lib/vfs/interface.c

   1 /*
   2    Virtual File System: interface functions
   3
   4    Copyright (C) 2011
   5    The Free Software Foundation, Inc.
   6
   7    Written by:
   8    Slava Zanko <slavazanko@gmail.com>, 2011
   9
  10    This file is part of the Midnight Commander.
  11
  12    The Midnight Commander is free software: you can redistribute it
  13    and/or modify it under the terms of the GNU General Public License as
  14    published by the Free Software Foundation, either version 3 of the License,
  15    or (at your option) any later version.
  16
  17    The Midnight Commander is distributed in the hope that it will be useful,
  18    but WITHOUT ANY WARRANTY; without even the implied warranty of
  19    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20    GNU General Public License for more details.
  21
  22    You should have received a copy of the GNU General Public License
  23    along with this program.  If not, see <http://www.gnu.org/licenses/>.
  24  */
  25
  26 /**
  27  * \file
  28  * \brief Source: Virtual File System: path handlers
  29  * \author Slava Zanko
  30  * \date 2011
  31  */
  32
  33
  34 #include <config.h>
  35
  36 #include <stdio.h>
  37 #include <stdlib.h>             /* For atol() */
  38 #include <stdarg.h>
  39 #include <string.h>
  40 #include <errno.h>
  41 #include <sys/types.h>
  42 #include <signal.h>
  43 #include <ctype.h>              /* is_digit() */
  44 #include <fcntl.h>
  45 #include <sys/stat.h>
  46 #include <unistd.h>
  47 #include <dirent.h>
  48 #include <pwd.h>
  49 #include <grp.h>
  50
  51 #include "lib/global.h"
  52
  53 #include "lib/widget.h"         /* message() */
  54 #include "lib/strutil.h"        /* str_crt_conv_from() */
  55 #include "lib/util.h"
  56
  57 #include "vfs.h"
  58 #include "utilvfs.h"
  59 #include "path.h"
  60 #include "gc.h"
  61
  62 extern GString *vfs_str_buffer;
  63 extern struct vfs_class *current_vfs;
  64
  65 /*** global variables ****************************************************************************/
  66
  67 struct dirent *mc_readdir_result = NULL;
  68
  69 /*** file scope macro definitions ****************************************************************/
  70
  71 /*** file scope type declarations ****************************************************************/
  72
  73 /*** file scope variables ************************************************************************/
  74
  75 /*** file scope functions ************************************************************************/
  76 /* --------------------------------------------------------------------------------------------- */
  77
  78 static vfs_path_t *
  79 mc_def_getlocalcopy (const vfs_path_t * filename_vpath)
  80 {
  81     vfs_path_t *tmp_vpath = NULL;
  82     int fdin = -1, fdout = -1;
  83     ssize_t i;
  84     char buffer[BUF_1K * 8];
  85     struct stat mystat;
  86
  87     fdin = mc_open (filename_vpath, O_RDONLY | O_LINEAR);
  88     if (fdin == -1)
  89         goto fail;
  90
  91     fdout = vfs_mkstemps (&tmp_vpath, "vfs", vfs_path_get_last_path_str (filename_vpath));
  92     if (fdout == -1)
  93         goto fail;
  94
  95     while ((i = mc_read (fdin, buffer, sizeof (buffer))) > 0)
  96     {
  97         if (write (fdout, buffer, i) != i)
  98             goto fail;
  99     }
 100     if (i == -1)
 101         goto fail;
 102     i = mc_close (fdin);
 103     fdin = -1;
 104     if (i == -1)
 105         goto fail;
 106     i = close (fdout);
 107     fdout = -1;
 108     if (i == -1)
 109     {
 110         fdout = -1;
 111         goto fail;
 112     }
 113
 114     if (mc_stat (filename_vpath, &mystat) != -1)
 115         mc_chmod (tmp_vpath, mystat.st_mode);
 116
 117     return tmp_vpath;
 118
 119   fail:
 120     vfs_path_free (tmp_vpath);
 121     if (fdout != -1)
 122         close (fdout);
 123     if (fdin != -1)
