summaryrefslogtreecommitdiffstats
path: root/src/corelib/tools/qbitarray.cpp
blob: 6181c825804b7dc226a3cecd50fadb7a877f77b8 (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
/****************************************************************************
**
** Copyright (C) 2011 Nokia Corporation and/or its subsidiary(-ies).
** All rights reserved.
** Contact: Nokia Corporation (qt-info@nokia.com)
**
** This file is part of the QtCore module of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL$
** No Commercial Usage
** This file contains pre-release code and may not be distributed.
** You may use this file in accordance with the terms and conditions
** contained in the Technology Preview License Agreement accompanying
** this package.
**
** GNU Lesser General Public License Usage
** Alternatively, this file may be used under the terms of the GNU Lesser
** General Public License version 2.1 as published by the Free Software
** Foundation and appearing in the file LICENSE.LGPL included in the
** packaging of this file.  Please review the following information to
** ensure the GNU Lesser General Public License version 2.1 requirements
** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
**
** In addition, as a special exception, Nokia gives you certain additional
** rights.  These rights are described in the Nokia Qt LGPL Exception
** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
**
** If you have questions regarding the use of this file, please contact
** Nokia at qt-info@nokia.com.
**
**
**
**
**
**
**
**
** $QT_END_LICENSE$
**
****************************************************************************/

#include "qbitarray.h"
#include <qdatastream.h>
#include <qdebug.h>
#include <string.h>

QT_BEGIN_NAMESPACE

/*!
    \class QBitArray
    \brief The QBitArray class provides an array of bits.

    \ingroup tools
    \ingroup shared
    \reentrant

    A QBitArray is an array that gives access to individual bits and
    provides operators (\link operator&() AND\endlink, \link
    operator|() OR\endlink, \link operator^() XOR\endlink, and \link
    operator~() NOT\endlink) that work on entire arrays of bits. It
    uses \l{implicit sharing} (copy-on-write) to reduce memory usage
    and to avoid the needless copying of data.

    The following code constructs a QBitArray containing 200 bits
    initialized to false (0):

    \snippet doc/src/snippets/code/src_corelib_tools_qbitarray.cpp 0

    To initialize the bits to true, either pass \c true as second
    argument to the constructor, or call fill() later on.

    QBitArray uses 0-based indexes, just like C++ arrays. To access
    the bit at a particular index position, you can use operator[]().
    On non-const bit arrays, operator[]() returns a reference to a
    bit that can be used on the left side of an assignment. For
    example:

    \snippet doc/src/snippets/code/src_corelib_tools_qbitarray.cpp 1

    For technical reasons, it is more efficient to use testBit() and
    setBit() to access bits in the array than operator[](). For
    example:

    \snippet doc/src/snippets/code/src_corelib_tools_qbitarray.cpp 2

    QBitArray supports \c{&} (\link operator&() AND\endlink), \c{|}
    (\link operator|() OR\endlink), \c{^} (\link operator^()
    XOR\endlink), \c{~} (\link operator~() NOT\endlink), as well as
    \c{&=}, \c{|=}, and \c{^=}. These operators work in the same way
    as the built-in C++ bitwise operators of the same name. For
    example:

    \snippet doc/src/snippets/code/src_corelib_tools_qbitarray.cpp 3

    For historical reasons, QBitArray distinguishes between a null
    bit array and an empty bit array. A \e null bit array is a bit
    array that is initialized using QBitArray's default constructor.
    An \e empty bit array is any bit array with size 0. A null bit
    array is always empty, but an empty bit array isn't necessarily
    null:

    \snippet doc/src/snippets/code/src_corelib_tools_qbitarray.cpp 4

    All functions except isNull() treat null bit arrays the same as
    empty bit arrays; for example, QBitArray() compares equal to
    QBitArray(0). We recommend that you always use isEmpty() and
    avoid isNull().

    \sa QByteArray, QVector
*/

/*! \fn QBitArray::QBitArray()

    Constructs an empty bit array.

