org.netbeans.editor

Class Syntax

java.lang.Object

org.netbeans.editor.Syntax

Direct Known Subclasses:

MultiSyntax

public class Syntax
extends Object

Lexical analyzer that works on a given text buffer. It allows to sequentially parse a given character buffer by calling nextToken() that returns the token-ids. After the token is found by calling the nextToken method, the getTokenOffset() method can be used to get the starting offset of the current token in the buffer. The getTokenLength() gives the length of the current token. The heart of the analyzer is the parseToken() method which parses the text and returns the token-id of the last token found. The parseToken() method is called from the nextToken(). It operates with two important variables. The offset variable identifies the currently scanned character in the buffer. The tokenOffset is the begining of the current token. The state variable that identifies the current internal state of the analyzer is set accordingly when the characters are parsed. If the parseToken() recognizes a token, it returns its ID and the tokenOffset is its begining in the buffer and offset - tokenOffset is its length. When the token is processed the value of tokenOffset is set to be the same as current value of the offset and the parsing continues. Internal states are the integer constants used internally by analyzer. They are assigned to the state variable to express that the analyzer has moved from one state to another. They are usually numbered starting from zero but they don't have to. The only reserved value is -1 which is reserved for the INIT state - the initial internal state of the analyzer. There is also the support for defining the persistent info about the current state of the analyzer. This info can be later used to restore the parsing from some particular state instead of parsing from the begining of the buffer. This feature is very useful if there are the modifications performed in the document. The info is stored in the StateInfo interface with the BaseStateInfo as the basic implementation. It enables to get and set the two important values from the persistent point of view. The first one is the value of the state variable. The other one is the difference offset - tokenOffset which is called pre-scan. The particular analyzer can define additional values important for the persistent storage. The createStateInfo() can be overriden to create custom state-info and loadState() and storeState() can be overriden to get/set the additional values. The load() method sets the buffer to be parsed. There is a special parameter in the load() method called position that allows a relation of the character buffer passed to the load() method and the position of the buffer's data in the document. For this extended functionality the document must be passed to the constructor of the lexical analyzer at some level.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	Syntax.BaseStateInfo Base implementation of the StateInfo interface
static interface	Syntax.StateInfo Interface that stores two basic pieces of information about the state of the whole lexical analyzer - its internal state and preScan.

Field Summary

Fields

Modifier and Type	Field and Description
protected char[]	buffer Text buffer to scan
static int	DIFFERENT_STATE Is the state of analyzer different from given state info?
static int	EQUAL_STATE Is the state of analyzer equal to a given state info?
static int	INIT Initial internal state of the analyzer
protected boolean	lastBuffer Setting this flag to true means that there are currently no more buffers available so that analyzer should return all the tokens including those whose successful scanning would be otherwise left for later when the next buffer will be available.
protected int	offset Current offset in the buffer
protected int	state Internal state of the lexical analyzer.
protected int	stopOffset On which offset in the buffer scanning should stop.
protected int	stopPosition The position in the document that logically corresponds to the stopOffset value.
protected TokenID	supposedTokenID This variable can be populated by the parseToken() method in case the user types an errorneous construction but it's clear what correct token he meant to write.
protected TokenContextPath	tokenContextPath Path from which the found token-id comes from.
protected int	tokenLength This variable is the length of the token that was found
protected int	tokenOffset Offset holding the begining of the current token

Constructor Summary

Constructors

Constructor and Description
Syntax()

Method Summary

Modifier and Type	Method and Description
int	compareState(Syntax.StateInfo stateInfo) Compare state of this analyzer to given state info
Syntax.StateInfo	createStateInfo() Create state info appropriate for particular analyzer
char[]	getBuffer() Get the current buffer
int	getOffset() Get the current scanning offset
int	getPreScan() Get the pre-scan which is a number of characters between offset and tokenOffset.
String	getStateName(int stateNumber) Get state name as string.
TokenID	getSupposedTokenID()
TokenContextPath	getTokenContextPath() Get the token-context-path of the returned token.
int	getTokenLength() Get length of token in scanned buffer.
int	getTokenOffset() Get start of token in scanned buffer.
void	load(Syntax.StateInfo stateInfo, char[] buffer, int offset, int len, boolean lastBuffer, int stopPosition) Load the state from syntax mark into analyzer.
void	loadInitState() Initialize the analyzer when scanning from the begining of the document or when the state stored in syntax mark is null for some reason or to explicitly reset the analyzer to the initial state.
void	loadState(Syntax.StateInfo stateInfo) Load valid mark state into the analyzer.
TokenID	nextToken() Function that should be called externally to scan the text.
protected TokenID	parseToken() This is core function of analyzer and it returns either the token-id or null to indicate that the end of buffer was found.
void	relocate(char[] buffer, int offset, int len, boolean lastBuffer, int stopPosition) Relocate scanning to another buffer.
void	reset()
void	storeState(Syntax.StateInfo stateInfo) Store state of this analyzer into given mark state.
String	toString() Syntax information as String

