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org.apache.derby.iapi.services.io
Class FormatableBitSet  

java.lang.Object
  org.apache.derby.iapi.services.io.FormatableBitSet

All Implemented Interfaces:

java.lang.Cloneable, java.io.Externalizable, Formatable, java.io.Serializable, TypedFormat

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public final class FormatableBitSet

extends java.lang.Object

implements Formatable, java.lang.Cloneable

FormatableBitSet is implemented as a packed array of bytes.

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Field Summary
private  short	bitsInLastByte
private static char[]	decodeArray
private  int	lengthAsBits
private  byte[]	value           Bits are stored as an array of bytes.

 

Constructor Summary

FormatableBitSet()           Niladic Constructor

FormatableBitSet(byte[] newValue)           Constructs a Bit from an array of bytes.

FormatableBitSet(byte[] newValue, int numBits)           Constructs a Bit from an array of bytes.

FormatableBitSet(FormatableBitSet original)           Copy constructor

FormatableBitSet(int numBits)           Constructs a Bit with the initial number of bits

 

Method Summary
void	and(FormatableBitSet otherBit)           Bitwise AND this Bit with another Bit.
int	anySetBit()           If any bit is set, return the bit number of a bit that is set.
int	anySetBit(int beyondBit)           Like anySetBit(), but return any set bit whose number is bigger than beyondBit.
private  int	calculateLength(int realByteLength)
void	clear()           Clear all the bits in this FormatableBitSet
void	clear(int position)           Bit clear
java.lang.Object	clone()           This method may be called to create a new copy of the Object.
int	compare(FormatableBitSet other)           Bit comparison.
FormatableBitSet	concatenate(FormatableBitSet other)           Bit concatenation.
boolean	equals(FormatableBitSet other)           Bit equivalence.
boolean	get(int position)           Bit get -- alias for isSet()
byte[]	getByteArray()           Get the value of the byte array
int	getLength()           Get the length in bits
int	getLengthInBytes()           Get the length in bytes of a Bit value
int	getNumBitsSet()           Get a count of the number of bits that are set.
int	getTypeFormatId()           Get the formatID which corresponds to this class.
void	grow(int n)           Grow (widen) a FormatableBitSet to N bis
int	hashCode()           Produce a hash code by putting the value bytes into an int, exclusive OR'ing if there are more than 4 bytes.
private static byte	hexCharToByte(char hexChar)           Translate a hex character to a byte.
private  void	initializeBits(int numBits)
boolean	isNull()           Set the value of the byte array
boolean	isSet(int position)           Bit isSet
static int	maxBitsForSpace(int numBytes)           Statically calculates how many bits can fit into the number of bytes if this Bit object is externalized.
private static short	numBitsInLastByte(int bits)           Figure out how many bits are in the last byte from the total number of bits.
protected static int	numBytesFromBits(int bits)           Figure out how many bytes are needed to store the input number of bits.
void	or(FormatableBitSet otherBit)           Bitwise OR this Bit with another Bit.
void	readExternal(java.io.ObjectInput in)           Note: gracefully handles zero length bits -- will create a zero length array with no bits being used.
void	readExternalFromArray(ArrayInputStream in)
void	set(int position)           Bit set
FormatableBitSet	shrink(int n)           Shrink (narrow) a FormatableBitSet to N bits
int	size()           Get the length in bits -- alias for getLength()
java.lang.String	toString()           Format the string into BitSet format: {0, 2, 4, 8} if bits 0, 2, 4, 8 are set.
void	writeExternal(java.io.ObjectOutput out)           Format: int length in bits byte[]
void	xor(FormatableBitSet set)           Logically XORs this FormatableBitSet with the specified FormatableBitSet.

 

Methods inherited from class java.lang.Object

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

 

Field Detail

value

private byte[] value

Bits are stored as an array of bytes. Bits are numbered starting at 0. Bits 0..7 go in byte[0], 8..15 in byte[1] and so on. The number of bytes is tracked as part of the byte array. The number of bits being used is derived by the number of bytes being used and the number of bits being used by the last byte. The partially unused byte is always byte[byte.length] with the lowest bits being unused. Zero length bits are stored using a zero length byte array, with all bits marked as unused.

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bitsInLastByte

private short bitsInLastByte

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lengthAsBits

private transient int lengthAsBits

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decodeArray

private static char[] decodeArray

Constructor Detail

FormatableBitSet

public FormatableBitSet()

Niladic Constructor

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FormatableBitSet

public FormatableBitSet(int numBits)

Constructs a Bit with the initial number of bits

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FormatableBitSet

public FormatableBitSet(byte[] newValue)

Constructs a Bit from an array of bytes. Assume bytes are all being used.

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FormatableBitSet

public FormatableBitSet(byte[] newValue,
                        int numBits)

Constructs a Bit from an array of bytes.

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FormatableBitSet

public FormatableBitSet(FormatableBitSet original)

Copy constructor

Method Detail

initializeBits

private void initializeBits(int numBits)

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clone

public java.lang.Object clone()

Description copied from class: java.lang.Object

This method may be called to create a new copy of the Object. The typical behavior is as follows:

• o == o.clone() is false
• o.getClass() == o.clone().getClass() is true
• o.equals(o) is true

However, these are not strict requirements, and may be violated if necessary. Of the three requirements, the last is the most commonly violated, particularly if the subclass does not override Object.equals(Object)>Object.equals(Object) 55 .

