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SWT LPEX
v3.0.0

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com.ibm.lpex.core
Class LpexCharStream

java.lang.Object
  com.ibm.lpex.core.LpexCharStream

All Implemented Interfaces:

com.ibm.lpex.cc.UCode_CharStream

public class LpexCharStream

extends Object

implements com.ibm.lpex.cc.UCode_CharStream

A stream interface for LPEX document parsers. This class feeds a lexer with the text in an LPEX document view, formatted as a stream of Unicode characters. It also provides methods for a document parser to set element classes and styles in the text.

Field Summary

StringBuffer

bufferStyles The current styles for the text element in the stream buffer.

Fields inherited from interface com.ibm.lpex.cc.UCode_CharStream

staticFlag

Constructor Summary

LpexCharStream(LpexView lpexView)
Constructor.

Method Summary

void	backup(int amount) Back up input stream by amount steps.
void	backupToStart() Go (back) to the start of the current element.
char	BeginToken() Return the next character that marks the beginning of the next token.
void	Done() The lexer calls this method to indicate it is done with the stream, so that we can free any resources we hold.
boolean	EOFSeen() Check whether EOF was encountered on the last character read.
int	Expand(int endElement) Expand the existing stream in the same LpexView with one or more elements.
int	getBeginColumn() Return ONE-based column number of the first character for the current token (being matched after the last call to BeginToken()).
int	getBeginLine() Return the element number of the first character for the current token (being matched after the last call to BeginToken()).
int	getEndColumn() Return ONE-based column number of the last character for the current token (being matched after the last call to BeginToken()).
int	getEndElement() Return the end element of the parse range.
int	getEndLine() Return the element number of the last character for the current token (being matched after the last call to BeginToken()).
String	GetImage() Return the string from the marked token-beginning to the current buffer position.
LpexView	getLpexView() Return the document view that provides this input stream.
char[]	GetSuffix(int len) Return an array of characters that make up the suffix of length len for the currently matched token.
void	Init(int beginElement, int beginPosition, int endElement, long classClear, long classSet, char styleDefault, boolean clearPending) Initialize the stream for a parse range, for a specific document parser.
void	Init(int beginElement, int endElement, long classClear, long classSet, char styleDefault, boolean clearPending) Initialize the stream for a parse range, for a specific document parser.
char	readChar() Return the next character in the stream.
void	setClasses(long classes) Set additional classes in the current element.
void	setCurrentStyles() Set the styles and classes of the current element in the editor.
boolean	setMargins(int beginMargin, int endMargin, char outMarginsStyle) Set a begin and/or an end margin for the characters to return.
void	setStyles(int beginCol, int endCol, char style) Set additional styles in the current element.
void	skipChar() Skip a character in the stream.

Methods inherited from class java.lang.Object

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

Field Detail

bufferStyles

public StringBuffer bufferStyles

The current styles for the text element in the stream buffer. The document parser sets, through e.g., setStyles(), the appropriate styles as it parses the tokens; then, the entire styles string is automatically set in LPEX by LpexCharStream, through setCurrentStyles(), when a new element is read in.

See Also:

setCurrentStyles()

Constructor Detail

LpexCharStream

public LpexCharStream(LpexView lpexView)

Constructor.

Parameters:

lpexView - the LpexView that provides the input stream

Method Detail

readChar

public final char readChar()
                    throws IOException

Return the next character in the stream. This method can throw any java.io.IOException.

An attempt to read a character beyond the end element of the stream will throw a java.io.EOFException. The range of elements in the stream is specified by beginElement .. endElement in methods Init() and Expand().

Specified by:

readChar in interface com.ibm.lpex.cc.UCode_CharStream

Throws:

IOException

See Also:

Init(int,int,long,long,char,boolean), Expand(int)

getEndColumn

public final int getEndColumn()

Return ONE-based column number of the last character for the current token (being matched after the last call to BeginToken()).

