org.waxeye.parser.Parser Maven / Gradle / Ivy
/*
* Waxeye Parser Generator
* www.waxeye.org
* Copyright (C) 2008-2010 Orlando Hill
* Licensed under the MIT license. See 'LICENSE' for details.
*/
package org.waxeye.parser;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Stack;
import org.waxeye.ast.AST;
import org.waxeye.ast.Char;
import org.waxeye.ast.Empty;
import org.waxeye.ast.IAST;
import org.waxeye.ast.Position;
import org.waxeye.input.IParserInput;
/**
* Implements the logic of the parser.
*
* @param The node types for the AST.
*
* @author Orlando Hill
*/
public abstract class Parser > implements IParser
{
/** The empty node. */
private final IAST empty;
/** The char type. */
private final E charType;
/** The pos type. */
private final E posType;
/** The neg type. */
private final E negType;
/** The automata of the parser. */
private final List> automata;
/** Whether to check that all input gets parsed. */
private final boolean eofCheck;
/** The starting automaton. */
private final int start;
/**
* Creates a new Parser.
*
* @param automata The automata of the parser.
*
* @param eofCheck Whether to check that all input gets parsed.
*
* @param start The starting automaton.
*
* @param emptyType The empty type.
*
* @param charType The char type.
*
* @param posType The positive check type.
*
* @param negType The negative check type.
*/
public Parser(final List> automata, final boolean eofCheck,
final int start,
final E emptyType, final E charType, final E posType, final E negType)
{
this.automata = automata;
this.eofCheck = eofCheck;
this.start = start;
this.empty = new Empty(emptyType);
this.charType = charType;
this.posType = posType;
this.negType = negType;
}
/** {@inheritDoc} */
public final ParseResult parse(final IParserInput input)
{
return new InnerParser(input).parse();
}
/**
* A hidden inner class so that we can visit the transition costs without
* exposing things to the API user.
*
* @author Orlando Hill
*/
private final class InnerParser implements ITransitionVisitor
{
/** The input to parse. */
private final IParserInput input;
/** The automata stack. */
private final Stack> faStack;
/** The result cache. */
private final HashMap> cache;
/** The line number. */
private int line;
/** The column number. */
private int column;
/** Whether the last character was a carriage return. */
private boolean lastCR;
/** The position of the deepest error. */
private int errorPos;
/** The line of the deepest error. */
private int errorLine;
/** The column of the deepest error. */
private int errorCol;
/** The nt deepest error. */
private String errorNT;
/**
* Creates a new Parser.
*
* @param input The input to parse.
*/
InnerParser(final IParserInput input)
{
this.input = input;
this.faStack = new Stack>();
this.cache = new HashMap>();
this.line = 1;
this.column = 0;
this.lastCR = false;
this.errorPos = 0;
this.errorLine = 1;
this.errorCol = 0;
this.errorNT = automata.get(start).getType().name();
}
/**
* Parses the input.
*
* @return The result of the parse.
*/
ParseResult parse()
{
IAST ast = matchAutomaton(start);
ParseError error = null;
if (ast == null)
{
// Create a parse error
error = new ParseError(errorPos, errorLine, errorCol, errorNT);
}
else
{
// Check that all input was consumed
if (eofCheck && input.peek() != IParserInput.EOF)
{
// Create a parse error - Not all input consumed
error = new ParseError(errorPos, errorLine, errorCol, errorNT);
ast = null;
}
}
return new ParseResult(ast, error);
}
/**
* Restores the input position to the given values.
*
* @param pos The position.
*
* @param line The line.
*
* @param col The column.
*
* @param cr Whether the last character was a CR.
*/
private void restorePos(final int pos, final int line, final int col,
final boolean cr)
{
this.input.setPosition(pos);
this.line = line;
this.column = col;
this.lastCR = cr;
}
/**
* Matches the automaton at the given index.
*
* @param index The index.
*
* @return The result.
*/
private IAST matchAutomaton(final int index)
{
final int startPos = input.getPosition();
final CacheKey key = new CacheKey(index, startPos);
final CacheItem cachedItem = cache.get(key);
if (cachedItem != null)
{
restorePos(cachedItem.getPosition(), cachedItem.getLine(),
cachedItem.getColumn(), cachedItem.getLastCR());
return cachedItem.getResult();
}
final int startLine = line;
final int startCol = column;
final boolean startCR = lastCR;
final FA automaton = automata.get(index);
final E type = automaton.getType();
final int mode = automaton.getMode();
faStack.push(automaton);
final List> res = matchState(0);
faStack.pop();
IAST value;
if (type.equals(posType))
{
restorePos(startPos, startLine, startCol, startCR);
if (res == null)
{
value = null;
}
else
{
value = empty;
}
}
else
{
if (type.equals(negType))
{
restorePos(startPos, startLine, startCol, startCR);
if (res == null)
{
value = empty;
}
else
{
updateError();
value = null;
}
}
else
{
if (res == null)
{
updateError();
value = null;
}
else
{
switch (mode)
{
case FA.VOID:
{
value = empty;
break;
}
case FA.PRUNE:
{
switch (res.size())
{
case 0:
{
value = empty;
break;
}
case 1:
{
value = res.get(0);
break;
}
default:
{
value = new AST(type, res, new Position(startPos, input.getPosition()));
break;
}
}
break;
}
default:
{
value = new AST(type, res, new Position(startPos, input.getPosition()));
break;
}
}
}
}
}
cache.put(key, new CacheItem(value, input.getPosition(), line,
column, lastCR));
return value;
}
/**
* Matches the state at the given index.
*
* @param index The index.
*
* @return The result.
*/
private List> matchState(final int index)
{
final State state = faStack.peek().getStates().get(index);
final List> res = matchEdges(state.getEdges(), 0);
if (res == null)
{
if (state.isMatch())
{
return new ArrayList>();
}
else
{
return null;
}
}
else
{
return res;
}
}
/**
* Matches the given edges starting from the given index.
*
* @param edges The edges.
*
* @param index The index.
*
* @return The result.
*/
private List> matchEdges(final List> edges, final int index)
{
if (index < edges.size())
{
final List> res = matchEdge(edges.get(index));
if (res == null)
{
return matchEdges(edges, index + 1);
}
else
{
return res;
}
}
else
{
return null;
}
}
/**
* Matches the given edge.
*
* @param edge The edge.
*
* @return The result.
*/
private List> matchEdge(final Edge edge)
{
final int startPos = input.getPosition();
final int startLine = line;
final int startCol = column;
final boolean startCR = lastCR;
final IAST res = edge.getTrans().acceptVisitor(this);
if (res == null)
{
return null;
}
else
{
final List> transRes = matchState(edge.getState());
if (transRes == null)
{
restorePos(startPos, startLine, startCol, startCR);
return null;
}
else
{
if (edge.isVoided() || res.equals(empty))
{
return transRes;
}
else
{
// Note: If we were to memoize state results,
// this would need to be changed.
transRes.add(0, res);
return transRes;
}
}
}
}
/**
* Updates the line and column numbers.
*
* @param ch The character being consumed.
*/
private void updateLineCol(final char ch)
{
if (ch == '\r')
{
line++;
column = 0;
lastCR = true;
}
else
{
if (ch == '\n')
{
if (!lastCR)
{
line++;
column = 0;
}
}
else
{
column++;
}
lastCR = false;
}
}
/**
* Updates the error info if needed.
*/
private void updateError()
{
if (errorPos < input.getPosition())
{
errorPos = input.getPosition();
errorLine = line;
errorCol = column;
errorNT = faStack.peek().getType().name();
}
}
/** {@inheritDoc} */
public IAST visitAutomatonTransition(final AutomatonTransition t)
{
return matchAutomaton(t.getIndex());
}
/** {@inheritDoc} */
public IAST visitCharTransition(final CharTransition t)
{
if (input.peek() != IParserInput.EOF)
{
final char c = (char) input.peek();
if (t.withinSet(c))
{
input.consume();
updateLineCol(c);
return new Char(c, charType);
}
}
updateError();
return null;
}
/** {@inheritDoc} */
public IAST visitWildCardTransition(final WildCardTransition t)
{
if (input.peek() == IParserInput.EOF)
{
updateError();
return null;
}
final char c = (char) input.consume();
updateLineCol(c);
return new Char(c, charType);
}
}
}
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