Package org.antlr.runtime

Class BufferedTokenStream

  • All Implemented Interfaces:
    IntStream, TokenStream
    Direct Known Subclasses:
    CommonTokenStream
    public class BufferedTokenStream
extends Object
implements TokenStream
    Buffer all input tokens but do on-demand fetching of new tokens from lexer. Useful when the parser or lexer has to set context/mode info before proper lexing of future tokens. The ST template parser needs this, for example, because it has to constantly flip back and forth between inside/output templates. E.g., <names:{hi, <it>}> has to parse names as part of an expression but "hi, <it>" as a nested template. You can't use this stream if you pass whitespace or other off-channel tokens to the parser. The stream can't ignore off-channel tokens. (UnbufferedTokenStream is the same way.) This is not a subclass of UnbufferedTokenStream because I don't want to confuse small moving window of tokens it uses for the full buffer.

    • Field Summary

      Fields 
      Modifier and Type Field Description
      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 int range  
      protected List<Token> tokens
      Record every single token pulled from the source so we can reproduce chunks of it later.
      protected TokenSource tokenSource  

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      void consume()
      Move the input pointer to the next incoming token.
      protected void fetch​(int n)
      add n elements to buffer
      void fill()
      Get all tokens from lexer until EOF
      Token get​(int i)
      Get a token at an absolute index i; 0..n-1.
      List<? extends Token> get​(int start, int stop)
      Get all tokens from start..stop inclusively
      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<? extends Token> getTokens()  
      List<? extends Token> getTokens​(int start, int stop)  
      List<? extends Token> getTokens​(int start, int stop, int ttype)  
      List<? extends Token> getTokens​(int start, int stop, List<Integer> types)  
      List<? extends Token> getTokens​(int start, int stop, BitSet types)
      Given a start and stop index, return a List of all tokens in the token type BitSet.
      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)  
      Token LT​(int k)
      Get Token at current input pointer + i ahead where i=1 is next Token.
      int mark()
      Tell the stream to start buffering if it hasn't already.
      int range()
      How far ahead has the stream been asked to look? The return value is a valid index from 0..n-1.
      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.
      protected void setup()  
      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 void sync​(int i)
      Make sure index i in tokens has a token.
      String toString()
      Grab *all* tokens from stream and return string
      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.

    • Field Detail

      • tokens

        protected List<Token> tokens
        Record every single token pulled from the source so we can reproduce chunks of it later. The buffer in LookaheadStream overlaps sometimes as its moving window moves through the input. This list captures everything so we can access complete input text.

      • 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). tokens[p] should be LT(1). p=-1 indicates need to initialize with first token. The ctor doesn't get a token. First call to LT(1) or whatever gets the first token and sets p=0;

      • range

        protected int range

    • Constructor Detail

      • BufferedTokenStream

        public BufferedTokenStream()

      • BufferedTokenStream

        public BufferedTokenStream​(TokenSource tokenSource)

    • Method Detail

      • 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

      • 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

      • range

        public int range()
        Description copied from interface: TokenStream
        How far ahead has the stream been asked to look? The return value is a valid index from 0..n-1.
        Specified by:
        range in interface TokenStream

      • 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

      • 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

      • 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

      • 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

      • sync

        protected void sync​(int i)
        Make sure index i in tokens has a token.

      • fetch

        protected void fetch​(int n)
        add n elements to buffer

      • get

        public Token get​(int i)
        Description copied from interface: TokenStream
        Get a token at an absolute index i; 0..n-1. This is really only needed for profiling and debugging and token stream rewriting. If you don't want to buffer up tokens, then this method makes no sense for you. Naturally you can't use the rewrite stream feature. I believe DebugTokenStream can easily be altered to not use this method, removing the dependency.
        Specified by:
        get in interface TokenStream

      • get

        public List<? extends Token> get​(int start,
                                 int stop)
        Get all tokens from start..stop inclusively

      • 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

      • LB

        protected Token LB​(int k)

      • LT

        public Token LT​(int k)
        Description copied from interface: TokenStream
        Get Token at current input pointer + i ahead where i=1 is next Token. i<0 indicates tokens in the past. So -1 is previous token and -2 is two tokens ago. LT(0) is undefined. For i>=n, return Token.EOFToken. Return null for LT(0) and any index that results in an absolute address that is negative.
        Specified by:
        LT in interface TokenStream

      • setup

        protected void setup()

      • setTokenSource

        public void setTokenSource​(TokenSource tokenSource)
        Reset this token stream by setting its token source.

      • getTokens

        public List<? extends Token> getTokens()

      • getTokens

        public List<? extends Token> getTokens​(int start,
                                       int stop)

      • getTokens

        public List<? extends Token> 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<? extends Token> getTokens​(int start,
                                       int stop,
                                       List<Integer> types)

      • getTokens

        public List<? extends Token> getTokens​(int start,
                                       int stop,
                                       int ttype)

      • 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()
        Grab *all* tokens from stream and return string
        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

      • fill

        public void fill()
        Get all tokens from lexer until EOF