whitespace.java

java1.6众多例子参考

/*
 * Copyright 2001-2004 The Apache Software Foundation.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
/*
 * $Id: Whitespace.java,v 1.5 2005/09/28 13:48:18 pvedula Exp $
 */

package com.sun.org.apache.xalan.internal.xsltc.compiler;

import java.util.StringTokenizer;
import java.util.Vector;

import com.sun.org.apache.bcel.internal.generic.ALOAD;
import com.sun.org.apache.bcel.internal.generic.BranchHandle;
import com.sun.org.apache.bcel.internal.generic.ConstantPoolGen;
import com.sun.org.apache.bcel.internal.generic.IF_ICMPEQ;
import com.sun.org.apache.bcel.internal.generic.ILOAD;
import com.sun.org.apache.bcel.internal.generic.INVOKEINTERFACE;
import com.sun.org.apache.bcel.internal.generic.INVOKEVIRTUAL;
import com.sun.org.apache.bcel.internal.generic.InstructionHandle;
import com.sun.org.apache.bcel.internal.generic.InstructionList;
import com.sun.org.apache.bcel.internal.generic.PUSH;
import com.sun.org.apache.xalan.internal.xsltc.compiler.util.ClassGenerator;
import com.sun.org.apache.xalan.internal.xsltc.compiler.util.ErrorMsg;
import com.sun.org.apache.xalan.internal.xsltc.compiler.util.MethodGenerator;
import com.sun.org.apache.xalan.internal.xsltc.compiler.util.Type;
import com.sun.org.apache.xalan.internal.xsltc.compiler.util.TypeCheckError;
import com.sun.org.apache.xalan.internal.xsltc.compiler.util.Util;

/**
 * @author Morten Jorgensen
 */
final class Whitespace extends TopLevelElement {
    // Three possible actions for the translet:
    public static final int USE_PREDICATE  = 0;
    public static final int STRIP_SPACE    = 1;
    public static final int PRESERVE_SPACE = 2;

    // The 3 different categories of strip/preserve rules (order important)
    public static final int RULE_NONE      = 0; 
    public static final int RULE_ELEMENT   = 1; // priority 0
    public static final int RULE_NAMESPACE = 2; // priority -1/4
    public static final int RULE_ALL       = 3; // priority -1/2

    private String _elementList;
    private int    _action;
    private int    _importPrecedence;

    /**
     * Auxillary class for encapsulating a single strip/preserve rule
     */
    private final static class WhitespaceRule {
	private final int _action;
	private String _namespace; // Should be replaced by NS type (int)
	private String _element;   // Should be replaced by node type (int)
	private int    _type;
	private int    _priority;
	
	/**
	 * Strip/preserve rule constructor
	 */
	public WhitespaceRule(int action, String element, int precedence) {
 	    // Determine the action (strip or preserve) for this rule
	    _action = action;

	    // Get the namespace and element name for this rule
	    final int colon = element.lastIndexOf(':');
	    if (colon >= 0) {
		_namespace = element.substring(0,colon);
		_element = element.substring(colon+1,element.length());
	    }
	    else {
		_namespace = Constants.EMPTYSTRING;
		_element = element;
	    }

	    // Determine the initial priority for this rule
	    _priority = precedence << 2;

	    // Get the strip/preserve type; either "NS:EL", "NS:*" or "*"
	    if (_element.equals("*")) {
		if (_namespace == Constants.EMPTYSTRING) {
		    _type = RULE_ALL;       // Strip/preserve _all_ elements
		    _priority += 2;         // Lowest priority
		}
		else {
		    _type = RULE_NAMESPACE; // Strip/reserve elements within NS
		    _priority += 1;         // Medium priority
		}
	    }
	    else {
		_type = RULE_ELEMENT;       // Strip/preserve single element
	    }
	}

