summaryrefslogtreecommitdiffstats
path: root/Modules/_io/bytesio.c
blob: a1ba121e2622ff8d2f85f8f3a56ca9a55f907b15 (plain)
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
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
#include "Python.h"
#include "structmember.h"       /* for offsetof() */
#include "_iomodule.h"

/*[clinic input]
module _io
class _io.BytesIO "bytesio *" "&PyBytesIO_Type"
[clinic start generated code]*/
/*[clinic end generated code: output=da39a3ee5e6b4b0d input=7f50ec034f5c0b26]*/

typedef struct {
    PyObject_HEAD
    PyObject *buf;
    Py_ssize_t pos;
    Py_ssize_t string_size;
    PyObject *dict;
    PyObject *weakreflist;
    Py_ssize_t exports;
} bytesio;

typedef struct {
    PyObject_HEAD
    bytesio *source;
} bytesiobuf;

/* The bytesio object can be in three states:
  * Py_REFCNT(buf) == 1, exports == 0.
  * Py_REFCNT(buf) > 1.  exports == 0,
    first modification or export causes the internal buffer copying.
  * exports > 0.  Py_REFCNT(buf) == 1, any modifications are forbidden.
*/

#define CHECK_CLOSED(self)                                  \
    if ((self)->buf == NULL) {                              \
        PyErr_SetString(PyExc_ValueError,                   \
                        "I/O operation on closed file.");   \
        return NULL;                                        \
    }

#define CHECK_EXPORTS(self) \
    if ((self)->exports > 0) { \
        PyErr_SetString(PyExc_BufferError, \
                        "Existing exports of data: object cannot be re-sized"); \
        return NULL; \
    }

#define SHARED_BUF(self) (Py_REFCNT((self)->buf) > 1)


/* Internal routine to get a line from the buffer of a BytesIO
   object. Returns the length between the current position to the
   next newline character. */
static Py_ssize_t
scan_eol(bytesio *self, Py_ssize_t len)
{
    const char *start, *n;
    Py_ssize_t maxlen;

    assert(self->buf != NULL);
    assert(self->pos >= 0);

    if (self->pos >= self->string_size)
        return 0;

    /* Move to the end of the line, up to the end of the string, s. */
    maxlen = self->string_size - self->pos;
    if (len < 0 || len > maxlen)
        len = maxlen;

    if (len) {
        start = PyBytes_AS_STRING(self->buf) + self->pos;
        n = memchr(start, '\n', len);
        if (n)
            /* Get the length from the current position to the end of
               the line. */
            len = n - start + 1;
    }
    assert(len >= 0);
    assert(self->pos < PY_SSIZE_T_MAX - len);

    return len;
}

/* Internal routine for detaching the shared buffer of BytesIO objects.
   The caller should ensure that the 'size' argument is non-negative and
   not lesser than self->string_size.  Returns 0 on success, -1 otherwise. */
static int
unshare_buffer(bytesio *self, size_t size)
{
    PyObject *new_buf;
    assert(SHARED_BUF(self));
    assert(self->exports == 0);
    assert(size >= (size_t)self->string_size);
    new_buf = PyBytes_FromStringAndSize(NULL, size);
    if (new_buf == NULL)
        return -1;
    memcpy(PyBytes_AS_STRING(new_buf), PyBytes_AS_STRING(self->buf),
           self->string_size);
    Py_SETREF(self->buf, new_buf);
    return 0;
}

/* Internal routine for changing the size of the buffer of BytesIO objects.
   The caller should ensure that the 'size' argument is non-negative.  Returns
   0 on success, -1 otherwise. */
static int
resize_buffer(bytesio *self, size_t size)
{
    /* Here, unsigned types are used to avoid dealing with signed integer
       overflow, which is undefined in C. */
    size_t alloc = PyBytes_GET_SIZE(self->buf);

    assert(self->buf != NULL);

    /* For simplicity, stay in the range of the signed type. Anyway, Python
       doesn't allow strings to be longer than this. */
    if (size > PY_SSIZE_T_MAX)
        goto overflow;

    if (size < alloc / 2) {
        /* Major downsize; resize down to exact size. */
        alloc = size + 1;
    }
    else if (size < alloc) {
        /* Within allocated size; quick exit */
        return 0;
    }
    else if (size <= alloc * 1.125) {
        /* Moderate upsize; overallocate similar to list_resize() */
        alloc = size + (size >> 3) + (size < 9 ? 3 : 6);
    }
    else {
        /* Major upsize; resize up to exact size */
        alloc = size + 1;
    }

    if (alloc > ((size_t)-1) / sizeof(char))
        goto overflow;

    if (SHARED_BUF(self)) {
        if (unshare_buffer(self, alloc) < 0)
            return -1;
    }
    else {
        if (_PyBytes_Resize(&self->buf, alloc) < 0)
            return -1;
    }

    return 0;

  overflow:
    PyErr_SetString(PyExc_OverflowError,
                    "new buffer size too large");
    return -1;
}

