org.apache.derby.iapi.util
Class UTF8Util

java.lang.Object
  extended by org.apache.derby.iapi.util.UTF8Util

public final class UTF8Util
extends java.lang.Object

Utility methods for handling UTF-8 encoded byte streams.

Note that when the skip methods mention detection of invalid UTF-8 encodings, it only checks the first byte of a character. For multibyte encodings, the second and third byte are not checked for correctness, just skipped and ignored.

See Also:
DataInput

Nested Class Summary
private static class UTF8Util.SkipCount
          Helper class to hold skip counts; one for chars and one for bytes.
 
Constructor Summary
private UTF8Util()
          This class cannot be instantiated.
 
Method Summary
private static UTF8Util.SkipCount internalSkip(java.io.InputStream in, long charsToSkip)
          Skip characters in the stream.
static long skipFully(java.io.InputStream in, long charsToSkip)
          Skip the requested number of characters from the stream.
static long skipUntilEOF(java.io.InputStream in)
          Skip until the end-of-stream is reached.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

UTF8Util

private UTF8Util()
This class cannot be instantiated.

Method Detail

skipUntilEOF

public static final long skipUntilEOF(java.io.InputStream in)
                               throws java.io.IOException
Skip until the end-of-stream is reached.

Parameters:
in - byte stream with UTF-8 encoded characters
Returns:
The number of characters skipped.
Throws:
java.io.IOException - if reading from the stream fails
java.io.UTFDataFormatException - if an invalid UTF-8 encoding is detected

skipFully

public static final long skipFully(java.io.InputStream in,
                                   long charsToSkip)
                            throws java.io.EOFException,
                                   java.io.IOException
Skip the requested number of characters from the stream.

Parameters:
in - byte stream with UTF-8 encoded characters
charsToSkip - number of characters to skip
Returns:
The number of bytes skipped.
Throws:
java.io.EOFException - if end-of-stream is reached before the requested number of characters are skipped
java.io.IOException - if reading from the stream fails
java.io.UTFDataFormatException - if an invalid UTF-8 encoding is detected

internalSkip

private static final UTF8Util.SkipCount internalSkip(java.io.InputStream in,
                                                     long charsToSkip)
                                              throws java.io.IOException
Skip characters in the stream.

Note that a smaller number than requested might be skipped if the end-of-stream is reached before the specified number of characters has been decoded. It is up to the caller to decide if this is an error or not. For instance, when determining the character length of a stream, Long.MAX_VALUE could be passed as the requested number of characters to skip.

Parameters:
in - byte stream with UTF-8 encoded characters
charsToSkip - the number of characters to skip
Returns:
A long array with counts; the characters skipped at position CHAR_COUNT, the bytes skipped at position BYTE_COUNT. Note that the number of characters skipped may be smaller than the requested number.
Throws:
java.io.IOException - if reading from the stream fails
java.io.UTFDataFormatException - if an invalid UTF-8 encoding is detected

Built on Thu 2010-12-23 20:49:13+0000, from revision ???

Apache Derby V10.6 Internals - Copyright © 2004,2007 The Apache Software Foundation. All Rights Reserved.