Package org.antlr.runtime

Class 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

      Fields 
      Modifier and Type Field Description
      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<CharStreamState> 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

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      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()  

    • 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<CharStreamState> 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

      • 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