/* Internal routine for writing a string of bytes to the buffer of a BytesIO
   object. Returns the number of bytes written, or -1 on error. */
static Py_ssize_t
write_bytes(bytesio *self, const char *bytes, Py_ssize_t len)
{
    size_t endpos;
    assert(self->buf != NULL);
    assert(self->pos >= 0);
    assert(len >= 0);

    endpos = (size_t)self->pos + len;
    if (endpos > (size_t)PyBytes_GET_SIZE(self->buf)) {
        if (resize_buffer(self, endpos) < 0)
            return -1;
    }
    else if (SHARED_BUF(self)) {
        if (unshare_buffer(self, Py_MAX(endpos, (size_t)self->string_size)) < 0)
            return -1;
    }

    if (self->pos > self->string_size) {
        /* In case of overseek, pad with null bytes the buffer region between
           the end of stream and the current position.

          0   lo      string_size                           hi
          |   |<---used--->|<----------available----------->|
          |   |            <--to pad-->|<---to write--->    |
          0   buf                   position
        */
        memset(PyBytes_AS_STRING(self->buf) + self->string_size, '\0',
               (self->pos - self->string_size) * sizeof(char));
    }

    /* Copy the data to the internal buffer, overwriting some of the existing
       data if self->pos < self->string_size. */
    memcpy(PyBytes_AS_STRING(self->buf) + self->pos, bytes, len);
    self->pos = endpos;

    /* Set the new length of the internal string if it has changed. */
    if ((size_t)self->string_size < endpos) {
        self->string_size = endpos;
    }

    return len;
}

static PyObject *
bytesio_get_closed(bytesio *self)
{
    if (self->buf == NULL) {
        Py_RETURN_TRUE;
    }
    else {
        Py_RETURN_FALSE;
    }
}

/*[clinic input]
_io.BytesIO.readable

Returns True if the IO object can be read.
[clinic start generated code]*/

static PyObject *
_io_BytesIO_readable_impl(bytesio *self)
/*[clinic end generated code: output=4e93822ad5b62263 input=96c5d0cccfb29f5c]*/
{
    CHECK_CLOSED(self);
    Py_RETURN_TRUE;
}

/*[clinic input]
_io.BytesIO.writable

Returns True if the IO object can be written.
[clinic start generated code]*/

static PyObject *
_io_BytesIO_writable_impl(bytesio *self)
/*[clinic end generated code: output=64ff6a254b1150b8 input=700eed808277560a]*/
{
    CHECK_CLOSED(self);
    Py_RETURN_TRUE;
}

/*[clinic input]
_io.BytesIO.seekable

Returns True if the IO object can be seeked.
[clinic start generated code]*/

static PyObject *
_io_BytesIO_seekable_impl(bytesio *self)
/*[clinic end generated code: output=6b417f46dcc09b56 input=9421f65627a344dd]*/
{
    CHECK_CLOSED(self);
    Py_RETURN_TRUE;
}

/*[clinic input]
_io.BytesIO.flush

Does nothing.
[clinic start generated code]*/

static PyObject *
_io_BytesIO_flush_impl(bytesio *self)
/*[clinic end generated code: output=187e3d781ca134a0 input=561ea490be4581a7]*/
{
    CHECK_CLOSED(self);
    Py_RETURN_NONE;
}

/*[clinic input]
_io.BytesIO.getbuffer

Get a read-write view over the contents of the BytesIO object.
[clinic start generated code]*/

static PyObject *
_io_BytesIO_getbuffer_impl(bytesio *self)
/*[clinic end generated code: output=72cd7c6e13aa09ed input=8f738ef615865176]*/
{
    PyTypeObject *type = &_PyBytesIOBuffer_Type;
    bytesiobuf *buf;
    PyObject *view;

    CHECK_CLOSED(self);

    buf = (bytesiobuf *) type->tp_alloc(type, 0);
    if (buf == NULL)
        return NULL;
    Py_INCREF(self);
    buf->source = self;
    view = PyMemoryView_FromObject((PyObject *) buf);
    Py_DECREF(buf);
    return view;
}

