org.entityfs.util.io
Class InputStreamBackedRandomAccess

java.lang.Object
  org.entityfs.util.io.InputStreamBackedRandomAccess

All Implemented Interfaces:

DataSink, DataSource, RandomAccess

public class InputStreamBackedRandomAccess
extends Object
implements RandomAccess

This is a read only RandomAccess that reads its data from a backing InputStream. Since input streams only can be read forwards, this object discards and creates input streams as needed using a ObjectFactory for InputStream:s.

The InputStreamBackedRandomAccess can be used to use a file in a file system that does not support the FSCRandomAccessFiles capability as a read only RandomAccess anyway. See also the TempFileBackedRandomAccess class that supports writing and may be faster if there are many random reads.

This object is not thread safe. Depending on the type of ObjectFactory used, it may be possible to make it thread safe by using an appropriate synchronization strategy.

Since:

1.0

Author:

Karl Gustafsson

See Also:

TempFileBackedRandomAccess

Constructor Summary

InputStreamBackedRandomAccess(ObjectFactory<? extends InputStream> isf)
Create a InputStreamBackedRandomAccess that is backed by the input streams created by the supplied factory.

InputStreamBackedRandomAccess(ObjectFactory<? extends InputStream> isf, long fileLen)
Create a InputStreamBackedRandomAccess that is backed by the input streams created by the supplied factory.

Method Summary

void	addCloseObserver(RandomAccessCloseObserver raco) Add an observer that is notified when this RandomAccess is closed.
int	available() Returns an estimate of the number of bytes that can be read from this data source without blocking by the next invocation of a method for this data source.
void	close() Close the sink and free all resources associated with it.
protected void	finalize()
void	flush() Flush changes made to the sink to the underlying storage.
long	getFilePointer() Get the current offset in the file.
RandomAccessMode	getMode() Get the mode that this RandomAccess was opened in.
long	length() Get the file's current length.
int	read() Read a byte of data from the source.
int	read(byte[] barr) Read up to b.length bytes of data from the source into the array.
int	read(byte[] barr, int off, int len) Read up to len bytes of data from the source into the array.
void	seek(long pos) Set the file pointer offset, measured from the beginning of the file.
void	setLength(long l) Set the length of the file.
long	skipBytes(long n) Attempt to skip over n bytes in the source.
void	write(byte[] barr) Write the contents of the array to the sink, starting at the current file pointer.
void	write(byte[] barr, int off, int len) Write len bytes from the array, starting at the offset off to this sink.
void	write(int b) Write a byte to the sink.

Methods inherited from class java.lang.Object

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

Constructor Detail

InputStreamBackedRandomAccess

public InputStreamBackedRandomAccess(ObjectFactory<? extends InputStream> isf)

Create a InputStreamBackedRandomAccess that is backed by the input streams created by the supplied factory.

If you know how much data that can be read from the backing streams, use the InputStreamBackedRandomAccess(ObjectFactory, long) constructor instead.

Parameters:

isf - A factory for input streams.

InputStreamBackedRandomAccess

public InputStreamBackedRandomAccess(ObjectFactory<? extends InputStream> isf,
                                     long fileLen)

Create a InputStreamBackedRandomAccess that is backed by the input streams created by the supplied factory.

Parameters:

isf - A factory for input streams.

fileLen - The amount of data that can be read from the backing streams. By setting this, the length() method does not have to calculate the file length.

Method Detail

available

public int available()

Description copied from interface: DataSource

Returns an estimate of the number of bytes that can be read from this data source without blocking by the next invocation of a method for this data source.

Specified by:

available in interface DataSource

Returns:

An estimate of the number of bytes that can be read without blocking.

See Also:

InputStream.available()

getFilePointer

public long getFilePointer()

Description copied from interface: RandomAccess

Get the current offset in the file.

Specified by:

getFilePointer in interface RandomAccess

Returns:

The offset from the beginning of the file.

length

public long length()

Description copied from interface: RandomAccess

Get the file's current length.

Specified by:

length in interface RandomAccess

Returns:

The file's current length.

read

public int read()

Description copied from interface: DataSource

Read a byte of data from the source. The byte is returned as an integer in the range 0 to 255 (0x00-0x0ff).

