org.apache.commons.io.input

Class NullInputStream

java.lang.Object

java.io.InputStream

org.apache.commons.io.input.NullInputStream

All Implemented Interfaces:

java.io.Closeable, java.lang.AutoCloseable

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

Field Summary

Fields

Modifier and Type	Field and Description
private boolean	eof
static NullInputStream	INSTANCE The singleton instance.
private long	mark
private boolean	markSupported
private long	position
private long	readLimit
private long	size
private boolean	throwEofException

Constructor Summary

Constructors

Constructor and Description
NullInputStream() Constructs an InputStream that emulates a size 0 stream which supports marking and does not throw EOFException.
NullInputStream(long size) Constructs an InputStream that emulates a specified size which supports marking and does not throw EOFException.
NullInputStream(long size, boolean markSupported, boolean throwEofException) Constructs an InputStream that emulates a specified size with option settings.

Method Summary

Modifier and Type	Method and Description
int	available() Returns the number of bytes that can be read.
private void	checkThrowEof(java.lang.String message) Throws EOFException if throwEofException is enabled.
void	close() Closes this input stream - resets the internal state to the initial values.
long	getPosition() Gets the current position.
long	getSize() Gets the size this InputStream emulates.
private int	handleEof() Handles End of File.
void	mark(int readLimit) Marks the current position.
boolean	markSupported() Tests whether mark is supported.
protected int	processByte() Returns a byte value for the read() method.
protected void	processBytes(byte[] bytes, int offset, int length) Processes the bytes for the read(byte[], offset, length) method.
int	read() Reads a byte.
int	read(byte[] bytes) Reads some bytes into the specified array.
int	read(byte[] bytes, int offset, int length) Reads the specified number bytes into an array.
void	reset() Resets the stream to the point when mark was last called.
long	skip(long numberOfBytes) Skips a specified number of bytes.

Methods inherited from class java.lang.Object

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

Field Detail

INSTANCE

public static final NullInputStream INSTANCE

The singleton instance.

Since:

2.12.0

size

private final long size

position

private long position

mark

private long mark

readLimit

private long readLimit

eof

private boolean eof

throwEofException

private final boolean throwEofException

markSupported

private final boolean markSupported

Constructor Detail

NullInputStream

public NullInputStream()

Constructs an InputStream that emulates a size 0 stream which supports marking and does not throw EOFException.

Since:

2.7

NullInputStream

public NullInputStream(long size)

Constructs 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)

Constructs 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

available

public int available()

Returns the number of bytes that can be read.

Overrides:

available in class java.io.InputStream

Returns:

The number of bytes that can be read.

checkThrowEof

private void checkThrowEof(java.lang.String message)
                    throws java.io.EOFException

Throws EOFException if throwEofException is enabled.

Parameters:

message - The EOFException message.

Throws:

java.io.EOFException - Thrown if throwEofException is enabled.

close

public void close()
           throws java.io.IOException

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

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 error occurs.

getPosition

public long getPosition()

Gets the current position.

Returns:

the current position.

getSize

public long getSize()

Gets the size this InputStream emulates.

Returns:

The size of the input stream to emulate.

handleEof

private int handleEof()
               throws java.io.EOFException

Handles End of File.

Returns:

-1 if throwEofException is set to false

Throws:

java.io.EOFException - if throwEofException is set to true.

mark

public void mark(int readLimit)

Marks 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()

Tests whether mark is supported.

Overrides:

markSupported in class java.io.InputStream

Returns:

Whether mark is supported or not.

processByte

protected int processByte()

Returns 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)

Processes 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 java.io.IOException

Reads 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

Reads 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

Reads 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

Resets 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 exceeded since the last position was marked.

skip

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

Skips 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.