Methods inherited from class java.lang.Object

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

Field Detail

EQUAL_STATE

public static final int EQUAL_STATE

Is the state of analyzer equal to a given state info?

See Also:

Constant Field Values

DIFFERENT_STATE

public static final int DIFFERENT_STATE

Is the state of analyzer different from given state info?

See Also:

Constant Field Values

INIT

public static final int INIT

Initial internal state of the analyzer

See Also:

Constant Field Values

state

protected int state

Internal state of the lexical analyzer. At the begining it's set to INIT value but it is changed by parseToken() as the characters are processed one by one.

buffer

protected char[] buffer

Text buffer to scan

offset

protected int offset

Current offset in the buffer

tokenOffset

protected int tokenOffset

Offset holding the begining of the current token

tokenLength

protected int tokenLength

This variable is the length of the token that was found

tokenContextPath

protected TokenContextPath tokenContextPath

Path from which the found token-id comes from. The TokenContext.getContextPath() can be used to get the path. If the lexical analyzer doesn't use any children token-contexts it can assign the path in the constructor.

lastBuffer

protected boolean lastBuffer

Setting this flag to true means that there are currently no more buffers available so that analyzer should return all the tokens including those whose successful scanning would be otherwise left for later when the next buffer will be available. Setting this flag to true ensures that all the characters in the current buffer will be processed. The lexical analyzer should on one hand process all the characters but on the other hand it should "save" its context. For example if the scanner finds the unclosed comment at the end of the buffer it should return the comment token but stay in the "being in comment" internal state.

stopOffset

protected int stopOffset

On which offset in the buffer scanning should stop.

stopPosition

protected int stopPosition

The position in the document that logically corresponds to the stopOffset value. If there's no relation to the document, it's -1. The reason why the relation to the document's data is expressed through the stopOffset to stopPosition relation is because the stopOffset is the only offset that doesn't change rapidly in the operation of the lexical analyzer.

supposedTokenID

protected TokenID supposedTokenID

This variable can be populated by the parseToken() method in case the user types an errorneous construction but it's clear what correct token he meant to write. For example if the user writes a single '0x' it's an errorneous construct but it's clear that the user wants to enter the hexa-number. In this situation the parseToken() should report error, but it should also set the supposedTokenID to the hexa-number token. This information is used while drawing the text. If the caret stand inside or around such token, it calls the getSupposedTokenID() after calling the nextToken() and if it's non-null it uses it instead of the original token.

Constructor Detail

Syntax

public Syntax()

Method Detail

nextToken

public TokenID nextToken()

Function that should be called externally to scan the text. It manages the call to parseToken() and cares about the proper setting of the offsets. It can be extended to support any custom debugging required.

parseToken

protected TokenID parseToken()

This is core function of analyzer and it returns either the token-id or null to indicate that the end of buffer was found. The function scans the active character and does one or more of the following actions: 1. change internal analyzer state 2. set the token-context-path and return token-id 3. adjust current position to signal different end of token; the character that offset points to is not included in the token

load

public void load(Syntax.StateInfo stateInfo,
                 char[] buffer,
                 int offset,
                 int len,
                 boolean lastBuffer,
                 int stopPosition)

Load the state from syntax mark into analyzer. This method is used when

Parameters:

stateInfo - info about the state of the lexical analyzer to load. It can be null to indicate there's no previous state so the analyzer starts from its initial state.

buffer - buffer that will be scanned

offset - offset of the first character that will be scanned

len - length of the area to be scanned

lastBuffer - whether this is the last buffer in the document. All the tokens will be returned including the last possibly incomplete one. If the data come from the document, the simple rule for this parameter is (doc.getLength() == stop-position) where stop-position is the position corresponding to the (offset + len) in the buffer that comes from the document data.

