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
  49 #include "lib/global.h"
  50
  51 #include "lib/widget.h"         /* message() */
  52 #include "lib/strutil.h"        /* str_crt_conv_from() */
  53
  54 #include "vfs.h"
  55 #include "utilvfs.h"
  56 #include "path.h"
  57 #include "gc.h"
  58
  59 extern GString *vfs_str_buffer;
  60 extern struct vfs_class *current_vfs;
  61
  62 /*** global variables ****************************************************************************/
  63
  64 struct dirent *mc_readdir_result = NULL;
  65
  66 /*** file scope macro definitions ****************************************************************/
  67
  68 /*** file scope type declarations ****************************************************************/
  69
  70 /*** file scope variables ************************************************************************/
  71
  72 /*** file scope functions ************************************************************************/
  73 /* --------------------------------------------------------------------------------------------- */
  74
  75 static char *
  76 mc_def_getlocalcopy (const char *filename)
  77 {
  78     char *tmp;
  79     int fdin, fdout;
  80     ssize_t i;
  81     char buffer[8192];
  82     struct stat mystat;
  83     vfs_path_t *vpath = vfs_path_from_str (filename);
  84
  85     fdin = mc_open (filename, O_RDONLY | O_LINEAR);
  86     if (fdin == -1)
  87         return NULL;
  88
  89     fdout = vfs_mkstemps (&tmp, "vfs", filename);
  90
  91     if (fdout == -1)
  92         goto fail;
  93     while ((i = mc_read (fdin, buffer, sizeof (buffer))) > 0)
  94     {
  95         if (write (fdout, buffer, i) != i)
  96             goto fail;
  97     }
  98     if (i == -1)
  99         goto fail;
 100     i = mc_close (fdin);
 101     fdin = -1;
 102     if (i == -1)
 103         goto fail;
 104     if (close (fdout) == -1)
 105     {
 106         fdout = -1;
 107         goto fail;
 108     }
 109
 110     if (mc_stat (vpath, &mystat) != -1)
 111         chmod (tmp, mystat.st_mode);
 112     vfs_path_free (vpath);
 113
 114     return tmp;
 115
 116   fail:
 117     vfs_path_free (vpath);
 118     if (fdout != -1)
 119         close (fdout);
 120     if (fdin != -1)
 121         mc_close (fdin);
 122     g_free (tmp);
 123     return NULL;
 124 }
 125
 126 /* --------------------------------------------------------------------------------------------- */
 127
 128 static int
 129 mc_def_ungetlocalcopy (struct vfs_class *vfs, const char *filename,
 130                        const char *local, int has_changed)
 131 {
 132     int fdin = -1, fdout = -1;
 133     if (has_changed)
 134     {
 135         char buffer[8192];
 136         ssize_t i;
 137
 138         if (!vfs->write)
 139             goto failed;
 140
 141         fdin = open (local, O_RDONLY);
 142         if (fdin == -1)
 143             goto failed;
 144         fdout = mc_open (filename, O_WRONLY | O_TRUNC);
 145         if (fdout == -1)
 146             goto failed;
 147         while ((i = read (fdin, buffer, sizeof (buffer))) > 0)
 148             if (mc_write (fdout, buffer, (size_t) i) != i)
 149                 goto failed;
 150         if (i == -1)
 151             goto failed;
 152
 153         if (close (fdin) == -1)
 154         {
 155             fdin = -1;
 156             goto failed;
 157         }
 158         fdin = -1;
 159         if (mc_close (fdout) == -1)
 160         {
 161             fdout = -1;
 162             goto failed;
 163         }
 164     }
 165     unlink (local);
 166     return 0;
 167
 168   failed:
 169     message (D_ERROR, _("Changes to file lost"), "%s", filename);
 170     if (fdout != -1)
 171         mc_close (fdout);
 172     if (fdin != -1)
 173         close (fdin);
 174     unlink (local);
 175     return -1;
 176 }
 177
 178 /* --------------------------------------------------------------------------------------------- */
 179 /*** public functions ****************************************************************************/
 180 /* --------------------------------------------------------------------------------------------- */
 181
 182 int
 183 mc_open (const char *filename, int flags, ...)
