Package org.parboiled.buffers

Class IndentDedentInputBuffer

java.lang.Object

org.parboiled.buffers.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

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.