stopPosition - position in the document that corresponds to (offset + len) offset in the provided buffer. It has only sense if the data in the buffer come from the document. It helps in writing the advanced analyzers that need to interact with some other data in the document than only those provided in the character buffer. If there is no relation to the document data, the stopPosition parameter must be filled with -1 which means an invalid value. The stop-position is passed (instead of start-position) because it doesn't change through the analyzer operation. It corresponds to the stopOffset that also doesn't change through the analyzer operation so any buffer-offset can be transferred to position by computing stopPosition + buffer-offset - stopOffset where stopOffset is the instance variable that is assigned to offset + len in the body of relocate().

relocate

public void relocate(char[] buffer,
                     int offset,
                     int len,
                     boolean lastBuffer,
                     int stopPosition)

Relocate scanning to another buffer. This is used to continue scanning after previously reported EOT. Relocation delta between current offset and the requested offset is computed and all the offsets are relocated. If there's a non-zero preScan in the analyzer, it is a caller's responsibility to provide all the preScan characters in the relocation buffer.

Parameters:

buffer - next buffer where the scan will continue.

offset - offset where the scan will continue. It's not decremented by the current preScan.

len - length of the area to be scanned. It's not extended by the current preScan.

lastBuffer - whether this is the last buffer in the document. All the tokens will be returned including the last possibly incomplete one. If the data come from the document, the simple rule for this parameter is (doc.getLength() == stop-position) where stop-position is the position corresponding to the (offset + len) in the buffer that comes from the document data.

stopPosition - position in the document that corresponds to (offset + len) offset in the provided buffer. It has only sense if the data in the buffer come from the document. It helps in writing the advanced analyzers that need to interact with some other data in the document than only those provided in the character buffer. If there is no relation to the document data, the stopPosition parameter must be filled with -1 which means an invalid value. The stop-position is passed (instead of start-position) because it doesn't change through the analyzer operation. It corresponds to the stopOffset that also doesn't change through the analyzer operation so any buffer-offset can be transferred to position by computing stopPosition + buffer-offset - stopOffset where stopOffset is the instance variable that is assigned to offset + len in the body of relocate().

getBuffer

public char[] getBuffer()

Get the current buffer

getOffset

public int getOffset()

Get the current scanning offset

getTokenOffset

public int getTokenOffset()

Get start of token in scanned buffer.

getTokenLength

public int getTokenLength()

Get length of token in scanned buffer.

getTokenContextPath

public TokenContextPath getTokenContextPath()

Get the token-context-path of the returned token.

getSupposedTokenID

public TokenID getSupposedTokenID()

getPreScan

public int getPreScan()

Get the pre-scan which is a number of characters between offset and tokenOffset. If there's no more characters in the current buffer, the analyzer returns EOT, but it can be in a state when there are already some characters parsed at the end of the current buffer but the token is still incomplete and it cannot be returned yet. The pre-scan value helps to determine how many characters from the end of the current buffer should be present at the begining of the next buffer so that the current incomplete token can be returned as the first token when parsing the next buffer.

loadInitState

public void loadInitState()

Initialize the analyzer when scanning from the begining of the document or when the state stored in syntax mark is null for some reason or to explicitly reset the analyzer to the initial state. The offsets must not be touched by this method.

reset

public void reset()

loadState

public void loadState(Syntax.StateInfo stateInfo)

Load valid mark state into the analyzer. Offsets are already initialized when this method is called. This method must get the state from the mark and set it to the analyzer. Then it must decrease tokenOffset by the preScan stored in the mark state.

Parameters:

stateInfo - mark state to be loaded into syntax. It must be non-null value.

storeState

public void storeState(Syntax.StateInfo stateInfo)

Store state of this analyzer into given mark state.

compareState

public int compareState(Syntax.StateInfo stateInfo)

Compare state of this analyzer to given state info

createStateInfo

public Syntax.StateInfo createStateInfo()

Create state info appropriate for particular analyzer

getStateName

public String getStateName(int stateNumber)

Get state name as string. It can be used for debugging purposes by developer of new syntax analyzer. The states that this function recognizes can include all constants used in analyzer so that it can be used everywhere in analyzer to convert numbers to more practical strings.

toString

public String toString()

Syntax information as String

Overrides:

toString in class Object