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 < length; i++) {
              bytes[i] = ... // set array value here
          }
      }
  }
 

Since: Commons IO 1.3

Version: $Revision: 463529 $

Field Summary
booleaneof
longmark
booleanmarkSupported
longposition
longreadlimit
longsize
booleanthrowEofException
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
intavailable()
Return the number of bytes that can be read.
voidclose()
Close this input stream - resets the internal state to the initial values.
intdoEndOfFile()
Handle End of File.
longgetPosition()
Return the current position.
longgetSize()
Return the size this InputStream emulates.
voidmark(int readlimit)
Mark the current position.
booleanmarkSupported()
Indicates whether mark is supported.
protected intprocessByte()
Return a byte value for the read() method.
protected voidprocessBytes(byte[] bytes, int offset, int length)
Process the bytes for the read(byte[], offset, length) method.
intread()
Read a byte.
intread(byte[] bytes)
Read some bytes into the specified array.
intread(byte[] bytes, int offset, int length)
Read the specified number bytes into an array.
voidreset()
Reset the stream to the point when mark was last called.
longskip(long numberOfBytes)
Skip a specified number of bytes.

Field Detail

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 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

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

Throws: IOException If an error occurs.

doEndOfFile

private int doEndOfFile()
Handle End of File.

Returns: -1 if throwEofException is set to false

Throws: EOFException if throwEofException is set to true.

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.

Throws: UnsupportedOperationException if mark is not supported.

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()
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.

Throws: EOFException if the end of file is reached and throwEofException is set to true. IOException if trying to read past the end of file.

read

public int read(byte[] bytes)
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.

Throws: EOFException if the end of file is reached and throwEofException is set to true. IOException if trying to read past the end of file.

read

public int read(byte[] bytes, int offset, int length)
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.

Throws: EOFException if the end of file is reached and throwEofException is set to true. IOException if trying to read past the end of file.

reset

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

Throws: UnsupportedOperationException if mark is not supported. 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)
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.

Throws: EOFException if the end of file is reached and throwEofException is set to true. IOException if trying to read past the end of file.

Copyright (c) 2002-2011 Apache Software Foundation