Apache Derby Database Engine and Embedded JDBC Driver 10.17.1.0 · org.apache.derby.impl.jdbc.UTF8Reader

Field Summary

Modifier and Type	Field and Description
private final char[]	buffer Internal character buffer storing characters read from the stream.
private int	charactersInBuffer The number of characters in the internal buffer.
private final CharacterStreamDescriptor	csd Descriptor containing information about the stream.
private InputStream	in The underlying data stream.
private static final int	MAXIMUM_BUFFER_SIZE Maximum size in number of chars for the internal character buffer.
private boolean	noMoreReads Tells if this reader has been closed.
private ConnectionChild	parent A reference to the parent object of the stream.
private final PositionedStream	positionedIn Stream that can reposition itself on request (may be `null`).
private long	rawStreamPos Store the last visited position in the store stream, if it is capable of repositioning itself (`positionedIn != null`).
private static final String	READER_CLOSED
private long	readerCharCount Number of characters read from the stream.
private int	readPositionInBuffer The position of the next character to read in the internal buffer.
private long	utfCount Number of bytes read from the stream, including any header bytes.

Inherited from java.io.Reader:: lock

Constructor Summary

Access	Constructor and Description
public	UTF8Reader(CharacterStreamDescriptor a description of and reference to the source stream csd, ConnectionChild the parent object / connection child conChild, Object synchronization object used when accessing the underlying data stream sync) Constructs a reader on top of the source UTF-8 encoded stream.

Method Summary

Modifier and Type	Method and Description
private final int	Returns: An (sub)optimal buffer size. calculateBufferSize(CharacterStreamDescriptor stream descriptor csd) Calculates an optimized buffer size.
public void	close() Implements abstract java.io.Reader.close. Implements java.io.Closeable.close. Close the reader, disallowing further reads.
private void	closeIn() Close the underlying stream if it is open.
private boolean	Returns: `true` if the end of the stream is reached, `false` if there is apparently more data to be read. fillBuffer() Fills the internal character buffer by decoding bytes from the stream.
private final void	persistentSkip(long number of characters to skip toSkip) Skips the requested number of characters.
public int	Returns: A character or `-1` if end of stream has been reached. read() Overrides java.io.Reader.read. Reads a single character from the stream.
public int	Returns: The number of characters read, or `-1` if the end of the stream has been reached. read(char[] Destination buffer cbuf, int Offset at which to start storing characters off, int Maximum number of characters to read len) Implements abstract java.io.Reader.read. Reads characters into an array.
pack-priv int	Returns: The number of characters read, or `-1` if the end of the stream is reached. readAsciiInto(byte[] the buffer to read into abuf, int the offset into the destination buffer off, int maximum number of characters to read len) Reads characters into an array as ASCII characters.
public int	Returns: The number of characters read, or `-1` if the end of the stream is reached. readInto(StringBuffer the destination buffer sb, int maximum number of characters to read len) Reads characters from the stream.
pack-priv void	reposition(long 1-based requested character position requestedCharPos) Repositions the stream so that the next character read will be the character at the requested position.
private void	resetUTF8Reader() Resets the reader.
public long	Returns: The number of characters actually skipped. skip(long the numbers of characters to skip len) Overrides java.io.Reader.skip. Skips characters.
private IOException	utfFormatException(String s) Convenience method generating an `UTFDataFormatException` and cleaning up the reader state.

Inherited from java.io.Reader:: mark markSupported nullReader read read ready reset transferTo

Field Detail

buffer	back to summary
private final char[] buffer Internal character buffer storing characters read from the stream.

charactersInBuffer	back to summary
private int charactersInBuffer The number of characters in the internal buffer.

csd	back to summary
private final CharacterStreamDescriptor csd Descriptor containing information about the stream. Except for the current positions, the information in this object is considered permanent and valid for the life-time of the stream.

in	back to summary
private InputStream in The underlying data stream.

MAXIMUM_BUFFER_SIZE	back to summary
private static final int MAXIMUM_BUFFER_SIZE Maximum size in number of chars for the internal character buffer.

noMoreReads	back to summary
private boolean noMoreReads Tells if this reader has been closed.

parent	back to summary
private ConnectionChild parent A reference to the parent object of the stream. The reference is kept so that the parent object can't get garbage collected until we are done with the stream.

parent

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private ConnectionChild parent

A reference to the parent object of the stream.