Specified by:

read in interface DataSource

Returns:

The next byte of data, or -1 if the end of the source has been reached.

read

public int read(byte[] barr)

Description copied from interface: DataSource

Read up to b.length bytes of data from the source into the array.

Specified by:

read in interface DataSource

Parameters:

barr - The byte array into which data is read.

Returns:

The total number of bytes read into the array, or -1 if no data could be read because the the end of the source was reached before the read started.

read

public int read(byte[] barr,
                int off,
                int len)

Description copied from interface: DataSource

Read up to len bytes of data from the source into the array.

Specified by:

read in interface DataSource

Parameters:

barr - The byte array into which data is read.

off - The start offset in the array b at which data is written.

len - The maximum number of bytes to read.

Returns:

The total number of bytes read into the array, or -1 if no data could be read because the end of the source was reached before the read started.

seek

public void seek(long pos)

Description copied from interface: RandomAccess

Set the file pointer offset, measured from the beginning of the file. If the offset is set beyond the end of the file does not change the file length until something is written to it.

Specified by:

seek in interface RandomAccess

Parameters:

pos - The new file pointer offset, measured from the beginning of the file.

See Also:

DataSource.skipBytes(long)

setLength

public void setLength(long l)
               throws ReadOnlyException

Description copied from interface: RandomAccess

Set the length of the file.

If the present length of the file is greater than the l argument, the file will be truncated.

If the new length is bigger than the current length of the file, the file will be extended. The contents of the extended portion of the file are not defined.

The current file pointer is not changed, unless the file pointer offset is greater than the new file length. If so, it will be set to the new length.

Specified by:

setLength in interface RandomAccess

Parameters:

l - The new length of the file.

Throws:

ReadOnlyException - Always.

skipBytes

public long skipBytes(long n)

Description copied from interface: DataSource

Attempt to skip over n bytes in the source. If n is negative, no bytes are skipped.

The pointer in the source cannot be moved beyond EOF using this method (unlike RandomAccess.seek(long)).

Specified by:

skipBytes in interface DataSource

Parameters:

n - The number of bytes to increment the source pointer with.

Returns:

The number of bytes actually skipped.

See Also:

RandomAccess.seek(long)

write

public void write(byte[] barr)
           throws ReadOnlyException

Description copied from interface: DataSink

Write the contents of the array to the sink, starting at the current file pointer.

Specified by:

write in interface DataSink

Parameters:

barr - The array to write.

Throws:

ReadOnlyException - Always.

write

public void write(byte[] barr,
                  int off,
                  int len)
           throws ReadOnlyException

Description copied from interface: DataSink

Write len bytes from the array, starting at the offset off to this sink.

Specified by:

write in interface DataSink

Parameters:

barr - The byte array.

off - The starting offset in the array.

len - The number of bytes to write.

Throws:

ReadOnlyException - Always.

write

public void write(int b)
           throws ReadOnlyException

Description copied from interface: DataSink

Write a byte to the sink.

Specified by:

write in interface DataSink

Parameters:

b - The byte to write.

Throws:

ReadOnlyException - Always.

flush

public void flush()
           throws ReadOnlyException

Description copied from interface: DataSink

Flush changes made to the sink to the underlying storage. This is optional to implement, but read only sinks should always throw ReadOnlyException.

Specified by:

flush in interface DataSink

Throws:

ReadOnlyException - Always.

close

public void close()

Description copied from interface: DataSink

Close the sink and free all resources associated with it. If the object is already closed, this method does nothing.

Specified by:

close in interface DataSink

Specified by:

close in interface DataSource

addCloseObserver

public void addCloseObserver(RandomAccessCloseObserver raco)

Description copied from interface: RandomAccess

Add an observer that is notified when this RandomAccess is closed. The observers are called just after the RandomAccess has been closed.

Specified by:

addCloseObserver in interface RandomAccess

Parameters:

raco - The observer.

getMode

public RandomAccessMode getMode()

Description copied from interface: RandomAccess

Get the mode that this RandomAccess was opened in.

This method does not throw an IllegalStateException if it is called after the RandomAccess has been closed.

Specified by:

getMode in interface RandomAccess

Returns:

The mode that this RandomAccess was opened in.

finalize

protected void finalize()
                 throws Throwable

Overrides:

finalize in class Object

Throws:

Throwable