Source

pypy-postgresql / lib-python / 2.7 / test / test_mmap.py

  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
from test.test_support import (TESTFN, run_unittest, import_module, unlink,
                               requires, _2G, _4G)
import unittest
import os, re, itertools, socket, sys

mmap = import_module('mmap')

PAGESIZE = mmap.PAGESIZE

class MmapTests(unittest.TestCase):

    def setUp(self):
        if os.path.exists(TESTFN):
            os.unlink(TESTFN)

    def tearDown(self):
        try:
            os.unlink(TESTFN)
        except OSError:
            pass

    def test_basic(self):
        # Test mmap module on Unix systems and Windows

        # Create a file to be mmap'ed.
        f = open(TESTFN, 'w+')
        try:
            # Write 2 pages worth of data to the file
            f.write('\0'* PAGESIZE)
            f.write('foo')
            f.write('\0'* (PAGESIZE-3) )
            f.flush()
            m = mmap.mmap(f.fileno(), 2 * PAGESIZE)
            f.close()

            # Simple sanity checks

            tp = str(type(m))  # SF bug 128713:  segfaulted on Linux
            self.assertEqual(m.find('foo'), PAGESIZE)

            self.assertEqual(len(m), 2*PAGESIZE)

            self.assertEqual(m[0], '\0')
            self.assertEqual(m[0:3], '\0\0\0')

            # Shouldn't crash on boundary (Issue #5292)
            self.assertRaises(IndexError, m.__getitem__, len(m))
            self.assertRaises(IndexError, m.__setitem__, len(m), '\0')

            # Modify the file's content
            m[0] = '3'
            m[PAGESIZE +3: PAGESIZE +3+3] = 'bar'

            # Check that the modification worked
            self.assertEqual(m[0], '3')
            self.assertEqual(m[0:3], '3\0\0')
            self.assertEqual(m[PAGESIZE-1 : PAGESIZE + 7], '\0foobar\0')

            m.flush()

            # Test doing a regular expression match in an mmap'ed file
            match = re.search('[A-Za-z]+', m)
            if match is None:
                self.fail('regex match on mmap failed!')
            else:
                start, end = match.span(0)
                length = end - start

                self.assertEqual(start, PAGESIZE)
                self.assertEqual(end, PAGESIZE + 6)

            # test seeking around (try to overflow the seek implementation)
            m.seek(0,0)
            self.assertEqual(m.tell(), 0)
            m.seek(42,1)
            self.assertEqual(m.tell(), 42)
            m.seek(0,2)
            self.assertEqual(m.tell(), len(m))

            # Try to seek to negative position...
            self.assertRaises(ValueError, m.seek, -1)

            # Try to seek beyond end of mmap...
            self.assertRaises(ValueError, m.seek, 1, 2)

            # Try to seek to negative position...
            self.assertRaises(ValueError, m.seek, -len(m)-1, 2)

            # Try resizing map
            try:
                m.resize(512)
            except SystemError:
                # resize() not supported
                # No messages are printed, since the output of this test suite
                # would then be different across platforms.
                pass
            else:
                # resize() is supported
                self.assertEqual(len(m), 512)
                # Check that we can no longer seek beyond the new size.
                self.assertRaises(ValueError, m.seek, 513, 0)

                # Check that the underlying file is truncated too
                # (bug #728515)
                f = open(TESTFN)
                f.seek(0, 2)
                self.assertEqual(f.tell(), 512)
                f.close()
                self.assertEqual(m.size(), 512)

            m.close()

        finally:
            try:
                f.close()
            except OSError:
                pass

    def test_access_parameter(self):
        # Test for "access" keyword parameter
        mapsize = 10
        with open(TESTFN, "wb") as f:
            f.write("a"*mapsize)
        f = open(TESTFN, "rb")
        m = mmap.mmap(f.fileno(), mapsize, access=mmap.ACCESS_READ)
        self.assertEqual(m[:], 'a'*mapsize, "Readonly memory map data incorrect.")

