race */
 787   is_symlink = g_file_test (filename, G_FILE_TEST_IS_SYMLINK);
 788 #endif
 789
 790   if (fd == -1)
 791     {
 792       char *display_name = g_filename_display_name (filename);
 793       g_set_error (error, G_IO_ERROR,
 794                    g_io_error_from_errno (errsv),
 795                    _("Error opening file “%s”: %s"),
 796                    display_name, g_strerror (errsv));
 797       g_free (display_name);
 798       return -1;
 799     }
 800
 801 #ifdef G_OS_WIN32
 802   res = GLIB_PRIVATE_CALL (g_win32_fstat) (fd, &original_stat);
 803 #else
 804   res = fstat (fd, &original_stat);
 805 #endif
 806   errsv = errno;
 807
 808   if (res != 0)
 809     {
 810       char *display_name = g_filename_display_name (filename);
 811       g_set_error (error, G_IO_ERROR,
 812                    g_io_error_from_errno (errsv),
 813                    _("Error when getting information for file “%s”: %s"),
 814                    display_name, g_strerror (errsv));
 815       g_free (display_name);
 816       goto err_out;
 817     }
 818
 819   /* not a regular file */
 820   if (!S_ISREG (original_stat.st_mode))
 821     {
 822       if (S_ISDIR (original_stat.st_mode))
 823         g_set_error_literal (error,
 824                              G_IO_ERROR,
 825                              G_IO_ERROR_IS_DIRECTORY,
 826                              _("Target file is a directory"));
 827       else
 828         g_set_error_literal (error,
 829                              G_IO_ERROR,
 830                              G_IO_ERROR_NOT_REGULAR_FILE,
 831                              _("Target file is not a regular file"));
 832       goto err_out;
 833     }
 834
 835   if (etag != NULL)
 836     {
 837       current_etag = _g_local_file_info_create_etag (&original_stat);
 838       if (strcmp (etag, current_etag) != 0)
 839         {
 840           g_set_error_literal (error,
 841                                G_IO_ERROR,
 842                                G_IO_ERROR_WRONG_ETAG,
 843                                _("The file was externally modified"));
 844           g_free (current_etag);
 845           goto err_out;
 846         }
 847       g_free (current_etag);
 848     }
 849
 850   /* We use two backup strategies.
 851    * The first one (which is faster) consist in saving to a
 852    * tmp file then rename the original file to the backup and the
 853    * tmp file to the original name. This is fast but doesn't work
 854    * when the file is a link (hard or symbolic) or when we can't
 855    * write to the current dir or can't set the permissions on the
 856    * new file.
 857    * The second strategy consist simply in copying the old file
 858    * to a backup file and rewrite the contents of the file.
 859    */
 860
 861   if ((flags & G_FILE_CREATE_REPLACE_DESTINATION) ||
 862       (!(original_stat.st_nlink > 1) && !is_symlink))
 863     {
 864       char *dirname, *tmp_filename;
 865       int tmpfd;
 866
 867       dirname = g_path_get_dirname (filename);
 868       tmp_filename = g_build_filename (dirname, ".goutputstream-XXXXXX", NULL);
 869       g_free (dirname);
 870
 871       tmpfd = g_mkstemp_full (tmp_filename, (readable ? O_RDWR : O_WRONLY) | O_BINARY, mode);
 872       if (tmpfd == -1)
 873         {
 874           g_free (tmp_filename);
 875           goto fallback_strategy;
 876         }
 877
 878       /* try to keep permissions (unless replacing) */
 879
 880       if ( ! (flags & G_FILE_CREATE_REPLACE_DESTINATION) &&
 881            (
 882 #ifdef HAVE_FCHOWN
 883             fchown (tmpfd, original_stat.st_uid, original_stat.st_gid) == -1 ||
 884 #endif
 885 #ifdef HAVE_FCHMOD
 886             fchmod (tmpfd, original_stat.st_mode) == -1 ||
 887 #endif
 888             0
 889             )
 890           )
 891         {
 892           GLocalFileStat tmp_statbuf;
 893           int tres;
 894
 895 #ifdef G_OS_WIN32
 896           tres = GLIB_PRIVATE_CALL (g_win32_fstat) (tmpfd, &tmp_statbuf);
 897 #else
 898           tres = fstat (tmpfd, &tmp_statbuf);
 899 #endif
 900           /* Check that we really needed to change something */
 901           if (tres != 0 ||
 902               original_stat.st_uid != tmp_statbuf.st_uid ||
 903               original_stat.st_gid != tmp_statbuf.st_gid ||
 904               original_stat.st_mode != tmp_statbuf.st_mode)
 905             {
 906               g_close (tmpfd, NULL);
