org.antlr.runtime
Class ANTLRStringStream

java.lang.Object
  org.antlr.runtime.ANTLRStringStream

All Implemented Interfaces:

CharStream, IntStream

Direct Known Subclasses:

ANTLRFileStream, ANTLRReaderStream

public class ANTLRStringStream
extends Object
implements CharStream

A pretty quick CharStream that pulls all data from an array directly. Every method call counts in the lexer. Java's strings aren't very good so I'm avoiding.

Field Summary

protected int	charPositionInLine The index of the character relative to the beginning of the line 0..n-1
protected char[]	data The data being scanned
protected int	lastMarker Track the last mark() call result value for use in rewind().
protected int	line line number 1..n within the input
protected int	markDepth tracks how deep mark() calls are nested
protected List	markers A list of CharStreamState objects that tracks the stream state values line, charPositionInLine, and p that can change as you move through the input stream.
protected int	n How many characters are actually in the buffer
String	name What is name or source of this char stream?
protected int	p 0..n-1 index into string of next char

Fields inherited from interface org.antlr.runtime.CharStream

EOF

Constructor Summary

ANTLRStringStream()

ANTLRStringStream(char[] data, int numberOfActualCharsInArray)
This is the preferred constructor as no data is copied

ANTLRStringStream(String input)
Copy data in string to a local char array

Method Summary

void	consume()
int	getCharPositionInLine() The index of the character relative to the beginning of the line 0..n-1
int	getLine() ANTLR tracks the line information automatically
String	getSourceName() Where are you getting symbols from? Normally, implementations will pass the buck all the way to the lexer who can ask its input stream for the file name or whatever.
int	index() Return the current input symbol index 0..n where n indicates the last symbol has been read.
int	LA(int i) Get int at current input pointer + i ahead where i=1 is next int.
int	LT(int i) Get the ith character of lookahead.
int	mark() Tell the stream to start buffering if it hasn't already.
void	release(int marker) You may want to commit to a backtrack but don't want to force the stream to keep bookkeeping objects around for a marker that is no longer necessary.
void	reset() Reset the stream so that it's in the same state it was when the object was created *except* the data array is not touched.
void	rewind() Rewind to the input position of the last marker.
void	rewind(int m) Reset the stream so that next call to index would return marker.
void	seek(int index) consume() ahead until p==index; can't just set p=index as we must update line and charPositionInLine.
void	setCharPositionInLine(int pos)
void	setLine(int line) Because this stream can rewind, we need to be able to reset the line
int	size() Only makes sense for streams that buffer everything up probably, but might be useful to display the entire stream or for testing.
String	substring(int start, int stop) For infinite streams, you don't need this; primarily I'm providing a useful interface for action code.
String	toString()

Methods inherited from class java.lang.Object

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

Field Detail

data

protected char[] data

The data being scanned

n

protected int n

How many characters are actually in the buffer

p

protected int p

0..n-1 index into string of next char

line

protected int line

line number 1..n within the input

charPositionInLine

protected int charPositionInLine

The index of the character relative to the beginning of the line 0..n-1

markDepth

protected int markDepth

tracks how deep mark() calls are nested

markers

protected List markers

A list of CharStreamState objects that tracks the stream state values line, charPositionInLine, and p that can change as you move through the input stream. Indexed from 1..markDepth. A null is kept @ index 0. Create upon first call to mark().

lastMarker

protected int lastMarker

Track the last mark() call result value for use in rewind().

name

public String name

What is name or source of this char stream?

Constructor Detail

ANTLRStringStream

public ANTLRStringStream()

ANTLRStringStream

public ANTLRStringStream(String input)

Copy data in string to a local char array

ANTLRStringStream

public ANTLRStringStream(char[] data,
                         int numberOfActualCharsInArray)

This is the preferred constructor as no data is copied

Method Detail

reset

public void reset()

Reset the stream so that it's in the same state it was when the object was created *except* the data array is not touched.

consume

public void consume()

Specified by:

consume in interface IntStream

LA

public int LA(int i)

Description copied from interface: IntStream

Get int at current input pointer + i ahead where i=1 is next int. Negative indexes are allowed. LA(-1) is previous token (token just matched). LA(-i) where i is before first token should yield -1, invalid char / EOF.