    \sa isEmpty()
*/

/*!
    Constructs a bit array containing \a size bits. The bits are
    initialized with \a value, which defaults to false (0).
*/
QBitArray::QBitArray(int size, bool value)
{
    if (!size) {
        d.resize(0);
        return;
    }
    d.resize(1 + (size+7)/8);
    uchar* c = reinterpret_cast<uchar*>(d.data());
    memset(c, value ? 0xff : 0, d.size());
    *c = d.size()*8 - size;
    if (value && size && size % 8)
        *(c+1+size/8) &= (1 << (size%8)) - 1;
}

/*! \fn int QBitArray::size() const

    Returns the number of bits stored in the bit array.

    \sa resize()
*/

/*! \fn int QBitArray::count() const

    Same as size().
*/

/*!
    If \a on is true, this function returns the number of
    1-bits stored in the bit array; otherwise the number
    of 0-bits is returned.
*/
int QBitArray::count(bool on) const
{
    int numBits = 0;
    int len = size();
#if 0
    for (int i = 0; i < len; ++i)
        numBits += testBit(i);
#else
    // See http://graphics.stanford.edu/~seander/bithacks.html#CountBitsSetParallel
    const quint8 *bits = reinterpret_cast<const quint8 *>(d.data()) + 1;
    while (len >= 32) {
        quint32 v = quint32(bits[0]) | (quint32(bits[1]) << 8) | (quint32(bits[2]) << 16) | (quint32(bits[3]) << 24);
        quint32 c = ((v & 0xfff) * Q_UINT64_C(0x1001001001001) & Q_UINT64_C(0x84210842108421)) % 0x1f;
        c += (((v & 0xfff000) >> 12) * Q_UINT64_C(0x1001001001001) & Q_UINT64_C(0x84210842108421)) % 0x1f;
        c += ((v >> 24) * Q_UINT64_C(0x1001001001001) & Q_UINT64_C(0x84210842108421)) % 0x1f;
        len -= 32;
        bits += 4;
        numBits += int(c);
    }
    while (len >= 24) {
        quint32 v = quint32(bits[0]) | (quint32(bits[1]) << 8) | (quint32(bits[2]) << 16);
        quint32 c =  ((v & 0xfff) * Q_UINT64_C(0x1001001001001) & Q_UINT64_C(0x84210842108421)) % 0x1f;
        c += (((v & 0xfff000) >> 12) * Q_UINT64_C(0x1001001001001) & Q_UINT64_C(0x84210842108421)) % 0x1f;    
        len -= 24;
        bits += 3;
        numBits += int(c);
    }
    while (len >= 0) {
        if (bits[len / 8] & (1 << ((len - 1) & 7)))
            ++numBits;
        --len;
    }
#endif
    return on ? numBits : size() - numBits;
}

/*!
    Resizes the bit array to \a size bits.

    If \a size is greater than the current size, the bit array is
    extended to make it \a size bits with the extra bits added to the
    end. The new bits are initialized to false (0).

    If \a size is less than the current size, bits are removed from
    the end.

    \sa size()
*/
void QBitArray::resize(int size)
{
    if (!size) {
        d.resize(0);
    } else {
        int s = d.size();
        d.resize(1 + (size+7)/8);
        uchar* c = reinterpret_cast<uchar*>(d.data());
        if (size > (s << 3))
            memset(c + s, 0, d.size() - s);
        else if ( size % 8)
            *(c+1+size/8) &= (1 << (size%8)) - 1;
        *c = d.size()*8 - size;
    }
}

/*! \fn bool QBitArray::isEmpty() const

    Returns true if this bit array has size 0; otherwise returns
    false.

    \sa size()
*/

/*! \fn bool QBitArray::isNull() const

    Returns true if this bit array is null; otherwise returns false.

    Example:
    \snippet doc/src/snippets/code/src_corelib_tools_qbitarray.cpp 5

    Qt makes a distinction between null bit arrays and empty bit
    arrays for historical reasons. For most applications, what
    matters is whether or not a bit array contains any data,
    and this can be determined using isEmpty().

    \sa isEmpty()
*/

/*! \fn bool QBitArray::fill(bool value, int size = -1)

    Sets every bit in the bit array to \a value, returning true if successful;
    otherwise returns false. If \a size is different from -1 (the default),
    the bit array is resized to \a size beforehand.

    Example:
    \snippet doc/src/snippets/code/src_corelib_tools_qbitarray.cpp 6

    \sa resize()
*/

/*!
    \overload

    Sets bits at index positions \a begin up to and excluding \a end
    to \a value.