 907               g_unlink (tmp_filename);
 908               g_free (tmp_filename);
 909               goto fallback_strategy;
 910             }
 911         }
 912
 913       g_close (fd, NULL);
 914       *temp_filename = tmp_filename;
 915       return tmpfd;
 916     }
 917
 918  fallback_strategy:
 919
 920   if (create_backup)
 921     {
 922 #if defined(HAVE_FCHOWN) && defined(HAVE_FCHMOD)
 923       struct stat tmp_statbuf;
 924 #endif
 925       char *backup_filename;
 926       int bfd;
 927
 928       backup_filename = create_backup_filename (filename);
 929
 930       if (g_unlink (backup_filename) == -1 && errno != ENOENT)
 931         {
 932           g_set_error_literal (error,
 933                                G_IO_ERROR,
 934                                G_IO_ERROR_CANT_CREATE_BACKUP,
 935                                _("Backup file creation failed"));
 936           g_free (backup_filename);
 937           goto err_out;
 938         }
 939
 940       bfd = g_open (backup_filename,
 941                     O_WRONLY | O_CREAT | O_EXCL | O_BINARY,
 942                     original_stat.st_mode & 0777);
 943
 944       if (bfd == -1)
 945         {
 946           g_set_error_literal (error,
 947                                G_IO_ERROR,
 948                                G_IO_ERROR_CANT_CREATE_BACKUP,
 949                                _("Backup file creation failed"));
 950           g_free (backup_filename);
 951           goto err_out;
 952         }
 953
 954       /* If needed, Try to set the group of the backup same as the
 955        * original file. If this fails, set the protection
 956        * bits for the group same as the protection bits for
 957        * others. */
 958 #if defined(HAVE_FCHOWN) && defined(HAVE_FCHMOD)
 959       if (fstat (bfd, &tmp_statbuf) != 0)
 960         {
 961           g_set_error_literal (error,
 962                                G_IO_ERROR,
 963                                G_IO_ERROR_CANT_CREATE_BACKUP,
 964                                _("Backup file creation failed"));
 965           g_unlink (backup_filename);
 966           g_close (bfd, NULL);
 967           g_free (backup_filename);
 968           goto err_out;
 969         }
 970
 971       if ((original_stat.st_gid != tmp_statbuf.st_gid)  &&
 972           fchown (bfd, (uid_t) -1, original_stat.st_gid) != 0)
 973         {
 974           if (fchmod (bfd,
 975                       (original_stat.st_mode & 0707) |
 976                       ((original_stat.st_mode & 07) << 3)) != 0)
 977             {
 978               g_set_error_literal (error,
 979                                    G_IO_ERROR,
 980                                    G_IO_ERROR_CANT_CREATE_BACKUP,
 981                                    _("Backup file creation failed"));
 982               g_unlink (backup_filename);
 983               g_close (bfd, NULL);
 984               g_free (backup_filename);
 985               goto err_out;
 986             }
 987         }
 988 #endif
 989
 990       if (!copy_file_data (fd, bfd, NULL))
 991         {
 992           g_set_error_literal (error,
 993                                G_IO_ERROR,
 994                                G_IO_ERROR_CANT_CREATE_BACKUP,
 995                                _("Backup file creation failed"));
 996           g_unlink (backup_filename);
 997           g_close (bfd, NULL);
 998           g_free (backup_filename);
 999
1000           goto err_out;
1001         }
1002
1003       g_close (bfd, NULL);
1004       g_free (backup_filename);
1005
1006       /* Seek back to the start of the file after the backup copy */
1007       if (lseek (fd, 0, SEEK_SET) == -1)
1008         {
1009           int errsv = errno;
1010
1011           g_set_error (error, G_IO_ERROR,
1012                        g_io_error_from_errno (errsv),
1013                        _("Error seeking in file: %s"),
1014                        g_strerror (errsv));
1015           goto err_out;
1016         }
1017     }
1018
1019   if (flags & G_FILE_CREATE_REPLACE_DESTINATION)
1020     {
1021       g_close (fd, NULL);
1022
1023       if (g_unlink (filename) != 0)
1024         {
1025           int errsv = errno;
1026
1027           g_set_error (error, G_IO_ERROR,
1028                        g_io_error_from_errno (errsv),
1029                        _("Error removing old file: %s"),
1030                        g_strerror (errsv));
1031           goto err_out2;
1032         }
1033