/*[clinic input]
_io.BytesIO.getvalue

Retrieve the entire contents of the BytesIO object.
[clinic start generated code]*/

static PyObject *
_io_BytesIO_getvalue_impl(bytesio *self)
/*[clinic end generated code: output=b3f6a3233c8fd628 input=4b403ac0af3973ed]*/
{
    CHECK_CLOSED(self);
    if (self->string_size <= 1 || self->exports > 0)
        return PyBytes_FromStringAndSize(PyBytes_AS_STRING(self->buf),
                                         self->string_size);

    if (self->string_size != PyBytes_GET_SIZE(self->buf)) {
        if (SHARED_BUF(self)) {
            if (unshare_buffer(self, self->string_size) < 0)
                return NULL;
        }
        else {
            if (_PyBytes_Resize(&self->buf, self->string_size) < 0)
                return NULL;
        }
    }
    Py_INCREF(self->buf);
    return self->buf;
}

/*[clinic input]
_io.BytesIO.isatty

Always returns False.

BytesIO objects are not connected to a TTY-like device.
[clinic start generated code]*/

static PyObject *
_io_BytesIO_isatty_impl(bytesio *self)
/*[clinic end generated code: output=df67712e669f6c8f input=6f97f0985d13f827]*/
{
    CHECK_CLOSED(self);
    Py_RETURN_FALSE;
}

/*[clinic input]
_io.BytesIO.tell

Current file position, an integer.
[clinic start generated code]*/

static PyObject *
_io_BytesIO_tell_impl(bytesio *self)
/*[clinic end generated code: output=b54b0f93cd0e5e1d input=b106adf099cb3657]*/
{
    CHECK_CLOSED(self);
    return PyLong_FromSsize_t(self->pos);
}

static PyObject *
read_bytes(bytesio *self, Py_ssize_t size)
{
    char *output;

    assert(self->buf != NULL);
    assert(size <= self->string_size);
    if (size > 1 &&
        self->pos == 0 && size == PyBytes_GET_SIZE(self->buf) &&
        self->exports == 0) {
        self->pos += size;
        Py_INCREF(self->buf);
        return self->buf;
    }

    output = PyBytes_AS_STRING(self->buf) + self->pos;
    self->pos += size;
    return PyBytes_FromStringAndSize(output, size);
}

/*[clinic input]
_io.BytesIO.read
    size as arg: object = None
    /

Read at most size bytes, returned as a bytes object.

If the size argument is negative, read until EOF is reached.
Return an empty bytes object at EOF.
[clinic start generated code]*/

static PyObject *
_io_BytesIO_read_impl(bytesio *self, PyObject *arg)
/*[clinic end generated code: output=85dacb535c1e1781 input=cc7ba4a797bb1555]*/
{
    Py_ssize_t size, n;

    CHECK_CLOSED(self);

    if (PyLong_Check(arg)) {
        size = PyLong_AsSsize_t(arg);
        if (size == -1 && PyErr_Occurred())
            return NULL;
    }
    else if (arg == Py_None) {
        /* Read until EOF is reached, by default. */
        size = -1;
    }
    else {
        PyErr_Format(PyExc_TypeError, "integer argument expected, got '%s'",
                     Py_TYPE(arg)->tp_name);
        return NULL;
    }

    /* adjust invalid sizes */
    n = self->string_size - self->pos;
    if (size < 0 || size > n) {
        size = n;
        if (size < 0)
            size = 0;
    }

    return read_bytes(self, size);
}


/*[clinic input]
_io.BytesIO.read1
    size: object
    /

Read at most size bytes, returned as a bytes object.

If the size argument is negative or omitted, read until EOF is reached.
Return an empty bytes object at EOF.
[clinic start generated code]*/

static PyObject *
_io_BytesIO_read1(bytesio *self, PyObject *size)
/*[clinic end generated code: output=16021f5d0ac3d4e2 input=d4f40bb8f2f99418]*/
{
    return _io_BytesIO_read_impl(self, size);
}

/*[clinic input]
_io.BytesIO.readline
    size as arg: object = None
    /

Next line from the file, as a bytes object.