    \a begin and \a end must be a valid index position in the bit
    array (i.e., 0 <= \a begin <= size() and 0 <= \a end <= size()).
*/

void QBitArray::fill(bool value, int begin, int end)
{
    while (begin < end && begin & 0x7)
        setBit(begin++, value);
    int len = end - begin;
    if (len <= 0)
        return;
    int s = len & ~0x7;
    uchar *c = reinterpret_cast<uchar*>(d.data());
    memset(c + (begin >> 3) + 1, value ? 0xff : 0, s >> 3);
    begin += s;
    while (begin < end)
        setBit(begin++, value);
}

/*! \fn bool QBitArray::isDetached() const

    \internal
*/

/*! \fn void QBitArray::detach()

    \internal
*/

/*! \fn void QBitArray::clear()

    Clears the contents of the bit array and makes it empty.

    \sa resize(), isEmpty()
*/

/*! \fn void QBitArray::truncate(int pos)

    Truncates the bit array at index position \a pos.

    If \a pos is beyond the end of the array, nothing happens.

    \sa resize()
*/

/*! \fn bool QBitArray::toggleBit(int i)

    Inverts the value of the bit at index position \a i, returning the
    previous value of that bit as either true (if it was set) or false (if
    it was unset).

    If the previous value was 0, the new value will be 1. If the
    previous value was 1, the new value will be 0.

    \a i must be a valid index position in the bit array (i.e., 0 <=
    \a i < size()).

    \sa setBit(), clearBit()
*/

/*! \fn bool QBitArray::testBit(int i) const

    Returns true if the bit at index position \a i is 1; otherwise
    returns false.

    \a i must be a valid index position in the bit array (i.e., 0 <=
    \a i < size()).

    \sa setBit(), clearBit()
*/

/*! \fn bool QBitArray::setBit(int i)

    Sets the bit at index position \a i to 1.

    \a i must be a valid index position in the bit array (i.e., 0 <=
    \a i < size()).

    \sa clearBit(), toggleBit()
*/

/*! \fn void QBitArray::setBit(int i, bool value)

    \overload

    Sets the bit at index position \a i to \a value.
*/

/*! \fn void QBitArray::clearBit(int i)

    Sets the bit at index position \a i to 0.

    \a i must be a valid index position in the bit array (i.e., 0 <=
    \a i < size()).

    \sa setBit(), toggleBit()
*/

/*! \fn bool QBitArray::at(int i) const

    Returns the value of the bit at index position \a i.

    \a i must be a valid index position in the bit array (i.e., 0 <=
    \a i < size()).

    \sa operator[]()
*/

/*! \fn QBitRef QBitArray::operator[](int i)

    Returns the bit at index position \a i as a modifiable reference.

    \a i must be a valid index position in the bit array (i.e., 0 <=
    \a i < size()).

    Example:
    \snippet doc/src/snippets/code/src_corelib_tools_qbitarray.cpp 7

    The return value is of type QBitRef, a helper class for QBitArray.
    When you get an object of type QBitRef, you can assign to
    it, and the assignment will apply to the bit in the QBitArray
    from which you got the reference.

    The functions testBit(), setBit(), and clearBit() are slightly
    faster.

    \sa at(), testBit(), setBit(), clearBit()
*/

/*! \fn bool QBitArray::operator[](int i) const

    \overload
*/

/*! \fn bool QBitArray::operator[](uint i)

    \overload
*/

/*! \fn bool QBitArray::operator[](uint i) const

    \overload
*/

/*! \fn QBitArray::QBitArray(const QBitArray &other)

    Constructs a copy of \a other.

    This operation takes \l{constant time}, because QBitArray is
    \l{implicitly shared}. This makes returning a QBitArray from a
    function very fast. If a shared instance is modified, it will be
    copied (copy-on-write), and that takes \l{linear time}.

    \sa operator=()
*/

/*! \fn QBitArray &QBitArray::operator=(const QBitArray &other)

    Assigns \a other to this bit array and returns a reference to
    this bit array.
*/

/*! \fn void QBitArray::swap(QBitArray &other)
    \since 4.8

    Swaps bit array \a other with this bit array. This operation is very
    fast and never fails.
*/

/*! \fn bool QBitArray::operator==(const QBitArray &other) const

    Returns true if \a other is equal to this bit array; otherwise
    returns false.

