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QBitArray Class Reference

\inmodule QtCore More...

#include <qbitarray.h>

Collaboration diagram for QBitArray:

Public Types

typedef QByteArray::DataPointer DataPtr

Public Member Functions

 QBitArray () noexcept
 Constructs an empty bit array.
 QBitArray (qsizetype size, bool val=false)
 Constructs a bit array containing size bits.
void swap (QBitArray &other) noexcept
qsizetype size () const
 Returns the number of bits stored in the bit array.
qsizetype count () const
 Same as size().
qsizetype count (bool on) const
 If on is true, this function returns the number of 1-bits stored in the bit array; otherwise the number of 0-bits is returned.
bool isEmpty () const
 Returns true if this bit array has size 0; otherwise returns false.
bool isNull () const
 Returns true if this bit array is null; otherwise returns false.
void resize (qsizetype size)
 Resizes the bit array to size bits.
void detach ()
bool isDetached () const
void clear ()
 Clears the contents of the bit array and makes it empty.
bool testBit (qsizetype i) const
 Returns true if the bit at index position i is 1; otherwise returns false.
void setBit (qsizetype i)
 Sets the bit at index position i to 1.
void setBit (qsizetype i, bool val)
 This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Sets the bit at index position i to value.
void clearBit (qsizetype i)
 Sets the bit at index position i to 0.
bool toggleBit (qsizetype i)
 Inverts the value of the bit at index position i, returning the previous value of that bit as either true (if it was set) or false (if it was unset).
bool at (qsizetype i) const
 Returns the value of the bit at index position i.
QBitRef operator[] (qsizetype i)
 Returns the bit at index position i as a modifiable reference.
bool operator[] (qsizetype i) const
 This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.
QBitArrayoperator&= (QBitArray &&)
 Performs the AND operation between all bits in this bit array and other.
QBitArrayoperator|= (QBitArray &&)
 Performs the OR operation between all bits in this bit array and other.
QBitArrayoperator^= (QBitArray &&)
 Performs the XOR operation between all bits in this bit array and other.
QBitArrayoperator&= (const QBitArray &)
QBitArrayoperator|= (const QBitArray &)
QBitArrayoperator^= (const QBitArray &)
bool fill (bool aval, qsizetype asize=-1)
 Sets every bit in the bit array to value, returning true if successful; otherwise returns false.
void fill (bool val, qsizetype first, qsizetype last)
 This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Sets bits at index positions begin up to (but not including) end to value.
void truncate (qsizetype pos)
 Truncates the bit array at index position pos.
const char * bits () const
quint32 toUInt32 (QSysInfo::Endian endianness, bool *ok=nullptr) const noexcept
DataPtrdata_ptr ()
const DataPtrdata_ptr () const

Static Public Member Functions

static QBitArray fromBits (const char *data, qsizetype len)

Friends

Q_CORE_EXPORT friend QBitArray operator& (const QBitArray &a1, const QBitArray &a2)
QBitArray operator& (QBitArray &&a1, const QBitArray &a2)
QBitArray operator& (const QBitArray &a1, QBitArray &&a2)
QBitArray operator& (QBitArray &&a1, QBitArray &&a2)
 Returns a bit array that is the AND of the bit arrays a1 and a2.
Q_CORE_EXPORT friend QBitArray operator| (const QBitArray &a1, const QBitArray &a2)
QBitArray operator| (QBitArray &&a1, const QBitArray &a2)
QBitArray operator| (const QBitArray &a1, QBitArray &&a2)
QBitArray operator| (QBitArray &&a1, QBitArray &&a2)
 Returns a bit array that is the OR of the bit arrays a1 and a2.
Q_CORE_EXPORT friend QBitArray operator^ (const QBitArray &a1, const QBitArray &a2)
QBitArray operator^ (QBitArray &&a1, const QBitArray &a2)
QBitArray operator^ (const QBitArray &a1, QBitArray &&a2)
QBitArray operator^ (QBitArray &&a1, QBitArray &&a2)
 Returns a bit array that is the XOR of the bit arrays a1 and a2.
Q_CORE_EXPORT QDataStreamoperator<< (QDataStream &, const QBitArray &)
 Writes bit array ba to stream out.
Q_CORE_EXPORT QDataStreamoperator>> (QDataStream &, QBitArray &)
 Reads a bit array into ba from stream in.
Q_CORE_EXPORT size_t qHash (const QBitArray &key, size_t seed=0)
QBitArray operator~ (QBitArray a)
 Returns a bit array that contains the inverted bits of the bit array a.
bool comparesEqual (const QBitArray &lhs, const QBitArray &rhs) noexcept

