antlr
Class InputBuffer

java.lang.Object
  |
  +--antlr.InputBuffer
Direct Known Subclasses:
ByteBuffer, CharBuffer, DebuggingInputBuffer

public abstract class InputBuffer
extends Object

A Stream of characters fed to the lexer from a InputStream that can be rewound via mark()/rewind() methods.

A dynamic array is used to buffer up all the input characters. Normally, "k" characters are stored in the buffer. More characters may be stored during guess mode (testing syntactic predicate), or when LT(i>k) is referenced. Consumption of characters is deferred. In other words, reading the next character is not done by conume(), but deferred until needed by LA or LT.

See Also:
CharQueue

Field Summary
protected  int markerOffset
           
protected  int nMarkers
           
protected  int numToConsume
           
protected  CharQueue queue
           
 
Constructor Summary
InputBuffer()
          Create an input buffer
 
Method Summary
 void commit()
          This method updates the state of the input buffer so that the text matched since the most recent mark() is no longer held by the buffer.
 void consume()
          Mark another character for deferred consumption
abstract  void fill(int amount)
          Ensure that the input buffer is sufficiently full
 String getLAChars()
           
 String getMarkedChars()
           
 boolean isMarked()
           
 char LA(int i)
          Get a lookahead character
 int mark()
          Return an integer marker that can be used to rewind the buffer to its current state.
 void reset()
          Reset the input buffer
 void rewind(int mark)
          Rewind the character buffer to a marker.
protected  void syncConsume()
          Sync up deferred consumption
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

nMarkers

protected int nMarkers

markerOffset

protected int markerOffset

numToConsume

protected int numToConsume

queue

protected CharQueue queue
Constructor Detail

InputBuffer

public InputBuffer()
Create an input buffer

Method Detail

commit

public void commit()
This method updates the state of the input buffer so that the text matched since the most recent mark() is no longer held by the buffer. So, you either do a mark/rewind for failed predicate or mark/commit to keep on parsing without rewinding the input.


consume

public void consume()
Mark another character for deferred consumption


fill

public abstract void fill(int amount)
                   throws CharStreamException
Ensure that the input buffer is sufficiently full

CharStreamException

getLAChars

public String getLAChars()

getMarkedChars

public String getMarkedChars()

isMarked

public boolean isMarked()

LA

public char LA(int i)
        throws CharStreamException
Get a lookahead character

CharStreamException

mark

public int mark()
Return an integer marker that can be used to rewind the buffer to its current state.


rewind

public void rewind(int mark)
Rewind the character buffer to a marker.

Parameters:
mark - Marker returned previously from mark()

reset

public void reset()
Reset the input buffer


syncConsume

protected void syncConsume()
Sync up deferred consumption



Copyright 1999-2003 Oliver Zeigermann. All Rights Reserved.