Class IndentDedentInputBuffer

  • All Implemented Interfaces:
    InputBuffer

    public class IndentDedentInputBuffer
    extends java.lang.Object
    implements InputBuffer
    Special, immutable InputBuffer implementation for indentation based grammars.

    This InputBuffer collapses all space and tab characters at the beginning of a text line into either nothing (if the line has the same indentation level as the previous line), a special Chars.INDENT character (if the line has a greater indentation level than the previous line) or one or more Chars.DEDENT characters (if the line has a lower indentation level than the previous line).

    Blank lines (lines containing nothing but whitespace) are removed from the input and the buffer can, optionally, remove line comments (i.e. comments that start with a predefined character sequence and go to the end of the line).

    This means that the highest index of this InputBuffer is probably smaller than that of the original input text buffer, since all line indentations and blank lines have been collapsed. However, the implementation will make sure that getPosition(int), extract(int, int), etc. will work as expected and always return the "correct" result from the underlying, original input buffer.

    If the input contains illegal indentation the buffer throws an IllegalIndentationException during construction

    • Constructor Summary

      Constructors 
      Constructor Description
      IndentDedentInputBuffer​(char[] input, int tabStop, java.lang.String lineCommentStart, boolean strict)
      Creates a new IndentDedentInputBuffer around the given char array.
      IndentDedentInputBuffer​(char[] input, int tabStop, java.lang.String lineCommentStart, boolean strict, boolean skipEmptyLines)
      Creates a new IndentDedentInputBuffer around the given char array.
    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      char charAt​(int index)
      Returns the character at the given index.
      java.lang.String extract​(int start, int end)
      Constructs a new String from all character between the given indices.
      java.lang.String extract​(IndexRange range)
      Constructs a new String from all character covered by the given IndexRange.
      java.lang.String extractLine​(int lineNumber)
      Constructs a new String containing all characters with the given line number except for the trailing newline.
      int getLineCount()
      Returns the number of lines in the input buffer.
      int getOriginalIndex​(int index)
      Translates the given index from the scope of this InputBuffer to the scope of the original, underlying char array.
      Position getPosition​(int index)
      Returns the line and column number of the character with the given index encapsulated in a Position object.
      boolean test​(int index, char[] characters)
      Determines whether the characters starting at the given index match the ones from the given array (in order).
      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
    • Constructor Detail

      • IndentDedentInputBuffer

        public IndentDedentInputBuffer​(char[] input,
                                       int tabStop,
                                       java.lang.String lineCommentStart,
                                       boolean strict)
        Creates a new IndentDedentInputBuffer around the given char array. Note that for performance reasons the given char array is not defensively copied.
        Parameters:
        input - the input text.
        tabStop - the number of characters in a tab stop.
        lineCommentStart - the string starting a line comment or null, if line comments are not defined
        strict - signals whether the buffer should throw an IllegalIndentationException on "semi-dedents", if false the buffer silently accepts these
        Throws:
        IllegalIndentationException - if the input contains illegal indentations and the strict flag is set
      • IndentDedentInputBuffer

        public IndentDedentInputBuffer​(char[] input,
                                       int tabStop,
                                       java.lang.String lineCommentStart,
                                       boolean strict,
                                       boolean skipEmptyLines)
        Creates a new IndentDedentInputBuffer around the given char array. Note that for performance reasons the given char array is not defensively copied.
        Parameters:
        input - the input text.
        tabStop - the number of characters in a tab stop.
        lineCommentStart - the string starting a line comment or null, if line comments are not defined
        strict - signals whether the buffer should throw an IllegalIndentationException on "semi-dedents", if false the buffer silently accepts these
        skipEmptyLines - signals whether the buffer should swallow empty lines
        Throws:
        IllegalIndentationException - if the input contains illegal indentations and the strict flag is set
    • Method Detail

      • charAt

        public char charAt​(int index)
        Description copied from interface: InputBuffer
        Returns the character at the given index. If the index is invalid the method returns Chars.EOI.
        Specified by:
        charAt in interface InputBuffer
        Parameters:
        index - the index
        Returns:
        the character at the given index or Chars.EOI.
      • test

        public boolean test​(int index,
                            char[] characters)
        Description copied from interface: InputBuffer
        Determines whether the characters starting at the given index match the ones from the given array (in order).
        Specified by:
        test in interface InputBuffer
        Parameters:
        index - the index into the input buffer where to start the comparison
        characters - the characters to test against the input buffer
        Returns:
        true if matched
      • extract

        public java.lang.String extract​(int start,
                                        int end)
        Description copied from interface: InputBuffer
        Constructs a new String from all character between the given indices. Invalid indices are automatically adjusted to their respective boundary.
        Specified by:
        extract in interface InputBuffer
        Parameters:
        start - the start index (inclusively)
        end - the end index (exclusively)
        Returns:
        a new String (non-interned)
      • extract

        public java.lang.String extract​(IndexRange range)
        Description copied from interface: InputBuffer
        Constructs a new String from all character covered by the given IndexRange.
        Specified by:
        extract in interface InputBuffer
        Parameters:
        range - the IndexRange
        Returns:
        a new String (non-interned)
      • getPosition

        public Position getPosition​(int index)
        Description copied from interface: InputBuffer
        Returns the line and column number of the character with the given index encapsulated in a Position object. The very first character has the line number 1 and the column number 1.
        Specified by:
        getPosition in interface InputBuffer
        Parameters:
        index - the index of the character to get the line number of
        Returns:
        the line number
      • getOriginalIndex

        public int getOriginalIndex​(int index)
        Description copied from interface: InputBuffer
        Translates the given index from the scope of this InputBuffer to the scope of the original, underlying char array. The DefaultInputBuffer implementation simply returns the given index, but other implementations like the IndentDedentInputBuffer or the MutableInputBuffer need to "undo" all compressions and index shiftings performed internally in order to return the underlying index.
        Specified by:
        getOriginalIndex in interface InputBuffer
        Parameters:
        index - the index relative to this InputBuffer
        Returns:
        the index relative to the underlying string or char array
      • extractLine

        public java.lang.String extractLine​(int lineNumber)
        Description copied from interface: InputBuffer
        Constructs a new String containing all characters with the given line number except for the trailing newline.
        Specified by:
        extractLine in interface InputBuffer
        Parameters:
        lineNumber - the line number to get
        Returns:
        the string
      • getLineCount

        public int getLineCount()
        Description copied from interface: InputBuffer
        Returns the number of lines in the input buffer.
        Specified by:
        getLineCount in interface InputBuffer
        Returns:
        number of lines in the input buffer.