        # Ensuring that readonly mmap can't be slice assigned
        try:
            m[:] = 'b'*mapsize
        except TypeError:
            pass
        else:
            self.fail("Able to write to readonly memory map")

        # Ensuring that readonly mmap can't be item assigned
        try:
            m[0] = 'b'
        except TypeError:
            pass
        else:
            self.fail("Able to write to readonly memory map")

        # Ensuring that readonly mmap can't be write() to
        try:
            m.seek(0,0)
            m.write('abc')
        except TypeError:
            pass
        else:
            self.fail("Able to write to readonly memory map")

        # Ensuring that readonly mmap can't be write_byte() to
        try:
            m.seek(0,0)
            m.write_byte('d')
        except TypeError:
            pass
        else:
            self.fail("Able to write to readonly memory map")

        # Ensuring that readonly mmap can't be resized
        try:
            m.resize(2*mapsize)
        except SystemError:   # resize is not universally supported
            pass
        except TypeError:
            pass
        else:
            self.fail("Able to resize readonly memory map")
        f.close()
        m.close()
        del m, f
        with open(TESTFN, "rb") as f:
            self.assertEqual(f.read(), 'a'*mapsize,
                "Readonly memory map data file was modified")

        # Opening mmap with size too big
        import sys
        f = open(TESTFN, "r+b")
        try:
            m = mmap.mmap(f.fileno(), mapsize+1)
        except ValueError:
            # we do not expect a ValueError on Windows
            # CAUTION:  This also changes the size of the file on disk, and
            # later tests assume that the length hasn't changed.  We need to
            # repair that.
            if sys.platform.startswith('win'):
                self.fail("Opening mmap with size+1 should work on Windows.")
        else:
            # we expect a ValueError on Unix, but not on Windows
            if not sys.platform.startswith('win'):
                self.fail("Opening mmap with size+1 should raise ValueError.")
            m.close()
        f.close()
        if sys.platform.startswith('win'):
            # Repair damage from the resizing test.
            f = open(TESTFN, 'r+b')
            f.truncate(mapsize)
            f.close()

        # Opening mmap with access=ACCESS_WRITE
        f = open(TESTFN, "r+b")
        m = mmap.mmap(f.fileno(), mapsize, access=mmap.ACCESS_WRITE)
        # Modifying write-through memory map
        m[:] = 'c'*mapsize
        self.assertEqual(m[:], 'c'*mapsize,
               "Write-through memory map memory not updated properly.")
        m.flush()
        m.close()
        f.close()
        f = open(TESTFN, 'rb')
        stuff = f.read()
        f.close()
        self.assertEqual(stuff, 'c'*mapsize,
               "Write-through memory map data file not updated properly.")

        # Opening mmap with access=ACCESS_COPY
        f = open(TESTFN, "r+b")
        m = mmap.mmap(f.fileno(), mapsize, access=mmap.ACCESS_COPY)
        # Modifying copy-on-write memory map
        m[:] = 'd'*mapsize
        self.assertEqual(m[:], 'd' * mapsize,
               "Copy-on-write memory map data not written correctly.")
        m.flush()
        f.close()
        with open(TESTFN, "rb") as f:
            self.assertEqual(f.read(), 'c'*mapsize,
                "Copy-on-write test data file should not be modified.")
        # Ensuring copy-on-write maps cannot be resized
        self.assertRaises(TypeError, m.resize, 2*mapsize)
        m.close()
        del m, f

        # Ensuring invalid access parameter raises exception
        f = open(TESTFN, "r+b")
        self.assertRaises(ValueError, mmap.mmap, f.fileno(), mapsize, access=4)
        f.close()

        if os.name == "posix":
            # Try incompatible flags, prot and access parameters.
            f = open(TESTFN, "r+b")
            self.assertRaises(ValueError, mmap.mmap, f.fileno(), mapsize,
                              flags=mmap.MAP_PRIVATE,
                              prot=mmap.PROT_READ, access=mmap.ACCESS_WRITE)
            f.close()

