org.apache.commons.io.input

Class NullInputStream


public class NullInputStream
extends InputStream

A functional, light weight InputStream that emulates a stream of a specified size.

This implementation provides a light weight object for testing with an InputStream where the contents don't matter.

One use case would be for testing the handling of large InputStream as it can emulate that scenario without the overhead of actually processing large numbers of bytes - significantly speeding up test execution times.

This implementation returns zero from the method that reads a byte and leaves the array unchanged in the read methods that are passed a byte array. If alternative data is required the processByte() and processBytes() methods can be implemented to generate data, for example:

  public class TestInputStream extends NullInputStream {
      public TestInputStream(int size) {
          super(size);
      }
      protected int processByte() {
          return ... // return required value here
      }
      protected void processBytes(byte[] bytes, int offset, int length) {
          for (int i = offset; i <32length; i++) {
              bytes[i] = ... // set array value here
          }
      }
  }
 
Version:
$Revision: 463529 $
Since:
Commons IO 1.3

Field Summary

private boolean
eof
private long
mark
private boolean
markSupported
private long
position
private long
readlimit
private long
size
private boolean
throwEofException

Constructor Summary

NullInputStream(long size)
Create an InputStream that emulates a specified size which supports marking and does not throw EOFException.
NullInputStream(long size, boolean markSupported, boolean throwEofException)
Create an InputStream that emulates a specified size with option settings.

Method Summary

int
available()
Return the number of bytes that can be read.
void
close()
Close this input stream - resets the internal state to the initial values.
private int
doEndOfFile()
Handle End of File.
long
getPosition()
Return the current position.
long
getSize()
Return the size this InputStream emulates.
void
mark(int readlimit)
Mark the current position.
boolean
markSupported()
Indicates whether mark is supported.
protected int
processByte()
Return a byte value for the read() method.
protected void
processBytes(byte[] bytes, int offset, int length)
Process the bytes for the read(byte[], offset, length) method.
int
read()
Read a byte.
int
read(byte[] bytes)
Read some bytes into the specified array.
int
read(byte[] bytes, int offset, int length)
Read the specified number bytes into an array.
void
reset()
Reset the stream to the point when mark was last called.
long
skip(long numberOfBytes)
Skip a specified number of bytes.

Field Details

eof

private boolean eof

mark

private long mark

markSupported

private boolean markSupported

position

private long position

readlimit

private long readlimit

size

private long size

throwEofException

private boolean throwEofException

Constructor Details

NullInputStream

public NullInputStream(long size)
Create an InputStream that emulates a specified size which supports marking and does not throw EOFException.
Parameters:
size - The size of the input stream to emulate.

NullInputStream

public NullInputStream(long size,
                       boolean markSupported,
                       boolean throwEofException)
Create an InputStream that emulates a specified size with option settings.
Parameters:
size - The size of the input stream to emulate.
markSupported - Whether this instance will support the mark() functionality.
throwEofException - Whether this implementation will throw an EOFException or return -1 when the end of file is reached.

Method Details

available

public int available()
Return the number of bytes that can be read.
Returns:
The number of bytes that can be read.

close

public void close()
            throws IOException
Close this input stream - resets the internal state to the initial values.

doEndOfFile

private int doEndOfFile()
            throws EOFException
Handle End of File.
Returns:
-1 if throwEofException is set to false

getPosition

public long getPosition()
Return the current position.
Returns:
the current position.

getSize

public long getSize()
Return the size this InputStream emulates.
Returns:
The size of the input stream to emulate.

mark

public void mark(int readlimit)
Mark the current position.
Parameters:
readlimit - The number of bytes before this marked position is invalid.

markSupported

public boolean markSupported()
Indicates whether mark is supported.
Returns:
Whether mark is supported or not.

processByte

protected int processByte()
Return a byte value for the read() method.

This implementation returns zero.

Returns:
This implementation always returns zero.

processBytes

protected void processBytes(byte[] bytes,
                            int offset,
                            int length)
Process the bytes for the read(byte[], offset, length) method.

This implementation leaves the byte array unchanged.

Parameters:
bytes - The byte array
offset - The offset to start at.
length - The number of bytes.

read

public int read()
            throws IOException
Read a byte.
Returns:
Either The byte value returned by processByte() or -1 if the end of file has been reached and throwEofException is set to false.

read

public int read(byte[] bytes)
            throws IOException
Read some bytes into the specified array.
Parameters:
bytes - The byte array to read into
Returns:
The number of bytes read or -1 if the end of file has been reached and throwEofException is set to false.

read

public int read(byte[] bytes,
                int offset,
                int length)
            throws IOException
Read the specified number bytes into an array.
Parameters:
bytes - The byte array to read into.
offset - The offset to start reading bytes into.
length - The number of bytes to read.
Returns:
The number of bytes read or -1 if the end of file has been reached and throwEofException is set to false.

reset

public void reset()
            throws IOException
Reset the stream to the point when mark was last called.

skip

public long skip(long numberOfBytes)
            throws IOException
Skip a specified number of bytes.
Parameters:
numberOfBytes - The number of bytes to skip.
Returns:
The number of bytes skipped or -1 if the end of file has been reached and throwEofException is set to false.