Retain newline.  A non-negative size argument limits the maximum
number of bytes to return (an incomplete line may be returned then).
Return an empty bytes object at EOF.
[clinic start generated code]*/

static PyObject *
_io_BytesIO_readline_impl(bytesio *self, PyObject *arg)
/*[clinic end generated code: output=1c2115534a4f9276 input=ca31f06de6eab257]*/
{
    Py_ssize_t size, n;

    CHECK_CLOSED(self);

    if (PyLong_Check(arg)) {
        size = PyLong_AsSsize_t(arg);
        if (size == -1 && PyErr_Occurred())
            return NULL;
    }
    else if (arg == Py_None) {
        /* No size limit, by default. */
        size = -1;
    }
    else {
        PyErr_Format(PyExc_TypeError, "integer argument expected, got '%s'",
                     Py_TYPE(arg)->tp_name);
        return NULL;
    }

    n = scan_eol(self, size);

    return read_bytes(self, n);
}

/*[clinic input]
_io.BytesIO.readlines
    size as arg: object = None
    /

List of bytes objects, each a line from the file.

Call readline() repeatedly and return a list of the lines so read.
The optional size argument, if given, is an approximate bound on the
total number of bytes in the lines returned.
[clinic start generated code]*/

static PyObject *
_io_BytesIO_readlines_impl(bytesio *self, PyObject *arg)
/*[clinic end generated code: output=09b8e34c880808ff input=691aa1314f2c2a87]*/
{
    Py_ssize_t maxsize, size, n;
    PyObject *result, *line;
    char *output;

    CHECK_CLOSED(self);

    if (PyLong_Check(arg)) {
        maxsize = PyLong_AsSsize_t(arg);
        if (maxsize == -1 && PyErr_Occurred())
            return NULL;
    }
    else if (arg == Py_None) {
        /* No size limit, by default. */
        maxsize = -1;
    }
    else {
        PyErr_Format(PyExc_TypeError, "integer argument expected, got '%s'",
                     Py_TYPE(arg)->tp_name);
        return NULL;
    }

    size = 0;
    result = PyList_New(0);
    if (!result)
        return NULL;

    output = PyBytes_AS_STRING(self->buf) + self->pos;
    while ((n = scan_eol(self, -1)) != 0) {
        self->pos += n;
        line = PyBytes_FromStringAndSize(output, n);
        if (!line)
            goto on_error;
        if (PyList_Append(result, line) == -1) {
            Py_DECREF(line);
            goto on_error;
        }
        Py_DECREF(line);
        size += n;
        if (maxsize > 0 && size >= maxsize)
            break;
        output += n;
    }
    return result;

  on_error:
    Py_DECREF(result);
    return NULL;
}

/*[clinic input]
_io.BytesIO.readinto
    buffer: Py_buffer(accept={rwbuffer})
    /

Read bytes into buffer.

Returns number of bytes read (0 for EOF), or None if the object
is set not to block and has no data to read.
[clinic start generated code]*/

static PyObject *
_io_BytesIO_readinto_impl(bytesio *self, Py_buffer *buffer)
/*[clinic end generated code: output=a5d407217dcf0639 input=1424d0fdce857919]*/
{
    Py_ssize_t len, n;

    CHECK_CLOSED(self);

    /* adjust invalid sizes */
    len = buffer->len;
    n = self->string_size - self->pos;
    if (len > n) {
        len = n;
        if (len < 0)
            len = 0;
    }

    memcpy(buffer->buf, PyBytes_AS_STRING(self->buf) + self->pos, len);
    assert(self->pos + len < PY_SSIZE_T_MAX);
    assert(len >= 0);
    self->pos += len;

    return PyLong_FromSsize_t(len);
}

/*[clinic input]
_io.BytesIO.truncate
    size as arg: object = None
    /

Truncate the file to at most size bytes.

Size defaults to the current file position, as returned by tell().
The current file position is unchanged.  Returns the new size.
[clinic start generated code]*/

static PyObject *
_io_BytesIO_truncate_impl(bytesio *self, PyObject *arg)
/*[clinic end generated code: output=81e6be60e67ddd66 input=11ed1966835462ba]*/
{
    Py_ssize_t size;

    CHECK_CLOSED(self);
    CHECK_EXPORTS(self);

    if (PyLong_Check(arg)) {
        size = PyLong_AsSsize_t(arg);
        if (size == -1 && PyErr_Occurred())
            return NULL;
    }
    else if (arg == Py_None) {
        /* Truncate to current position if no argument is passed. */
        size = self->pos;
    }
    else {
        PyErr_Format(PyExc_TypeError, "integer argument expected, got '%s'",
                     Py_TYPE(arg)->tp_name);
        return NULL;
    }

    if (size < 0) {
        PyErr_Format(PyExc_ValueError,
                     "negative size value %zd", size);
        return NULL;
    }

    if (size < self->string_size) {
        self->string_size = size;
        if (resize_buffer(self, size) < 0)
            return NULL;
    }

    return PyLong_FromSsize_t(size);
}

static PyObject *
bytesio_iternext(bytesio *self)
{
    Py_ssize_t n;

    CHECK_CLOSED(self);

    n = scan_eol(self, -1);

    if (n == 0)
        return NULL;

    return read_bytes(self, n);
}

/*[clinic input]
_io.BytesIO.seek
    pos: Py_ssize_t
    whence: int = 0
    /

Change stream position.