If the Object you call clone() on does not implement java.lang.Cloneable (which is a placeholder interface), then a CloneNotSupportedException is thrown. Notice that Object does not implement Cloneable; this method exists as a convenience for subclasses that do.

Object's implementation of clone allocates space for the new Object using the correct class, without calling any constructors, and then fills in all of the new field values with the old field values. Thus, it is a shallow copy. However, subclasses are permitted to make a deep copy.

All array types implement Cloneable, and override this method as follows (it should never fail):

 public Object clone()
 {
   try
     {
       super.clone();
     }
   catch (CloneNotSupportedException e)
     {
       throw new InternalError(e.getMessage());
     }
 }
 

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getLengthInBytes

public int getLengthInBytes()

Get the length in bytes of a Bit value

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getLength

public int getLength()

Get the length in bits

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calculateLength

private int calculateLength(int realByteLength)

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size

public int size()

Get the length in bits -- alias for getLength()

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getByteArray

public byte[] getByteArray()

Get the value of the byte array

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isNull

public boolean isNull()

Set the value of the byte array

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grow

public void grow(int n)

Grow (widen) a FormatableBitSet to N bis

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shrink

public FormatableBitSet shrink(int n)

Shrink (narrow) a FormatableBitSet to N bits

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equals

public boolean equals(FormatableBitSet other)

Bit equivalence. Compare this with other. If the length is different, then cannot be equal so short circuit. Otherwise, rely on compare(). Note that two zero length bits are considered equal.

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compare

public int compare(FormatableBitSet other)

Bit comparison. Compare this with other. Will always do a byte by byte compare. Given 2 similar bits of unequal lengths (x and y), where x.getLength() < y.getLength() but where: x[0..x.getLength()] == y[0..x.getLength()] then x < y.

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concatenate

public FormatableBitSet concatenate(FormatableBitSet other)

Bit concatenation.

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hashCode

public int hashCode()

Produce a hash code by putting the value bytes into an int, exclusive OR'ing if there are more than 4 bytes.

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isSet

public final boolean isSet(int position)

Bit isSet

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get

public final boolean get(int position)

Bit get -- alias for isSet()

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set

public void set(int position)

Bit set

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clear

public void clear(int position)

Bit clear

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clear

public void clear()

Clear all the bits in this FormatableBitSet

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numBytesFromBits

protected static int numBytesFromBits(int bits)

Figure out how many bytes are needed to store the input number of bits.

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numBitsInLastByte

private static short numBitsInLastByte(int bits)

Figure out how many bits are in the last byte from the total number of bits.

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hexCharToByte

private static byte hexCharToByte(char hexChar)

Translate a hex character to a byte.

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toString

public java.lang.String toString()

Format the string into BitSet format: {0, 2, 4, 8} if bits 0, 2, 4, 8 are set.

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maxBitsForSpace

public static int maxBitsForSpace(int numBytes)

Statically calculates how many bits can fit into the number of bytes if this Bit object is externalized. Only valid for this implementation of Bit.

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anySetBit

public int anySetBit()

If any bit is set, return the bit number of a bit that is set. If no bit is set, return -1;

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anySetBit

public int anySetBit(int beyondBit)

Like anySetBit(), but return any set bit whose number is bigger than beyondBit. If no bit is set after beyondBit, -1 is returned. By using anySetBit() and anySetBit(beyondBit), one can quickly go thru the entire bit array to return all set bit.

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or

public void or(FormatableBitSet otherBit)

Bitwise OR this Bit with another Bit.

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and

public void and(FormatableBitSet otherBit)

Bitwise AND this Bit with another Bit.

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xor

public void xor(FormatableBitSet set)

Logically XORs this FormatableBitSet with the specified FormatableBitSet.

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getNumBitsSet

public int getNumBitsSet()

Get a count of the number of bits that are set.

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writeExternal

public void writeExternal(java.io.ObjectOutput out)
                   throws java.io.IOException

Format:

• int length in bits
• byte[]

Specified by:

writeExternal in interface java.io.Externalizable

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readExternal

public void readExternal(java.io.ObjectInput in)
                  throws java.io.IOException

Note: gracefully handles zero length bits -- will create a zero length array with no bits being used. Fortunately in.read() is ok with a zero length array so no special code.

WARNING: this method cannot be changed w/o changing SQLBit because SQLBit calls this directly w/o calling read/writeObject(), so the format id is not stored in that case.

Specified by:

readExternal in interface java.io.Externalizable

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readExternalFromArray

public void readExternalFromArray(ArrayInputStream in)
                           throws java.io.IOException

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getTypeFormatId

public int getTypeFormatId()

Get the formatID which corresponds to this class.

Specified by:

getTypeFormatId in interface TypedFormat

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Overview  Package   Class  Use  Deprecated  Index
Home >> All >> org >> apache >> derby >> iapi >> services >> [ io overview ]	PREV CLASS  NEXT CLASS
SUMMARY:  JAVADOC |  SOURCE |  DOWNLOAD | NESTED | FIELD | CONSTR | METHOD	DETAIL: FIELD | CONSTR | METHOD

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