Detailed Description

\inmodule QtCore

The QBitArray class provides an array of bits.

\reentrant

\compares equality

A QBitArray is an array that gives access to individual bits and provides operators (\l{operator&()}{AND}, \l{operator|()}{OR}, \l{operator^()}{XOR}, and \l{operator~()}{NOT}) 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):

To initialize the bits to true, either pass 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:

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

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

x.setBit(3, true);
// x: [ 0, 0, 0, 1, 0 ]
y.setBit(4, true);
// y: [ 0, 0, 0, 0, 1 ]
x |= y;
// x: [ 0, 0, 0, 1, 1 ]

For historical reasons, QBitArray distinguishes between a null bit array and an empty bit array. A null bit array is a bit array that is initialized using QBitArray's default constructor. An 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:

QBitArray().isNull(); // returns true
QBitArray().isEmpty(); // returns true
QBitArray(0).isNull(); // returns false
QBitArray(0).isEmpty(); // returns true
QBitArray(3).isNull(); // returns false
QBitArray(3).isEmpty(); // returns false

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().

See also
QByteArray, QList

Definition at line 13 of file qbitarray.h.

Member Typedef Documentation

◆ DataPtr

Definition at line 137 of file qbitarray.h.

Constructor & Destructor Documentation

◆ QBitArray() [1/2]

QBitArray::QBitArray ( )
inlinenoexcept

Constructs an empty bit array.

See also
isEmpty()

Definition at line 65 of file qbitarray.h.

◆ QBitArray() [2/2]

QBitArray::QBitArray ( qsizetype size,
bool value = false )
explicit

Constructs a bit array containing size bits.

The bits are initialized with value, which defaults to false (0).

Definition at line 140 of file qbitarray.cpp.

Member Function Documentation

◆ at()

bool QBitArray::at ( qsizetype i) const
inline

Returns the value of the bit at index position i.

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

See also
operator[]()

Definition at line 106 of file qbitarray.h.

◆ bits()

const char * QBitArray::bits ( ) const
inline
Since
5.11

Returns a pointer to a dense bit array for this QBitArray. Bits are counted upwards from the least significant bit in each byte. The number of bits relevant in the last byte is given by {size() % 8}.

See also
fromBits(), size()

Definition at line 131 of file qbitarray.h.

◆ clear()

void QBitArray::clear ( )
inline

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

See also
resize(), isEmpty()

Definition at line 88 of file qbitarray.h.

◆ clearBit()

void QBitArray::clearBit ( qsizetype i)
inline

Sets the bit at index position i to 0.

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

See also
setBit(), toggleBit()

Definition at line 96 of file qbitarray.h.

◆ count() [1/2]

qsizetype QBitArray::count ( ) const
inline

Same as size().

Definition at line 78 of file qbitarray.h.

◆ count() [2/2]

qsizetype QBitArray::count ( bool on) const

If on is true, this function returns the number of 1-bits stored in the bit array; otherwise the number of 0-bits is returned.

Definition at line 167 of file qbitarray.cpp.

◆ data_ptr() [1/2]

DataPtr & QBitArray::data_ptr ( )
inline

Definition at line 138 of file qbitarray.h.

