org.apache.derby.impl.jdbc

Class UTF8Reader

java.lang.Object

java.io.Reader

org.apache.derby.impl.jdbc.UTF8Reader

All Implemented Interfaces:

java.io.Closeable, java.lang.AutoCloseable, java.lang.Readable

public final class UTF8Reader
extends java.io.Reader

Class for reading characters from streams encoded in the modified UTF-8 format.

Note that we often operate on a special Derby stream. A Derby stream is possibly different from a "normal" stream in two ways; an encoded length is inserted at the head of the stream, and if the encoded length is 0 a Derby-specific end of stream marker is appended to the data.

If the underlying stream is capable of repositioning itself on request, this class supports multiple readers on the same source stream in such a way that the various readers do not interfere with each other (except for serializing access). Each reader instance will have its own pointer into the stream, and request that the stream repositions itself before calling read/skip on the stream.

See Also:

PositionedStoreStream

Constructor Summary

Constructors

Constructor and Description
UTF8Reader(CharacterStreamDescriptor csd, org.apache.derby.impl.jdbc.ConnectionChild conChild, java.lang.Object sync) Constructs a reader on top of the source UTF-8 encoded stream.

Method Summary

Modifier and Type	Method and Description
void	close() Close the reader, disallowing further reads.
int	read() Reads a single character from the stream.
int	read(char[] cbuf, int off, int len) Reads characters into an array.
int	readInto(java.lang.StringBuffer sb, int len) Reads characters from the stream.
long	skip(long len) Skips characters.

Methods inherited from class java.io.Reader

mark, markSupported, read, read, ready, reset

Methods inherited from class java.lang.Object

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

Constructor Detail

UTF8Reader

public UTF8Reader(CharacterStreamDescriptor csd,
                  org.apache.derby.impl.jdbc.ConnectionChild conChild,
                  java.lang.Object sync)
           throws java.io.IOException

Constructs a reader on top of the source UTF-8 encoded stream.

Parameters:

csd - a description of and reference to the source stream

conChild - the parent object / connection child

sync - synchronization object used when accessing the underlying data stream

Throws:

java.io.IOException - if reading from the underlying stream fails

Method Detail

read

public int read()
         throws java.io.IOException

Reads a single character from the stream.

Overrides:

read in class java.io.Reader

Returns:

A character or -1 if end of stream has been reached.

Throws:

java.io.IOException - if the stream has been closed, or an exception is raised while reading from the underlying stream

read

public int read(char[] cbuf,
                int off,
                int len)
         throws java.io.IOException

Reads characters into an array.

Specified by:

read in class java.io.Reader

Returns:

The number of characters read, or -1 if the end of the stream has been reached.

Throws:

java.io.IOException

skip

public long skip(long len)
          throws java.io.IOException

Skips characters.

Overrides:

skip in class java.io.Reader

Parameters:

len - the numbers of characters to skip

Returns:

The number of characters actually skipped.

Throws:

java.lang.IllegalArgumentException - if the number of characters to skip is negative

java.io.IOException - if accessing the underlying stream fails

close

public void close()

Close the reader, disallowing further reads.

Specified by:

close in interface java.io.Closeable

Specified by:

close in interface java.lang.AutoCloseable

Specified by:

close in class java.io.Reader

readInto

public int readInto(java.lang.StringBuffer sb,
                    int len)
             throws java.io.IOException

Reads characters from the stream.

Due to internal buffering a smaller number of characters than what is requested might be returned. To ensure that the request is fulfilled, call this method in a loop until the requested number of characters is read or -1 is returned.

Parameters:

sb - the destination buffer

len - maximum number of characters to read

Returns:

The number of characters read, or -1 if the end of the stream is reached.

Throws:

java.io.IOException