Specified by:

getEndColumn in interface com.ibm.lpex.cc.UCode_CharStream

getEndLine

public final int getEndLine()

Return the element number of the last character for the current token (being matched after the last call to BeginToken()).

Specified by:

getEndLine in interface com.ibm.lpex.cc.UCode_CharStream

getBeginColumn

public final int getBeginColumn()

Return ONE-based column number of the first character for the current token (being matched after the last call to BeginToken()).

Specified by:

getBeginColumn in interface com.ibm.lpex.cc.UCode_CharStream

getBeginLine

public final int getBeginLine()

Return the element number of the first character for the current token (being matched after the last call to BeginToken()).

Specified by:

getBeginLine in interface com.ibm.lpex.cc.UCode_CharStream

backup

public final void backup(int amount)

Back up input stream by amount steps. The lexer calls this method if it had already read some characters, but couldn't use them to match a (longer) token: so they'll be used again as the prefix of the next token.

This method may back up to a previous element (an element previously readChar()-ed in this stream). The same margins setting is assumed for previous elements as is now in effect.

Specified by:

backup in interface com.ibm.lpex.cc.UCode_CharStream

Parameters:

amount - number of characters to back up (push back) in the stream

BeginToken

public final char BeginToken()
                      throws IOException

Return the next character that marks the beginning of the next token.

Note: LpexCharStream guarantees that all the characters remain in the buffer between two successive calls to this method (i.e., the characters from tokenBegin on), so that backup() works correctly.

Specified by:

BeginToken in interface com.ibm.lpex.cc.UCode_CharStream

Throws:

IOException

GetImage

public String GetImage()

Return the string from the marked token-beginning to the current buffer position.

The current implementation of this method always returns an empty string ("").

Specified by:

GetImage in interface com.ibm.lpex.cc.UCode_CharStream

GetSuffix

public char[] GetSuffix(int len)

Return an array of characters that make up the suffix of length len for the currently matched token. Used to build up the matched string for use in actions in the case of MORE.

The current implementation of this method always returns an array which contains just one ('\n') character.

Specified by:

GetSuffix in interface com.ibm.lpex.cc.UCode_CharStream

Parameters:

len - number of characters in the suffix

Done

public void Done()

The lexer calls this method to indicate it is done with the stream, so that we can free any resources we hold.

Specified by:

Done in interface com.ibm.lpex.cc.UCode_CharStream

Init

public final void Init(int beginElement,
                       int endElement,
                       long classClear,
                       long classSet,
                       char styleDefault,
                       boolean clearPending)

Initialize the stream for a parse range, for a specific document parser. Parsing starts at the first character in beginElement, subject to the margin settings in effect.

Parameters:

beginElement - begin element in the parse range

endElement - end element of the parse range. EOF will be returned when trying to read characters past it

classClear - class bit(s) to be cleared for a new element read in - the classClear bit(s) usually represent all the classes assigned to, and handled by, the parser

classSet - class bit(s) to be set by default in a new element read in - the classSet bit(s), usually set by the parser to indicate blank elements, are cleared in method setClasses()

styleDefault - the default style character to be set for the entire element when read in

clearPending - true = once done with an element, remove it from the parse-pending list. This is used in incremental parsing, when looking ahead of just the current element which triggered the parse action: it prevents LPEX from calling the parser once again for this element, it it was itself modified (e.g., in a block-copy operation)

See Also:

Init(int,int,int,long,long,char,boolean)

Init

public final void Init(int beginElement,
                       int beginPosition,
                       int endElement,
                       long classClear,
                       long classSet,
                       char styleDefault,
                       boolean clearPending)

Initialize the stream for a parse range, for a specific document parser. Parsing starts from the given beginPosition in beginElement, subject to the margin settings in effect. The first position in an element is 1. The original element classes and the styles prior to beginPosition are kept.

See Also:

Init(int,int,long,long,char,boolean)

setMargins

public final boolean setMargins(int beginMargin,
                                int endMargin,
                                char outMarginsStyle)

Set a begin and/or an end margin for the characters to return. Next call to readChar() will return the next character positioned inside the margins set by this method.

