org.apache.derby.impl.jdbc
Class TemporaryClob.CharToBytePositionCache

java.lang.Object
  org.apache.derby.impl.jdbc.TemporaryClob.CharToBytePositionCache

Enclosing class:

TemporaryClob

private static class TemporaryClob.CharToBytePositionCache
extends java.lang.Object

A simple class to hold the byte position for a character position.

The implementation is very simple and is basically intended to speed up writing a sequence of consequtive characters one character at a time. Even though this should be avoided if possible, the penalty of updating a large Clob this way and finding the correct byte position by navigating from the start of the byte stream each time is so severe that a simple caching mechanism should be in place. Note that for other encodings than UTF-8, this might not be a problem if the mapping between character position and byte position is one-to-one.

Note that to ensure consistency between character and byte positions, access to this class must be synchronized externally to avoid caller 1 getting the character position, then caller 2 updates the cached values and then caller 1 gets the updated byte position.

Field Summary

private long	bytePos
private long	charPos

Constructor Summary

TemporaryClob.CharToBytePositionCache()

Method Summary

(package private) long	getBytePos() Returns the last cached byte position.
(package private) long	getCharPos() Returns the last cached character position.
(package private) void	reset() Resets the position cache.
(package private) void	updateCachedPos(long charPos, long bytePos) Updates the position cache.

Methods inherited from class java.lang.Object

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

Field Detail

charPos

private long charPos

bytePos

private long bytePos

Constructor Detail

TemporaryClob.CharToBytePositionCache

TemporaryClob.CharToBytePositionCache()

Method Detail

getBytePos

long getBytePos()

Returns the last cached byte position.

Returns:

The byte position for the last cached character position.

getCharPos

long getCharPos()

Returns the last cached character position.

Returns:

The last cached character position.

updateCachedPos

void updateCachedPos(long charPos,
                     long bytePos)

Updates the position cache.

Parameters:

charPos - the character position to cache the byte position for

bytePos - byte position for the specified character position

reset

void reset()

Resets the position cache.