Module org.postgresql.pljava.internal

Package org.postgresql.pljava.internal

Class MarkableSequenceInputStream

java.lang.Object

java.io.InputStream

org.postgresql.pljava.internal.MarkableSequenceInputStream

All Implemented Interfaces:

Closeable, AutoCloseable

public class MarkableSequenceInputStream
extends InputStream

Version of SequenceInputStream that supports mark and reset, to the extent its constituent input streams do.

This class implements mark and reset by calling the corresponding methods on the underlying streams; it does not add buffering or have any means of providing mark and reset support if the underlying streams do not.

As with SequenceInputStream, each underlying stream, when completely read and no longer needed, is closed to free resources. This instance itself will remain in "open at EOF" condition until explicitly closed, but does not prevent reclamation of the underlying streams.

Unlike SequenceInputStream, this class can keep underlying streams open, after fully reading them, if a mark has been set, so that reset will be possible. When a mark is no longer needed, it can be canceled (by calling mark with a readlimit of 0) to again allow the underlying streams to be reclaimed as soon as possible.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	MarkableSequenceInputStream.FetchingListIterator<E>	A ListIterator that will fetch an element from a BlockingQueue whenever hasNext would (otherwise) return false, adding it to the end of the list where the next next() will retrieve it.

Field Summary

Fields

Modifier and Type	Field	Description
static final InputStream	NO_MORE	A sentinel value, needed because a BlockingQueue does not allow a null value to be enqueued.

Constructor Summary

Constructors

Constructor	Description
MarkableSequenceInputStream(InputStream... streams)	Create a MarkableSequenceInputStream from one or more existing input streams.
MarkableSequenceInputStream(BlockingQueue<InputStream> queue)	A MarkableSequenceInputStream that will receive streams to read, in order, over a BlockingQueue.

Method Summary

Modifier and Type	Method	Description
int	available()
void	close()
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()
int	read(byte[] b, int off, int len)
void	reset()
long	skip(long n)

Methods inherited from class java.io.InputStream

nullInputStream, read, readAllBytes, readNBytes, readNBytes, skipNBytes, transferTo

Methods inherited from class java.lang.Object

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

Field Details

NO_MORE

public static final InputStream NO_MORE

A sentinel value, needed because a BlockingQueue does not allow a null value to be enqueued.

Constructor Details

MarkableSequenceInputStream

public MarkableSequenceInputStream(InputStream... streams)

Create a MarkableSequenceInputStream from one or more existing input streams.

Parameters:

streams - Sequence of InputStreams that will be read from in order.

Throws:

NullPointerException - if streams is null, or contains null for any stream.

MarkableSequenceInputStream

public MarkableSequenceInputStream(BlockingQueue<InputStream> queue)

A MarkableSequenceInputStream that will receive streams to read, in order, over a BlockingQueue.

The thread supplying the queue should enqueue the value NO_MORE following the last actual InputStream to read. (The sentinel is needed because a BlockingQueue does not allow null values.)

Parameters:

queue - Source of input streams to read.

Throws:

NullPointerException - if queue is null.

Method Details

read

public int read()
         throws IOException

Specified by:

read in class InputStream

Throws:

IOException

read

public int read(byte[] b,
 int off,
 int len)
         throws IOException

Overrides:

read in class InputStream

Throws:

IOException

skip

public long skip(long n)
          throws IOException

Overrides:

skip in class InputStream

Throws:

IOException

available

public int available()
              throws IOException

Overrides:

available in class InputStream

Throws:

IOException

close

public void close()
           throws IOException

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Closeable

Overrides:

close in class InputStream

Throws:

IOException

mark

public void mark(int readlimit)

Marks the current position in this input stream. In this implementation, it is possible to 'cancel' a mark, by passing this method a readlimit of zero, returning the stream immediately to the state of having no mark.

Overrides:

mark in class InputStream

reset

public void reset()
           throws IOException

Overrides:

reset in class InputStream

Throws:

IOException

markSupported

public boolean markSupported()

Tests if this input stream supports the mark and reset methods.

By the API spec, this method's return is "an invariant property of a particular input stream instance." For any instance of this class, the result is determined by the first call to this method, and does not change thereafter. At the first call, the result is determined only by the underlying input streams remaining to be read (or, if a mark has been set, which is possible before checking this method, then by the underlying input streams including and following the one that was current when the mark was set). The result will be true unless any of those underlying streams reports it as false.

Overrides:

markSupported in class InputStream