org.apache.drill.exec.expr.fn.impl

Class CharSequenceWrapper

java.lang.Object

org.apache.drill.exec.expr.fn.impl.CharSequenceWrapper

All Implemented Interfaces:

CharSequence

public class CharSequenceWrapper
extends Object
implements CharSequence

A CharSequence is a readable sequence of char values. This interface provides uniform, read-only access to many different kinds of char sequences. A char value represents a character in the Basic Multilingual Plane (BMP) or a surrogate. Refer to Unicode Character Representation for details.
Specifically this implementation of the CharSequence adapts a Drill DrillBuf to the CharSequence. The implementation is meant to be re-used that is allocated once and then passed DrillBuf to adapt. This can be handy to exploit API that consume CharSequence avoiding the need to create string objects.

Constructor Summary

Constructors

Constructor and Description
CharSequenceWrapper()
CharSequenceWrapper(int start, int end, DrillBuf buffer)

Method Summary

Modifier and Type	Method and Description
char	charAt(int index)
int	length()
void	setBuffer(int start, int end, DrillBuf buffer) Set the DrillBuf to adapt to a CharSequence.
CharSequence	subSequence(int start, int end) When using the Java regex Matcher the subSequence is only called when capturing groups.
String	toString() The regexp_replace function is implemented in a way to avoid the call to toString() not to uselessly create a string object.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Methods inherited from interface java.lang.CharSequence

chars, codePoints

Constructor Detail

CharSequenceWrapper

public CharSequenceWrapper()

CharSequenceWrapper

public CharSequenceWrapper(int start,
                           int end,
                           DrillBuf buffer)

Method Detail

length

public int length()

Specified by:

length in interface CharSequence

charAt

public char charAt(int index)

Specified by:

charAt in interface CharSequence

subSequence

public CharSequence subSequence(int start,
                                int end)

When using the Java regex Matcher the subSequence is only called when capturing groups. Drill does not currently use capture groups in the UDF so this method is not required.
It could be implemented by creating a new CharSequenceWrapper however this would imply newly allocated objects which is what this wrapper tries to avoid.

Specified by:

subSequence in interface CharSequence

setBuffer

public void setBuffer(int start,
                      int end,
                      DrillBuf buffer)

Set the DrillBuf to adapt to a CharSequence. This method can be used to replace any previous DrillBuf thus avoiding recreating the CharSequenceWrapper and thus re-using the CharSequenceWrapper object.

Parameters:

start -

end -

buffer -

toString

public String toString()

The regexp_replace function is implemented in a way to avoid the call to toString() not to uselessly create a string object.

Specified by:

toString in interface CharSequence

Overrides:

toString in class Object