com.google.zxing.common

Class BitArray

java.lang.Object

com.google.zxing.common.BitArray

All Implemented Interfaces:

Cloneable

public final class BitArray
extends Object
implements Cloneable

A simple, fast array of bits, represented compactly by an array of ints internally.

Constructor Summary

Constructors

Constructor and Description
BitArray() Creates a new empty BitArray with zero size.
BitArray(int size) Creates a new BitArray with the specified size.
BitArray(int[] bits, int size)

Method Summary

Modifier and Type	Method and Description
void	appendBit(boolean bit) Appends a single bit to the end of the array.
void	appendBitArray(BitArray other) Appends another BitArray to the end of this array.
void	appendBits(int value, int numBits) Appends the least-significant bits, from value, in order from most-significant to least-significant.
void	clear() Clears all bits (sets to false).
BitArray	clone()
boolean	equals(Object o)
void	flip(int i) Flips bit i.
boolean	get(int i)
int[]	getBitArray()
int	getNextSet(int from)
int	getNextUnset(int from)
int	getSize()
int	getSizeInBytes()
int	hashCode()
boolean	isRange(int start, int end, boolean value) Efficient method to check if a range of bits is set, or not set.
void	reverse() Reverses all bits in the array.
void	set(int i) Sets bit i.
void	setBulk(int i, int newBits) Sets a block of 32 bits, starting at bit i.
void	setRange(int start, int end) Sets a range of bits.
void	toBytes(int bitOffset, byte[] array, int offset, int numBytes)
String	toString()
void	xor(BitArray other) Performs a bitwise XOR of this array with another.

Methods inherited from class java.lang.Object

finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

BitArray

public BitArray()

Creates a new empty BitArray with zero size.

BitArray

public BitArray(int size)

Creates a new BitArray with the specified size.

Parameters:

size - the number of bits in the array

BitArray

BitArray(int[] bits,
         int size)

Method Detail

appendBit

public void appendBit(boolean bit)

Appends a single bit to the end of the array.

Parameters:

bit - the bit value to append

appendBitArray

public void appendBitArray(BitArray other)

Appends another BitArray to the end of this array.

Parameters:

other - the BitArray to append

appendBits

public void appendBits(int value,
                       int numBits)

Appends the least-significant bits, from value, in order from most-significant to least-significant. For example, appending 6 bits from 0x000001E will append the bits 0, 1, 1, 1, 1, 0 in that order.

Parameters:

value - int containing bits to append

numBits - bits from value to append

clear

public void clear()

Clears all bits (sets to false).

clone

public BitArray clone()

Overrides:

clone in class Object

Returns:

a copy of this BitArray

equals

public boolean equals(Object o)

Overrides:

equals in class Object

Parameters:

o - the object to compare

Returns:

true if this BitArray equals the given object

flip

public void flip(int i)

Flips bit i.

Parameters:

i - bit to set

get

public boolean get(int i)

Parameters:

i - bit to get

Returns:

true iff bit i is set

getBitArray

public int[] getBitArray()

Returns:

underlying array of ints. The first element holds the first 32 bits, and the least significant bit is bit 0.

getNextSet

public int getNextSet(int from)

Parameters:

from - first bit to check

Returns:

index of first bit that is set, starting from the given index, or size if none are set at or beyond this given index

See Also:

getNextUnset(int)

getNextUnset

public int getNextUnset(int from)

Parameters:

from - index to start looking for unset bit

Returns:

index of next unset bit, or size if none are unset until the end

See Also:

getNextSet(int)

getSize

public int getSize()

Returns:

the number of bits in the array

getSizeInBytes

public int getSizeInBytes()

Returns:

the size of the array in bytes (rounded up)

hashCode

public int hashCode()

Overrides:

hashCode in class Object

Returns:

the hash code value for this BitArray

isRange

public boolean isRange(int start,
                       int end,
                       boolean value)

Efficient method to check if a range of bits is set, or not set.

Parameters:

start - start of range, inclusive.

end - end of range, exclusive

value - if true, checks that bits in range are set, otherwise checks that they are not set

Returns:

true iff all bits are set or not set in range, according to value argument

Throws:

IllegalArgumentException - if end is less than start or the range is not contained in the array

reverse

public void reverse()

Reverses all bits in the array.

set

public void set(int i)

Sets bit i.

Parameters:

i - bit to set

setBulk

public void setBulk(int i,
                    int newBits)

Sets a block of 32 bits, starting at bit i.

Parameters:

i - first bit to set

newBits - the new value of the next 32 bits. Note again that the least-significant bit corresponds to bit i, the next-least-significant to i+1, and so on.

setRange

public void setRange(int start,
                     int end)

Sets a range of bits.

Parameters:

start - start of range, inclusive.

end - end of range, exclusive

toBytes

public void toBytes(int bitOffset,
                    byte[] array,
                    int offset,
                    int numBytes)

Parameters:

bitOffset - first bit to start writing

array - array to write into. Bytes are written most-significant byte first. This is the opposite of the internal representation, which is exposed by getBitArray()

offset - position in array to start writing

numBytes - how many bytes to write

toString

public String toString()

Overrides:

toString in class Object

Returns:

a string representation of this BitArray

xor

public void xor(BitArray other)

Performs a bitwise XOR of this array with another.

Parameters:

other - the BitArray to XOR with

Throws:

IllegalArgumentException - if sizes don't match