 184 {
 185     int mode = 0, result = -1;
 186     vfs_path_t *vpath;
 187     vfs_path_element_t *path_element;
 188
 189     vpath = vfs_path_from_str (filename);
 190     if (vpath == NULL)
 191         return -1;
 192
 193     /* Get the mode flag */
 194     if (flags & O_CREAT)
 195     {
 196         va_list ap;
 197         va_start (ap, flags);
 198         mode = va_arg (ap, int);
 199         va_end (ap);
 200     }
 201
 202     path_element = vfs_path_get_by_index (vpath, -1);
 203     if (vfs_path_element_valid (path_element) && path_element->class->open != NULL)
 204     {
 205         void *info;
 206         /* open must be supported */
 207         info = path_element->class->open (vpath, flags, mode);
 208         if (info == NULL)
 209             errno = vfs_ferrno (path_element->class);
 210         else
 211             result = vfs_new_handle (path_element->class, info);
 212     }
 213     else
 214         errno = -EOPNOTSUPP;
 215
 216     vfs_path_free (vpath);
 217     return result;
 218 }
 219
 220 /* --------------------------------------------------------------------------------------------- */
 221
 222 /* *INDENT-OFF* */
 223
 224 #define MC_NAMEOP(name, inarg, callarg) \
 225 int mc_##name inarg \
 226 { \
 227     int result; \
 228     vfs_path_element_t *path_element; \
 229 \
 230     if (vpath == NULL) \
 231         return -1; \
 232 \
 233     path_element = vfs_path_get_by_index (vpath, -1); \
 234     if (!vfs_path_element_valid (path_element)) \
 235     { \
 236         return -1; \
 237     } \
 238 \
 239     result = path_element->class->name != NULL ? path_element->class->name callarg : -1; \
 240     if (result == -1) \
 241         errno = path_element->class->name != NULL ? vfs_ferrno (path_element->class) : E_NOTSUPP; \
 242     return result; \
 243 }
 244
 245 MC_NAMEOP (chmod, (const vfs_path_t *vpath, mode_t mode), (vpath, mode))
 246 MC_NAMEOP (chown, (const vfs_path_t *vpath, uid_t owner, gid_t group), (vpath, owner, group))
 247 MC_NAMEOP (utime, (const vfs_path_t *vpath, struct utimbuf * times), (vpath, times))
 248 MC_NAMEOP (readlink, (const vfs_path_t *vpath, char *buf, size_t bufsiz), (vpath, buf, bufsiz))
 249 MC_NAMEOP (unlink, (const vfs_path_t *vpath), (vpath))
 250 MC_NAMEOP (mkdir, (const vfs_path_t *vpath, mode_t mode), (vpath, mode))
 251 MC_NAMEOP (rmdir, (const vfs_path_t *vpath), (vpath))
 252 MC_NAMEOP (mknod, (const vfs_path_t *vpath, mode_t mode, dev_t dev), (vpath, mode, dev))
 253
 254 /* *INDENT-ON* */
 255
 256 /* --------------------------------------------------------------------------------------------- */
 257
 258 int
 259 mc_symlink (const vfs_path_t *vpath1, const vfs_path_t *vpath2)
 260 {
 261     int result = -1;
 262
 263     if (vpath1 == NULL)
 264         return -1;
 265
 266     if (vpath1 != NULL)
 267     {
 268         vfs_path_element_t *path_element;
 269
 270         path_element = vfs_path_get_by_index (vpath2, -1);
 271         if (vfs_path_element_valid (path_element))
 272         {
 273             result =
 274                 path_element->class->symlink != NULL ?
 275                 path_element->class->symlink (vpath1, vpath2) : -1;
 276
 277             if (result == -1)
 278                 errno =
 279                     path_element->class->symlink != NULL ?
