Package org.apache.commons.io.input

Class NullInputStream

java.lang.Object

java.io.InputStream

org.apache.commons.io.input.NullInputStream

public class NullInputStream
extends java.io.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 < length; i++) {
              bytes[i] = ... // set array value here
          }
      }
  }
 

Since:

1.3

Version:

$Id$

Constructor Summary

Constructors

Constructor	Description
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

Modifier and Type	Method	Description
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.
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.

Methods inherited from class java.io.InputStream

readAllBytes, readNBytes, transferTo

Methods inherited from class java.lang.Object

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

Constructor Detail

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 Detail

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.

available

public int available()

Return the number of bytes that can be read.

Overrides:

available in class java.io.InputStream

Returns:

The number of bytes that can be read.

close

public void close()
           throws java.io.IOException

Close this input stream - resets the internal state to the initial values.

Overrides:

close in class java.io.InputStream

Throws:

java.io.IOException - If an error occurs.

mark

public void mark(int readlimit)

Mark the current position.

Overrides:

mark in class java.io.InputStream

Parameters:

readlimit - The number of bytes before this marked position is invalid.

Throws:

java.lang.UnsupportedOperationException - if mark is not supported.

markSupported

public boolean markSupported()

Indicates whether mark is supported.

Overrides:

markSupported in class java.io.InputStream

Returns:

Whether mark is supported or not.

read

public int read()
         throws java.io.IOException

Read a byte.

Specified by:

read in class java.io.InputStream

Returns:

Either The byte value returned by processByte() or -1 if the end of file has been reached and throwEofException is set to false.

Throws:

java.io.EOFException - if the end of file is reached and throwEofException is set to true.

java.io.IOException - if trying to read past the end of file.

read

public int read(byte[] bytes)
         throws java.io.IOException

Read some bytes into the specified array.

Overrides:

read in class java.io.InputStream

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.

Throws:

java.io.EOFException - if the end of file is reached and throwEofException is set to true.

java.io.IOException - if trying to read past the end of file.

read

public int read(byte[] bytes,
                int offset,
                int length)
         throws java.io.IOException

Read the specified number bytes into an array.

Overrides:

read in class java.io.InputStream

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.

Throws:

java.io.EOFException - if the end of file is reached and throwEofException is set to true.

java.io.IOException - if trying to read past the end of file.

reset

public void reset()
           throws java.io.IOException

Reset the stream to the point when mark was last called.

Overrides:

reset in class java.io.InputStream

Throws:

java.lang.UnsupportedOperationException - if mark is not supported.

java.io.IOException - If no position has been marked or the read limit has been exceed since the last position was marked.

skip

public long skip(long numberOfBytes)
          throws java.io.IOException

Skip a specified number of bytes.

Overrides:

skip in class java.io.InputStream

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.

Throws:

java.io.EOFException - if the end of file is reached and throwEofException is set to true.

java.io.IOException - if trying to read past the end of file.

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.