The reference is kept so that the parent object can't get garbage collected until we are done with the stream.

positionedIn	back to summary
private final PositionedStream positionedIn Stream that can reposition itself on request (may be `null`).

rawStreamPos	back to summary
private long rawStreamPos Store the last visited position in the store stream, if it is capable of repositioning itself (`positionedIn != null`).

READER_CLOSED	back to summary
private static final String READER_CLOSED

readerCharCount	back to summary
private long readerCharCount Number of characters read from the stream.

readPositionInBuffer	back to summary
private int readPositionInBuffer The position of the next character to read in the internal buffer.

utfCount	back to summary
private long utfCount Number of bytes read from the stream, including any header bytes.

Constructor Detail

UTF8Reader	back to summary
public UTF8Reader(CharacterStreamDescriptor csd, ConnectionChild conChild, Object sync) throws IOException Constructs a reader on top of the source UTF-8 encoded stream. Parameters csd:CharacterStreamDescriptor a description of and reference to the source stream conChild:ConnectionChild the parent object / connection child sync:Object synchronization object used when accessing the underlying data stream Exceptions IOException: if reading from the underlying stream fails

UTF8Reader

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public UTF8Reader(CharacterStreamDescriptor csd, ConnectionChild conChild, Object sync) throws IOException

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

Parameters

csd:CharacterStreamDescriptor: a description of and reference to the source stream
conChild:ConnectionChild: the parent object / connection child
sync:Object: synchronization object used when accessing the underlying data stream

Exceptions

IOException:: if reading from the underlying stream fails

Method Detail

calculateBufferSize	back to summary
private final int calculateBufferSize(CharacterStreamDescriptor csd) Calculates an optimized buffer size. The maximum size allowed is returned if the specified values don't give enough information to say a smaller buffer size is preferable. Parameters csd:CharacterStreamDescriptor stream descriptor Returns:int An (sub)optimal buffer size.

calculateBufferSize

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private final int calculateBufferSize(CharacterStreamDescriptor csd)

Calculates an optimized buffer size.

The maximum size allowed is returned if the specified values don't give enough information to say a smaller buffer size is preferable.

Parameters

csd:CharacterStreamDescriptor: stream descriptor

Returns:int

An (sub)optimal buffer size.

close	back to summary
public void close() Implements abstract java.io.Reader.close. Implements java.io.Closeable.close. Close the reader, disallowing further reads.

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public void close()

Implements abstract java.io.Reader.close.

Implements java.io.Closeable.close.

Close the reader, disallowing further reads.

closeIn	back to summary
private void closeIn() Close the underlying stream if it is open.

fillBuffer back to summary

fillBuffer	back to summary
private boolean fillBuffer() throws IOException Fills the internal character buffer by decoding bytes from the stream. Returns:boolean `true` if the end of the stream is reached, `false` if there is apparently more data to be read.

private boolean fillBuffer() throws IOException

Fills the internal character buffer by decoding bytes from the stream.

Returns:boolean: true if the end of the stream is reached, false if there is apparently more data to be read.

persistentSkip	back to summary
private final void persistentSkip(long toSkip) throws IOException Skips the requested number of characters. Parameters toSkip:long number of characters to skip Exceptions IOException: if reading from the stream fails EOFException: if there are too few characters in the stream

persistentSkip

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private final void persistentSkip(long toSkip) throws IOException

Skips the requested number of characters.

Parameters

toSkip:long: number of characters to skip

Exceptions

IOException:: if reading from the stream fails
EOFException:: if there are too few characters in the stream

read back to summary

read	back to summary
public int read() throws IOException Overrides java.io.Reader.read. Reads a single character from the stream. Returns:int A character or `-1` if end of stream has been reached. Exceptions IOException: if the stream has been closed, or an exception is raised while reading from the underlying stream

public int read() throws IOException

Overrides java.io.Reader.read.

Reads a single character from the stream.

Returns:int

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

Exceptions

IOException:: if the stream has been closed, or an exception is raised while reading from the underlying stream

read back to summary

read	back to summary
public int read(char[] cbuf, int off, int len) throws IOException Implements abstract java.io.Reader.read. Reads characters into an array. Parameters cbuf:char[] Doc from java.io.Reader.read. Destination buffer off:int Doc from java.io.Reader.read. Offset at which to start storing characters len:int Doc from java.io.Reader.read. Maximum number of characters to read Returns:int The number of characters read, or `-1` if the end of the stream has been reached. Exceptions IOException: Doc from java.io.Reader.read. If an I/O error occurs

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

Implements abstract java.io.Reader.read.