 124         mc_close (fdin);
 125     return NULL;
 126 }
 127
 128 /* --------------------------------------------------------------------------------------------- */
 129
 130 static int
 131 mc_def_ungetlocalcopy (const vfs_path_t * filename_vpath,
 132                        const vfs_path_t * local_vpath, gboolean has_changed)
 133 {
 134     int fdin = -1, fdout = -1;
 135     const char *local;
 136
 137     local = vfs_path_get_last_path_str (local_vpath);
 138
 139     if (has_changed)
 140     {
 141         char buffer[BUF_1K * 8];
 142         ssize_t i;
 143
 144         if (vfs_path_get_last_path_vfs (filename_vpath)->write == NULL)
 145             goto failed;
 146
 147         fdin = open (local, O_RDONLY);
 148         if (fdin == -1)
 149             goto failed;
 150         fdout = mc_open (filename_vpath, O_WRONLY | O_TRUNC);
 151         if (fdout == -1)
 152             goto failed;
 153         while ((i = read (fdin, buffer, sizeof (buffer))) > 0)
 154             if (mc_write (fdout, buffer, (size_t) i) != i)
 155                 goto failed;
 156         if (i == -1)
 157             goto failed;
 158
 159         if (close (fdin) == -1)
 160         {
 161             fdin = -1;
 162             goto failed;
 163         }
 164         fdin = -1;
 165         if (mc_close (fdout) == -1)
 166         {
 167             fdout = -1;
 168             goto failed;
 169         }
 170     }
 171     unlink (local);
 172     return 0;
 173
 174   failed:
 175     message (D_ERROR, _("Changes to file lost"), "%s", vfs_path_get_last_path_str (filename_vpath));
 176     if (fdout != -1)
 177         mc_close (fdout);
 178     if (fdin != -1)
 179         close (fdin);
 180     unlink (local);
 181     return -1;
 182 }
 183
 184 /* --------------------------------------------------------------------------------------------- */
 185 /*** public functions ****************************************************************************/
 186 /* --------------------------------------------------------------------------------------------- */
 187
 188 int
 189 mc_open (const vfs_path_t * vpath, int flags, ...)
 190 {
 191     int mode = 0, result = -1;
 192     const vfs_path_element_t *path_element;
 193
 194     if (vpath == NULL)
 195         return -1;
 196
 197     /* Get the mode flag */
 198     if (flags & O_CREAT)
 199     {
 200         va_list ap;
 201         va_start (ap, flags);
 202         mode = va_arg (ap, int);
 203         va_end (ap);
 204     }
 205
 206     path_element = vfs_path_get_by_index (vpath, -1);
 207     if (vfs_path_element_valid (path_element) && path_element->class->open != NULL)
 208     {
 209         void *info;
 210         /* open must be supported */
 211         info = path_element->class->open (vpath, flags, mode);
 212         if (info == NULL)
 213             errno = vfs_ferrno (path_element->class);
 214         else
 215             result = vfs_new_handle (path_element->class, info);
 216     }
 217     else
 218         errno = -EOPNOTSUPP;
 219
 220     return result;
 221 }
 222
 223 /* --------------------------------------------------------------------------------------------- */
 224
 225 /* *INDENT-OFF* */
 226
 227 #define MC_NAMEOP(name, inarg, callarg) \
 228 int mc_##name inarg \
 229 { \
 230     int result; \
 231     const vfs_path_element_t *path_element; \
 232 \
 233     if (vpath == NULL) \
 234         return -1; \
 235 \
 236     path_element = vfs_path_get_by_index (vpath, -1); \
 237     if (!vfs_path_element_valid (path_element)) \
 238     { \
 239         return -1; \
 240     } \
 241 \
 242     result = path_element->class->name != NULL ? path_element->class->name callarg : -1; \
 243     if (result == -1) \
 244         errno = path_element->class->name != NULL ? vfs_ferrno (path_element->class) : E_NOTSUPP; \
 245     return result; \
 246 }
 247