◆ data_ptr() [2/2]

const DataPtr & QBitArray::data_ptr ( ) const
inline

Definition at line 139 of file qbitarray.h.

◆ detach()

void QBitArray::detach ( )
inline

Definition at line 86 of file qbitarray.h.

◆ fill() [1/2]

bool QBitArray::fill ( bool value,
qsizetype size = -1 )
inline

Sets every bit in the bit array to value, returning true if successful; otherwise returns false.

If size is different from -1 (the default), the bit array is resized to size beforehand.

Example:

QBitArray ba(8);
ba.fill(true);
// ba: [ 1, 1, 1, 1, 1, 1, 1, 1 ]
ba.fill(false, 2);
// ba: [ 0, 0 ]
See also
resize()

Definition at line 125 of file qbitarray.h.

◆ fill() [2/2]

void QBitArray::fill ( bool value,
qsizetype begin,
qsizetype end )

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Sets bits at index positions begin up to (but not including) end to value.

begin must be a valid index position in the bit array (0 <= begin < size()).

end must be either a valid index position or equal to size(), in which case the fill operation runs until the end of the array (0 <= end <= size()).

Example:

QBitArray ba(4);
ba.fill(true, 1, 2); // ba: [ 0, 1, 0, 0 ]
ba.fill(true, 1, 3); // ba: [ 0, 1, 1, 0 ]
ba.fill(true, 1, 4); // ba: [ 0, 1, 1, 1 ]

Definition at line 272 of file qbitarray.cpp.

◆ fromBits()

QBitArray QBitArray::fromBits ( const char * data,
qsizetype size )
static
Since
5.11

Creates a QBitArray with the dense bit array located at data, with size bits. The byte array at data must be at least size / 8 (rounded up) bytes long.

If size is not a multiple of 8, this function will include the lowest size % 8 bits from the last byte in data.

See also
bits()

Definition at line 310 of file qbitarray.cpp.

◆ isDetached()

bool QBitArray::isDetached ( ) const
inline

Definition at line 87 of file qbitarray.h.

◆ isEmpty()

bool QBitArray::isEmpty ( ) const
inline

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

See also
size()

Definition at line 81 of file qbitarray.h.

◆ isNull()

bool QBitArray::isNull ( ) const
inline

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

Example:

QBitArray().isNull(); // returns true
QBitArray(0).isNull(); // returns false
QBitArray(3).isNull(); // returns false

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().

See also
isEmpty()

Definition at line 82 of file qbitarray.h.

◆ operator&=() [1/2]

QBitArray & QBitArray::operator&= ( const QBitArray & other)

Definition at line 666 of file qbitarray.cpp.

◆ operator&=() [2/2]

QBitArray & QBitArray::operator&= ( QBitArray && other)

Performs the AND operation between all bits in this bit array and 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:

a[0] = 1; a[1] = 0; a[2] = 1; // a: [ 1, 0, 1 ]
b[0] = 1; b[1] = 1; // b: [ 1, 1 ]
a &= b; // a: [ 1, 0, 0 ]
See also
operator&(), operator|=(), operator^=(), operator~()

Definition at line 661 of file qbitarray.cpp.

◆ operator[]() [1/2]

QBitRef QBitArray::operator[] ( qsizetype i)
inline

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

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

Example:

a[0] = false;
a[1] = true;
a[2] = a[0] ^ a[1];

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.

See also
at(), testBit(), setBit(), clearBit()

Definition at line 164 of file qbitarray.h.

◆ operator[]() [2/2]

bool QBitArray::operator[] ( qsizetype i) const
inline

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

Definition at line 108 of file qbitarray.h.

◆ operator^=() [1/2]

QBitArray & QBitArray::operator^= ( const QBitArray & other)

Definition at line 722 of file qbitarray.cpp.