            # Try writing with PROT_EXEC and without PROT_WRITE
            prot = mmap.PROT_READ | getattr(mmap, 'PROT_EXEC', 0)
            with open(TESTFN, "r+b") as f:
                m = mmap.mmap(f.fileno(), mapsize, prot=prot)
                self.assertRaises(TypeError, m.write, b"abcdef")
                self.assertRaises(TypeError, m.write_byte, 0)
                m.close()

    def test_bad_file_desc(self):
        # Try opening a bad file descriptor...
        self.assertRaises(mmap.error, mmap.mmap, -2, 4096)

    def test_tougher_find(self):
        # Do a tougher .find() test.  SF bug 515943 pointed out that, in 2.2,
        # searching for data with embedded \0 bytes didn't work.
        f = open(TESTFN, 'w+')

        data = 'aabaac\x00deef\x00\x00aa\x00'
        n = len(data)
        f.write(data)
        f.flush()
        m = mmap.mmap(f.fileno(), n)
        f.close()

        for start in range(n+1):
            for finish in range(start, n+1):
                slice = data[start : finish]
                self.assertEqual(m.find(slice), data.find(slice))
                self.assertEqual(m.find(slice + 'x'), -1)
        m.close()

    def test_find_end(self):
        # test the new 'end' parameter works as expected
        f = open(TESTFN, 'w+')
        data = 'one two ones'
        n = len(data)
        f.write(data)
        f.flush()
        m = mmap.mmap(f.fileno(), n)
        f.close()

        self.assertEqual(m.find('one'), 0)
        self.assertEqual(m.find('ones'), 8)
        self.assertEqual(m.find('one', 0, -1), 0)
        self.assertEqual(m.find('one', 1), 8)
        self.assertEqual(m.find('one', 1, -1), 8)
        self.assertEqual(m.find('one', 1, -2), -1)
        m.close()


    def test_rfind(self):
        # test the new 'end' parameter works as expected
        f = open(TESTFN, 'w+')
        data = 'one two ones'
        n = len(data)
        f.write(data)
        f.flush()
        m = mmap.mmap(f.fileno(), n)
        f.close()

        self.assertEqual(m.rfind('one'), 8)
        self.assertEqual(m.rfind('one '), 0)
        self.assertEqual(m.rfind('one', 0, -1), 8)
        self.assertEqual(m.rfind('one', 0, -2), 0)
        self.assertEqual(m.rfind('one', 1, -1), 8)
        self.assertEqual(m.rfind('one', 1, -2), -1)
        m.close()


    def test_double_close(self):
        # make sure a double close doesn't crash on Solaris (Bug# 665913)
        f = open(TESTFN, 'w+')

        f.write(2**16 * 'a') # Arbitrary character
        f.close()

        f = open(TESTFN)
        mf = mmap.mmap(f.fileno(), 2**16, access=mmap.ACCESS_READ)
        mf.close()
        mf.close()
        f.close()

    def test_entire_file(self):
        # test mapping of entire file by passing 0 for map length
        if hasattr(os, "stat"):
            f = open(TESTFN, "w+")

            f.write(2**16 * 'm') # Arbitrary character
            f.close()

            f = open(TESTFN, "rb+")
            mf = mmap.mmap(f.fileno(), 0)
            self.assertEqual(len(mf), 2**16, "Map size should equal file size.")
            self.assertEqual(mf.read(2**16), 2**16 * "m")
            mf.close()
            f.close()

    def test_length_0_offset(self):
        # Issue #10916: test mapping of remainder of file by passing 0 for
        # map length with an offset doesn't cause a segfault.
        if not hasattr(os, "stat"):
            self.skipTest("needs os.stat")
        # NOTE: allocation granularity is currently 65536 under Win64,
        # and therefore the minimum offset alignment.
        with open(TESTFN, "wb") as f:
            f.write((65536 * 2) * b'm') # Arbitrary character

        with open(TESTFN, "rb") as f:
            mf = mmap.mmap(f.fileno(), 0, offset=65536, access=mmap.ACCESS_READ)
            try:
                self.assertRaises(IndexError, mf.__getitem__, 80000)
            finally:
                mf.close()