 248 MC_NAMEOP (chmod, (const vfs_path_t *vpath, mode_t mode), (vpath, mode))
 249 MC_NAMEOP (chown, (const vfs_path_t *vpath, uid_t owner, gid_t group), (vpath, owner, group))
 250 MC_NAMEOP (utime, (const vfs_path_t *vpath, struct utimbuf * times), (vpath, times))
 251 MC_NAMEOP (readlink, (const vfs_path_t *vpath, char *buf, size_t bufsiz), (vpath, buf, bufsiz))
 252 MC_NAMEOP (unlink, (const vfs_path_t *vpath), (vpath))
 253 MC_NAMEOP (mkdir, (const vfs_path_t *vpath, mode_t mode), (vpath, mode))
 254 MC_NAMEOP (rmdir, (const vfs_path_t *vpath), (vpath))
 255 MC_NAMEOP (mknod, (const vfs_path_t *vpath, mode_t mode, dev_t dev), (vpath, mode, dev))
 256
 257 /* *INDENT-ON* */
 258
 259 /* --------------------------------------------------------------------------------------------- */
 260
 261 int
 262 mc_symlink (const vfs_path_t * vpath1, const vfs_path_t * vpath2)
 263 {
 264     int result = -1;
 265
 266     if (vpath1 == NULL)
 267         return -1;
 268
 269     if (vpath1 != NULL)
 270     {
 271         const vfs_path_element_t *path_element;
 272
 273         path_element = vfs_path_get_by_index (vpath2, -1);
 274         if (vfs_path_element_valid (path_element))
 275         {
 276             result =
 277                 path_element->class->symlink != NULL ?
 278                 path_element->class->symlink (vpath1, vpath2) : -1;
 279
 280             if (result == -1)
 281                 errno =
 282                     path_element->class->symlink != NULL ?
 283                     vfs_ferrno (path_element->class) : E_NOTSUPP;
 284         }
 285     }
 286     return result;
 287 }
 288
 289 /* --------------------------------------------------------------------------------------------- */
 290
 291 /* *INDENT-OFF* */
 292
 293 #define MC_HANDLEOP(name, inarg, callarg) \
 294 ssize_t mc_##name inarg \
 295 { \
 296     struct vfs_class *vfs; \
 297     int result; \
 298     if (handle == -1) \
 299         return -1; \
 300     vfs = vfs_class_find_by_handle (handle); \
 301     if (vfs == NULL) \
 302         return -1; \
 303     result = vfs->name != NULL ? vfs->name callarg : -1; \
 304     if (result == -1) \
 305         errno = vfs->name != NULL ? vfs_ferrno (vfs) : E_NOTSUPP; \
 306     return result; \
 307 }
 308
 309 MC_HANDLEOP (read, (int handle, void *buffer, size_t count), (vfs_class_data_find_by_handle (handle), buffer, count))
 310 MC_HANDLEOP (write, (int handle, const void *buf, size_t nbyte), (vfs_class_data_find_by_handle (handle), buf, nbyte))
 311
 312 /* --------------------------------------------------------------------------------------------- */
 313
 314 #define MC_RENAMEOP(name) \
 315 int mc_##name (const vfs_path_t *vpath1, const vfs_path_t *vpath2) \
 316 { \
 317     int result; \
 318     const vfs_path_element_t *path_element1; \
 319     const vfs_path_element_t *path_element2; \
 320 \
 321     if (vpath1 == NULL || vpath2 == NULL) \
 322         return -1; \
 323 \
 324     path_element1 = vfs_path_get_by_index (vpath1, - 1); \
 325     path_element2 = vfs_path_get_by_index (vpath2, - 1); \
 326 \
 327     if (!vfs_path_element_valid (path_element1) || !vfs_path_element_valid (path_element2) || \
 328         path_element1->class != path_element2->class) \
 329     { \
 330         errno = EXDEV; \
 331         return -1; \
 332     }\
 333 \
 334     result = path_element1->class->name != NULL \
 335         ? path_element1->class->name (vpath1, vpath2) \
 336         : -1; \
 337     if (result == -1) \
 338         errno = path_element1->class->name != NULL ? vfs_ferrno (path_element1->class) : E_NOTSUPP; \
 339     return result; \
 340 }
 341
 342 MC_RENAMEOP (link)
 343 MC_RENAMEOP (rename)
 344
 345 /* *INDENT-ON* */
 346
 347 /* --------------------------------------------------------------------------------------------- */
 348
 349 int
 350 mc_ctl (int handle, int ctlop, void *arg)
 351 {
