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java.lang.Objectcom.trolltech.qt.QSignalEmitter
com.trolltech.qt.QtJambiObject
com.trolltech.qt.core.QBitArray
public class QBitArray
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.
Nested Class Summary |
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Nested classes/interfaces inherited from class com.trolltech.qt.QSignalEmitter |
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QSignalEmitter.AbstractSignal, QSignalEmitter.Signal0, QSignalEmitter.Signal1<A>, QSignalEmitter.Signal2<A,B>, QSignalEmitter.Signal3<A,B,C>, QSignalEmitter.Signal4<A,B,C,D>, QSignalEmitter.Signal5<A,B,C,D,E>, QSignalEmitter.Signal6<A,B,C,D,E,F>, QSignalEmitter.Signal7<A,B,C,D,E,F,G>, QSignalEmitter.Signal8<A,B,C,D,E,F,G,H>, QSignalEmitter.Signal9<A,B,C,D,E,F,G,H,I> |
Constructor Summary | |
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QBitArray()
Constructs an empty bit array. |
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QBitArray(int size)
Equivalent to QBitArray(size, false). |
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QBitArray(int size,
boolean val)
Constructs a bit array containing size bits. |
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QBitArray(QBitArray other)
Constructs a copy of other. |
Method Summary | |
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void |
and(QBitArray other)
Returns a bit array that is the AND of this bit array and other. |
boolean |
at(int i)
Returns the value of the bit at index position i. |
void |
clear()
Clears the contents of the bit array and makes it empty. |
void |
clearBit(int i)
Sets the bit at index position i to 0. |
int |
count()
Same as size. |
int |
count(boolean on)
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. |
boolean |
equals(java.lang.Object other)
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boolean |
fill(boolean val)
Equivalent to fill(val, -1). |
boolean |
fill(boolean val,
int size)
Sets every bit in the bit array to val, returning true if successful; otherwise returns false. |
void |
fill(boolean val,
int first,
int last)
Sets bits at index positions first up to and excluding last to val. |
static QBitArray |
fromNativePointer(QNativePointer nativePointer)
This function returns the QBitArray instance pointed to by nativePointer |
int |
hashCode()
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QBitArray |
inverted()
Returns a bit array that contains the inverted bits of this bit array. |
boolean |
isEmpty()
Returns true if this bit array has size 0; otherwise returns false. |
boolean |
isNull()
Returns true if this bit array is null; otherwise returns false. |
static QNativePointer |
nativePointerArray(QBitArray[] array)
This function returns a QNativePointer that is pointing to the specified QBitArray array. |
void |
or(QBitArray other)
Returns a bit array that is the OR of this bit array and other. |
void |
readFrom(QDataStream arg__1)
Reads a QBitArray from arg__1. |
void |
resize(int size)
Resizes the bit array to size bits. |
void |
set(QBitArray other)
This function sets the contents of this array to the same as others. |
void |
setBit(int i)
Sets the bit at index position i to 1. |
void |
setBit(int i,
boolean val)
Sets the bit at index position i to val. |
int |
size()
Returns the number of bits stored in the bit array. |
boolean |
testBit(int i)
Returns true if the bit at index position i is 1; otherwise returns false. |
boolean |
toggleBit(int 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). |
void |
truncate(int pos)
Truncates the bit array at index position pos. |
void |
writeTo(QDataStream arg__1)
Writes thisQBitArray to arg__1. |
void |
xor(QBitArray other)
Returns a bit array that is the XOR of this bit array and other. |
Methods inherited from class com.trolltech.qt.QtJambiObject |
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dispose, disposed, finalize, reassignNativeResources, tr, tr, tr |
Methods inherited from class com.trolltech.qt.QSignalEmitter |
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blockSignals, disconnect, disconnect, signalsBlocked, signalSender, thread |
Methods inherited from class java.lang.Object |
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clone, getClass, notify, notifyAll, toString, wait, wait, wait |
Methods inherited from interface com.trolltech.qt.QtJambiInterface |
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disableGarbageCollection, nativeId, nativePointer, reenableGarbageCollection, setJavaOwnership |
Constructor Detail |
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public QBitArray(int size)
Equivalent to QBitArray(size, false).
public QBitArray(int size, boolean val)
Constructs a bit array containing size bits. The bits are initialized with val, which defaults to false (0).
public QBitArray(QBitArray other)
Constructs a copy of other.
This operation takes constant time, because QBitArray is 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 linear time.
public QBitArray()
Constructs an empty bit array.
Method Detail |
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public final boolean at(int i)
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).
public final void clear()
Clears the contents of the bit array and makes it empty.
public final void clearBit(int i)
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).
public final int count(boolean on)
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.
public final int count()
Same as size.
public final void fill(boolean val, int first, int last)
Sets bits at index positions first up to and excluding last to val.
first and last must be a valid index position in the bit array (i.e., 0 <= first <= size and 0 <= last <= size).
public final boolean fill(boolean val)
Equivalent to fill(val, -1).
public final boolean fill(boolean val, int size)
Sets every bit in the bit array to val, 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 ]
public final boolean isEmpty()
Returns true if this bit array has size 0; otherwise returns false.
public final boolean isNull()
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.
public final void writeTo(QDataStream arg__1)
public final void readFrom(QDataStream arg__1)
public final void resize(int 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.
public final void setBit(int i)
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).
public final void setBit(int i, boolean val)
Sets the bit at index position i to val.
public final int size()
Returns the number of bits stored in the bit array.
public final boolean testBit(int i)
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).
public final boolean toggleBit(int 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).
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).
public final void truncate(int pos)
Truncates the bit array at index position pos.
If pos is beyond the end of the array, nothing happens.
public static QBitArray fromNativePointer(QNativePointer nativePointer)
nativePointer
- the QNativePointer of which object should be returned.public static QNativePointer nativePointerArray(QBitArray[] array)
array
- the array that the returned pointer will point to.
public boolean equals(java.lang.Object other)
equals
in class java.lang.Object
public int hashCode()
hashCode
in class java.lang.Object
public void xor(QBitArray other)
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:
QBitArray a(3);
QBitArray b(2);
QBitArray c;
a[0] = 1; a[1] = 0; a[2] = 1; // a: [ 1, 0, 1 ]
b[0] = 1; b[1] = 0; // b: [ 1, 1 ]
c = a ^ b; // c: [ 0, 1, 1 ]
public void and(QBitArray other)
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:
QBitArray a(3);
QBitArray b(2);
QBitArray c;
a[0] = 1; a[1] = 0; a[2] = 1; // a: [ 1, 0, 1 ]
b[0] = 1; b[1] = 0; // b: [ 1, 1 ]
c = a & b; // c: [ 1, 0, 0 ]
public void or(QBitArray other)
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:
QBitArray a(3);
QBitArray b(2);
QBitArray c;
a[0] = 1; a[1] = 0; a[2] = 1; // a: [ 1, 0, 1 ]
b[0] = 1; b[1] = 0; // b: [ 1, 1 ]
c = a | b; // c: [ 1, 1, 1 ]
public void set(QBitArray other)
public QBitArray inverted()
Example:
QBitArray a(3);
QBitArray b;
a[0] = 1; a[1] = 0; a[2] = 1; // a: [ 1, 0, 1 ]
b = ~a; // b: [ 0, 1, 0 ]
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