Seek to byte offset pos relative to position indicated by whence:
     0  Start of stream (the default).  pos should be >= 0;
     1  Current position - pos may be negative;
     2  End of stream - pos usually negative.
Returns the new absolute position.
[clinic start generated code]*/

static PyObject *
_io_BytesIO_seek_impl(bytesio *self, Py_ssize_t pos, int whence)
/*[clinic end generated code: output=c26204a68e9190e4 input=1e875e6ebc652948]*/
{
    CHECK_CLOSED(self);

    if (pos < 0 && whence == 0) {
        PyErr_Format(PyExc_ValueError,
                     "negative seek value %zd", pos);
        return NULL;
    }

    /* whence = 0: offset relative to beginning of the string.
       whence = 1: offset relative to current position.
       whence = 2: offset relative the end of the string. */
    if (whence == 1) {
        if (pos > PY_SSIZE_T_MAX - self->pos) {
            PyErr_SetString(PyExc_OverflowError,
                            "new position too large");
            return NULL;
        }
        pos += self->pos;
    }
    else if (whence == 2) {
        if (pos > PY_SSIZE_T_MAX - self->string_size) {
            PyErr_SetString(PyExc_OverflowError,
                            "new position too large");
            return NULL;
        }
        pos += self->string_size;
    }
    else if (whence != 0) {
        PyErr_Format(PyExc_ValueError,
                     "invalid whence (%i, should be 0, 1 or 2)", whence);
        return NULL;
    }

    if (pos < 0)
        pos = 0;
    self->pos = pos;

    return PyLong_FromSsize_t(self->pos);
}

/*[clinic input]
_io.BytesIO.write
    b: object
    /

Write bytes to file.

Return the number of bytes written.
[clinic start generated code]*/

static PyObject *
_io_BytesIO_write(bytesio *self, PyObject *b)
/*[clinic end generated code: output=53316d99800a0b95 input=f5ec7c8c64ed720a]*/
{
    Py_ssize_t n = 0;
    Py_buffer buf;

    CHECK_CLOSED(self);
    CHECK_EXPORTS(self);

    if (PyObject_GetBuffer(b, &buf, PyBUF_CONTIG_RO) < 0)
        return NULL;

    if (buf.len != 0)
        n = write_bytes(self, buf.buf, buf.len);

    PyBuffer_Release(&buf);
    return n >= 0 ? PyLong_FromSsize_t(n) : NULL;
}

/*[clinic input]
_io.BytesIO.writelines
    lines: object
    /

Write lines to the file.

Note that newlines are not added.  lines can be any iterable object
producing bytes-like objects. This is equivalent to calling write() for
each element.
[clinic start generated code]*/

static PyObject *
_io_BytesIO_writelines(bytesio *self, PyObject *lines)
/*[clinic end generated code: output=7f33aa3271c91752 input=e972539176fc8fc1]*/
{
    PyObject *it, *item;
    PyObject *ret;

    CHECK_CLOSED(self);

    it = PyObject_GetIter(lines);
    if (it == NULL)
        return NULL;

    while ((item = PyIter_Next(it)) != NULL) {
        ret = _io_BytesIO_write(self, item);
        Py_DECREF(item);
        if (ret == NULL) {
            Py_DECREF(it);
            return NULL;
        }
        Py_DECREF(ret);
    }
    Py_DECREF(it);

    /* See if PyIter_Next failed */
    if (PyErr_Occurred())
        return NULL;

    Py_RETURN_NONE;
}

/*[clinic input]
_io.BytesIO.close

Disable all I/O operations.
[clinic start generated code]*/

static PyObject *
_io_BytesIO_close_impl(bytesio *self)
/*[clinic end generated code: output=1471bb9411af84a0 input=37e1f55556e61f60]*/
{
    CHECK_EXPORTS(self);
    Py_CLEAR(self->buf);
    Py_RETURN_NONE;
}

/* Pickling support.

   Note that only pickle protocol 2 and onward are supported since we use
   extended __reduce__ API of PEP 307 to make BytesIO instances picklable.

   Providing support for protocol < 2 would require the __reduce_ex__ method
   which is notably long-winded when defined properly.