    def test_length_0_large_offset(self):
        # Issue #10959: test mapping of a file by passing 0 for
        # map length with a large offset doesn't cause a segfault.
        if not hasattr(os, "stat"):
            self.skipTest("needs os.stat")

        with open(TESTFN, "wb") as f:
            f.write(115699 * b'm') # Arbitrary character

        with open(TESTFN, "w+b") as f:
            self.assertRaises(ValueError, mmap.mmap, f.fileno(), 0,
                              offset=2147418112)

    def test_move(self):
        # make move works everywhere (64-bit format problem earlier)
        f = open(TESTFN, 'w+')

        f.write("ABCDEabcde") # Arbitrary character
        f.flush()

        mf = mmap.mmap(f.fileno(), 10)
        mf.move(5, 0, 5)
        self.assertEqual(mf[:], "ABCDEABCDE", "Map move should have duplicated front 5")
        mf.close()
        f.close()

        # more excessive test
        data = "0123456789"
        for dest in range(len(data)):
            for src in range(len(data)):
                for count in range(len(data) - max(dest, src)):
                    expected = data[:dest] + data[src:src+count] + data[dest+count:]
                    m = mmap.mmap(-1, len(data))
                    m[:] = data
                    m.move(dest, src, count)
                    self.assertEqual(m[:], expected)
                    m.close()

        # segfault test (Issue 5387)
        m = mmap.mmap(-1, 100)
        offsets = [-100, -1, 0, 1, 100]
        for source, dest, size in itertools.product(offsets, offsets, offsets):
            try:
                m.move(source, dest, size)
            except ValueError:
                pass

        offsets = [(-1, -1, -1), (-1, -1, 0), (-1, 0, -1), (0, -1, -1),
                   (-1, 0, 0), (0, -1, 0), (0, 0, -1)]
        for source, dest, size in offsets:
            self.assertRaises(ValueError, m.move, source, dest, size)

        m.close()

        m = mmap.mmap(-1, 1) # single byte
        self.assertRaises(ValueError, m.move, 0, 0, 2)
        self.assertRaises(ValueError, m.move, 1, 0, 1)
        self.assertRaises(ValueError, m.move, 0, 1, 1)
        m.move(0, 0, 1)
        m.move(0, 0, 0)


    def test_anonymous(self):
        # anonymous mmap.mmap(-1, PAGE)
        m = mmap.mmap(-1, PAGESIZE)
        for x in xrange(PAGESIZE):
            self.assertEqual(m[x], '\0', "anonymously mmap'ed contents should be zero")

        for x in xrange(PAGESIZE):
            m[x] = ch = chr(x & 255)
            self.assertEqual(m[x], ch)

    def test_extended_getslice(self):
        # Test extended slicing by comparing with list slicing.
        s = "".join(chr(c) for c in reversed(range(256)))
        m = mmap.mmap(-1, len(s))
        m[:] = s
        self.assertEqual(m[:], s)
        indices = (0, None, 1, 3, 19, 300, -1, -2, -31, -300)
        for start in indices:
            for stop in indices:
                # Skip step 0 (invalid)
                for step in indices[1:]:
                    self.assertEqual(m[start:stop:step],
                                     s[start:stop:step])

    def test_extended_set_del_slice(self):
        # Test extended slicing by comparing with list slicing.
        s = "".join(chr(c) for c in reversed(range(256)))
        m = mmap.mmap(-1, len(s))
        indices = (0, None, 1, 3, 19, 300, -1, -2, -31, -300)
        for start in indices:
            for stop in indices:
                # Skip invalid step 0
                for step in indices[1:]:
                    m[:] = s
                    self.assertEqual(m[:], s)
                    L = list(s)
                    # Make sure we have a slice of exactly the right length,
                    # but with different data.
                    data = L[start:stop:step]
                    data = "".join(reversed(data))
                    L[start:stop:step] = data
                    m[start:stop:step] = data
                    self.assertEqual(m[:], "".join(L))

