Modules/_fileio.c

   1 /* Author: Daniel Stutzbach */
   2
   3 #define PY_SSIZE_T_CLEAN
   4 #include "Python.h"
   5 #include <sys/types.h>
   6 #include <sys/stat.h>
   7 #include <fcntl.h>
   8 #include <stddef.h> /* For offsetof */
   9
  10 /*
  11  * Known likely problems:
  12  *
  13  * - Files larger then 2**32-1
  14  * - Files with unicode filenames
  15  * - Passing numbers greater than 2**32-1 when an integer is expected
  16  * - Making it work on Windows and other oddball platforms
  17  *
  18  * To Do:
  19  *
  20  * - autoconfify header file inclusion
  21  */
  22
  23 #ifdef MS_WINDOWS
  24 /* can simulate truncate with Win32 API functions; see file_truncate */
  25 #define HAVE_FTRUNCATE
  26 #define WIN32_LEAN_AND_MEAN
  27 #include <windows.h>
  28 #endif
  29
  30 typedef struct {
  31         PyObject_HEAD
  32         int fd;
  33         unsigned readable : 1;
  34         unsigned writable : 1;
  35         int seekable : 2; /* -1 means unknown */
  36         int closefd : 1;
  37         PyObject *weakreflist;
  38 } PyFileIOObject;
  39
  40 PyTypeObject PyFileIO_Type;
  41
  42 #define PyFileIO_Check(op) (PyObject_TypeCheck((op), &PyFileIO_Type))
  43
  44 /* Returns 0 on success, errno (which is < 0) on failure. */
  45 static int
  46 internal_close(PyFileIOObject *self)
  47 {
  48         int save_errno = 0;
  49         if (self->fd >= 0) {
  50                 int fd = self->fd;
  51                 self->fd = -1;
  52                 Py_BEGIN_ALLOW_THREADS
  53                 if (close(fd) < 0)
  54                         save_errno = errno;
  55                 Py_END_ALLOW_THREADS
  56         }
  57         return save_errno;
  58 }
  59
  60 static PyObject *
  61 fileio_close(PyFileIOObject *self)
  62 {
  63         if (!self->closefd) {
  64                 if (PyErr_WarnEx(PyExc_RuntimeWarning,
  65                                  "Trying to close unclosable fd!", 3) < 0) {
  66                         return NULL;
  67                 }
  68                 Py_RETURN_NONE;
  69         }
  70         errno = internal_close(self);
  71         if (errno < 0) {
  72                 PyErr_SetFromErrno(PyExc_IOError);
  73                 return NULL;
  74         }
  75
  76         Py_RETURN_NONE;
  77 }
  78
  79 static PyObject *
  80 fileio_new(PyTypeObject *type, PyObject *args, PyObject *kews)
  81 {
  82         PyFileIOObject *self;
  83
  84         assert(type != NULL && type->tp_alloc != NULL);
  85
  86         self = (PyFileIOObject *) type->tp_alloc(type, 0);
  87         if (self != NULL) {
  88                 self->fd = -1;
  89                 self->weakreflist = NULL;
  90         }
  91
  92         return (PyObject *) self;
  93 }
  94
  95 /* On Unix, open will succeed for directories.
