Package org.apache.tika.io

Class LookaheadInputStream

java.lang.Object

java.io.InputStream

org.apache.tika.io.LookaheadInputStream

All Implemented Interfaces:

Closeable, AutoCloseable

public class LookaheadInputStream
extends InputStream

Stream wrapper that make it easy to read up to n bytes ahead from a stream that supports the mark feature. This class insulates the underlying stream from things like possible mark(), reset() and close() calls by external components that might otherwise invalidate the marked state of a stream.

The recommended usage pattern of this class is:

     try (InputStream lookahead = new LookaheadInputStream(stream, n)) {
         processStream(lookahead);
     }
 

This usage pattern guarantees that only up to n bytes from the original stream can ever be read, and that the stream will have been marked and then reset to its original state once the above code block exits. No code in the fictional processStream() method can affect the the state of the original stream.

Since:

Apache Tika 0.10

Constructor Summary

Constructors

Constructor	Description
LookaheadInputStream(InputStream stream, int n)	Creates a lookahead wrapper for the given input stream.

Method Summary

Modifier and Type	Method	Description
int	available()
void	close()
void	mark(int readlimit)
boolean	markSupported()
int	read()
int	read(byte[] b, int off, int len)
void	reset()
long	skip(long n)

Methods inherited from class java.io.InputStream

nullInputStream, read, readAllBytes, readNBytes, readNBytes, transferTo

Methods inherited from class java.lang.Object

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

Constructor Detail

LookaheadInputStream

public LookaheadInputStream(InputStream stream,
                            int n)

Creates a lookahead wrapper for the given input stream. The given input stream should support the mark feature, as otherwise the state of that stream will be undefined after the lookahead wrapper has been closed. As a special case a null stream is treated as an empty stream.

Parameters:

stream - input stream, can be null

n - maximum number of bytes to look ahead

Method Detail

close

public void close()
           throws IOException

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Closeable

Overrides:

close in class InputStream

Throws:

IOException

read

public int read()
         throws IOException

Specified by:

read in class InputStream

Throws:

IOException

read

public int read(byte[] b,
                int off,
                int len)
         throws IOException

Overrides:

read in class InputStream

Throws:

IOException

skip

public long skip(long n)
          throws IOException

Overrides:

skip in class InputStream

Throws:

IOException

available

public int available()

Overrides:

available in class InputStream

markSupported

public boolean markSupported()

Overrides:

markSupported in class InputStream

mark

public void mark(int readlimit)

Overrides:

mark in class InputStream

reset

public void reset()

Overrides:

reset in class InputStream