1034       if (readable)
1035         open_flags = O_RDWR | O_CREAT | O_BINARY;
1036       else
1037         open_flags = O_WRONLY | O_CREAT | O_BINARY;
1038       fd = g_open (filename, open_flags, mode);
1039       if (fd == -1)
1040         {
1041           int errsv = errno;
1042           char *display_name = g_filename_display_name (filename);
1043           g_set_error (error, G_IO_ERROR,
1044                        g_io_error_from_errno (errsv),
1045                        _("Error opening file “%s”: %s"),
1046                        display_name, g_strerror (errsv));
1047           g_free (display_name);
1048           goto err_out2;
1049         }
1050     }
1051   else
1052     {
1053       /* Truncate the file at the start */
1054 #ifdef G_OS_WIN32
1055       if (g_win32_ftruncate (fd, 0) == -1)
1056 #else
1057         if (ftruncate (fd, 0) == -1)
1058 #endif
1059           {
1060             int errsv = errno;
1061
1062             g_set_error (error, G_IO_ERROR,
1063                          g_io_error_from_errno (errsv),
1064                          _("Error truncating file: %s"),
1065                          g_strerror (errsv));
1066             goto err_out;
1067           }
1068     }
1069
1070   return fd;
1071
1072  err_out:
1073   g_close (fd, NULL);
1074  err_out2:
1075   return -1;
1076 }
1077
1078 GFileOutputStream *
1079 _g_local_file_output_stream_replace (const char        *filename,
1080                                      gboolean          readable,
1081                                      const char        *etag,
1082                                      gboolean           create_backup,
1083                                      GFileCreateFlags   flags,
1084                                      GFileInfo         *reference_info,
1085                                      GCancellable      *cancellable,
1086                                      GError           **error)
1087 {
1088   GLocalFileOutputStream *stream;
1089   int mode;
1090   int fd;
1091   char *temp_file;
1092   gboolean sync_on_close;
1093   int open_flags;
1094
1095   if (g_cancellable_set_error_if_cancelled (cancellable, error))
1096     return NULL;
1097
1098   temp_file = NULL;
1099
1100   mode = mode_from_flags_or_info (flags, reference_info);
1101   sync_on_close = FALSE;
1102
1103   /* If the file doesn't exist, create it */
1104   open_flags = O_CREAT | O_EXCL | O_BINARY;
1105   if (readable)
1106     open_flags |= O_RDWR;
1107   else
1108     open_flags |= O_WRONLY;
1109   fd = g_open (filename, open_flags, mode);
1110
1111   if (fd == -1 && errno == EEXIST)
1112     {
1113       /* The file already exists */
1114       fd = handle_overwrite_open (filename, readable, etag,
1115                                   create_backup, &temp_file,
1116                                   flags, reference_info,
1117                                   cancellable, error);
1118       if (fd == -1)
1119         return NULL;
1120
1121       /* If the final destination exists, we want to sync the newly written
1122        * file to ensure the data is on disk when we rename over the destination.
1123        * otherwise if we get a system crash we can lose both the new and the
1124        * old file on some filesystems. (I.E. those that don't guarantee the
1125        * data is written to the disk before the metadata.)
1126        */
1127       sync_on_close = TRUE;
1128     }
1129   else if (fd == -1)
1130     {
1131       set_error_from_open_errno (filename, error);
1132       return NULL;
1133     }
1134
1135
1136   stream = g_object_new (G_TYPE_LOCAL_FILE_OUTPUT_STREAM, NULL);
1137   stream->priv->fd = fd;
1138   stream->priv->sync_on_close = sync_on_close;
1139   stream->priv->tmp_filename = temp_file;
1140   if (create_backup)
1141     stream->priv->backup_filename = create_backup_filename (filename);
1142   stream->priv->original_filename =  g_strdup (filename);
1143
1144   return G_FILE_OUTPUT_STREAM (stream);
1145 }
1146
1147 gint
1148 _g_local_file_output_stream_get_fd (GLocalFileOutputStream *stream)
1149 {
1150   g_return_val_if_fail (G_IS_LOCAL_FILE_OUTPUT_STREAM (stream), -1);
1151   return stream->priv->fd;
1152 }
1153
1154 #ifdef G_OS_UNIX
1155 static int
1156 g_local_file_output_stream_get_fd (GFileDescriptorBased *fd_based)
1157 {
1158   GLocalFileOutputStream *stream = G_LOCAL_FILE_OUTPUT_STREAM (fd_based);
1159   return _g_local_file_output_stream_get_fd (stream);
1160 }
1161 #endif