org.apache.derby.impl.jdbc
Class LOBInputStream

java.lang.Object
  extended by java.io.InputStream
      extended by org.apache.derby.impl.jdbc.LOBInputStream
All Implemented Interfaces:
java.io.Closeable, PositionedStream

public class LOBInputStream
extends java.io.InputStream
implements PositionedStream

This input stream is built on top of LOBStreamControl.

All the read methods are routed to LOBStreamControl.


Field Summary
private  boolean closed
           
private  LOBStreamControl control
           
private  long pos
           
private  long updateCount
           
 
Constructor Summary
LOBInputStream(LOBStreamControl control, long position)
           
 
Method Summary
 java.io.InputStream asInputStream()
          Returns a reference to self as an InputStream.
 void close()
          Closes this input stream and releases any system resources associated with the stream.
 long getPosition()
          Returns the current byte position.
(package private)  boolean isObsolete()
          Checks if underlying StreamControl has been updated.
(package private)  long length()
          Returns size of stream in bytes.
 int read()
          Reads the next byte of data from the input stream.
 int read(byte[] b, int off, int len)
          Reads up to len bytes of data from the input stream into an array of bytes.
(package private)  void reInitialize()
          Reinitializes the stream and sets the current pointer to zero.
 void reposition(long requestedPos)
          Repositions the stream to the requested byte position.
 
Methods inherited from class java.io.InputStream
available, mark, markSupported, read, reset, skip
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

closed

private boolean closed

control

private final LOBStreamControl control

pos

private long pos

updateCount

private long updateCount
Constructor Detail

LOBInputStream

LOBInputStream(LOBStreamControl control,
               long position)
Method Detail

read

public int read(byte[] b,
                int off,
                int len)
         throws java.io.IOException
Reads up to len bytes of data from the input stream into an array of bytes. An attempt is made to read as many as len bytes, but a smaller number may be read. The number of bytes actually read is returned as an integer.

This method blocks until input data is available, end of file is detected, or an exception is thrown.

If b is null, a NullPointerException is thrown.

If off is negative, or len is negative, or off+len is greater than the length of the array b, then an IndexOutOfBoundsException is thrown.

If len is zero, then no bytes are read and 0 is returned; otherwise, there is an attempt to read at least one byte. If no byte is available because the stream is at end of file, the value -1 is returned; otherwise, at least one byte is read and stored into b.

The first byte read is stored into element b[off], the next one into b[off+1], and so on. The number of bytes read is, at most, equal to len. Let k be the number of bytes actually read; these bytes will be stored in elements b[off] through b[off+k-1], leaving elements b[off+k] through b[off+len-1] unaffected.

In every case, elements b[0] through b[off] and elements b[off+len] through b[b.length-1] are unaffected.

If the first byte cannot be read for any reason other than end of file, then an IOException is thrown. In particular, an IOException is thrown if the input stream has been closed.

The read(b, off, len) method for class InputStream simply calls the method read() repeatedly. If the first such call results in an IOException, that exception is returned from the call to the read(b, off, len) method. If any subsequent call to read() results in a IOException, the exception is caught and treated as if it were end of file; the bytes read up to that point are stored into b and the number of bytes read before the exception occurred is returned. Subclasses are encouraged to provide a more efficient implementation of this method.

Overrides:
read in class java.io.InputStream
Parameters:
b - the buffer into which the data is read.
off - the start offset in array b at which the data is written.
len - the maximum number of bytes to read.
Returns:
the total number of bytes read into the buffer, or -1 if there is no more data because the end of the stream has been reached.
Throws:
java.io.IOException - if an I/O error occurs.
java.lang.NullPointerException - if b is null.
See Also:
InputStream.read()

close

public void close()
           throws java.io.IOException
Closes this input stream and releases any system resources associated with the stream.

The close method of InputStream does nothing.

Specified by:
close in interface java.io.Closeable
Overrides:
close in class java.io.InputStream
Throws:
java.io.IOException - if an I/O error occurs.

read

public int read()
         throws java.io.IOException
Reads the next byte of data from the input stream. The value byte is returned as an int in the range 0 to 255. If no byte is available because the end of the stream has been reached, the value -1 is returned. This method blocks until input data is available, the end of the stream is detected, or an exception is thrown.

A subclass must provide an implementation of this method.

Specified by:
read in class java.io.InputStream
Returns:
the next byte of data, or -1 if the end of the stream is reached.
Throws:
java.io.IOException - if an I/O error occurs.

isObsolete

boolean isObsolete()
Checks if underlying StreamControl has been updated.

Returns:
if stream is modified since created

reInitialize

void reInitialize()
Reinitializes the stream and sets the current pointer to zero.


length

long length()
      throws java.io.IOException
Returns size of stream in bytes.

Returns:
size of stream.
Throws:
java.io.IOException

asInputStream

public java.io.InputStream asInputStream()
Description copied from interface: PositionedStream
Returns a reference to self as an InputStream.

This method is not allowed to return null.

Specified by:
asInputStream in interface PositionedStream
Returns:
An InputStream reference to self.

getPosition

public long getPosition()
Returns the current byte position.

Specified by:
getPosition in interface PositionedStream
Returns:
The current byte position.

reposition

public void reposition(long requestedPos)
                throws java.io.IOException
Repositions the stream to the requested byte position.

Specified by:
reposition in interface PositionedStream
Parameters:
requestedPos - the requested position, starting at 0
Throws:
java.io.EOFException - if the requested position is larger than the length
java.io.IOException - if obtaining the stream length fails

Built on Thu 2012-03-29 21:53:33+0000, from revision ???

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