  96    In Python, there should be no file objects referring to
  97    directories, so we need a check.  */
  98
  99 static int
 100 dircheck(PyFileIOObject* self)
 101 {
 102 #if defined(HAVE_FSTAT) && defined(S_IFDIR) && defined(EISDIR)
 103         struct stat buf;
 104         if (self->fd < 0)
 105                 return 0;
 106         if (fstat(self->fd, &buf) == 0 && S_ISDIR(buf.st_mode)) {
 107                 char *msg = strerror(EISDIR);
 108                 PyObject *exc;
 109                 internal_close(self);
 110
 111                 exc = PyObject_CallFunction(PyExc_IOError, "(is)",
 112                                             EISDIR, msg);
 113                 PyErr_SetObject(PyExc_IOError, exc);
 114                 Py_XDECREF(exc);
 115                 return -1;
 116         }
 117 #endif
 118         return 0;
 119 }
 120
 121
 122 static int
 123 fileio_init(PyObject *oself, PyObject *args, PyObject *kwds)
 124 {
 125         PyFileIOObject *self = (PyFileIOObject *) oself;
 126         static char *kwlist[] = {"file", "mode", "closefd", NULL};
 127         char *name = NULL;
 128         char *mode = "r";
 129         char *s;
 130 #ifdef MS_WINDOWS
 131         Py_UNICODE *widename = NULL;
 132 #endif
 133         int ret = 0;
 134         int rwa = 0, plus = 0, append = 0;
 135         int flags = 0;
 136         int fd = -1;
 137         int closefd = 1;
 138
 139         assert(PyFileIO_Check(oself));
 140         if (self->fd >= 0) {
 141                 /* Have to close the existing file first. */
 142                 if (internal_close(self) < 0)
 143                         return -1;
 144         }
 145
 146         if (PyArg_ParseTupleAndKeywords(args, kwds, "i|si:fileio",
 147                                         kwlist, &fd, &mode, &closefd)) {
 148                 if (fd < 0) {
 149                         PyErr_SetString(PyExc_ValueError,
 150                                         "Negative filedescriptor");
 151                         return -1;
 152                 }
 153         }
 154         else {
 155                 PyErr_Clear();
 156
 157 #ifdef Py_WIN_WIDE_FILENAMES
 158             if (GetVersion() < 0x80000000) {
 159                 /* On NT, so wide API available */
 160                 PyObject *po;
 161                 if (PyArg_ParseTupleAndKeywords(args, kwds, "U|si:fileio",
 162                                                 kwlist, &po, &mode, &closefd)
 163                                                 ) {
 164                         widename = PyUnicode_AS_UNICODE(po);
 165                 } else {
 166                         /* Drop the argument parsing error as narrow
 167                            strings are also valid. */
 168                         PyErr_Clear();
 169                 }
 170             }
 171             if (widename == NULL)
 172 #endif
 173             {
 174                 if (!PyArg_ParseTupleAndKeywords(args, kwds, "et|si:fileio",
 175                                                  kwlist,
 176                                                  Py_FileSystemDefaultEncoding,
 177                                                  &name, &mode, &closefd))
 178                         goto error;
 179             }
 180         }
 181
 182         self->readable = self->writable = 0;
 183         self->seekable = -1;
 184         s = mode;
 185         while (*s) {
 186                 switch (*s++) {
 187                 case 'r':
 188                         if (rwa) {
 189                         bad_mode:
 190                                 PyErr_SetString(PyExc_ValueError,
 191                                                 "Must have exactly one of read/write/append mode");
 192                                 goto error;
 193                         }
 194                         rwa = 1;
 195                         self->readable = 1;
 196                         break;
 197                 case 'w':
 198                         if (rwa)
 199                                 goto bad_mode;
 200                         rwa = 1;
 201                         self->writable = 1;
 202                         flags |= O_CREAT | O_TRUNC;
 203                         break;
 204                 case 'a':
 205                         if (rwa)
 206                                 goto bad_mode;
 207                         rwa = 1;