 280                     vfs_ferrno (path_element->class) : E_NOTSUPP;
 281         }
 282     }
 283     return result;
 284 }
 285
 286 /* --------------------------------------------------------------------------------------------- */
 287
 288 /* *INDENT-OFF* */
 289
 290 #define MC_HANDLEOP(name, inarg, callarg) \
 291 ssize_t mc_##name inarg \
 292 { \
 293     struct vfs_class *vfs; \
 294     int result; \
 295     if (handle == -1) \
 296         return -1; \
 297     vfs = vfs_class_find_by_handle (handle); \
 298     if (vfs == NULL) \
 299         return -1; \
 300     result = vfs->name != NULL ? vfs->name callarg : -1; \
 301     if (result == -1) \
 302         errno = vfs->name != NULL ? vfs_ferrno (vfs) : E_NOTSUPP; \
 303     return result; \
 304 }
 305
 306 MC_HANDLEOP (read, (int handle, void *buffer, size_t count), (vfs_class_data_find_by_handle (handle), buffer, count))
 307 MC_HANDLEOP (write, (int handle, const void *buf, size_t nbyte), (vfs_class_data_find_by_handle (handle), buf, nbyte))
 308
 309 /* --------------------------------------------------------------------------------------------- */
 310
 311 #define MC_RENAMEOP(name) \
 312 int mc_##name (const vfs_path_t *vpath1, const vfs_path_t *vpath2) \
 313 { \
 314     int result; \
 315     vfs_path_element_t *path_element1, *path_element2; \
 316 \
 317     if (vpath1 == NULL || vpath2 == NULL) \
 318         return -1; \
 319 \
 320     path_element1 = vfs_path_get_by_index (vpath1, - 1); \
 321     path_element2 = vfs_path_get_by_index (vpath2, - 1); \
 322 \
 323     if (!vfs_path_element_valid (path_element1) || !vfs_path_element_valid (path_element2) || \
 324         path_element1->class != path_element2->class) \
 325     { \
 326         errno = EXDEV; \
 327         return -1; \
 328     }\
 329 \
 330     result = path_element1->class->name != NULL \
 331         ? path_element1->class->name (vpath1, vpath2) \
 332         : -1; \
 333     if (result == -1) \
 334         errno = path_element1->class->name != NULL ? vfs_ferrno (path_element1->class) : E_NOTSUPP; \
 335     return result; \
 336 }
 337
 338 MC_RENAMEOP (link)
 339 MC_RENAMEOP (rename)
 340
 341 /* *INDENT-ON* */
 342
 343 /* --------------------------------------------------------------------------------------------- */
 344
 345 int
 346 mc_ctl (int handle, int ctlop, void *arg)
 347 {
 348     struct vfs_class *vfs = vfs_class_find_by_handle (handle);
 349
 350     if (vfs == NULL)
 351         return 0;
 352
 353     return vfs->ctl ? (*vfs->ctl) (vfs_class_data_find_by_handle (handle), ctlop, arg) : 0;
 354 }
 355
 356 /* --------------------------------------------------------------------------------------------- */
 357
 358 int
 359 mc_setctl (const vfs_path_t * vpath, int ctlop, void *arg)
 360 {
 361     int result = -1;
 362
 363     vfs_path_element_t *path_element;
 364
 365     if (vpath == NULL)
 366         vfs_die ("You don't want to pass NULL to mc_setctl.");
 367
 368     path_element = vfs_path_get_by_index (vpath, -1);
 369     if (vfs_path_element_valid (path_element))
 370         result =
 371             path_element->class->setctl != NULL ? path_element->class->setctl (vpath,
 372                                                                                ctlop, arg) : 0;
 373
 374     return result;
 375 }
 376
 377 /* --------------------------------------------------------------------------------------------- */
 378
 379 int
 380 mc_close (int handle)
 381 {
 382     struct vfs_class *vfs;
 383     int result;
 384
 385     if (handle == -1 || !vfs_class_data_find_by_handle (handle))
 386         return -1;
 387
 388     vfs = vfs_class_find_by_handle (handle);
 389     if (vfs == NULL)
 390         return -1;
 391
 392     if (handle < 3)
 393         return close (handle);
 394
 395     if (!vfs->close)
 396         vfs_die ("VFS must support close.\n");
