Detailed Description
The QBitArray class provides an array of bits.
Because QBitArray is a QMemArray, it uses explicit sharing with a reference count.
A QBitArray is a special byte array that can access individual
bits and perform bit-operations (AND, OR, XOR and NOT) on entire
arrays or bits.
Bits can be manipulated by the setBit() and clearBit() functions,
but it is also possible to use the indexing [] operator to test
and set individual bits. The [] operator is a little slower than
setBit() and clearBit() because some tricks are required to
implement single-bit assignments.
Example:
QBitArray a(3);
a.setBit( 0 );
a.clearBit( 1 );
a.setBit( 2 ); // a = [1 0 1]
QBitArray b(3);
b[0] = 1;
b[1] = 1;
b[2] = 0; // b = [1 1 0]
QBitArray c;
c = ~a & b; // c = [0 1 0]
When a QBitArray is constructed the bits are uninitialized. Use
fill() to set all the bits to 0 or 1. The array can be resized
with resize() and copied with copy(). Bits can be set with
setBit() and cleared with clearBit(). Bits can be toggled with
toggleBit(). A bit's value can be obtained with testBit() and with
at().
QBitArray supports the & (AND), | (OR), ^ (XOR) and ~ (NOT)
operators.
See also Collection Classes, Implicitly and Explicitly Shared Classes, and Non-GUI Classes.
Member Function Documentation
QBitArray::QBitArray ()
Constructs an empty bit array.
QBitArray::QBitArray ( uint size )
Constructs a bit array of size bits. The bits are uninitialized.
See also fill().
QBitArray::QBitArray ( const QBitArray & a )
Constructs a shallow copy of a.
bool QBitArray::at ( uint index ) const
Returns the value (0 or 1) of the bit at position index.
See also operator[]().
void QBitArray::clearBit ( uint index )
Clears the bit at position index, i.e. sets it to 0.
See also setBit() and toggleBit().
QBitArray QBitArray::copy () const
Returns a deep copy of the bit array.
See also detach().
void QBitArray::detach () [virtual]
Detaches from shared bit array data and makes sure that this bit
array is the only one referring to the data.
If multiple bit arrays share common data, this bit array
dereferences the data and gets a copy of the data. Nothing happens
if there is only a single reference.
See also copy().
Reimplemented from QMemArray.
bool QBitArray::fill ( bool v, int size = -1 )
Fills the bit array with v (1's if v is TRUE, or 0's if v
is FALSE).
fill() resizes the bit array to size bits if size is
nonnegative.
Returns FALSE if a nonnegative size was specified and the bit
array could not be resized; otherwise returns TRUE.
See also resize().
QBitArray & QBitArray::operator&= ( const QBitArray & a )
Performs the AND operation between all bits in this bit array and
a. Returns a reference to this bit array.
The result has the length of the longest of the two bit arrays,
with any missing bits (i.e. if one array is shorter than the
other), taken to be 0.
QBitArray a( 3 ), b( 2 );
a[0] = 1; a[1] = 0; a[2] = 1; // a = [1 0 1]
b[0] = 1; b[1] = 0; // b = [1 0]
a &= b; // a = [1 0 0]
See also operator|=(), operator^=(), and operator~().
QBitArray & QBitArray::operator= ( const QBitArray & a )
Assigns a shallow copy of a to this bit array and returns a
reference to this array.
QBitVal QBitArray::operator[] ( int index )
Implements the [] operator for bit arrays.
The returned QBitVal is a context object. It makes it possible to
get and set a single bit value by its index position.
Example:
QBitArray a( 3 );
a[0] = 0;
a[1] = 1;
a[2] = a[0] ^ a[1];
The functions testBit(), setBit() and clearBit() are faster.
See also at().
bool QBitArray::operator[] ( int index ) const
This is an overloaded member function, provided for convenience. It behaves essentially like the above function.
Implements the [] operator for constant bit arrays.
QBitArray & QBitArray::operator^= ( const QBitArray & a )
Performs the XOR operation between all bits in this bit array and
a. Returns a reference to this bit array.
The result has the length of the longest of the two bit arrays,
with any missing bits (i.e. if one array is shorter than the
other), taken to be 0.
QBitArray a( 3 ), b( 2 );
a[0] = 1; a[1] = 0; a[2] = 1; // a = [1 0 1]
b[0] = 1; b[1] = 0; // b = [1 0]
a ^= b; // a = [0 0 1]
See also operator&=(), operator|=(), and operator~().
QBitArray & QBitArray::operator|= ( const QBitArray & a )
Performs the OR operation between all bits in this bit array and
a. Returns a reference to this bit array.
The result has the length of the longest of the two bit arrays,
with any missing bits (i.e. if one array is shorter than the
other), taken to be 0.
QBitArray a( 3 ), b( 2 );
a[0] = 1; a[1] = 0; a[2] = 1; // a = [1 0 1]
b[0] = 1; b[1] = 0; // b = [1 0]
a |= b; // a = [1 0 1]
See also operator&=(), operator^=(), and operator~().
QBitArray QBitArray::operator~ () const
Returns a bit array that contains the inverted bits of this bit array.
Example:
QBitArray a( 3 ), b;
a[0] = 1; a[1] = 0; a[2] = 1; // a = [1 0 1]
b = ~a; // b = [0 1 0]
bool QBitArray::resize ( uint size )
Resizes the bit array to size bits and returns TRUE if the bit
array could be resized; otherwise returns FALSE. The array becomes
a null array if size == 0.
If the array is expanded, the new bits are set to 0.
See also size().
void QBitArray::setBit ( uint index, bool value )
Sets the bit at position index to value.
Equivalent to:
if ( value )
setBit( index );
else
clearBit( index );
See also clearBit() and toggleBit().
void QBitArray::setBit ( uint index )
This is an overloaded member function, provided for convenience. It behaves essentially like the above function.
Sets the bit at position index to 1.
See also clearBit() and toggleBit().
uint QBitArray::size () const
Returns the bit array's size (number of bits).
See also resize().
bool QBitArray::testBit ( uint index ) const
Returns TRUE if the bit at position index is set, i.e. is 1;
otherwise returns FALSE.
See also setBit() and clearBit().
bool QBitArray::toggleBit ( uint index )
Toggles the bit at position index.
If the previous value was 0, the new value will be 1. If the
previous value was 1, the new value will be 0.
See also setBit() and clearBit().
Related Functions
Returns the AND result between the bit arrays a1 and a2.
The result has the length of the longest of the two bit arrays,
with any missing bits (i.e. if one array is shorter than the
other), taken to be 0.
See also QBitArray::operator&=().
Writes bit array a to stream s.
See also Format of the QDataStream operators.
Reads a bit array into a from stream s.
See also Format of the QDataStream operators.
Returns the XOR result between the bit arrays a1 and a2.
The result has the length of the longest of the two bit arrays,
with any missing bits (i.e. if one array is shorter than the
other), taken to be 0.
See also QBitArray::operator^().
Returns the OR result between the bit arrays a1 and a2.
The result has the length of the longest of the two bit arrays,
with any missing bits (i.e. if one array is shorter than the
other), taken to be 0.
See also QBitArray::operator|=().
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