 208                         self->writable = 1;
 209                         flags |= O_CREAT;
 210                         append = 1;
 211                         break;
 212                 case '+':
 213                         if (plus)
 214                                 goto bad_mode;
 215                         self->readable = self->writable = 1;
 216                         plus = 1;
 217                         break;
 218                 default:
 219                         PyErr_Format(PyExc_ValueError,
 220                                      "invalid mode: %.200s", mode);
 221                         goto error;
 222                 }
 223         }
 224
 225         if (!rwa)
 226                 goto bad_mode;
 227
 228         if (self->readable && self->writable)
 229                 flags |= O_RDWR;
 230         else if (self->readable)
 231                 flags |= O_RDONLY;
 232         else
 233                 flags |= O_WRONLY;
 234
 235 #ifdef O_BINARY
 236         flags |= O_BINARY;
 237 #endif
 238
 239 #ifdef O_APPEND
 240         if (append)
 241                 flags |= O_APPEND;
 242 #endif
 243
 244         if (fd >= 0) {
 245                 self->fd = fd;
 246                 self->closefd = closefd;
 247         }
 248         else {
 249                 self->closefd = 1;
 250                 if (!closefd) {
 251                         PyErr_SetString(PyExc_ValueError,
 252                             "Cannot use closefd=True with file name");
 253                         goto error;
 254                 }
 255
 256                 Py_BEGIN_ALLOW_THREADS
 257                 errno = 0;
 258 #ifdef MS_WINDOWS
 259                 if (widename != NULL)
 260                         self->fd = _wopen(widename, flags, 0666);
 261                 else
 262 #endif
 263                         self->fd = open(name, flags, 0666);
 264                 Py_END_ALLOW_THREADS
 265                 if (self->fd < 0 || dircheck(self) < 0) {
 266 #ifdef MS_WINDOWS
 267                         PyErr_SetFromErrnoWithUnicodeFilename(PyExc_IOError, widename);
 268 #else
 269                         PyErr_SetFromErrnoWithFilename(PyExc_IOError, name);
 270 #endif
 271                         goto error;
 272                 }
 273         }
 274
 275         goto done;
 276
 277  error:
 278         ret = -1;
 279
 280  done:
 281         PyMem_Free(name);
 282         return ret;
 283 }
 284
 285 static void
 286 fileio_dealloc(PyFileIOObject *self)
 287 {
 288         if (self->weakreflist != NULL)
 289                 PyObject_ClearWeakRefs((PyObject *) self);
 290
 291         if (self->fd >= 0 && self->closefd) {
 292                 errno = internal_close(self);
 293                 if (errno < 0) {
 294                         PySys_WriteStderr("close failed: [Errno %d] %s\n",
 295                                           errno, strerror(errno));
 296                 }
 297         }
 298
 299         Py_TYPE(self)->tp_free((PyObject *)self);
 300 }
 301
 302 static PyObject *
 303 err_closed(void)
 304 {
 305         PyErr_SetString(PyExc_ValueError, "I/O operation on closed file");
 306         return NULL;
 307 }
 308
 309 static PyObject *
 310 err_mode(char *action)
 311 {
 312         PyErr_Format(PyExc_ValueError, "File not open for %s", action);
 313         return NULL;
 314 }
 315
 316 static PyObject *
 317 fileio_fileno(PyFileIOObject *self)
 318 {
 319         if (self->fd < 0)
 320                 return err_closed();
 321         return PyInt_FromLong((long) self->fd);
 322 }
 323
 324 static PyObject *
 325 fileio_readable(PyFileIOObject *self)
 326 {
 327         if (self->fd < 0)
 328                 return err_closed();
 329         return PyBool_FromLong((long) self->readable);
 330 }
 331
 332 static PyObject *
 333 fileio_writable(PyFileIOObject *self)
 334 {
 335         if (self->fd < 0)
 336                 return err_closed();
 337         return PyBool_FromLong((long) self->writable);
 338 }
 339
 340 static PyObject *
 341 fileio_seekable(PyFileIOObject *self)
 342 {
 343         if (self->fd < 0)
 344                 return err_closed();
 345         if (self->seekable < 0) {
 346                 int ret;
 347                 Py_BEGIN_ALLOW_THREADS
 348                 ret = lseek(self->fd, 0, SEEK_CUR);
 349                 Py_END_ALLOW_THREADS
 350                 if (ret < 0)
 351                         self->seekable = 0;