 352     struct vfs_class *vfs = vfs_class_find_by_handle (handle);
 353
 354     if (vfs == NULL)
 355         return 0;
 356
 357     return vfs->ctl ? (*vfs->ctl) (vfs_class_data_find_by_handle (handle), ctlop, arg) : 0;
 358 }
 359
 360 /* --------------------------------------------------------------------------------------------- */
 361
 362 int
 363 mc_setctl (const vfs_path_t * vpath, int ctlop, void *arg)
 364 {
 365     int result = -1;
 366     const vfs_path_element_t *path_element;
 367
 368     if (vpath == NULL)
 369         vfs_die ("You don't want to pass NULL to mc_setctl.");
 370
 371     path_element = vfs_path_get_by_index (vpath, -1);
 372     if (vfs_path_element_valid (path_element))
 373         result =
 374             path_element->class->setctl != NULL ? path_element->class->setctl (vpath,
 375                                                                                ctlop, arg) : 0;
 376
 377     return result;
 378 }
 379
 380 /* --------------------------------------------------------------------------------------------- */
 381
 382 int
 383 mc_close (int handle)
 384 {
 385     struct vfs_class *vfs;
 386     int result;
 387
 388     if (handle == -1 || !vfs_class_data_find_by_handle (handle))
 389         return -1;
 390
 391     vfs = vfs_class_find_by_handle (handle);
 392     if (vfs == NULL)
 393         return -1;
 394
 395     if (handle < 3)
 396         return close (handle);
 397
 398     if (!vfs->close)
 399         vfs_die ("VFS must support close.\n");
 400     result = (*vfs->close) (vfs_class_data_find_by_handle (handle));
 401     vfs_free_handle (handle);
 402     if (result == -1)
 403         errno = vfs_ferrno (vfs);
 404
 405     return result;
 406 }
 407
 408 /* --------------------------------------------------------------------------------------------- */
 409
 410 DIR *
 411 mc_opendir (const vfs_path_t * vpath)
 412 {
 413     int handle, *handlep;
 414     void *info;
 415     vfs_path_element_t *path_element;
 416
 417     if (vpath == NULL)
 418         return NULL;
 419
 420     path_element = (vfs_path_element_t *) vfs_path_get_by_index (vpath, -1);
 421
 422     if (!vfs_path_element_valid (path_element))
 423     {
 424         errno = E_NOTSUPP;
 425         return NULL;
 426     }
 427
 428     info = path_element->class->opendir ? (*path_element->class->opendir) (vpath) : NULL;
 429
 430     if (info == NULL)
 431     {
 432         errno = path_element->class->opendir ? vfs_ferrno (path_element->class) : E_NOTSUPP;
 433         return NULL;
 434     }
 435
 436     path_element->dir.info = info;
 437
 438     path_element->dir.converter = (path_element->encoding != NULL) ?
 439         str_crt_conv_from (path_element->encoding) : str_cnv_from_term;
 440     if (path_element->dir.converter == INVALID_CONV)
 441         path_element->dir.converter = str_cnv_from_term;
 442
 443     handle = vfs_new_handle (path_element->class, vfs_path_element_clone (path_element));
 444
 445     handlep = g_new (int, 1);
 446     *handlep = handle;
 447     return (DIR *) handlep;
 448 }
 449
 450 /* --------------------------------------------------------------------------------------------- */
 451
 452 struct dirent *
 453 mc_readdir (DIR * dirp)
 454 {
 455     int handle;
 456     struct vfs_class *vfs;
 457     struct dirent *entry = NULL;
 458     vfs_path_element_t *vfs_path_element;
 459     estr_t state;
 460
 461     if (!mc_readdir_result)
 462     {
 463         /* We can't just allocate struct dirent as (see man dirent.h)
 464          * struct dirent has VERY nonnaive semantics of allocating
 465          * d_name in it. Moreover, linux's glibc-2.9 allocates dirents _less_,
 466          * than 'sizeof (struct dirent)' making full bitwise (sizeof dirent) copy
 467          * heap corrupter. So, allocate longliving dirent with at least
 468          * (MAXNAMLEN + 1) for d_name in it.
