org.antlr.runtime

Class CommonTokenStream

java.lang.Object

org.antlr.runtime.CommonTokenStream

All Implemented Interfaces:

IntStream, TokenStream

Direct Known Subclasses:

TokenRewriteStream

public class CommonTokenStream
extends Object
implements TokenStream

The most common stream of tokens is one where every token is buffered up and tokens are prefiltered for a certain channel (the parser will only see these tokens and cannot change the filter channel number during the parse). TODO: how to access the full token stream? How to track all tokens matched per rule?

Field Summary

Fields

Modifier and Type	Field and Description
protected int	channel Skip tokens on any channel but this one; this is how we skip whitespace...
protected Map	channelOverrideMap Map to override some Tokens' channel numbers
protected boolean	discardOffChannelTokens By default, track all incoming tokens
protected Set	discardSet Set; discard any tokens with this type
protected int	lastMarker Track the last mark() call result value for use in rewind().
protected int	p The index into the tokens list of the current token (next token to consume).
protected List	tokens Record every single token pulled from the source so we can reproduce chunks of it later.
protected TokenSource	tokenSource

Constructor Summary

Constructors

Constructor and Description
CommonTokenStream()
CommonTokenStream(TokenSource tokenSource)
CommonTokenStream(TokenSource tokenSource, int channel)

Method Summary

Methods

Modifier and Type	Method and Description
void	consume() Move the input pointer to the next incoming token.
void	discardOffChannelTokens(boolean discardOffChannelTokens)
void	discardTokenType(int ttype)
protected void	fillBuffer() Load all tokens from the token source and put in tokens.
Token	get(int i) Return absolute token i; ignore which channel the tokens are on; that is, count all tokens not just on-channel tokens.
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.
List	getTokens()
List	getTokens(int start, int stop)
List	getTokens(int start, int stop, BitSet types) Given a start and stop index, return a List of all tokens in the token type BitSet.
List	getTokens(int start, int stop, int ttype)
List	getTokens(int start, int stop, List types)
TokenSource	getTokenSource() Where is this stream pulling tokens from? This is not the name, but the object that provides Token objects.
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.
protected Token	LB(int k) Look backwards k tokens on-channel tokens
Token	LT(int k) Get the ith token from the current position 1..n where k=1 is the first symbol 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()
void	rewind() Rewind to the input position of the last marker.
void	rewind(int marker) Reset the stream so that next call to index would return marker.
void	seek(int index) Set the input cursor to the position indicated by index.
void	setTokenSource(TokenSource tokenSource) Reset this token stream by setting its token source.
void	setTokenTypeChannel(int ttype, int channel) A simple filter mechanism whereby you can tell this token stream to force all tokens of type ttype to be on channel.
int	size() Only makes sense for streams that buffer everything up probably, but might be useful to display the entire stream or for testing.
protected int	skipOffTokenChannels(int i) Given a starting index, return the index of the first on-channel token.
protected int	skipOffTokenChannelsReverse(int i)
String	toString()
String	toString(int start, int stop) Return the text of all tokens from start to stop, inclusive.
String	toString(Token start, Token stop) Because the user is not required to use a token with an index stored in it, we must provide a means for two token objects themselves to indicate the start/end location.

Methods inherited from class java.lang.Object

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

Field Detail

tokenSource

protected TokenSource tokenSource

tokens

protected List tokens

Record every single token pulled from the source so we can reproduce chunks of it later.

channelOverrideMap

protected Map channelOverrideMap

Map to override some Tokens' channel numbers

discardSet

protected Set discardSet

Set; discard any tokens with this type

channel

protected int channel

Skip tokens on any channel but this one; this is how we skip whitespace...

discardOffChannelTokens

protected boolean discardOffChannelTokens

By default, track all incoming tokens

lastMarker

protected int lastMarker

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

p

protected int p

The index into the tokens list of the current token (next token to consume). p==-1 indicates that the tokens list is empty

Constructor Detail

CommonTokenStream

public CommonTokenStream()

CommonTokenStream

public CommonTokenStream(TokenSource tokenSource)

CommonTokenStream

public CommonTokenStream(TokenSource tokenSource,
                 int channel)

Method Detail

setTokenSource

public void setTokenSource(TokenSource tokenSource)

Reset this token stream by setting its token source.

fillBuffer

protected void fillBuffer()

Load all tokens from the token source and put in tokens. This is done upon first LT request because you might want to set some token type / channel overrides before filling buffer.

consume

public void consume()

Move the input pointer to the next incoming token. The stream must become active with LT(1) available. consume() simply moves the input pointer so that LT(1) points at the next input symbol. Consume at least one token. Walk past any token not on the channel the parser is listening to.