 352                 else
 353                         self->seekable = 1;
 354         }
 355         return PyBool_FromLong((long) self->seekable);
 356 }
 357
 358 static PyObject *
 359 fileio_readinto(PyFileIOObject *self, PyObject *args)
 360 {
 361         char *ptr;
 362         Py_ssize_t n;
 363
 364         if (self->fd < 0)
 365                 return err_closed();
 366         if (!self->readable)
 367                 return err_mode("reading");
 368
 369         if (!PyArg_ParseTuple(args, "w#", &ptr, &n))
 370                 return NULL;
 371
 372         Py_BEGIN_ALLOW_THREADS
 373         errno = 0;
 374         n = read(self->fd, ptr, n);
 375         Py_END_ALLOW_THREADS
 376         if (n < 0) {
 377                 if (errno == EAGAIN)
 378                         Py_RETURN_NONE;
 379                 PyErr_SetFromErrno(PyExc_IOError);
 380                 return NULL;
 381         }
 382
 383         return PyLong_FromSsize_t(n);
 384 }
 385
 386 #define DEFAULT_BUFFER_SIZE (8*1024)
 387
 388 static PyObject *
 389 fileio_readall(PyFileIOObject *self)
 390 {
 391         PyObject *result;
 392         Py_ssize_t total = 0;
 393         int n;
 394
 395         result = PyString_FromStringAndSize(NULL, DEFAULT_BUFFER_SIZE);
 396         if (result == NULL)
 397                 return NULL;
 398
 399         while (1) {
 400                 Py_ssize_t newsize = total + DEFAULT_BUFFER_SIZE;
 401                 if (PyString_GET_SIZE(result) < newsize) {
 402                         if (_PyString_Resize(&result, newsize) < 0) {
 403                                 if (total == 0) {
 404                                         Py_DECREF(result);
 405                                         return NULL;
 406                                 }
 407                                 PyErr_Clear();
 408                                 break;
 409                         }
 410                 }
 411                 Py_BEGIN_ALLOW_THREADS
 412                 errno = 0;
 413                 n = read(self->fd,
 414                          PyString_AS_STRING(result) + total,
 415                          newsize - total);
 416                 Py_END_ALLOW_THREADS
 417                 if (n == 0)
 418                         break;
 419                 if (n < 0) {
 420                         if (total > 0)
 421                                 break;
 422                         if (errno == EAGAIN) {
 423                                 Py_DECREF(result);
 424                                 Py_RETURN_NONE;
 425                         }
 426                         Py_DECREF(result);
 427                         PyErr_SetFromErrno(PyExc_IOError);
 428                         return NULL;
 429                 }
 430                 total += n;
 431         }
 432
 433         if (PyString_GET_SIZE(result) > total) {
 434                 if (_PyString_Resize(&result, total) < 0) {
 435                         /* This should never happen, but just in case */
 436                         Py_DECREF(result);
 437                         return NULL;
 438                 }
 439         }
 440         return result;
 441 }
 442
 443 static PyObject *
 444 fileio_read(PyFileIOObject *self, PyObject *args)
 445 {
 446         char *ptr;
 447         Py_ssize_t n;
 448         Py_ssize_t size = -1;
 449         PyObject *bytes;
 450
 451         if (self->fd < 0)
 452                 return err_closed();
 453         if (!self->readable)
 454                 return err_mode("reading");
 455
 456         if (!PyArg_ParseTuple(args, "|n", &size))
 457                 return NULL;
 458
 459         if (size < 0) {
 460                 return fileio_readall(self);
 461         }
 462
 463         bytes = PyString_FromStringAndSize(NULL, size);
 464         if (bytes == NULL)
 465                 return NULL;
 466         ptr = PyString_AS_STRING(bytes);
 467
 468         Py_BEGIN_ALLOW_THREADS
 469         errno = 0;
 470         n = read(self->fd, ptr, size);
 471         Py_END_ALLOW_THREADS
 472
 473         if (n < 0) {
 474                 if (errno == EAGAIN)
 475                         Py_RETURN_NONE;
 476                 PyErr_SetFromErrno(PyExc_IOError);
 477                 return NULL;
 478         }
 479
 480         if (n != size) {
 481                 if (_PyString_Resize(&bytes, n) < 0) {
 482                         Py_DECREF(bytes);