 397     result = (*vfs->close) (vfs_class_data_find_by_handle (handle));
 398     vfs_free_handle (handle);
 399     if (result == -1)
 400         errno = vfs_ferrno (vfs);
 401
 402     return result;
 403 }
 404
 405 /* --------------------------------------------------------------------------------------------- */
 406
 407 DIR *
 408 mc_opendir (const vfs_path_t * vpath)
 409 {
 410     int handle, *handlep;
 411     void *info;
 412     vfs_path_element_t *path_element;
 413
 414     if (vpath == NULL)
 415         return NULL;
 416
 417     path_element = vfs_path_get_by_index (vpath, -1);
 418
 419     if (!vfs_path_element_valid (path_element))
 420     {
 421         errno = E_NOTSUPP;
 422         return NULL;
 423     }
 424
 425     info = path_element->class->opendir ? (*path_element->class->opendir) (vpath) : NULL;
 426
 427     if (info == NULL)
 428     {
 429         errno = path_element->class->opendir ? vfs_ferrno (path_element->class) : E_NOTSUPP;
 430         return NULL;
 431     }
 432
 433     path_element->dir.info = info;
 434
 435     path_element->dir.converter =
 436         (path_element->encoding !=
 437          NULL) ? str_crt_conv_from (path_element->encoding) : str_cnv_from_term;
 438     if (path_element->dir.converter == INVALID_CONV)
 439         path_element->dir.converter = str_cnv_from_term;
 440
 441     handle = vfs_new_handle (path_element->class, vfs_path_element_clone (path_element));
 442
 443     handlep = g_new (int, 1);
 444     *handlep = handle;
 445     return (DIR *) handlep;
 446 }
 447
 448 /* --------------------------------------------------------------------------------------------- */
 449
 450 struct dirent *
 451 mc_readdir (DIR * dirp)
 452 {
 453     int handle;
 454     struct vfs_class *vfs;
 455     struct dirent *entry = NULL;
 456     vfs_path_element_t *vfs_path_element;
 457     estr_t state;
 458
 459     if (!mc_readdir_result)
 460     {
 461         /* We can't just allocate struct dirent as (see man dirent.h)
 462          * struct dirent has VERY nonnaive semantics of allocating
 463          * d_name in it. Moreover, linux's glibc-2.9 allocates dirents _less_,
 464          * than 'sizeof (struct dirent)' making full bitwise (sizeof dirent) copy
 465          * heap corrupter. So, allocate longliving dirent with at least
 466          * (MAXNAMLEN + 1) for d_name in it.
 467          * Strictly saying resulting dirent is unusable as we don't adjust internal
 468          * structures, holding dirent size. But we don't use it in libc infrastructure.
 469          * TODO: to make simpler homemade dirent-alike structure.
 470          */
 471         mc_readdir_result = (struct dirent *) g_malloc (sizeof (struct dirent) + MAXNAMLEN + 1);
 472     }
 473
 474     if (!dirp)
 475     {
 476         errno = EFAULT;
 477         return NULL;
 478     }
 479     handle = *(int *) dirp;
 480
 481     vfs = vfs_class_find_by_handle (handle);
 482     if (vfs == NULL)
 483         return NULL;
 484
 485     vfs_path_element = vfs_class_data_find_by_handle (handle);
 486     if (vfs->readdir)
 487     {
 488         entry = (*vfs->readdir) (vfs_path_element->dir.info);
 489         if (entry == NULL)
 490             return NULL;
 491         g_string_set_size (vfs_str_buffer, 0);
 492         state =
 493             str_vfs_convert_from (vfs_path_element->dir.converter, entry->d_name, vfs_str_buffer);
 494         mc_readdir_result->d_ino = entry->d_ino;
 495         g_strlcpy (mc_readdir_result->d_name, vfs_str_buffer->str, MAXNAMLEN + 1);
 496     }
 497     if (entry == NULL)
 498         errno = vfs->readdir ? vfs_ferrno (vfs) : E_NOTSUPP;
 499     return (entry != NULL) ? mc_readdir_result : NULL;
 500 }
 501
 502 /* --------------------------------------------------------------------------------------------- */
 503
 504 int
 505 mc_closedir (DIR * dirp)
 506 {