Specified by:

consume in interface IntStream

skipOffTokenChannels

protected int skipOffTokenChannels(int i)

Given a starting index, return the index of the first on-channel token.

skipOffTokenChannelsReverse

protected int skipOffTokenChannelsReverse(int i)

setTokenTypeChannel

public void setTokenTypeChannel(int ttype,
                       int channel)

A simple filter mechanism whereby you can tell this token stream to force all tokens of type ttype to be on channel. For example, when interpreting, we cannot exec actions so we need to tell the stream to force all WS and NEWLINE to be a different, ignored channel.

discardTokenType

public void discardTokenType(int ttype)

discardOffChannelTokens

public void discardOffChannelTokens(boolean discardOffChannelTokens)

getTokens

public List getTokens()

getTokens

public List getTokens(int start,
             int stop)

getTokens

public List getTokens(int start,
             int stop,
             BitSet types)

Given a start and stop index, return a List of all tokens in the token type BitSet. Return null if no tokens were found. This method looks at both on and off channel tokens.

getTokens

public List getTokens(int start,
             int stop,
             List types)

getTokens

public List getTokens(int start,
             int stop,
             int ttype)

LT

public Token LT(int k)

Get the ith token from the current position 1..n where k=1 is the first symbol of lookahead.

Specified by:

LT in interface TokenStream

LB

protected Token LB(int k)

Look backwards k tokens on-channel tokens

get

public Token get(int i)

Return absolute token i; ignore which channel the tokens are on; that is, count all tokens not just on-channel tokens.

Specified by:

get in interface TokenStream

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

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

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

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

index

public int index()

Description copied from interface: IntStream

Return the current input symbol index 0..n where n indicates the last symbol has been read. The index is the symbol about to be read not the most recently read symbol.

Specified by:

index in interface IntStream

rewind

public void rewind(int marker)

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

reset

public void reset()

seek

public void seek(int index)

Description copied from interface: IntStream

Set the input cursor to the position indicated by index. This is normally used to seek ahead in the input stream. No buffering is required to do this unless you know your stream will use seek to move backwards such as when backtracking. This is different from rewind in its multi-directional requirement and in that its argument is strictly an input cursor (index). For char streams, seeking forward must update the stream state such as line number. For seeking backwards, you will be presumably backtracking using the mark/rewind mechanism that restores state and so this method does not need to update state when seeking backwards. Currently, this method is only used for efficient backtracking using memoization, but in the future it may be used for incremental parsing. The index is 0..n-1. A seek to position i means that LA(1) will return the ith symbol. So, seeking to 0 means LA(1) will return the first element in the stream.

Specified by:

seek in interface IntStream

getTokenSource

public TokenSource getTokenSource()

Description copied from interface: TokenStream

Where is this stream pulling tokens from? This is not the name, but the object that provides Token objects.

Specified by:

getTokenSource in interface TokenStream

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

toString

public String toString(int start,
              int stop)

Description copied from interface: TokenStream

Return the text of all tokens from start to stop, inclusive. If the stream does not buffer all the tokens then it can just return "" or null; Users should not access $ruleLabel.text in an action of course in that case.

Specified by:

toString in interface TokenStream

toString

public String toString(Token start,
              Token stop)

Description copied from interface: TokenStream

Because the user is not required to use a token with an index stored in it, we must provide a means for two token objects themselves to indicate the start/end location. Most often this will just delegate to the other toString(int,int). This is also parallel with the TreeNodeStream.toString(Object,Object).

Specified by:

toString in interface TokenStream