 483                         return NULL;
 484                 }
 485         }
 486
 487         return (PyObject *) bytes;
 488 }
 489
 490 static PyObject *
 491 fileio_write(PyFileIOObject *self, PyObject *args)
 492 {
 493         Py_ssize_t n;
 494         char *ptr;
 495
 496         if (self->fd < 0)
 497                 return err_closed();
 498         if (!self->writable)
 499                 return err_mode("writing");
 500
 501         if (!PyArg_ParseTuple(args, "s#", &ptr, &n))
 502                 return NULL;
 503
 504         Py_BEGIN_ALLOW_THREADS
 505         errno = 0;
 506         n = write(self->fd, ptr, n);
 507         Py_END_ALLOW_THREADS
 508
 509         if (n < 0) {
 510                 if (errno == EAGAIN)
 511                         Py_RETURN_NONE;
 512                 PyErr_SetFromErrno(PyExc_IOError);
 513                 return NULL;
 514         }
 515
 516         return PyLong_FromSsize_t(n);
 517 }
 518
 519 /* XXX Windows support below is likely incomplete */
 520
 521 #if defined(MS_WIN64) || defined(MS_WINDOWS)
 522 typedef PY_LONG_LONG Py_off_t;
 523 #else
 524 typedef off_t Py_off_t;
 525 #endif
 526
 527 /* Cribbed from posix_lseek() */
 528 static PyObject *
 529 portable_lseek(int fd, PyObject *posobj, int whence)
 530 {
 531         Py_off_t pos, res;
 532
 533 #ifdef SEEK_SET
 534         /* Turn 0, 1, 2 into SEEK_{SET,CUR,END} */
 535         switch (whence) {
 536 #if SEEK_SET != 0
 537         case 0: whence = SEEK_SET; break;
 538 #endif
 539 #if SEEK_CUR != 1
 540         case 1: whence = SEEK_CUR; break;
 541 #endif
 542 #if SEEL_END != 2
 543         case 2: whence = SEEK_END; break;
 544 #endif
 545         }
 546 #endif /* SEEK_SET */
 547
 548         if (posobj == NULL)
 549                 pos = 0;
 550         else {
 551                 if(PyFloat_Check(posobj)) {
 552                         PyErr_SetString(PyExc_TypeError, "an integer is required");
 553                         return NULL;
 554                 }
 555 #if !defined(HAVE_LARGEFILE_SUPPORT)
 556                 pos = PyLong_AsLong(posobj);
 557 #else
 558                 pos = PyLong_Check(posobj) ?
 559                         PyLong_AsLongLong(posobj) : PyLong_AsLong(posobj);
 560 #endif
 561                 if (PyErr_Occurred())
 562                         return NULL;
 563         }
 564
 565         Py_BEGIN_ALLOW_THREADS
 566 #if defined(MS_WIN64) || defined(MS_WINDOWS)
 567         res = _lseeki64(fd, pos, whence);
 568 #else
 569         res = lseek(fd, pos, whence);
 570 #endif
 571         Py_END_ALLOW_THREADS
 572         if (res < 0)
 573                 return PyErr_SetFromErrno(PyExc_IOError);
 574
 575 #if !defined(HAVE_LARGEFILE_SUPPORT)
 576         return PyLong_FromLong(res);
 577 #else
 578         return PyLong_FromLongLong(res);
 579 #endif
 580 }
 581
 582 static PyObject *
 583 fileio_seek(PyFileIOObject *self, PyObject *args)
 584 {
 585         PyObject *posobj;
 586         int whence = 0;
 587
 588         if (self->fd < 0)
 589                 return err_closed();
 590
 591         if (!PyArg_ParseTuple(args, "O|i", &posobj, &whence))
 592                 return NULL;
 593
 594         return portable_lseek(self->fd, posobj, whence);
 595 }
 596
 597 static PyObject *
 598 fileio_tell(PyFileIOObject *self, PyObject *args)
 599 {
 600         if (self->fd < 0)
 601                 return err_closed();
 602
 603         return portable_lseek(self->fd, NULL, 1);
 604 }
 605
 606 #ifdef HAVE_FTRUNCATE
 607 static PyObject *
 608 fileio_truncate(PyFileIOObject *self, PyObject *args)
 609 {
 610         PyObject *posobj = NULL;
 611         Py_off_t pos;
 612         int ret;
 613         int fd;
 614
 615         fd = self->fd;
 616         if (fd < 0)
 617                 return err_closed();
 618         if (!self->writable)
 619                 return err_mode("writing");
 620
 621         if (!PyArg_ParseTuple(args, "|O", &posobj))
 622                 return NULL;
 623
 624         if (posobj == Py_None || posobj == NULL) {
 625                 posobj = portable_lseek(fd, NULL, 1);
 626                 if (posobj == NULL)
 627                   return NULL;
 628         }
 629         else {
 630                 Py_INCREF(posobj);
 631         }
 632
 633 #if !defined(HAVE_LARGEFILE_SUPPORT)
 634         pos = PyLong_AsLong(posobj);
 635 #else
 636         pos = PyLong_Check(posobj) ?