 469          * Strictly saying resulting dirent is unusable as we don't adjust internal
 470          * structures, holding dirent size. But we don't use it in libc infrastructure.
 471          * TODO: to make simpler homemade dirent-alike structure.
 472          */
 473         mc_readdir_result = (struct dirent *) g_malloc (sizeof (struct dirent) + MAXNAMLEN + 1);
 474     }
 475
 476     if (!dirp)
 477     {
 478         errno = EFAULT;
 479         return NULL;
 480     }
 481     handle = *(int *) dirp;
 482
 483     vfs = vfs_class_find_by_handle (handle);
 484     if (vfs == NULL)
 485         return NULL;
 486
 487     vfs_path_element = vfs_class_data_find_by_handle (handle);
 488     if (vfs->readdir)
 489     {
 490         entry = (*vfs->readdir) (vfs_path_element->dir.info);
 491         if (entry == NULL)
 492             return NULL;
 493         g_string_set_size (vfs_str_buffer, 0);
 494         state =
 495             str_vfs_convert_from (vfs_path_element->dir.converter, entry->d_name, vfs_str_buffer);
 496         mc_readdir_result->d_ino = entry->d_ino;
 497         g_strlcpy (mc_readdir_result->d_name, vfs_str_buffer->str, MAXNAMLEN + 1);
 498     }
 499     if (entry == NULL)
 500         errno = vfs->readdir ? vfs_ferrno (vfs) : E_NOTSUPP;
 501     return (entry != NULL) ? mc_readdir_result : NULL;
 502 }
 503
 504 /* --------------------------------------------------------------------------------------------- */
 505
 506 int
 507 mc_closedir (DIR * dirp)
 508 {
 509     int handle = *(int *) dirp;
 510     struct vfs_class *vfs;
 511     int result = -1;
 512
 513     vfs = vfs_class_find_by_handle (handle);
 514     if (vfs != NULL)
 515     {
 516         vfs_path_element_t *vfs_path_element;
 517         vfs_path_element = vfs_class_data_find_by_handle (handle);
 518         if (vfs_path_element->dir.converter != str_cnv_from_term)
 519         {
 520             str_close_conv (vfs_path_element->dir.converter);
 521             vfs_path_element->dir.converter = INVALID_CONV;
 522         }
 523
 524         result = vfs->closedir ? (*vfs->closedir) (vfs_path_element->dir.info) : -1;
 525         vfs_free_handle (handle);
 526         vfs_path_element_free (vfs_path_element);
 527     }
 528     g_free (dirp);
 529     return result;
 530 }
 531
 532 /* --------------------------------------------------------------------------------------------- */
 533
 534 int
 535 mc_stat (const vfs_path_t * vpath, struct stat *buf)
 536 {
 537     int result = -1;
 538     const vfs_path_element_t *path_element;
 539
 540     if (vpath == NULL)
 541         return -1;
 542
 543     path_element = vfs_path_get_by_index (vpath, -1);
 544
 545     if (vfs_path_element_valid (path_element))
 546     {
 547         result = path_element->class->stat ? (*path_element->class->stat) (vpath, buf) : -1;
 548         if (result == -1)
 549             errno = path_element->class->name ? vfs_ferrno (path_element->class) : E_NOTSUPP;
 550     }
 551
 552     return result;
 553 }
 554
 555 /* --------------------------------------------------------------------------------------------- */
 556
 557 int
 558 mc_lstat (const vfs_path_t * vpath, struct stat *buf)
 559 {
 560     int result = -1;
 561     const vfs_path_element_t *path_element;
 562
 563     if (vpath == NULL)
 564         return -1;
 565
 566     path_element = vfs_path_get_by_index (vpath, -1);
 567
 568     if (vfs_path_element_valid (path_element))
 569     {
 570         result = path_element->class->lstat ? (*path_element->class->lstat) (vpath, buf) : -1;
 571         if (result == -1)
 572             errno = path_element->class->name ? vfs_ferrno (path_element->class) : E_NOTSUPP;
 573     }
 574
 575     return result;
 576 }
 577
 578 /* --------------------------------------------------------------------------------------------- */
 579
 580 int
 581 mc_fstat (int handle, struct stat *buf)
 582 {
 583     struct vfs_class *vfs;
 584     int result;
 585
 586     if (handle == -1)
 587         return -1;
 588
 589     vfs = vfs_class_find_by_handle (handle);
 590     if (vfs == NULL)
 591         return -1;
 592
 593     result = vfs->fstat ? (*vfs->fstat) (vfs_class_data_find_by_handle (handle), buf) : -1;
 594     if (result == -1)
 595         errno = vfs->name ? vfs_ferrno (vfs) : E_NOTSUPP;
 596     return result;
 597 }
 598
 599 /* --------------------------------------------------------------------------------------------- */
 600
 601 vfs_path_t *
 602 mc_getlocalcopy (const vfs_path_t * pathname_vpath)
 603 {
 604     vfs_path_t *result = NULL;
 605     const vfs_path_element_t *path_element;
 606
 607     if (pathname_vpath == NULL)
 608         return NULL;
 609
 610     path_element = vfs_path_get_by_index (pathname_vpath, -1);
 611
 612     if (vfs_path_element_valid (path_element))
 613     {
 614         result = path_element->class->getlocalcopy != NULL ?