◆ operator^=() [2/2]

QBitArray & QBitArray::operator^= ( QBitArray && other)

Performs the XOR operation between all bits in this bit array and 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:

a[0] = 1; a[1] = 0; a[2] = 1; // a: [ 1, 0, 1 ]
b[0] = 1; b[1] = 1; // b: [ 1, 1 ]
a ^= b; // a: [ 0, 1, 1 ]
See also
operator^(), operator&=(), operator|=(), operator~()

Definition at line 717 of file qbitarray.cpp.

◆ operator|=() [1/2]

QBitArray & QBitArray::operator|= ( const QBitArray & other)

Definition at line 694 of file qbitarray.cpp.

◆ operator|=() [2/2]

QBitArray & QBitArray::operator|= ( QBitArray && other)

Performs the OR operation between all bits in this bit array and 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:

a[0] = 1; a[1] = 0; a[2] = 1; // a: [ 1, 0, 1 ]
b[0] = 1; b[1] = 1; // b: [ 1, 1 ]
a |= b; // a: [ 1, 1, 1 ]
See also
operator|(), operator&=(), operator^=(), operator~()

Definition at line 689 of file qbitarray.cpp.

◆ resize()

void QBitArray::resize ( qsizetype size)

Resizes the bit array to size bits.

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

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

See also
size()

Definition at line 209 of file qbitarray.cpp.

◆ setBit() [1/2]

void QBitArray::setBit ( qsizetype i)
inline

Sets the bit at index position i to 1.

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

See also
clearBit(), toggleBit()

Definition at line 92 of file qbitarray.h.

◆ setBit() [2/2]

void QBitArray::setBit ( qsizetype i,
bool val )
inline

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.Sets the bit at index position i to value.

Definition at line 94 of file qbitarray.h.

◆ size()

qsizetype QBitArray::size ( ) const
inline

Returns the number of bits stored in the bit array.

See also
resize()

Definition at line 77 of file qbitarray.h.

◆ swap()

void QBitArray::swap ( QBitArray & other)
inlinenoexcept
Since
4.8 \memberswap{bit array}

Definition at line 75 of file qbitarray.h.

◆ testBit()

bool QBitArray::testBit ( qsizetype i) const
inline

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

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

See also
setBit(), clearBit()

Definition at line 90 of file qbitarray.h.

◆ toggleBit()

bool QBitArray::toggleBit ( qsizetype i)
inline

Inverts the value of the bit at index position 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.

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

See also
setBit(), clearBit()

Definition at line 98 of file qbitarray.h.

◆ toUInt32()

quint32 QBitArray::toUInt32 ( QSysInfo::Endian endianness,
bool * ok = nullptr ) const
noexcept
Since
6.0

Returns the array of bit converted to an int. The conversion is based on endianness. Converts up to the first 32 bits of the array to quint32 and returns it, obeying endianness. If ok is not a null pointer, and the array has more than 32 bits, ok is set to false and this function returns zero; otherwise, it's set to true.

Definition at line 333 of file qbitarray.cpp.

◆ truncate()

void QBitArray::truncate ( qsizetype pos)
inline

Truncates the bit array at index position pos.

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

See also
resize()

Definition at line 129 of file qbitarray.h.

◆ comparesEqual

bool comparesEqual ( const QBitArray & lhs,
const QBitArray & rhs )
friend

Definition at line 142 of file qbitarray.h.

◆ operator& [1/4]

Q_CORE_EXPORT friend QBitArray operator& ( const QBitArray & a1,
const QBitArray & a2 )
friend

Definition at line 788 of file qbitarray.cpp.

◆ operator& [2/4]

QBitArray operator& ( const QBitArray & a1,
QBitArray && a2 )
friend

Definition at line 18 of file qbitarray.h.

◆ operator& [3/4]

QBitArray operator& ( QBitArray && a1,
const QBitArray & a2 )
friend

Definition at line 16 of file qbitarray.h.