 507     int handle = *(int *) dirp;
 508     struct vfs_class *vfs;
 509     int result = -1;
 510
 511     vfs = vfs_class_find_by_handle (handle);
 512     if (vfs != NULL)
 513     {
 514         vfs_path_element_t *vfs_path_element;
 515         vfs_path_element = vfs_class_data_find_by_handle (handle);
 516         if (vfs_path_element->dir.converter != str_cnv_from_term)
 517         {
 518             str_close_conv (vfs_path_element->dir.converter);
 519             vfs_path_element->dir.converter = INVALID_CONV;
 520         }
 521
 522         result = vfs->closedir ? (*vfs->closedir) (vfs_path_element->dir.info) : -1;
 523         vfs_free_handle (handle);
 524         vfs_path_element_free (vfs_path_element);
 525     }
 526     g_free (dirp);
 527     return result;
 528 }
 529
 530 /* --------------------------------------------------------------------------------------------- */
 531
 532 int
 533 mc_stat (const vfs_path_t * vpath, struct stat *buf)
 534 {
 535     int result = -1;
 536     vfs_path_element_t *path_element;
 537
 538     if (vpath == NULL)
 539         return -1;
 540
 541     path_element = vfs_path_get_by_index (vpath, -1);
 542
 543     if (vfs_path_element_valid (path_element))
 544     {
 545         result = path_element->class->stat ? (*path_element->class->stat) (vpath, buf) : -1;
 546         if (result == -1)
 547             errno = path_element->class->name ? vfs_ferrno (path_element->class) : E_NOTSUPP;
 548     }
 549
 550     return result;
 551 }
 552
 553 /* --------------------------------------------------------------------------------------------- */
 554
 555 int
 556 mc_lstat (const vfs_path_t * vpath, struct stat *buf)
 557 {
 558     int result = -1;
 559     vfs_path_element_t *path_element;
 560
 561     if (vpath == NULL)
 562         return -1;
 563
 564     path_element = vfs_path_get_by_index (vpath, -1);
 565
 566     if (vfs_path_element_valid (path_element))
 567     {
 568         result = path_element->class->lstat ? (*path_element->class->lstat) (vpath, buf) : -1;
 569         if (result == -1)
 570             errno = path_element->class->name ? vfs_ferrno (path_element->class) : E_NOTSUPP;
 571     }
 572
 573     return result;
 574 }
 575
 576 /* --------------------------------------------------------------------------------------------- */
 577
 578 int
 579 mc_fstat (int handle, struct stat *buf)
 580 {
 581     struct vfs_class *vfs;
 582     int result;
 583
 584     if (handle == -1)
 585         return -1;
 586
 587     vfs = vfs_class_find_by_handle (handle);
 588     if (vfs == NULL)
 589         return -1;
 590
 591     result = vfs->fstat ? (*vfs->fstat) (vfs_class_data_find_by_handle (handle), buf) : -1;
 592     if (result == -1)
 593         errno = vfs->name ? vfs_ferrno (vfs) : E_NOTSUPP;
 594     return result;
 595 }
 596
 597 /* --------------------------------------------------------------------------------------------- */
 598 /**
 599  * Return current directory. If it's local, reread the current directory
 600  * from the OS. Put directory to the provided buffer.
 601  */
 602
 603 char *
 604 mc_get_current_wd (char *buffer, size_t size)
 605 {
 606     char *cwd = _vfs_get_cwd ();
 607
 608     g_strlcpy (buffer, cwd, size);
 609     g_free (cwd);
 610
 611     return buffer;
 612 }
 613
 614 /* --------------------------------------------------------------------------------------------- */
 615
 616 char *
 617 mc_getlocalcopy (const char *pathname)
 618 {
 619     char *result = NULL;
 620     vfs_path_t *vpath;
 621     vfs_path_element_t *path_element;
 622
 623     vpath = vfs_path_from_str (pathname);
 624     if (vpath == NULL)
 625         return NULL;
 626
 627     path_element = vfs_path_get_by_index (vpath, -1);
 628
 629     if (vfs_path_element_valid (path_element))
 630     {
 631         result = path_element->class->getlocalcopy != NULL ?