   For BytesIO, the implementation would similar to one coded for
   object.__reduce_ex__, but slightly less general. To be more specific, we
   could call bytesio_getstate directly and avoid checking for the presence of
   a fallback __reduce__ method. However, we would still need a __newobj__
   function to use the efficient instance representation of PEP 307.
 */

static PyObject *
bytesio_getstate(bytesio *self)
{
    PyObject *initvalue = _io_BytesIO_getvalue_impl(self);
    PyObject *dict;
    PyObject *state;

    if (initvalue == NULL)
        return NULL;
    if (self->dict == NULL) {
        Py_INCREF(Py_None);
        dict = Py_None;
    }
    else {
        dict = PyDict_Copy(self->dict);
        if (dict == NULL) {
            Py_DECREF(initvalue);
            return NULL;
        }
    }

    state = Py_BuildValue("(OnN)", initvalue, self->pos, dict);
    Py_DECREF(initvalue);
    return state;
}

static PyObject *
bytesio_setstate(bytesio *self, PyObject *state)
{
    PyObject *result;
    PyObject *position_obj;
    PyObject *dict;
    Py_ssize_t pos;

    assert(state != NULL);

    /* We allow the state tuple to be longer than 3, because we may need
       someday to extend the object's state without breaking
       backward-compatibility. */
    if (!PyTuple_Check(state) || Py_SIZE(state) < 3) {
        PyErr_Format(PyExc_TypeError,
                     "%.200s.__setstate__ argument should be 3-tuple, got %.200s",
                     Py_TYPE(self)->tp_name, Py_TYPE(state)->tp_name);
        return NULL;
    }
    CHECK_EXPORTS(self);
    /* Reset the object to its default state. This is only needed to handle
       the case of repeated calls to __setstate__. */
    self->string_size = 0;
    self->pos = 0;

    /* Set the value of the internal buffer. If state[0] does not support the
       buffer protocol, bytesio_write will raise the appropriate TypeError. */
    result = _io_BytesIO_write(self, PyTuple_GET_ITEM(state, 0));
    if (result == NULL)
        return NULL;
    Py_DECREF(result);

    /* Set carefully the position value. Alternatively, we could use the seek
       method instead of modifying self->pos directly to better protect the
       object internal state against errneous (or malicious) inputs. */
    position_obj = PyTuple_GET_ITEM(state, 1);
    if (!PyLong_Check(position_obj)) {
        PyErr_Format(PyExc_TypeError,
                     "second item of state must be an integer, not %.200s",
                     Py_TYPE(position_obj)->tp_name);
        return NULL;
    }
    pos = PyLong_AsSsize_t(position_obj);
    if (pos == -1 && PyErr_Occurred())
        return NULL;
    if (pos < 0) {
        PyErr_SetString(PyExc_ValueError,
                        "position value cannot be negative");
        return NULL;
    }
    self->pos = pos;

    /* Set the dictionary of the instance variables. */
    dict = PyTuple_GET_ITEM(state, 2);
    if (dict != Py_None) {
        if (!PyDict_Check(dict)) {
            PyErr_Format(PyExc_TypeError,
                         "third item of state should be a dict, got a %.200s",
                         Py_TYPE(dict)->tp_name);
            return NULL;
        }
        if (self->dict) {
            /* Alternatively, we could replace the internal dictionary
               completely. However, it seems more practical to just update it. */
            if (PyDict_Update(self->dict, dict) < 0)
                return NULL;
        }
        else {
            Py_INCREF(dict);
            self->dict = dict;
        }
    }

    Py_RETURN_NONE;
}

static void
bytesio_dealloc(bytesio *self)
{
    _PyObject_GC_UNTRACK(self);
    if (self->exports > 0) {
        PyErr_SetString(PyExc_SystemError,
                        "deallocated BytesIO object has exported buffers");
        PyErr_Print();
    }
    Py_CLEAR(self->buf);
    Py_CLEAR(self->dict);
    if (self->weakreflist != NULL)
        PyObject_ClearWeakRefs((PyObject *) self);
    Py_TYPE(self)->tp_free(self);
}

static PyObject *
bytesio_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
{
    bytesio *self;

    assert(type != NULL && type->tp_alloc != NULL);
    self = (bytesio *)type->tp_alloc(type, 0);
    if (self == NULL)
        return NULL;

    /* tp_alloc initializes all the fields to zero. So we don't have to
       initialize them here. */

    self->buf = PyBytes_FromStringAndSize(NULL, 0);
    if (self->buf == NULL) {
        Py_DECREF(self);
        return PyErr_NoMemory();
    }

    return (PyObject *)self;
}

/*[clinic input]
_io.BytesIO.__init__
    initial_bytes as initvalue: object(c_default="NULL") = b''