    \sa operator!=()
*/

/*! \fn bool QBitArray::operator!=(const QBitArray &other) const

    Returns true if \a other is not equal to this bit array;
    otherwise returns false.

    \sa operator==()
*/

/*!
    Performs the AND operation between all bits in this bit array and
    \a other. Assigns the result to this bit array, and returns a
    reference to it.

    The result has the length of the longest of the two bit arrays,
    with any missing bits (if one array is shorter than the other)
    taken to be 0.

    Example:
    \snippet doc/src/snippets/code/src_corelib_tools_qbitarray.cpp 8

    \sa operator&(), operator|=(), operator^=(), operator~()
*/

QBitArray &QBitArray::operator&=(const QBitArray &other)
{
    resize(qMax(size(), other.size()));
    uchar *a1 = reinterpret_cast<uchar*>(d.data()) + 1;
    const uchar *a2 = reinterpret_cast<const uchar*>(other.d.constData()) + 1;
    int n = other.d.size() -1 ; 
    int p = d.size() - 1 - n;
    while (n-- > 0)
        *a1++ &= *a2++;
    while (p-- > 0)
        *a1++ = 0;
    return *this;
}

/*!
    Performs the OR operation between all bits in this bit array and
    \a other. Assigns the result to this bit array, and returns a
    reference to it.

    The result has the length of the longest of the two bit arrays,
    with any missing bits (if one array is shorter than the other)
    taken to be 0.

    Example:
    \snippet doc/src/snippets/code/src_corelib_tools_qbitarray.cpp 9

    \sa operator|(), operator&=(), operator^=(), operator~()
*/

QBitArray &QBitArray::operator|=(const QBitArray &other)
{
    resize(qMax(size(), other.size()));
    uchar *a1 = reinterpret_cast<uchar*>(d.data()) + 1;
    const uchar *a2 = reinterpret_cast<const uchar *>(other.d.constData()) + 1;
    int n = other.d.size() - 1;   
    while (n-- > 0)
        *a1++ |= *a2++;
    return *this;
}

/*!
    Performs the XOR operation between all bits in this bit array and
    \a other. Assigns the result to this bit array, and returns a
    reference to it.

    The result has the length of the longest of the two bit arrays,
    with any missing bits (if one array is shorter than the other)
    taken to be 0.

    Example:
    \snippet doc/src/snippets/code/src_corelib_tools_qbitarray.cpp 10

    \sa operator^(), operator&=(), operator|=(), operator~()
*/

QBitArray &QBitArray::operator^=(const QBitArray &other)
{
    resize(qMax(size(), other.size()));
    uchar *a1 = reinterpret_cast<uchar*>(d.data()) + 1;
    const uchar *a2 = reinterpret_cast<const uchar *>(other.d.constData()) + 1;
    int n = other.d.size() - 1;
    while (n-- > 0)
        *a1++ ^= *a2++;
    return *this;
}

/*!
    Returns a bit array that contains the inverted bits of this bit
    array.

    Example:
    \snippet doc/src/snippets/code/src_corelib_tools_qbitarray.cpp 11

    \sa operator&(), operator|(), operator^()
*/

QBitArray QBitArray::operator~() const
{
    int sz = size();
    QBitArray a(sz);
    const uchar *a1 = reinterpret_cast<const uchar *>(d.constData()) + 1;
    uchar *a2 = reinterpret_cast<uchar*>(a.d.data()) + 1;
    int n = d.size() - 1;

    while (n-- > 0)
        *a2++ = ~*a1++;

    if (sz && sz%8)
        *(a2-1) &= (1 << (sz%8)) - 1;
    return a;
}

/*!
    \relates QBitArray

    Returns a bit array that is the AND of the bit arrays \a a1 and \a
    a2.

    The result has the length of the longest of the two bit arrays,
    with any missing bits (if one array is shorter than the other)
    taken to be 0.

    Example:
    \snippet doc/src/snippets/code/src_corelib_tools_qbitarray.cpp 12

    \sa QBitArray::operator&=(), operator|(), operator^()
*/

QBitArray operator&(const QBitArray &a1, const QBitArray &a2)
{
    QBitArray tmp = a1;
    tmp &= a2;
    return tmp;
}

/*!
    \relates QBitArray

    Returns a bit array that is the OR of the bit arrays \a a1 and \a
    a2.