Method readChar() only returns characters that are positioned in columns beginMargin .. endMargin of text elements. The first column of a text element is 1. Setting margins for the characters to be considered as part of the input stream buffer received by the parser is useful in certain column-sensitive languages, such as PL/I.

A call to Init() clears any margins in effect: all the characters in the text elements of the view will be returned by subsequent readChar() calls.

The style indicated will be set in the editor (by setCurrentStyles()) for the characters outside the margins in effect.

Parameters:

beginMargin - begin margin; 0 indicates no begin margin in effect

endMargin - end margin (must not be below beginMargin); 0 indicates no end margin in effect

outMarginsStyle - style to be set for characters located outside the margins

Returns:

true: all OK, the new margins are in effect

See Also:

Init(int,int,long,long,char,boolean), setCurrentStyles()

Expand

public final int Expand(int endElement)

Expand the existing stream in the same LpexView with one or more elements. For example, the end element in the parse range may be increased when it was determined that more incremental parsing needs to be done to complete a language construct.

If any margins were previously set, they remain in effect. If endElement is not above the current end element, no change takes place in the existing range.

Parameters:

endElement - new end element of the parse range. EOF will be returned when trying to read characters past it

Returns:

the end element of the parse range

getLpexView

public final LpexView getLpexView()

Return the document view that provides this input stream.

getEndElement

public final int getEndElement()

Return the end element of the parse range.

See Also:

Init(int,int,long,long,char,boolean), Expand(int)

EOFSeen

public final boolean EOFSeen()

Check whether EOF was encountered on the last character read. Useful in determining the cause of a TokenMgrError. The EOFSeen condition is cleared by Init(), Expand(), and backup().

See Also:

Init(int,int,long,long,char,boolean), Expand(int), backup(int)

skipChar

public final void skipChar()

Skip a character in the stream. Used to skip the last error character and continue parsing.

backupToStart

public final void backupToStart()

Go (back) to the start of the current element.

setStyles

public final void setStyles(int beginCol,
                            int endCol,
                            char style)

Set additional styles in the current element. The style for a token located at beginCol .. endCol is set to the specified style character. This method does not take into account any margin setting in effect.

Style characters for the text element in the stream buffer are being set by the document parser (e.g., through this method) as it parses the tokens; then, the entire styles string is automatically set in the editor by LpexCharStream (through setCurrentStyles()) when a new element is read in.

Parameters:

beginCol - begin column (first column in an element is 1)

endCol - end column

style - the style character

See Also:

setCurrentStyles()

setClasses

public final void setClasses(long classes)

Set additional classes in the current element. The classes bit-mask specified, if non-zero, is added to the current element after the default classSet bit(s) specified in Init() are first cleared.

The current classes for the text element in the stream buffer are being set by the document parser (through this method) as it parses the tokens; then, the accumulated classes bit-mask is automatically set in the editor by LpexCharStream (through setCurrentStyles()) when a new element is read in.

Parameters:

classes - the classes bit-mask to be added to the current element

See Also:

Init(int,int,long,long,char,boolean), setCurrentStyles()

setCurrentStyles

public final void setCurrentStyles()

Set the styles and classes of the current element in the editor. The styles (in bufferStyles) and the classes that have been set in the current element by the parser through setStyles() and setClasses(), are now set in the editor.

This method is called automatically by LpexCharStream when a new element is being read in an attempt to fill the stream buffer for the next readChar(). A parser may want to explicitly call this method when, for example, a lexical error caused by EOF was raised (i.e., after LpexCharStream has already called this method for the element), in order to update the element with this error's styles & classes. A parser may also call this method when switching to another subparser (lexer) for the rest of an element.

If margin settings are in effect, the style indicated by outMarginsStyle in setMargins() will be set in the editor for all the characters outside the margins.

See Also:

setStyles(int, int, char), setClasses(long), setMargins(int, int, char)