 637                 PyLong_AsLongLong(posobj) : PyLong_AsLong(posobj);
 638 #endif
 639         if (PyErr_Occurred()) {
 640                 Py_DECREF(posobj);
 641                 return NULL;
 642         }
 643
 644 #ifdef MS_WINDOWS
 645         /* MS _chsize doesn't work if newsize doesn't fit in 32 bits,
 646            so don't even try using it. */
 647         {
 648                 HANDLE hFile;
 649                 PyObject *pos2, *oldposobj;
 650
 651                 /* store the current position */
 652                 oldposobj = portable_lseek(self->fd, NULL, 1);
 653                 if (oldposobj == NULL) {
 654                         Py_DECREF(posobj);
 655                         return NULL;
 656                 }
 657
 658                 /* Have to move current pos to desired endpoint on Windows. */
 659                 errno = 0;
 660                 pos2 = portable_lseek(fd, posobj, SEEK_SET);
 661                 if (pos2 == NULL) {
 662                         Py_DECREF(posobj);
 663                         Py_DECREF(oldposobj);
 664                         return NULL;
 665                 }
 666                 Py_DECREF(pos2);
 667
 668                 /* Truncate.  Note that this may grow the file! */
 669                 Py_BEGIN_ALLOW_THREADS
 670                 errno = 0;
 671                 hFile = (HANDLE)_get_osfhandle(fd);
 672                 ret = hFile == (HANDLE)-1;
 673                 if (ret == 0) {
 674                         ret = SetEndOfFile(hFile) == 0;
 675                         if (ret)
 676                                 errno = EACCES;
 677                 }
 678                 Py_END_ALLOW_THREADS
 679
 680                 if (ret == 0) {
 681                         /* Move to the previous position in the file */
 682                         pos2 = portable_lseek(fd, oldposobj, SEEK_SET);
 683                         if (pos2 == NULL) {
 684                                 Py_DECREF(posobj);
 685                                 Py_DECREF(oldposobj);
 686                                 return NULL;
 687                         }
 688                 }
 689                 Py_DECREF(pos2);
 690                 Py_DECREF(oldposobj);
 691         }
 692 #else
 693         Py_BEGIN_ALLOW_THREADS
 694         errno = 0;
 695         ret = ftruncate(fd, pos);
 696         Py_END_ALLOW_THREADS
 697 #endif /* !MS_WINDOWS */
 698
 699         if (ret != 0) {
 700                 Py_DECREF(posobj);
 701                 PyErr_SetFromErrno(PyExc_IOError);
 702                 return NULL;
 703         }
 704
 705         return posobj;
 706 }
 707 #endif
 708
 709 static char *
 710 mode_string(PyFileIOObject *self)
 711 {
 712         if (self->readable) {
 713                 if (self->writable)
 714                         return "r+";
 715                 else
 716                         return "r";
 717         }
 718         else
 719                 return "w";
 720 }
 721
 722 static PyObject *
 723 fileio_repr(PyFileIOObject *self)
 724 {
 725         if (self->fd < 0)
 726                 return PyString_FromFormat("_fileio._FileIO(-1)");
 727
 728         return PyString_FromFormat("_fileio._FileIO(%d, '%s')",
 729                                    self->fd, mode_string(self));
 730 }
 731
 732 static PyObject *
 733 fileio_isatty(PyFileIOObject *self)
 734 {
 735         long res;
 736
 737         if (self->fd < 0)
 738                 return err_closed();
 739         Py_BEGIN_ALLOW_THREADS
 740         res = isatty(self->fd);
 741         Py_END_ALLOW_THREADS
 742         return PyBool_FromLong(res);
 743 }
 744
 745
 746 PyDoc_STRVAR(fileio_doc,
 747 "file(name: str[, mode: str]) -> file IO object\n"
 748 "\n"
 749 "Open a file.  The mode can be 'r', 'w' or 'a' for reading (default),\n"
 750 "writing or appending.  The file will be created if it doesn't exist\n"
 751 "when opened for writing or appending; it will be truncated when\n"