    The result has the length of the longest of the two bit arrays,
    with any missing bits (if one array is shorter than the other)
    taken to be 0.

    Example:
    \snippet doc/src/snippets/code/src_corelib_tools_qbitarray.cpp 13

    \sa QBitArray::operator|=(), operator&(), operator^()
*/

QBitArray operator|(const QBitArray &a1, const QBitArray &a2)
{
    QBitArray tmp = a1;
    tmp |= a2;
    return tmp;
}

/*!
    \relates QBitArray

    Returns a bit array that is the XOR of the bit arrays \a a1 and \a
    a2.

    The result has the length of the longest of the two bit arrays,
    with any missing bits (if one array is shorter than the other)
    taken to be 0.

    Example:
    \snippet doc/src/snippets/code/src_corelib_tools_qbitarray.cpp 14

    \sa QBitArray::operator^=(), operator&(), operator|()
*/

QBitArray operator^(const QBitArray &a1, const QBitArray &a2)
{
    QBitArray tmp = a1;
    tmp ^= a2;
    return tmp;
}

/*!
    \class QBitRef
    \reentrant
    \brief The QBitRef class is an internal class, used with QBitArray.

    \internal

    The QBitRef is required by the indexing [] operator on bit arrays.
    It is not for use in any other context.
*/

/*! \fn QBitRef::QBitRef (QBitArray& a, int i)

    Constructs a reference to element \a i in the QBitArray \a a.
    This is what QBitArray::operator[] constructs its return value
    with.
*/

/*! \fn QBitRef::operator bool() const

    Returns the value referenced by the QBitRef.
*/

/*! \fn bool QBitRef::operator!() const

    \internal
*/

/*! \fn QBitRef& QBitRef::operator= (const QBitRef& v)

    Sets the value referenced by the QBitRef to that referenced by
    QBitRef \a v.
*/

/*! \fn QBitRef& QBitRef::operator= (bool v)
    \overload

    Sets the value referenced by the QBitRef to \a v.
*/


/*****************************************************************************
  QBitArray stream functions
 *****************************************************************************/

#ifndef QT_NO_DATASTREAM
/*!
    \relates QBitArray

    Writes bit array \a ba to stream \a out.

    \sa \link datastreamformat.html Format of the QDataStream operators \endlink
*/

QDataStream &operator<<(QDataStream &out, const QBitArray &ba)
{
    quint32 len = ba.size();
    out << len;
    if (len > 0)
        out.writeRawData(ba.d.constData() + 1, ba.d.size() - 1);
    return out;
}

/*!
    \relates QBitArray

    Reads a bit array into \a ba from stream \a in.

    \sa \link datastreamformat.html Format of the QDataStream operators \endlink
*/

QDataStream &operator>>(QDataStream &in, QBitArray &ba)
{
    ba.clear();
    quint32 len;
    in >> len;
    if (len == 0) {
	ba.clear();
	return in;
    }

    const quint32 Step = 8 * 1024 * 1024;
    quint32 totalBytes = (len + 7) / 8;
    quint32 allocated = 0;

    while (allocated < totalBytes) {
        int blockSize = qMin(Step, totalBytes - allocated);
        ba.d.resize(allocated + blockSize + 1);
        if (in.readRawData(ba.d.data() + 1 + allocated, blockSize) != blockSize) {
            ba.clear();
            in.setStatus(QDataStream::ReadPastEnd);
            return in;
        }
        allocated += blockSize;
    }

    int paddingMask = ~((0x1 << (len & 0x7)) - 1);
    if (paddingMask != ~0x0 && (ba.d.constData()[ba.d.size() - 1] & paddingMask)) {
        ba.clear();
        in.setStatus(QDataStream::ReadCorruptData);
        return in;
    }

    *ba.d.data() = ba.d.size() * 8 - len;
    return in;
}
#endif // QT_NO_DATASTREAM

/*!
    \fn DataPtr &QBitArray::data_ptr()
    \internal
*/

/*!
    \typedef QBitArray::DataPtr
    \internal
*/

QT_END_NAMESPACE