 615             path_element->class->getlocalcopy (pathname_vpath) :
 616             mc_def_getlocalcopy (pathname_vpath);
 617         if (result == NULL)
 618             errno = vfs_ferrno (path_element->class);
 619     }
 620     return result;
 621 }
 622
 623 /* --------------------------------------------------------------------------------------------- */
 624
 625 int
 626 mc_ungetlocalcopy (const vfs_path_t * pathname_vpath, const vfs_path_t * local_vpath,
 627                    gboolean has_changed)
 628 {
 629     int return_value = -1;
 630     const vfs_path_element_t *path_element;
 631
 632     if (pathname_vpath == NULL)
 633         return -1;
 634
 635     path_element = vfs_path_get_by_index (pathname_vpath, -1);
 636
 637     if (vfs_path_element_valid (path_element))
 638         return_value = path_element->class->ungetlocalcopy != NULL ?
 639             path_element->class->ungetlocalcopy (pathname_vpath, local_vpath, has_changed) :
 640             mc_def_ungetlocalcopy (pathname_vpath, local_vpath, has_changed);
 641
 642     return return_value;
 643 }
 644
 645 /* --------------------------------------------------------------------------------------------- */
 646 /**
 647  * VFS chdir.
 648  *
 649  * @param vpath VFS-path
 650  *
 651  * @return 0 on success, -1 on failure.
 652  */
 653
 654 int
 655 mc_chdir (const vfs_path_t * vpath)
 656 {
 657     struct vfs_class *old_vfs;
 658     vfsid old_vfsid;
 659     int result;
 660     const vfs_path_element_t *path_element;
 661     vfs_path_t *abcolute_vpath;
 662
 663     if (vpath == NULL)
 664         return -1;
 665
 666     path_element = vfs_path_get_by_index (vpath, -1);
 667
 668     if (!vfs_path_element_valid (path_element) || path_element->class->chdir == NULL)
 669     {
 670         return -1;
 671     }
 672
 673     abcolute_vpath = vfs_path_to_absolute (vpath);
 674
 675     result = (*path_element->class->chdir) (abcolute_vpath);
 676
 677     if (result == -1)
 678     {
 679         vfs_path_free (abcolute_vpath);
 680         errno = vfs_ferrno (path_element->class);
 681         return -1;
 682     }
 683
 684     old_vfsid = vfs_getid (vfs_get_raw_current_dir ());
 685     old_vfs = current_vfs;
 686
 687     /* Actually change directory */
 688     vfs_set_raw_current_dir (abcolute_vpath);
 689
 690     current_vfs = path_element->class;
 691
 692     /* This function uses the new current_dir implicitly */
 693     vfs_stamp_create (old_vfs, old_vfsid);
 694
 695     /* Sometimes we assume no trailing slash on cwd */
 696     path_element = vfs_path_get_by_index (vfs_get_raw_current_dir (), -1);
 697     if (vfs_path_element_valid (path_element) && (*path_element->path != '\0'))
 698     {
 699         char *p;
 700         p = strchr (path_element->path, 0) - 1;
 701         if (*p == PATH_SEP && p > path_element->path)
 702             *p = 0;
 703     }
 704     return 0;
 705 }
 706
 707 /* --------------------------------------------------------------------------------------------- */
 708
 709 off_t
 710 mc_lseek (int fd, off_t offset, int whence)
 711 {
 712     struct vfs_class *vfs;
 713     off_t result;
 714
 715     if (fd == -1)
 716         return -1;
 717
 718     vfs = vfs_class_find_by_handle (fd);
 719     if (vfs == NULL)
 720         return -1;
 721
 722     result = vfs->lseek ? (*vfs->lseek) (vfs_class_data_find_by_handle (fd), offset, whence) : -1;
 723     if (result == -1)
 724         errno = vfs->lseek ? vfs_ferrno (vfs) : E_NOTSUPP;
 725     return result;
 726 }
 727
 728 /* --------------------------------------------------------------------------------------------- */
 729 /* Following code heavily borrows from libiberty, mkstemps.c */
 730 /*
 731  * Arguments:
 732  * pname (output) - pointer to the name of the temp file (needs g_free).