 632             path_element->class->getlocalcopy (vpath) : mc_def_getlocalcopy (pathname);
 633         if (result == NULL)
 634             errno = vfs_ferrno (path_element->class);
 635     }
 636     vfs_path_free (vpath);
 637     return result;
 638 }
 639
 640 /* --------------------------------------------------------------------------------------------- */
 641
 642 int
 643 mc_ungetlocalcopy (const char *pathname, const char *local, int has_changed)
 644 {
 645     int return_value = -1;
 646     vfs_path_t *vpath;
 647     vfs_path_element_t *path_element;
 648
 649     vpath = vfs_path_from_str (pathname);
 650     if (vpath == NULL)
 651         return -1;
 652
 653     path_element = vfs_path_get_by_index (vpath, -1);
 654
 655     if (vfs_path_element_valid (path_element))
 656     {
 657         return_value = path_element->class->ungetlocalcopy != NULL ?
 658             path_element->class->ungetlocalcopy (vpath, local,
 659                                                  has_changed) :
 660             mc_def_ungetlocalcopy (path_element->class, path_element->path, local, has_changed);
 661     }
 662     vfs_path_free (vpath);
 663     return return_value;
 664 }
 665
 666 /* --------------------------------------------------------------------------------------------- */
 667 /**
 668  * VFS chdir.
 669  *
 670  * @param vpath VFS-path
 671  *
 672  * @return 0 on success, -1 on failure.
 673  */
 674
 675 int
 676 mc_chdir (const vfs_path_t * vpath)
 677 {
 678     struct vfs_class *old_vfs;
 679     vfsid old_vfsid;
 680     int result;
 681     vfs_path_element_t *path_element;
 682
 683     if (vpath == NULL)
 684         return -1;
 685
 686     path_element = vfs_path_get_by_index (vpath, -1);
 687
 688     if (!vfs_path_element_valid (path_element) || path_element->class->chdir == NULL)
 689     {
 690         return -1;
 691     }
 692
 693     result = (*path_element->class->chdir) (vpath);
 694
 695     if (result == -1)
 696     {
 697         errno = vfs_ferrno (path_element->class);
 698         return -1;
 699     }
 700
 701     old_vfsid = vfs_getid (vfs_get_raw_current_dir ());
 702     old_vfs = current_vfs;
 703
 704     /* Actually change directory */
 705     vfs_set_raw_current_dir (vfs_path_clone (vpath));
 706     current_vfs = path_element->class;
 707
 708     /* This function uses the new current_dir implicitly */
 709     vfs_stamp_create (old_vfs, old_vfsid);
 710
 711     /* Sometimes we assume no trailing slash on cwd */
 712     path_element = vfs_path_get_by_index (vfs_get_raw_current_dir (), -1);
 713     if (vfs_path_element_valid (path_element) && (*path_element->path != '\0'))
 714     {
 715         char *p;
 716         p = strchr (path_element->path, 0) - 1;
 717         if (*p == PATH_SEP && p > path_element->path)
 718             *p = 0;
 719     }
 720     return 0;
 721 }
 722
 723 /* --------------------------------------------------------------------------------------------- */
 724
 725 off_t
 726 mc_lseek (int fd, off_t offset, int whence)
 727 {
 728     struct vfs_class *vfs;
 729     off_t result;
 730
 731     if (fd == -1)
 732         return -1;
 733
 734     vfs = vfs_class_find_by_handle (fd);
 735     if (vfs == NULL)
 736         return -1;
 737
 738     result = vfs->lseek ? (*vfs->lseek) (vfs_class_data_find_by_handle (fd), offset, whence) : -1;
 739     if (result == -1)
 740         errno = vfs->lseek ? vfs_ferrno (vfs) : E_NOTSUPP;
 741     return result;
 742 }
 743
 744 /* --------------------------------------------------------------------------------------------- */