qbitarray.cpp

Trolltech公司发布的图形界面操作系统。可在qt-embedded-2.3.10平台上编译为嵌入式图形界面操作系统。

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#include "qbitarray.h"
#include "qdatastream.h"

#define SHBLOCK	 ((bitarr_data*)(sharedBlock()))


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

    \ingroup collection

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

/*!
    \fn QBitVal::QBitVal (QBitArray* a, uint i)

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

/*!
    \fn QBitVal::operator int()

    Returns the value referenced by the QBitVal.
*/

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

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

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

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


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

    \ingroup collection
    \ingroup tools
    \ingroup shared

    Because QBitArray is a QMemArray, it uses explicit \link
    shclass.html sharing\endlink 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:
    \code
    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]
    \endcode

    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.
*/

/*! \class QBitArray::bitarr_data
  \brief The QBitArray::bitarr_data class is internal.
  \internal
*/


/*!
    Constructs an empty bit array.
*/

QBitArray::QBitArray() : QByteArray( 0, 0 )
{
    bitarr_data *x = new bitarr_data;
    Q_CHECK_PTR( x );
    x->nbits = 0;
    setSharedBlock( x );
}

/*!
    Constructs a bit array of \a size bits. The bits are uninitialized.

    \sa fill()
*/

QBitArray::QBitArray( uint size ) : QByteArray( 0, 0 )
{
    bitarr_data *x = new bitarr_data;
    Q_CHECK_PTR( x );
    x->nbits = 0;
    setSharedBlock( x );
    resize( size );
}

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

    Constructs a shallow copy of \a a.
*/

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

    Assigns a shallow copy of \a a to this bit array and returns a
    reference to this array.
*/


/*!
    Pad last byte with 0-bits.
*/
void QBitArray::pad0()
{
    uint sz = size();
    if ( sz && sz%8 )
	*(data()+sz/8) &= (1 << (sz%8)) - 1;
}


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

    Returns the bit array's size (number of bits).

    \sa resize()
*/

/*!
    Resizes the bit array to \a size bits and returns TRUE if the bit
    array could be resized; otherwise returns FALSE. The array becomes
    a null array if \a size == 0.

    If the array is expanded, the new bits are set to 0.

    \sa size()
*/

bool QBitArray::resize( uint size )
{
    uint s = this->size();
    if ( !QByteArray::resize( (size+7)/8 ) )
	return FALSE;				// cannot resize
    SHBLOCK->nbits = size;
    if ( size != 0 ) {				// not null array
	int ds = (int)(size+7)/8 - (int)(s+7)/8;// number of bytes difference
	if ( ds > 0 )				// expanding array
	    memset( data() + (s+7)/8, 0, ds );	//   reset new data
    }
    return TRUE;
}


/*!
    Fills the bit array with \a v (1's if \a v is TRUE, or 0's if \a v
    is FALSE).

    fill() resizes the bit array to \a size bits if \a size is
    nonnegative.

    Returns FALSE if a nonnegative \e size was specified and the bit
    array could not be resized; otherwise returns TRUE.

    \sa resize()
*/

bool QBitArray::fill( bool v, int size )
{
    if ( size >= 0 ) {				// resize first
	if ( !resize( size ) )
	    return FALSE;			// cannot resize
    } else {
	size = this->size();
    }
    if ( size > 0 )
	memset( data(), v ? 0xff : 0, (size + 7) / 8 );
    if ( v )
	pad0();
    return TRUE;
}


/*!
    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.

    \sa copy()
*/

void QBitArray::detach()
{
    int nbits = SHBLOCK->nbits;
    this->duplicate( *this );
    SHBLOCK->nbits = nbits;
}

/*!
    Returns a deep copy of the bit array.

    \sa detach()
*/

QBitArray QBitArray::copy() const
{
    QBitArray tmp;
    tmp.duplicate( *this );
    ((bitarr_data*)(tmp.sharedBlock()))->nbits = SHBLOCK->nbits;
    return tmp;
}


/*!
    Returns TRUE if the bit at position \a index is set, i.e. is 1;
    otherwise returns FALSE.

    \sa setBit(), clearBit()
*/

bool QBitArray::testBit( uint index ) const
{
#if defined(QT_CHECK_RANGE)
    if ( index >= size() ) {
	qWarning( "QBitArray::testBit: Index %d out of range", index );
	return FALSE;
    }
#endif
    return (*(data()+(index>>3)) & (1 << (index & 7))) != 0;
}

/*!
    \overload

    Sets the bit at position \a index to 1.

    \sa clearBit() toggleBit()
*/

void QBitArray::setBit( uint index )
{
#if defined(QT_CHECK_RANGE)
    if ( index >= size() ) {
	qWarning( "QBitArray::setBit: Index %d out of range", index );
	return;
    }
#endif
    *(data()+(index>>3)) |= (1 << (index & 7));
}

/*!
    \fn void QBitArray::setBit( uint index, bool value )

    Sets the bit at position \a index to \a value.

    Equivalent to:
    \code
    if ( value )
	setBit( index );
    else
	clearBit( index );
    \endcode