Package org.parboiled.buffers

Class IndentDedentInputBuffer

java.lang.Object
org.parboiled.buffers.IndentDedentInputBuffer
All Implemented Interfaces:
InputBuffer
public class IndentDedentInputBuffer extends 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, String lineCommentStart, boolean strict)
    Creates a new IndentDedentInputBuffer around the given char array.
    IndentDedentInputBuffer(char[] input, int tabStop, String lineCommentStart, boolean strict, boolean skipEmptyLines)
    Creates a new IndentDedentInputBuffer around the given char array.

  • Method Summary

    Modifier and Type
    Method
    Description
    char
    charAt(int index)
    Returns the character at the given index.
    String
    extract(int start, int end)
    Constructs a new String from all character between the given indices.
    String
    extract(IndexRange range)
    Constructs a new String from all character covered by the given IndexRange.
    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

    equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • Constructor Details

    • IndentDedentInputBuffer

      public IndentDedentInputBuffer(char[] input, int tabStop, 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, 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 Details

    • 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 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 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 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.