Buffered I/O implementation using an in-memory bytes buffer.
[clinic start generated code]*/

static int
_io_BytesIO___init___impl(bytesio *self, PyObject *initvalue)
/*[clinic end generated code: output=65c0c51e24c5b621 input=aac7f31b67bf0fb6]*/
{
    /* In case, __init__ is called multiple times. */
    self->string_size = 0;
    self->pos = 0;

    if (self->exports > 0) {
        PyErr_SetString(PyExc_BufferError,
                        "Existing exports of data: object cannot be re-sized");
        return -1;
    }
    if (initvalue && initvalue != Py_None) {
        if (PyBytes_CheckExact(initvalue)) {
            Py_INCREF(initvalue);
            Py_XSETREF(self->buf, initvalue);
            self->string_size = PyBytes_GET_SIZE(initvalue);
        }
        else {
            PyObject *res;
            res = _io_BytesIO_write(self, initvalue);
            if (res == NULL)
                return -1;
            Py_DECREF(res);
            self->pos = 0;
        }
    }

    return 0;
}

static PyObject *
bytesio_sizeof(bytesio *self, void *unused)
{
    Py_ssize_t res;

    res = _PyObject_SIZE(Py_TYPE(self));
    if (self->buf && !SHARED_BUF(self))
        res += _PySys_GetSizeOf(self->buf);
    return PyLong_FromSsize_t(res);
}

static int
bytesio_traverse(bytesio *self, visitproc visit, void *arg)
{
    Py_VISIT(self->dict);
    return 0;
}

static int
bytesio_clear(bytesio *self)
{
    Py_CLEAR(self->dict);
    return 0;
}


#include "clinic/bytesio.c.h"

static PyGetSetDef bytesio_getsetlist[] = {
    {"closed",  (getter)bytesio_get_closed, NULL,
     "True if the file is closed."},
    {NULL},            /* sentinel */
};

static struct PyMethodDef bytesio_methods[] = {
    _IO_BYTESIO_READABLE_METHODDEF
    _IO_BYTESIO_SEEKABLE_METHODDEF
    _IO_BYTESIO_WRITABLE_METHODDEF
    _IO_BYTESIO_CLOSE_METHODDEF
    _IO_BYTESIO_FLUSH_METHODDEF
    _IO_BYTESIO_ISATTY_METHODDEF
    _IO_BYTESIO_TELL_METHODDEF
    _IO_BYTESIO_WRITE_METHODDEF
    _IO_BYTESIO_WRITELINES_METHODDEF
    _IO_BYTESIO_READ1_METHODDEF
    _IO_BYTESIO_READINTO_METHODDEF
    _IO_BYTESIO_READLINE_METHODDEF
    _IO_BYTESIO_READLINES_METHODDEF
    _IO_BYTESIO_READ_METHODDEF
    _IO_BYTESIO_GETBUFFER_METHODDEF
    _IO_BYTESIO_GETVALUE_METHODDEF
    _IO_BYTESIO_SEEK_METHODDEF
    _IO_BYTESIO_TRUNCATE_METHODDEF
    {"__getstate__",  (PyCFunction)bytesio_getstate,  METH_NOARGS, NULL},
    {"__setstate__",  (PyCFunction)bytesio_setstate,  METH_O, NULL},
    {"__sizeof__", (PyCFunction)bytesio_sizeof,     METH_NOARGS, NULL},
    {NULL, NULL}        /* sentinel */
};