 733  *                  NULL if the function fails.
 734  * prefix - part of the filename before the random part.
 735  *          Prepend $TMPDIR or /tmp if there are no path separators.
 736  * suffix - if not NULL, part of the filename after the random part.
 737  *
 738  * Result:
 739  * handle of the open file or -1 if couldn't open any.
 740  */
 741
 742 int
 743 mc_mkstemps (vfs_path_t ** pname_vpath, const char *prefix, const char *suffix)
 744 {
 745     static const char letters[] = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
 746     static unsigned long value;
 747     struct timeval tv;
 748     char *tmpbase;
 749     char *tmpname;
 750     char *XXXXXX;
 751     char *ret_path;
 752     int count;
 753
 754     if (strchr (prefix, PATH_SEP) == NULL)
 755     {
 756         /* Add prefix first to find the position of XXXXXX */
 757         tmpbase = g_build_filename (mc_tmpdir (), prefix, NULL);
 758     }
 759     else
 760     {
 761         tmpbase = g_strdup (prefix);
 762     }
 763
 764     tmpname = g_strconcat (tmpbase, "XXXXXX", suffix, (char *) NULL);
 765     ret_path = tmpname;
 766     XXXXXX = &tmpname[strlen (tmpbase)];
 767     g_free (tmpbase);
 768
 769     /* Get some more or less random data.  */
 770     gettimeofday (&tv, NULL);
 771     value += (tv.tv_usec << 16) ^ tv.tv_sec ^ getpid ();
 772
 773     for (count = 0; count < TMP_MAX; ++count)
 774     {
 775         unsigned long v = value;
 776         int fd;
 777
 778         /* Fill in the random bits.  */
 779         XXXXXX[0] = letters[v % 62];
 780         v /= 62;
 781         XXXXXX[1] = letters[v % 62];
 782         v /= 62;
 783         XXXXXX[2] = letters[v % 62];
 784         v /= 62;
 785         XXXXXX[3] = letters[v % 62];
 786         v /= 62;
 787         XXXXXX[4] = letters[v % 62];
 788         v /= 62;
 789         XXXXXX[5] = letters[v % 62];
 790
 791         fd = open (tmpname, O_RDWR | O_CREAT | O_TRUNC | O_EXCL, S_IRUSR | S_IWUSR);
 792         if (fd >= 0)
 793         {
 794             /* Successfully created.  */
 795             *pname_vpath = vfs_path_from_str (ret_path);
 796             g_free (ret_path);
 797             return fd;
 798         }
 799
 800         /* This is a random value.  It is only necessary that the next
 801            TMP_MAX values generated by adding 7777 to VALUE are different
 802            with (module 2^32).  */
 803         value += 7777;
 804     }
 805
 806     /* Unsuccessful. Free the filename. */
 807     g_free (ret_path);
 808     *pname_vpath = NULL;
 809
 810     return -1;
 811 }
 812
 813 /* --------------------------------------------------------------------------------------------- */
 814 /**
 815  * Return the directory where mc should keep its temporary files.