    def make_mmap_file (self, f, halfsize):
        # Write 2 pages worth of data to the file
        f.write ('\0' * halfsize)
        f.write ('foo')
        f.write ('\0' * (halfsize - 3))
        f.flush ()
        return mmap.mmap (f.fileno(), 0)

    def test_offset (self):
        f = open (TESTFN, 'w+b')

        try: # unlink TESTFN no matter what
            halfsize = mmap.ALLOCATIONGRANULARITY
            m = self.make_mmap_file (f, halfsize)
            m.close ()
            f.close ()

            mapsize = halfsize * 2
            # Try invalid offset
            f = open(TESTFN, "r+b")
            for offset in [-2, -1, None]:
                try:
                    m = mmap.mmap(f.fileno(), mapsize, offset=offset)
                    self.assertEqual(0, 1)
                except (ValueError, TypeError, OverflowError):
                    pass
                else:
                    self.assertEqual(0, 0)
            f.close()

            # Try valid offset, hopefully 8192 works on all OSes
            f = open(TESTFN, "r+b")
            m = mmap.mmap(f.fileno(), mapsize - halfsize, offset=halfsize)
            self.assertEqual(m[0:3], 'foo')
            f.close()

            # Try resizing map
            try:
                m.resize(512)
            except SystemError:
                pass
            else:
                # resize() is supported
                self.assertEqual(len(m), 512)
                # Check that we can no longer seek beyond the new size.
                self.assertRaises(ValueError, m.seek, 513, 0)
                # Check that the content is not changed
                self.assertEqual(m[0:3], 'foo')

                # Check that the underlying file is truncated too
                f = open(TESTFN)
                f.seek(0, 2)
                self.assertEqual(f.tell(), halfsize + 512)
                f.close()
                self.assertEqual(m.size(), halfsize + 512)

            m.close()

        finally:
            f.close()
            try:
                os.unlink(TESTFN)
            except OSError:
                pass

    def test_subclass(self):
        class anon_mmap(mmap.mmap):
            def __new__(klass, *args, **kwargs):
                return mmap.mmap.__new__(klass, -1, *args, **kwargs)
        anon_mmap(PAGESIZE)

    def test_prot_readonly(self):
        if not hasattr(mmap, 'PROT_READ'):
            return
        mapsize = 10
        with open(TESTFN, "wb") as f:
            f.write("a"*mapsize)
        f = open(TESTFN, "rb")
        m = mmap.mmap(f.fileno(), mapsize, prot=mmap.PROT_READ)
        self.assertRaises(TypeError, m.write, "foo")
        f.close()

    def test_error(self):
        self.assertTrue(issubclass(mmap.error, EnvironmentError))
        self.assertIn("mmap.error", str(mmap.error))

    def test_io_methods(self):
        data = "0123456789"
        with open(TESTFN, "wb") as f:
            f.write("x"*len(data))
        f = open(TESTFN, "r+b")
        m = mmap.mmap(f.fileno(), len(data))
        f.close()
        # Test write_byte()
        for i in xrange(len(data)):
            self.assertEqual(m.tell(), i)
            m.write_byte(data[i])
            self.assertEqual(m.tell(), i+1)
        self.assertRaises(ValueError, m.write_byte, "x")
        self.assertEqual(m[:], data)
        # Test read_byte()
        m.seek(0)
        for i in xrange(len(data)):
            self.assertEqual(m.tell(), i)
            self.assertEqual(m.read_byte(), data[i])
            self.assertEqual(m.tell(), i+1)
        self.assertRaises(ValueError, m.read_byte)
        # Test read()
        m.seek(3)
        self.assertEqual(m.read(3), "345")
        self.assertEqual(m.tell(), 6)
        # Test write()
        m.seek(3)
        m.write("bar")
        self.assertEqual(m.tell(), 6)
        self.assertEqual(m[:], "012bar6789")
        m.seek(8)
        self.assertRaises(ValueError, m.write, "bar")
        m.close()

    if os.name == 'nt':
        def test_tagname(self):
            data1 = "0123456789"
            data2 = "abcdefghij"
            assert len(data1) == len(data2)