 752 "opened for writing.  Add a '+' to the mode to allow simultaneous\n"
 753 "reading and writing.");
 754
 755 PyDoc_STRVAR(read_doc,
 756 "read(size: int) -> bytes.  read at most size bytes, returned as bytes.\n"
 757 "\n"
 758 "Only makes one system call, so less data may be returned than requested\n"
 759 "In non-blocking mode, returns None if no data is available.\n"
 760 "On end-of-file, returns ''.");
 761
 762 PyDoc_STRVAR(readall_doc,
 763 "readall() -> bytes.  read all data from the file, returned as bytes.\n"
 764 "\n"
 765 "In non-blocking mode, returns as much as is immediately available,\n"
 766 "or None if no data is available.  On end-of-file, returns ''.");
 767
 768 PyDoc_STRVAR(write_doc,
 769 "write(b: bytes) -> int.  Write bytes b to file, return number written.\n"
 770 "\n"
 771 "Only makes one system call, so not all of the data may be written.\n"
 772 "The number of bytes actually written is returned.");
 773
 774 PyDoc_STRVAR(fileno_doc,
 775 "fileno() -> int. \"file descriptor\".\n"
 776 "\n"
 777 "This is needed for lower-level file interfaces, such the fcntl module.");
 778
 779 PyDoc_STRVAR(seek_doc,
 780 "seek(offset: int[, whence: int]) -> None.  Move to new file position.\n"
 781 "\n"
 782 "Argument offset is a byte count.  Optional argument whence defaults to\n"
 783 "0 (offset from start of file, offset should be >= 0); other values are 1\n"
 784 "(move relative to current position, positive or negative), and 2 (move\n"
 785 "relative to end of file, usually negative, although many platforms allow\n"
 786 "seeking beyond the end of a file)."
 787 "\n"
 788 "Note that not all file objects are seekable.");
 789
 790 #ifdef HAVE_FTRUNCATE
 791 PyDoc_STRVAR(truncate_doc,
 792 "truncate([size: int]) -> None.  Truncate the file to at most size bytes.\n"
 793 "\n"
 794 "Size defaults to the current file position, as returned by tell().");
 795 #endif
 796
 797 PyDoc_STRVAR(tell_doc,
 798 "tell() -> int.  Current file position");
 799
 800 PyDoc_STRVAR(readinto_doc,
 801 "readinto() -> Undocumented.  Don't use this; it may go away.");
 802
 803 PyDoc_STRVAR(close_doc,
 804 "close() -> None.  Close the file.\n"
 805 "\n"
 806 "A closed file cannot be used for further I/O operations.  close() may be\n"
 807 "called more than once without error.  Changes the fileno to -1.");
 808
 809 PyDoc_STRVAR(isatty_doc,
 810 "isatty() -> bool.  True if the file is connected to a tty device.");
 811
 812 PyDoc_STRVAR(seekable_doc,
 813 "seekable() -> bool.  True if file supports random-access.");
 814
 815 PyDoc_STRVAR(readable_doc,
 816 "readable() -> bool.  True if file was opened in a read mode.");
 817
 818 PyDoc_STRVAR(writable_doc,
 819 "writable() -> bool.  True if file was opened in a write mode.");
 820
 821 static PyMethodDef fileio_methods[] = {
 822         {"read",     (PyCFunction)fileio_read,     METH_VARARGS, read_doc},
 823         {"readall",  (PyCFunction)fileio_readall,  METH_NOARGS,  readall_doc},
 824         {"readinto", (PyCFunction)fileio_readinto, METH_VARARGS, readinto_doc},
 825         {"write",    (PyCFunction)fileio_write,    METH_VARARGS, write_doc},
 826         {"seek",     (PyCFunction)fileio_seek,     METH_VARARGS, seek_doc},
 827         {"tell",     (PyCFunction)fileio_tell,     METH_VARARGS, tell_doc},
 828 #ifdef HAVE_FTRUNCATE
 829         {"truncate", (PyCFunction)fileio_truncate, METH_VARARGS, truncate_doc},
 830 #endif
 831         {"close",    (PyCFunction)fileio_close,    METH_NOARGS,  close_doc},
 832         {"seekable", (PyCFunction)fileio_seekable, METH_NOARGS,  seekable_doc},
 833         {"readable", (PyCFunction)fileio_readable, METH_NOARGS,  readable_doc},
 834         {"writable", (PyCFunction)fileio_writable, METH_NOARGS,  writable_doc},
 835         {"fileno",   (PyCFunction)fileio_fileno,   METH_NOARGS,  fileno_doc},
 836         {"isatty",   (PyCFunction)fileio_isatty,   METH_NOARGS,  isatty_doc},