PyTypeObject PyBytesIO_Type = {
    PyVarObject_HEAD_INIT(NULL, 0)
    "_io.BytesIO",                             /*tp_name*/
    sizeof(bytesio),                     /*tp_basicsize*/
    0,                                         /*tp_itemsize*/
    (destructor)bytesio_dealloc,               /*tp_dealloc*/
    0,                                         /*tp_print*/
    0,                                         /*tp_getattr*/
    0,                                         /*tp_setattr*/
    0,                                         /*tp_reserved*/
    0,                                         /*tp_repr*/
    0,                                         /*tp_as_number*/
    0,                                         /*tp_as_sequence*/
    0,                                         /*tp_as_mapping*/
    0,                                         /*tp_hash*/
    0,                                         /*tp_call*/
    0,                                         /*tp_str*/
    0,                                         /*tp_getattro*/
    0,                                         /*tp_setattro*/
    0,                                         /*tp_as_buffer*/
    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE |
    Py_TPFLAGS_HAVE_GC,                        /*tp_flags*/
    _io_BytesIO___init____doc__,               /*tp_doc*/
    (traverseproc)bytesio_traverse,            /*tp_traverse*/
    (inquiry)bytesio_clear,                    /*tp_clear*/
    0,                                         /*tp_richcompare*/
    offsetof(bytesio, weakreflist),      /*tp_weaklistoffset*/
    PyObject_SelfIter,                         /*tp_iter*/
    (iternextfunc)bytesio_iternext,            /*tp_iternext*/
    bytesio_methods,                           /*tp_methods*/
    0,                                         /*tp_members*/
    bytesio_getsetlist,                        /*tp_getset*/
    0,                                         /*tp_base*/
    0,                                         /*tp_dict*/
    0,                                         /*tp_descr_get*/
    0,                                         /*tp_descr_set*/
    offsetof(bytesio, dict),             /*tp_dictoffset*/
    _io_BytesIO___init__,                      /*tp_init*/
    0,                                         /*tp_alloc*/
    bytesio_new,                               /*tp_new*/
};


/*
 * Implementation of the small intermediate object used by getbuffer().
 * getbuffer() returns a memoryview over this object, which should make it
 * invisible from Python code.
 */

static int
bytesiobuf_getbuffer(bytesiobuf *obj, Py_buffer *view, int flags)
{
    bytesio *b = (bytesio *) obj->source;

    if (view == NULL) {
        PyErr_SetString(PyExc_BufferError,
            "bytesiobuf_getbuffer: view==NULL argument is obsolete");
        return -1;
    }
    if (SHARED_BUF(b)) {
        if (unshare_buffer(b, b->string_size) < 0)
            return -1;
    }

    /* cannot fail if view != NULL and readonly == 0 */
    (void)PyBuffer_FillInfo(view, (PyObject*)obj,
                            PyBytes_AS_STRING(b->buf), b->string_size,
                            0, flags);
    b->exports++;
    return 0;
}

static void
bytesiobuf_releasebuffer(bytesiobuf *obj, Py_buffer *view)
{
    bytesio *b = (bytesio *) obj->source;
    b->exports--;
}

static int
bytesiobuf_traverse(bytesiobuf *self, visitproc visit, void *arg)
{
    Py_VISIT(self->source);
    return 0;
}

static void
bytesiobuf_dealloc(bytesiobuf *self)
{
    Py_CLEAR(self->source);
    Py_TYPE(self)->tp_free(self);
}

static PyBufferProcs bytesiobuf_as_buffer = {
    (getbufferproc) bytesiobuf_getbuffer,
    (releasebufferproc) bytesiobuf_releasebuffer,
};

PyTypeObject _PyBytesIOBuffer_Type = {
    PyVarObject_HEAD_INIT(NULL, 0)
    "_io._BytesIOBuffer",                      /*tp_name*/
    sizeof(bytesiobuf),                        /*tp_basicsize*/
    0,                                         /*tp_itemsize*/
    (destructor)bytesiobuf_dealloc,            /*tp_dealloc*/
    0,                                         /*tp_print*/
    0,                                         /*tp_getattr*/
    0,                                         /*tp_setattr*/
    0,                                         /*tp_reserved*/
    0,                                         /*tp_repr*/
    0,                                         /*tp_as_number*/
    0,                                         /*tp_as_sequence*/
    0,                                         /*tp_as_mapping*/
    0,                                         /*tp_hash*/
    0,                                         /*tp_call*/
    0,                                         /*tp_str*/
    0,                                         /*tp_getattro*/
    0,                                         /*tp_setattro*/
    &bytesiobuf_as_buffer,                     /*tp_as_buffer*/
    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC,   /*tp_flags*/
    0,                                         /*tp_doc*/
    (traverseproc)bytesiobuf_traverse,         /*tp_traverse*/
    0,                                         /*tp_clear*/
    0,                                         /*tp_richcompare*/
    0,                                         /*tp_weaklistoffset*/
    0,                                         /*tp_iter*/
    0,                                         /*tp_iternext*/
    0,                                         /*tp_methods*/
    0,                                         /*tp_members*/
    0,                                         /*tp_getset*/
    0,                                         /*tp_base*/
    0,                                         /*tp_dict*/
    0,                                         /*tp_descr_get*/
    0,                                         /*tp_descr_set*/
    0,                                         /*tp_dictoffset*/
    0,                                         /*tp_init*/
    0,                                         /*tp_alloc*/
    0,                                         /*tp_new*/
};