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The QBitArray class provides an array of bits. More...
The QBitArray class provides an array of bits.
A QBitArray is an array that gives access to individual bits and provides operators (AND, OR, XOR, and NOT) that work on entire arrays of bits. It uses 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):
QBitArray ba(200);
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:
QBitArray ba; ba.resize(3); ba[0] = true; ba[1] = false; ba[2] = true;
For technical reasons, it is more efficient to use testBit and setBit to access bits in the array than operator[](). For example:
QBitArray ba(3); ba.setBit(0, true); ba.setBit(1, false); ba.setBit(2, true);
QBitArray supports & (AND), | (OR), ^ (XOR), ~ (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:
QBitArray x(5); x.setBit(3, true); // x: [ 0, 0, 0, 1, 0 ] QBitArray y(5); 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 and QVector.
Copyright © 2008 Trolltech | Trademarks | Qt Jambi 4.3.5_01 |