◆ operator& [4/4]

QBitArray operator& ( QBitArray && a1,
QBitArray && a2 )
friend

Returns a bit array that is the AND of the bit arrays a1 and 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:

a[0] = 1; a[1] = 0; a[2] = 1; // a: [ 1, 0, 1 ]
b[0] = 1; b[1] = 1; // b: [ 1, 1 ]
c = a & b; // c: [ 1, 0, 0 ]
See also
{QBitArray::}{operator&=()}, {QBitArray::}{operator|()}, {QBitArray::}{operator^()}

Definition at line 20 of file qbitarray.h.

◆ operator<<

QDataStream & operator<< ( QDataStream & out,
const QBitArray & ba )
friend

Writes bit array ba to stream out.

See also
{Serializing Qt Data Types}{Format of the QDataStream operators}

Definition at line 901 of file qbitarray.cpp.

◆ operator>>

QDataStream & operator>> ( QDataStream & in,
QBitArray & ba )
friend

Reads a bit array into ba from stream in.

See also
{Serializing Qt Data Types}{Format of the QDataStream operators}

Definition at line 926 of file qbitarray.cpp.

◆ operator^ [1/4]

Q_CORE_EXPORT friend QBitArray operator^ ( const QBitArray & a1,
const QBitArray & a2 )
friend

Definition at line 840 of file qbitarray.cpp.

◆ operator^ [2/4]

QBitArray operator^ ( const QBitArray & a1,
QBitArray && a2 )
friend

Definition at line 34 of file qbitarray.h.

◆ operator^ [3/4]

QBitArray operator^ ( QBitArray && a1,
const QBitArray & a2 )
friend

Definition at line 32 of file qbitarray.h.

◆ operator^ [4/4]

QBitArray operator^ ( QBitArray && a1,
QBitArray && a2 )
friend

Returns a bit array that is the XOR of the bit arrays a1 and 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:

a[0] = 1; a[1] = 0; a[2] = 1; // a: [ 1, 0, 1 ]
b[0] = 1; b[1] = 1; // b: [ 1, 1 ]
c = a ^ b; // c: [ 0, 1, 1 ]
See also
{QBitArray}{operator^=()}, {QBitArray}{operator&()}, {QBitArray}{operator|()}

Definition at line 36 of file qbitarray.h.

◆ operator| [1/4]

Q_CORE_EXPORT friend QBitArray operator| ( const QBitArray & a1,
const QBitArray & a2 )
friend

Definition at line 814 of file qbitarray.cpp.

◆ operator| [2/4]

QBitArray operator| ( const QBitArray & a1,
QBitArray && a2 )
friend

Definition at line 26 of file qbitarray.h.

◆ operator| [3/4]

QBitArray operator| ( QBitArray && a1,
const QBitArray & a2 )
friend

Definition at line 24 of file qbitarray.h.

◆ operator| [4/4]

QBitArray operator| ( QBitArray && a1,
QBitArray && a2 )
friend

Returns a bit array that is the OR of the bit arrays a1 and 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:

a[0] = 1; a[1] = 0; a[2] = 1; // a: [ 1, 0, 1 ]
b[0] = 1; b[1] = 1; // b: [ 1, 1 ]
c = a | b; // c: [ 1, 1, 1 ]
See also
QBitArray::operator|=(), operator&(), operator^()

Definition at line 28 of file qbitarray.h.

◆ operator~

QBitArray operator~ ( QBitArray a)
friend

Returns a bit array that contains the inverted bits of the bit array a.

Example:

a[0] = 1; a[1] = 0; a[2] = 1; // a: [ 1, 0, 1 ]
b = ~a; // b: [ 0, 1, 0 ]
See also
operator&(), operator|(), operator^()

Definition at line 44 of file qbitarray.h.

◆ qHash

Q_CORE_EXPORT size_t qHash ( const QBitArray & key,
size_t seed = 0 )
friend

Definition at line 887 of file qhash.cpp.


The documentation for this class was generated from the following files: