com.github.fge.grappa.run.context

Class DefaultMatcherContext<V>

java.lang.Object

com.github.fge.grappa.run.context.DefaultMatcherContext<V>

All Implemented Interfaces:

Context<V>, MatcherContext<V>

public final class DefaultMatcherContext<V>
extends Object
implements MatcherContext<V>

The Context implementation orchestrating most of the matching process.

The parsing process works as following:

After the rule tree (which is in fact a directed and potentially even cyclic graph of Matcher instances) has been created a root MatcherContext is instantiated for the root rule (Matcher). A subsequent call to runMatcher() starts the parsing process.

The MatcherContext delegates to a given MatchHandler to call Matcher.match(MatcherContext), passing itself to the Matcher which executes its logic, potentially calling sub matchers. For each sub matcher the matcher creates/initializes a subcontext with Matcher.getSubContext(MatcherContext) and then calls runMatcher() on it.

This basically creates a stack of MatcherContexts, each corresponding to their rule matchers. The MatcherContext instances serve as companion objects to the matchers, providing them with support for building the parse tree nodes, keeping track of input locations and error recovery.

At each point during the parsing process the matchers and action expressions have access to the current MatcherContext and all "open" parent MatcherContexts through the getParent() chain.

For performance reasons subcontext instances are reused instead of being recreated. If a MatcherContext instance returns null on a getMatcher() call it has been retired (is invalid) and is waiting to be reinitialized with a new Matcher by its parent

Constructor Summary

Constructors

Constructor and Description
DefaultMatcherContext(InputBuffer inputBuffer, ValueStack<V> valueStack, MatchHandler matchHandler, Matcher matcher) Initializes a new root MatcherContext.

Method Summary

Methods

Modifier and Type	Method and Description
void	advanceIndex(int delta)
MatcherContext<V>	getBasicSubContext()
char	getCurrentChar() Returns the character at the current index..
int	getCurrentCodePoint() Return the code point at the current index
int	getCurrentIndex() Returns the current index in the input buffer.
char	getFirstMatchChar() Returns the first character of the input text matched by the rule immediately preceding the action expression that is currently being evaluated.
InputBuffer	getInputBuffer() Returns the InputBuffer the parser is currently running against
int	getLevel() Returns the current matcher level, with 0 being the root level, 1 being one level below the root and so on.
String	getMatch() Returns the input text matched by the rule immediately preceding the action expression that is currently being evaluated.
int	getMatchEndIndex() Returns the end index of the rule immediately preceding the action expression that is currently being evaluated.
Matcher	getMatcher() Returns the Matcher of this context or null, if this context is not valid anymore.
int	getMatchLength() Returns the number of characters matched by the rule immediately preceding the action expression that is currently being evaluated.
IndexRange	getMatchRange() Creates a new IndexRange instance covering the input text matched by the rule immediately preceding the action expression that is currently being evaluated.
int	getMatchStartIndex() Returns the start index of the rule immediately preceding the action expression that is currently being evaluated.
MatcherContext<V>	getParent()
Position	getPosition() Returns the current position in the underlying InputBuffer as a Position instance.
int	getStartIndex() Returns the index into the underlying input buffer where the matcher of this context started its match.
MatcherContext<V>	getSubContext(Matcher matcher)
ValueStack<V>	getValueStack() Returns the value stack instance used during this parsing run.
boolean	hasError() Determines if this context or any sub node recorded a parse error.
boolean	inPredicate() Determines if the current rule is running somewhere underneath a Test/TestNot rule.
boolean	runMatcher()
void	setCurrentIndex(int currentIndex)
void	setMatcher(Matcher matcher)
void	setStartIndex(int startIndex)
String	toString()

Methods inherited from class java.lang.Object

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

Constructor Detail

DefaultMatcherContext

public DefaultMatcherContext(@Nonnull
                     InputBuffer inputBuffer,
                     @Nonnull
                     ValueStack<V> valueStack,
                     @Nonnull
                     MatchHandler matchHandler,
                     @Nonnull
                     Matcher matcher)

Initializes a new root MatcherContext.

Parameters:

inputBuffer - the InputBuffer for the parsing run

valueStack - the ValueStack instance to use for the parsing run

matchHandler - the MatcherHandler to use for the parsing run

matcher - the root matcher

Method Detail

toString

public String toString()

Overrides:

toString in class Object

getParent

public MatcherContext<V> getParent()

Specified by:

getParent in interface MatcherContext<V>

getInputBuffer

@Nonnull
public InputBuffer getInputBuffer()

Description copied from interface: Context

Returns the InputBuffer the parser is currently running against

Specified by:

getInputBuffer in interface Context<V>

Returns:

the InputBuffer

getStartIndex

public int getStartIndex()

Description copied from interface: Context

Returns the index into the underlying input buffer where the matcher of this context started its match.

Specified by:

getStartIndex in interface Context<V>

Returns:

the start index

getMatcher

public Matcher getMatcher()

Description copied from interface: Context

Returns the Matcher of this context or null, if this context is not valid anymore.

Specified by:

getMatcher in interface Context<V>

Returns:

the matcher

getCurrentChar

public char getCurrentChar()

Description copied from interface: Context

Returns the character at the current index..

Specified by:

getCurrentChar in interface Context<V>

Returns:

the current character

getCurrentCodePoint

public int getCurrentCodePoint()

Description copied from interface: Context

Return the code point at the current index

Specified by:

getCurrentCodePoint in interface Context<V>

Returns:

the code point, or -1 if end of buffer

See Also:

InputBuffer.codePointAt(int)

getCurrentIndex

public int getCurrentIndex()

Description copied from interface: Context

Returns the current index in the input buffer.

Specified by:

getCurrentIndex in interface Context<V>

Returns:

the current index

getLevel

public int getLevel()

Description copied from interface: Context

Returns the current matcher level, with 0 being the root level, 1 being one level below the root and so on.

Specified by:

getLevel in interface Context<V>

Returns:

the current matcher level

inPredicate

public boolean inPredicate()

Description copied from interface: Context

Determines if the current rule is running somewhere underneath a Test/TestNot rule.

Specified by:

inPredicate in interface Context<V>

Returns:

true if the current context has a parent which corresponds to a Test/TestNot rule

hasError

public boolean hasError()

Description copied from interface: Context

Determines if this context or any sub node recorded a parse error.

Specified by:

hasError in interface Context<V>

Returns:

true if this context or any sub node recorded a parse error

getMatch

public String getMatch()

Description copied from interface: Context

Returns the input text matched by the rule immediately preceding the action expression that is currently being evaluated. This call can only be used in actions that are part of a Sequence rule and are not at first position in this Sequence.

Specified by:

getMatch in interface Context<V>

Returns:

the input text matched by the immediately preceding subcontext

getFirstMatchChar

public char getFirstMatchChar()

Description copied from interface: Context

Returns the first character of the input text matched by the rule immediately preceding the action expression that is currently being evaluated. This call can only be used in actions that are part of a Sequence rule and are not at first position in this Sequence.

If the immediately preceding rule did not match anything this method throws a GrammarException. If you need to able to handle that case use the getMatch() method.

Specified by:

getFirstMatchChar in interface Context<V>

Returns:

the input text matched by the immediately preceding subcontext

getMatchStartIndex

public int getMatchStartIndex()

Description copied from interface: Context

Returns the start index of the rule immediately preceding the action expression that is currently being evaluated. This call can only be used in actions that are part of a Sequence rule and are not at first position in this Sequence.

Specified by:

getMatchStartIndex in interface Context<V>

Returns:

the start index of the context immediately preceding current action

getMatchEndIndex

public int getMatchEndIndex()

Description copied from interface: Context

Returns the end index of the rule immediately preceding the action expression that is currently being evaluated. This call can only be used in actions that are part of a Sequence rule and are not at first position in this Sequence.

Specified by:

getMatchEndIndex in interface Context<V>

Returns:

the end index of the context immediately preceding current action, i.e. the index of the character immediately following the last matched character

getMatchLength

public int getMatchLength()

Description copied from interface: Context

Returns the number of characters matched by the rule immediately preceding the action expression that is currently being evaluated. This call can only be used in actions that are part of a Sequence rule and are not at first position in this Sequence.

Specified by:

getMatchLength in interface Context<V>

Returns:

the number of characters matched

getPosition

public Position getPosition()

Description copied from interface: Context

Returns the current position in the underlying InputBuffer as a Position instance.

Specified by:

getPosition in interface Context<V>

Returns:

the current position in the underlying inputbuffer

getMatchRange

public IndexRange getMatchRange()

Description copied from interface: Context

Creates a new IndexRange instance covering the input text matched by the rule immediately preceding the action expression that is currently being evaluated. This call can only be used in actions that are part of a Sequence rule and are not at first position in this Sequence.

Specified by:

getMatchRange in interface Context<V>

Returns:

a new IndexRange instance

getValueStack

public ValueStack<V> getValueStack()

Description copied from interface: Context

Returns the value stack instance used during this parsing run.

Specified by:

getValueStack in interface Context<V>

Returns:

the value stack

setMatcher

public void setMatcher(Matcher matcher)

Specified by:

setMatcher in interface MatcherContext<V>

setStartIndex

public void setStartIndex(int startIndex)

Specified by:

setStartIndex in interface MatcherContext<V>

setCurrentIndex

public void setCurrentIndex(int currentIndex)

Specified by:

setCurrentIndex in interface MatcherContext<V>

advanceIndex

public void advanceIndex(int delta)

Specified by:

advanceIndex in interface MatcherContext<V>

getBasicSubContext

public MatcherContext<V> getBasicSubContext()

Specified by:

getBasicSubContext in interface MatcherContext<V>

getSubContext

public MatcherContext<V> getSubContext(Matcher matcher)

Specified by:

getSubContext in interface MatcherContext<V>

runMatcher

public boolean runMatcher()

Specified by:

runMatcher in interface MatcherContext<V>