org.terrier.utility

Class LookAheadReader

java.lang.Object

java.io.Reader

org.terrier.utility.LookAheadReader

All Implemented Interfaces:

Closeable, AutoCloseable, Readable

public class LookAheadReader
extends Reader

Implements a Reader, that encapsulates another stream, but only upto the point that a pre-defined end marker in the stream is identified. The Reader will then become endOfFile, and refuse to return any more characters from the stream. Suppose that we create an instance of a LookAheadReader with the end marker END. For the following input: a b c d END e f g... the LookAheadReader will stop after reading the string END. Note that the end marker will be missing from the parent stream.

Author:

Craig Macdonald, Vassilis Plachouras

See Also:

LookAheadStream

Field Summary

Fields inherited from class java.io.Reader

lock

Constructor Summary

Constructors

Constructor and Description
LookAheadReader(Reader parent, String endMarker) Creates an instance of a LookAheadReader that will read from the given stream until the end marker is found.

Method Summary

Modifier and Type	Method and Description
void	close() Closes the current stream, by setting the end of file flag equal to true.
static void	main(String[] args) A testing method for
void	mark(int x) This method is not implemented.
boolean	markSupported() Support for marking is not implemented.
int	read() Read a character from the parent stream, first checking that it doesnt form part of the end marker.
int	read(char[] cbuf) Read characters into an array.
int	read(char[] cbuf, int offset, int len) Read characters into a portion of an array.
boolean	ready() Indicates whether there are more characters available to read from the stream.
void	reset() Reset the stream.
long	skip(long n) Skips n characters from the stream.

Methods inherited from class java.io.Reader

read

Methods inherited from class java.lang.Object

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

Constructor Detail

LookAheadReader

public LookAheadReader(Reader parent,
                       String endMarker)

Creates an instance of a LookAheadReader that will read from the given stream until the end marker is found.

Parameters:

parent - Reader the stream used for reading the input/

endMarker - String the marker which signifies the end of the stream.

Method Detail

read

public int read()
         throws IOException

Read a character from the parent stream, first checking that it doesnt form part of the end marker.

Overrides:

read in class Reader

Returns:

int the code of the read character, or -1 if the end of the stream has been reached.

Throws:

IOException - if there is any error while reading from the stream.

read

public int read(char[] cbuf)
         throws IOException

Read characters into an array. This method will read 100 characters or the array length, and until the end of the stream is reached. NB: Uses read() internally.

Overrides:

read in class Reader

Parameters:

cbuf - cbuf - Destination buffer

Returns:

The number of characters read, or -1 if the end of the stream has been reached.

Throws:

IOException - If an I/O error occurs

read

public int read(char[] cbuf,
                int offset,
                int len)
         throws IOException

Read characters into a portion of an array. It will try to read the specified number of characters into the buffer. NB:Implemented in terms of read().

Specified by:

read in class Reader

Parameters:

cbuf - Destination buffer

offset - Offset at which to start storing characters

len - Maximum number of characters to read

Returns:

The number of characters read, or -1 if the end of the stream has been reached

Throws:

IOException - If an I/O error occurs

reset

public void reset()
           throws IOException

Reset the stream. Attempts to reset it in some way appropriate to the particular stream, for example by positioning it to its starting point. Not all character-input streams support the reset() operation. Use at your own risk.

Overrides:

reset in class Reader

Throws:

IOException - thrown if ParentStream.reset();

skip

public long skip(long n)
          throws IOException

Skips n characters from the stream. If the end of the stream has been reached before reading n characters, then it returns. NB: This method uses read() internally.

Overrides:

skip in class Reader

Parameters:

n - long the number of characters to skip.

Returns:

long the number of characters skipped.

Throws:

IOException - if there is any error while reading from the stream.

ready

public boolean ready()
              throws IOException

Indicates whether there are more characters available to read from the stream.

Overrides:

ready in class Reader

Returns:

boolean true if there are more characters available for reading, otherwise it returns false.

Throws:

IOException - if there is any error while reading from the stream.

close

public void close()
           throws IOException

Closes the current stream, by setting the end of file flag equal to true.

Specified by:

close in interface Closeable

Specified by:

close in interface AutoCloseable

Specified by:

close in class Reader

Throws:

IOException

markSupported

public boolean markSupported()

Support for marking is not implemented.

Overrides:

markSupported in class Reader

Returns:

boolean false.

mark

public void mark(int x)
          throws IOException

This method is not implemented.

Overrides:

mark in class Reader

Throws:

IOException

main

public static void main(String[] args)

A testing method for

Parameters:

args - the command line arguments, which should contain the name of a file with documents delimited by the second command line argument.