scone.util.tokenstream
Class TokenInputStream

java.lang.Object
  scone.util.tokenstream.TokenInputStream

Direct Known Subclasses:

TokenInputStreamBufferImpl, TokenInputStreamTokenizerImpl

public abstract class TokenInputStream
extends java.lang.Object

an InputStream that works on Tokens.
TokenInputStreams are similar to MegInputStreams, but they operate on Token objects instead of bytes. TokenInputStream and TokenOutputStream are examples for the use of MegObject. This class provides static methods that create TokenInputStreams that read data from RequestEvents.

Version:

1.0

Author:

Volkert Buchmann, IBM Almaden Research Center, (c) Copyright IBM Corp 2000

Constructor Summary

TokenInputStream()

Method Summary

abstract void	close() Close the input stream.
static TokenInputStream	create(RequestEvent e) Returns a TokenInputStream that allows to acces the input data provided by the RequestEvent as Tokens.
static TokenInputStream	create(RequestEvent e, java.lang.String tokenizer) Returns a TokenInputStream that allows to acces the input data provided by the RequestEvent as Tokens.
abstract java.util.Hashtable	getMetaInfo() returns the meta info associated with this TokenInputStream
abstract boolean	isClosed() Determines if the input stream is closed.
abstract void	mark(int readAheadLimit) Mark the stream for later resetting
abstract boolean	markSupported() Test whether mark() and reset() are supported.
abstract Token	read() Read a Token from the input stream.
abstract int	read(Token[] buf) Read Tokens from the input stream filling the specified Token array.
abstract int	read(Token[] buf, int offset, int length) Read multiple Tokens from the input stream.
abstract void	reset() Reset the stream to its previous mark

Methods inherited from class java.lang.Object

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

Constructor Detail

TokenInputStream

public TokenInputStream()

Method Detail

create

public static TokenInputStream create(RequestEvent e,
                                      java.lang.String tokenizer)
                               throws java.lang.Exception

Returns a TokenInputStream that allows to acces the input data provided by the RequestEvent as Tokens. If the RequestEvent does not provide a TokenOutputStream as token source, the Tokenizer specified by the tokenizer string will parse the MegInputStream.

Parameters:

e - the RequestEvent

tokenizer - the class name of the tokenizer

Returns:

the TokenInputStream

Throws:

java.lang.Exception

create

public static TokenInputStream create(RequestEvent e)
                               throws java.lang.Exception

Returns a TokenInputStream that allows to acces the input data provided by the RequestEvent as Tokens. If the RequestEvent does not provide a TokenOutputStream as token source, the HtmlTokenizer is used to parse the MegReader.

Parameters:

e - the RequestEvent

Returns:

the TokenInputStream

Throws:

java.lang.Exception

read

public abstract Token read()
                    throws java.io.IOException

Read a Token from the input stream. Blocks if no data available and end of stream not yet reached. If no Token is available because the end of the stream has been reached, null is returned.

Returns:

The next Token from the stream, or null if the end of the stream has been reached

Throws:

java.io.IOException - If stream closed.

MarkPreservedException - If read would invalidate preserved mark

read

public abstract int read(Token[] buf,
                         int offset,
                         int length)
                  throws java.io.IOException

Read multiple Tokens from the input stream. Blocks if no data available and end of stream not yet reached.

Parameters:

buf - The Token buffer to populate.

offset - The offset in buf to starting writing to.

length - The amount of Tokens to write.

Returns:

The amount of Tokens read, or -1 if no more Tokens available to read.

Throws:

java.io.IOException - If stream closed.

MarkPreservedException - If read would invalidate preserved mark

read

public abstract int read(Token[] buf)
                  throws java.io.IOException

Read Tokens from the input stream filling the specified Token array. Blocks if no data available and end of stream not yet reached.

Parameters:

buf - The Token buffer to populate.

Returns:

The amount of Tokens read, or -1 if no more Tokens available to read.

Throws:

java.io.IOException - If stream closed.

MarkPreservedException - If read would invalidate preserved mark

close

public abstract void close()
                    throws java.io.IOException

Close the input stream. If the stream is already closed, this method has not effect.

Throws:

java.io.IOException

isClosed

public abstract boolean isClosed()

Determines if the input stream is closed.

Returns:

true if stream closed; else false.

markSupported

public abstract boolean markSupported()

Test whether mark() and reset() are supported.

Returns:

true if mark() and reset() are supported, false otherwise.

mark

public abstract void mark(int readAheadLimit)
                   throws java.io.IOException

Mark the stream for later resetting

Parameters:

readlimit - The number of Tokens read beyond which the mark will become invalid.

Throws:

java.io.IOException

reset

public abstract void reset()
                    throws java.io.IOException

Reset the stream to its previous mark

Throws:

java.io.IOException - if the stream was not marked or the mark has become invalid.

getMetaInfo

public abstract java.util.Hashtable getMetaInfo()

returns the meta info associated with this TokenInputStream

Returns:

the metaInfo