Reads characters into an array.

Parameters

cbuf:char[]

Doc from java.io.Reader.read.

Destination buffer

off:int

Doc from java.io.Reader.read.

Offset at which to start storing characters

len:int

Doc from java.io.Reader.read.

Maximum number of characters to read

Returns:int

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

Exceptions

IOException:

Doc from java.io.Reader.read.

If an I/O error occurs

readAsciiInto back to summary

readAsciiInto	back to summary
pack-priv int readAsciiInto(byte[] abuf, int off, int len) throws IOException Reads characters into an array as ASCII characters. 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. Characters outside the ASCII range are replaced with an out of range marker. Parameters abuf:byte[] the buffer to read into off:int the offset into the destination buffer len:int maximum number of characters to read Returns:int The number of characters read, or `-1` if the end of the stream is reached.

pack-priv int readAsciiInto(byte[] abuf, int off, int len) throws IOException

Reads characters into an array as ASCII characters.

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.

Characters outside the ASCII range are replaced with an out of range marker.

Parameters

abuf:byte[]: the buffer to read into
off:int: the offset into the destination buffer
len:int: maximum number of characters to read

Returns:int

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

readInto back to summary

readInto	back to summary
public int readInto(StringBuffer sb, int len) throws 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:StringBuffer the destination buffer len:int maximum number of characters to read Returns:int The number of characters read, or `-1` if the end of the stream is reached.

public int readInto(StringBuffer sb, int len) throws IOException

Reads characters from the stream.

Parameters

sb:StringBuffer: the destination buffer
len:int: maximum number of characters to read

Returns:int

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

reposition back to summary

reposition	back to summary
pack-priv void reposition(long requestedCharPos) throws IOException, StandardException Repositions the stream so that the next character read will be the character at the requested position. There are three types of repositioning, ordered after increasing cost: Reposition within current character buffer (small hops forwards and potentially backwards - in range 1 char to `MAXIMUM_BUFFER_SIZE` chars) Forward stream from current position (hops forwards) Reset stream and skip data (hops backwards) Parameters requestedCharPos:long 1-based requested character position Exceptions IOException: if resetting or reading from the stream fails StandardException: if resetting the stream fails

pack-priv void reposition(long requestedCharPos) throws IOException, StandardException

Repositions the stream so that the next character read will be the character at the requested position.

There are three types of repositioning, ordered after increasing cost:

Reposition within current character buffer (small hops forwards and potentially backwards - in range 1 char to MAXIMUM_BUFFER_SIZE chars)
Forward stream from current position (hops forwards)
Reset stream and skip data (hops backwards)

Parameters

requestedCharPos:long: 1-based requested character position

Exceptions

IOException:: if resetting or reading from the stream fails
StandardException:: if resetting the stream fails

resetUTF8Reader back to summary

resetUTF8Reader	back to summary
private void resetUTF8Reader() throws IOException, StandardException Resets the reader. This method is used internally to achieve better performance. Exceptions IOException: if resetting or reading from the stream fails StandardException: if resetting the stream fails See Also `reposition(long)`

private void resetUTF8Reader() throws IOException, StandardException

Resets the reader.

This method is used internally to achieve better performance.

Exceptions

IOException:: if resetting or reading from the stream fails
StandardException:: if resetting the stream fails

See Also

reposition(long)

skip	back to summary
public long skip(long len) throws IOException Overrides java.io.Reader.skip. Skips characters. Parameters len:long the numbers of characters to skip Returns:long The number of characters actually skipped. Exceptions IOException: if accessing the underlying stream fails IllegalArgumentException: if the number of characters to skip is negative

skip

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public long skip(long len) throws IOException

Overrides java.io.Reader.skip.

Skips characters.

Parameters

len:long: the numbers of characters to skip

Returns:long

The number of characters actually skipped.

Exceptions

IOException:: if accessing the underlying stream fails
IllegalArgumentException:: if the number of characters to skip is negative

utfFormatException	back to summary
private IOException utfFormatException(String s) Convenience method generating an `UTFDataFormatException` and cleaning up the reader state.

public final Class UTF8Reader

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