Specified by:

LA in interface IntStream

LT

public int LT(int i)

Description copied from interface: CharStream

Get the ith character of lookahead. This is the same usually as LA(i). This will be used for labels in the generated lexer code. I'd prefer to return a char here type-wise, but it's probably better to be 32-bit clean and be consistent with LA.

Specified by:

LT in interface CharStream

index

public int index()

Return the current input symbol index 0..n where n indicates the last symbol has been read. The index is the index of char to be returned from LA(1).

Specified by:

index in interface IntStream

size

public int size()

Description copied from interface: IntStream

Only makes sense for streams that buffer everything up probably, but might be useful to display the entire stream or for testing. This value includes a single EOF.

Specified by:

size in interface IntStream

mark

public int mark()

Description copied from interface: IntStream

Tell the stream to start buffering if it hasn't already. Return current input position, index(), or some other marker so that when passed to rewind() you get back to the same spot. rewind(mark()) should not affect the input cursor. The Lexer track line/col info as well as input index so its markers are not pure input indexes. Same for tree node streams.

Specified by:

mark in interface IntStream

rewind

public void rewind(int m)

Description copied from interface: IntStream

Reset the stream so that next call to index would return marker. The marker will usually be index() but it doesn't have to be. It's just a marker to indicate what state the stream was in. This is essentially calling release() and seek(). If there are markers created after this marker argument, this routine must unroll them like a stack. Assume the state the stream was in when this marker was created.

Specified by:

rewind in interface IntStream

rewind

public void rewind()

Description copied from interface: IntStream

Rewind to the input position of the last marker. Used currently only after a cyclic DFA and just before starting a sem/syn predicate to get the input position back to the start of the decision. Do not "pop" the marker off the state. mark(i) and rewind(i) should balance still. It is like invoking rewind(last marker) but it should not "pop" the marker off. It's like seek(last marker's input position).

Specified by:

rewind in interface IntStream

release

public void release(int marker)

Description copied from interface: IntStream

You may want to commit to a backtrack but don't want to force the stream to keep bookkeeping objects around for a marker that is no longer necessary. This will have the same behavior as rewind() except it releases resources without the backward seek. This must throw away resources for all markers back to the marker argument. So if you're nested 5 levels of mark(), and then release(2) you have to release resources for depths 2..5.

Specified by:

release in interface IntStream

seek

public void seek(int index)

consume() ahead until p==index; can't just set p=index as we must update line and charPositionInLine.

Specified by:

seek in interface IntStream

substring

public String substring(int start,
                        int stop)

Description copied from interface: CharStream

For infinite streams, you don't need this; primarily I'm providing a useful interface for action code. Just make sure actions don't use this on streams that don't support it.

Specified by:

substring in interface CharStream

getLine

public int getLine()

Description copied from interface: CharStream

ANTLR tracks the line information automatically

Specified by:

getLine in interface CharStream

getCharPositionInLine

public int getCharPositionInLine()

Description copied from interface: CharStream

The index of the character relative to the beginning of the line 0..n-1

Specified by:

getCharPositionInLine in interface CharStream

setLine

public void setLine(int line)

Description copied from interface: CharStream

Because this stream can rewind, we need to be able to reset the line

Specified by:

setLine in interface CharStream

setCharPositionInLine

public void setCharPositionInLine(int pos)

Specified by:

setCharPositionInLine in interface CharStream

getSourceName

public String getSourceName()

Description copied from interface: IntStream

Where are you getting symbols from? Normally, implementations will pass the buck all the way to the lexer who can ask its input stream for the file name or whatever.

Specified by:

getSourceName in interface IntStream

toString

public String toString()

Overrides:

toString in class Object