            # Test same tag
            m1 = mmap.mmap(-1, len(data1), tagname="foo")
            m1[:] = data1
            m2 = mmap.mmap(-1, len(data2), tagname="foo")
            m2[:] = data2
            self.assertEqual(m1[:], data2)
            self.assertEqual(m2[:], data2)
            m2.close()
            m1.close()

            # Test different tag
            m1 = mmap.mmap(-1, len(data1), tagname="foo")
            m1[:] = data1
            m2 = mmap.mmap(-1, len(data2), tagname="boo")
            m2[:] = data2
            self.assertEqual(m1[:], data1)
            self.assertEqual(m2[:], data2)
            m2.close()
            m1.close()

        def test_crasher_on_windows(self):
            # Should not crash (Issue 1733986)
            m = mmap.mmap(-1, 1000, tagname="foo")
            try:
                mmap.mmap(-1, 5000, tagname="foo")[:] # same tagname, but larger size
            except:
                pass
            m.close()

            # Should not crash (Issue 5385)
            with open(TESTFN, "wb") as f:
                f.write("x"*10)
            f = open(TESTFN, "r+b")
            m = mmap.mmap(f.fileno(), 0)
            f.close()
            try:
                m.resize(0) # will raise WindowsError
            except:
                pass
            try:
                m[:]
            except:
                pass
            m.close()

        def test_invalid_descriptor(self):
            # socket file descriptors are valid, but out of range
            # for _get_osfhandle, causing a crash when validating the
            # parameters to _get_osfhandle.
            s = socket.socket()
            try:
                with self.assertRaises(mmap.error):
                    m = mmap.mmap(s.fileno(), 10)
            finally:
                s.close()


class LargeMmapTests(unittest.TestCase):

    def setUp(self):
        unlink(TESTFN)

    def tearDown(self):
        unlink(TESTFN)

    def _make_test_file(self, num_zeroes, tail):
        if sys.platform[:3] == 'win' or sys.platform == 'darwin':
            requires('largefile',
                'test requires %s bytes and a long time to run' % str(0x180000000))
        f = open(TESTFN, 'w+b')
        try:
            f.seek(num_zeroes)
            f.write(tail)
            f.flush()
        except (IOError, OverflowError):
            f.close()
            raise unittest.SkipTest("filesystem does not have largefile support")
        return f

    def test_large_offset(self):
        with self._make_test_file(0x14FFFFFFF, b" ") as f:
            m = mmap.mmap(f.fileno(), 0, offset=0x140000000, access=mmap.ACCESS_READ)
            try:
                self.assertEqual(m[0xFFFFFFF], b" ")
            finally:
                m.close()

    def test_large_filesize(self):
        with self._make_test_file(0x17FFFFFFF, b" ") as f:
            m = mmap.mmap(f.fileno(), 0x10000, access=mmap.ACCESS_READ)
            try:
                self.assertEqual(m.size(), 0x180000000)
            finally:
                m.close()

    # Issue 11277: mmap() with large (~4GB) sparse files crashes on OS X.

    def _test_around_boundary(self, boundary):
        tail = b'  DEARdear  '
        start = boundary - len(tail) // 2
        end = start + len(tail)
        with self._make_test_file(start, tail) as f:
            m = mmap.mmap(f.fileno(), 0, access=mmap.ACCESS_READ)
            try:
                self.assertEqual(m[start:end], tail)
            finally:
                m.close()

    @unittest.skipUnless(sys.maxsize > _4G, "test cannot run on 32-bit systems")
    def test_around_2GB(self):
        self._test_around_boundary(_2G)

    @unittest.skipUnless(sys.maxsize > _4G, "test cannot run on 32-bit systems")
    def test_around_4GB(self):
        self._test_around_boundary(_4G)


def test_main():
    run_unittest(MmapTests, LargeMmapTests)

if __name__ == '__main__':
    test_main()