org.postgresql.largeobject

Class BlobInputStream

java.lang.Object

java.io.InputStream

org.postgresql.largeobject.BlobInputStream

All Implemented Interfaces:

java.io.Closeable, java.lang.AutoCloseable

public class BlobInputStream
extends java.io.InputStream

This is an implementation of an InputStream from a large object.

Field Summary

Fields

Modifier and Type	Field and Description
private long	absolutePosition The absolute position.
private byte[]	buffer Buffer used to improve performance.
private int	bufferPosition Position within buffer.
(package private) static int	DEFAULT_MAX_BUFFER_SIZE
(package private) static int	INITIAL_BUFFER_SIZE
private int	lastBufferSize The amount of bytes to read on the next read.
private long	limit The limit.
private LargeObject	lo The parent LargeObject.
private ResourceLock	lock
private long	markPosition The mark position.
private int	maxBufferSize The buffer size.

Constructor Summary

Constructors

Constructor and Description
BlobInputStream(LargeObject lo)
BlobInputStream(LargeObject lo, int bsize)
BlobInputStream(LargeObject lo, int bsize, long limit)

Method Summary

Modifier and Type	Method and Description
void	close() Closes this input stream and releases any system resources associated with the stream.
private LargeObject	getLo()
private int	getNextBufferSize(int len) Computes the next buffer size to use for reading data from the large object.
void	mark(int readlimit) Marks the current position in this input stream.
boolean	markSupported() Tests if this input stream supports the mark and reset methods.
int	read() The minimum required to implement input stream.
int	read(byte[] dest, int off, int len)
void	reset() Repositions this stream to the position at the time the mark method was last called on this input stream.

Methods inherited from class java.io.InputStream

available, read, skip

Methods inherited from class java.lang.Object

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

Field Detail

DEFAULT_MAX_BUFFER_SIZE

static final int DEFAULT_MAX_BUFFER_SIZE

See Also:

Constant Field Values

INITIAL_BUFFER_SIZE

static final int INITIAL_BUFFER_SIZE

See Also:

Constant Field Values

lo

private LargeObject lo

The parent LargeObject.

lock

private final ResourceLock lock

absolutePosition

private long absolutePosition

The absolute position.

buffer

private byte[] buffer

Buffer used to improve performance.

bufferPosition

private int bufferPosition

Position within buffer.

lastBufferSize

private int lastBufferSize

The amount of bytes to read on the next read. Currently, we nullify buffer, so we can't use buffer.length.

maxBufferSize

private final int maxBufferSize

The buffer size.

markPosition

private long markPosition

The mark position.

limit

private final long limit

The limit.

Constructor Detail

BlobInputStream

public BlobInputStream(LargeObject lo)

Parameters:

lo - LargeObject to read from

BlobInputStream

public BlobInputStream(LargeObject lo,
                       int bsize)

Parameters:

lo - LargeObject to read from

bsize - buffer size

BlobInputStream

public BlobInputStream(LargeObject lo,
                       int bsize,
                       long limit)

Parameters:

lo - LargeObject to read from

bsize - buffer size

limit - max number of bytes to read

Method Detail

read

public int read()
         throws java.io.IOException

The minimum required to implement input stream.

Specified by:

read in class java.io.InputStream

Throws:

java.io.IOException

getNextBufferSize

private int getNextBufferSize(int len)

Computes the next buffer size to use for reading data from the large object. The idea is to avoid allocating too much memory, especially if the user will use just a few bytes of the data.

Parameters:

len - estimated read request

Returns:

next buffer size or maxBufferSize if the buffer should not be increased

read

public int read(byte[] dest,
                int off,
                int len)
         throws java.io.IOException

Overrides:

read in class java.io.InputStream

Throws:

java.io.IOException

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

Specified by:

close in interface java.lang.AutoCloseable

Overrides:

close in class java.io.InputStream

Throws:

java.io.IOException - if an I/O error occurs.

mark

public void mark(int readlimit)

Marks the current position in this input stream. A subsequent call to the reset method repositions this stream at the last marked position so that subsequent reads re-read the same bytes.

The readlimit arguments tells this input stream to allow that many bytes to be read before the mark position gets invalidated.

The general contract of mark is that, if the method markSupported returns true, the stream somehow remembers all the bytes read after the call to mark and stands ready to supply those same bytes again if and whenever the method reset is called. However, the stream is not required to remember any data at all if more than readlimit bytes are read from the stream before reset is called.

Marking a closed stream should not have any effect on the stream.

Overrides:

mark in class java.io.InputStream

Parameters:

readlimit - the maximum limit of bytes that can be read before the mark position becomes invalid.

See Also:

InputStream.reset()

reset

public void reset()
           throws java.io.IOException

Repositions this stream to the position at the time the mark method was last called on this input stream. NB: If mark is not called we move to the beginning.

Overrides:

reset in class java.io.InputStream

Throws:

java.io.IOException

See Also:

InputStream.mark(int), IOException

markSupported

public boolean markSupported()

Tests if this input stream supports the mark and reset methods. The markSupported method of InputStream returns false.

Overrides:

markSupported in class java.io.InputStream

Returns:

true if this true type supports the mark and reset method; false otherwise.

See Also:

InputStream.mark(int), InputStream.reset()

getLo

private LargeObject getLo()
                   throws java.io.IOException

Throws:

java.io.IOException