 816  * This directory is (in Bourne shell terms) "${TMPDIR=/tmp}/mc-$USER"
 817  * When called the first time, the directory is created if needed.
 818  * The first call should be done early, since we are using fprintf()
 819  * and not message() to report possible problems.
 820  */
 821
 822 const char *
 823 mc_tmpdir (void)
 824 {
 825     static char buffer[64];
 826     static const char *tmpdir;
 827     const char *sys_tmp;
 828     struct passwd *pwd;
 829     struct stat st;
 830     const char *error = NULL;
 831
 832     /* Check if already correctly initialized */
 833     if (tmpdir && lstat (tmpdir, &st) == 0 && S_ISDIR (st.st_mode) &&
 834         st.st_uid == getuid () && (st.st_mode & 0777) == 0700)
 835         return tmpdir;
 836
 837     sys_tmp = getenv ("TMPDIR");
 838     if (!sys_tmp || sys_tmp[0] != '/')
 839     {
 840         sys_tmp = TMPDIR_DEFAULT;
 841     }
 842
 843     pwd = getpwuid (getuid ());
 844
 845     if (pwd)
 846         g_snprintf (buffer, sizeof (buffer), "%s/mc-%s", sys_tmp, pwd->pw_name);
 847     else
 848         g_snprintf (buffer, sizeof (buffer), "%s/mc-%lu", sys_tmp, (unsigned long) getuid ());
 849
 850     canonicalize_pathname (buffer);
 851
 852     if (lstat (buffer, &st) == 0)
 853     {
 854         /* Sanity check for existing directory */
 855         if (!S_ISDIR (st.st_mode))
 856             error = _("%s is not a directory\n");
 857         else if (st.st_uid != getuid ())
 858             error = _("Directory %s is not owned by you\n");
 859         else if (((st.st_mode & 0777) != 0700) && (chmod (buffer, 0700) != 0))
 860             error = _("Cannot set correct permissions for directory %s\n");
 861     }
 862     else
 863     {
 864         /* Need to create directory */
 865         if (mkdir (buffer, S_IRWXU) != 0)
 866         {
 867             fprintf (stderr,
 868                      _("Cannot create temporary directory %s: %s\n"),
 869                      buffer, unix_error_string (errno));
 870             error = "";
 871         }
 872     }
 873
 874     if (error != NULL)
 875     {
 876         int test_fd;
 877         char *fallback_prefix;
 878         gboolean fallback_ok = FALSE;
 879         vfs_path_t *test_vpath;
 880
 881         if (*error)
 882             fprintf (stderr, error, buffer);
 883
 884         /* Test if sys_tmp is suitable for temporary files */
 885         fallback_prefix = g_strdup_printf ("%s/mctest", sys_tmp);
 886         test_fd = mc_mkstemps (&test_vpath, fallback_prefix, NULL);
 887         g_free (fallback_prefix);
 888         if (test_fd != -1)
 889         {
 890             char *test_fn;
 891
 892             test_fn = vfs_path_to_str (test_vpath);
 893             close (test_fd);
 894             test_fd = open (test_fn, O_RDONLY);
 895             g_free (test_fn);
 896             if (test_fd != -1)
 897             {
 898                 close (test_fd);
 899                 unlink (test_fn);
 900                 fallback_ok = TRUE;
 901             }
 902         }
 903
 904         if (fallback_ok)
 905         {
 906             fprintf (stderr, _("Temporary files will be created in %s\n"), sys_tmp);
 907             g_snprintf (buffer, sizeof (buffer), "%s", sys_tmp);
 908             error = NULL;
 909         }
 910         else
 911         {
 912             fprintf (stderr, _("Temporary files will not be created\n"));
 913             g_snprintf (buffer, sizeof (buffer), "%s", "/dev/null/");
 914         }
 915
 916         vfs_path_free (test_vpath);
 917         fprintf (stderr, "%s\n", _("Press any key to continue..."));
 918         getc (stdin);
 919     }
 920
 921     tmpdir = buffer;
 922
 923     if (!error)
 924         g_setenv ("MC_TMPDIR", tmpdir, TRUE);
 925
 926     return tmpdir;
 927 }
 928
 929 /* --------------------------------------------------------------------------------------------- */