 837         {NULL,       NULL}             /* sentinel */
 838 };
 839
 840 /* 'closed' and 'mode' are attributes for backwards compatibility reasons. */
 841
 842 static PyObject *
 843 get_closed(PyFileIOObject *self, void *closure)
 844 {
 845         return PyBool_FromLong((long)(self->fd < 0));
 846 }
 847
 848 static PyObject *
 849 get_mode(PyFileIOObject *self, void *closure)
 850 {
 851         return PyString_FromString(mode_string(self));
 852 }
 853
 854 static PyGetSetDef fileio_getsetlist[] = {
 855         {"closed", (getter)get_closed, NULL, "True if the file is closed"},
 856         {"mode", (getter)get_mode, NULL, "String giving the file mode"},
 857         {0},
 858 };
 859
 860 PyTypeObject PyFileIO_Type = {
 861         PyVarObject_HEAD_INIT(&PyType_Type, 0)
 862         "_FileIO",
 863         sizeof(PyFileIOObject),
 864         0,
 865         (destructor)fileio_dealloc,             /* tp_dealloc */
 866         0,                                      /* tp_print */
 867         0,                                      /* tp_getattr */
 868         0,                                      /* tp_setattr */
 869         0,                                      /* tp_compare */
 870         (reprfunc)fileio_repr,                  /* tp_repr */
 871         0,                                      /* tp_as_number */
 872         0,                                      /* tp_as_sequence */
 873         0,                                      /* tp_as_mapping */
 874         0,                                      /* tp_hash */
 875         0,                                      /* tp_call */
 876         0,                                      /* tp_str */
 877         PyObject_GenericGetAttr,                /* tp_getattro */
 878         0,                                      /* tp_setattro */
 879         0,                                      /* tp_as_buffer */
 880         Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE, /* tp_flags */
 881         fileio_doc,                             /* tp_doc */
 882         0,                                      /* tp_traverse */
 883         0,                                      /* tp_clear */
 884         0,                                      /* tp_richcompare */
 885         offsetof(PyFileIOObject, weakreflist),  /* tp_weaklistoffset */
 886         0,                                      /* tp_iter */
 887         0,                                      /* tp_iternext */
 888         fileio_methods,                         /* tp_methods */
 889         0,                                      /* tp_members */
 890         fileio_getsetlist,                      /* tp_getset */
 891         0,                                      /* tp_base */
 892         0,                                      /* tp_dict */
 893         0,                                      /* tp_descr_get */
 894         0,                                      /* tp_descr_set */
 895         0,                                      /* tp_dictoffset */
 896         fileio_init,                            /* tp_init */
 897         PyType_GenericAlloc,                    /* tp_alloc */
 898         fileio_new,                             /* tp_new */
 899         PyObject_Del,                           /* tp_free */
 900 };
 901
 902 static PyMethodDef module_methods[] = {
 903         {NULL, NULL}
 904 };
 905
 906 PyMODINIT_FUNC
 907 init_fileio(void)
 908 {
 909         PyObject *m;    /* a module object */
 910
 911         m = Py_InitModule3("_fileio", module_methods,
 912                            "Fast implementation of io.FileIO.");
 913         if (m == NULL)
 914                 return;
 915         if (PyType_Ready(&PyFileIO_Type) < 0)
 916                 return;
 917         Py_INCREF(&PyFileIO_Type);
 918         PyModule_AddObject(m, "_FileIO", (PyObject *) &PyFileIO_Type);
 919 }