	/**
	 * For sorting rules depending on priority
	 */
	public int compareTo(WhitespaceRule other) {
	    return _priority < other._priority
		? -1
		: _priority > other._priority ? 1 : 0;
	}

	public int getAction() { return _action; }
	public int getStrength() { return _type; }
	public int getPriority() { return _priority; }
	public String getElement() { return _element; }
	public String getNamespace() { return _namespace; }
    }

    /**
     * Parse the attributes of the xsl:strip/preserve-space element.
     * The element should have not contents (ignored if any).
     */
    public void parseContents(Parser parser) {
        // Determine if this is an xsl:strip- or preserve-space element
        _action = _qname.getLocalPart().endsWith("strip-space") 
            ? STRIP_SPACE : PRESERVE_SPACE;

        // Determine the import precedence
        _importPrecedence = parser.getCurrentImportPrecedence();

        // Get the list of elements to strip/preserve
        _elementList = getAttribute("elements");
        if (_elementList == null || _elementList.length() == 0) {
            reportError(this, parser, ErrorMsg.REQUIRED_ATTR_ERR, "elements");
            return;
        }

        final SymbolTable stable = parser.getSymbolTable();
        StringTokenizer list = new StringTokenizer(_elementList);
        StringBuffer elements = new StringBuffer(Constants.EMPTYSTRING);

        while (list.hasMoreElements()) {
            String token = list.nextToken();
            String prefix;
            String namespace;
            int col = token.indexOf(':');

            if (col != -1) {
                namespace = lookupNamespace(token.substring(0,col));
                if (namespace != null) {
                    elements.append(namespace+":"+
                                    token.substring(col+1,token.length()));
                } else {
                    elements.append(token);
                }
            } else {
                elements.append(token);
            }

            if (list.hasMoreElements())
                elements.append(" ");
        }
        _elementList = elements.toString();
    }


    /**
     * De-tokenize the elements listed in the 'elements' attribute and
     * instanciate a set of strip/preserve rules.
     */
    public Vector getRules() {
	final Vector rules = new Vector();
	// Go through each element and instanciate strip/preserve-object
	final StringTokenizer list = new StringTokenizer(_elementList);
	while (list.hasMoreElements()) {
	    rules.add(new WhitespaceRule(_action,
					 list.nextToken(),
					 _importPrecedence));
	}
	return rules;
    }
    
    
    /**
     * Scans through the rules vector and looks for a rule of higher
     * priority that contradicts the current rule.
     */
    private static WhitespaceRule findContradictingRule(Vector rules,
							WhitespaceRule rule) {
	for (int i = 0; i < rules.size(); i++) {
	    // Get the next rule in the prioritized list
	    WhitespaceRule currentRule = (WhitespaceRule)rules.elementAt(i);
	    // We only consider rules with higher priority
	    if (currentRule == rule) {
		return null;
	    }
	    
	    /*
	     * See if there is a contradicting rule with higher priority.
	     * If the rules has the same action then this rule is redundant,
	     * if they have different action then this rule will never win.
	     */
	    switch (currentRule.getStrength()) {
	    case RULE_ALL:
		return currentRule;
		
	    case RULE_ELEMENT:
		if (!rule.getElement().equals(currentRule.getElement())) {
		    break;
		}
		// intentional fall-through
	    case RULE_NAMESPACE:
		if (rule.getNamespace().equals(currentRule.getNamespace())) {
		    return currentRule;
		}
		break;
	    }
	}
	return null;
    }


    /**
     * Orders a set or rules by priority, removes redundant rules and rules
     * that are shadowed by stronger, contradicting rules.
     */
    private static int prioritizeRules(Vector rules) {
	WhitespaceRule currentRule;
	int defaultAction = PRESERVE_SPACE;

	// Sort all rules with regard to priority
	quicksort(rules, 0, rules.size()-1);

	// Check if there are any "xsl:strip-space" elements at all.
	// If there are no xsl:strip elements we can ignore all xsl:preserve
	// elements and signal that all whitespaces should be preserved
	boolean strip = false;
	for (int i = 0; i < rules.size(); i++) {
	    currentRule = (WhitespaceRule)rules.elementAt(i);
	    if (currentRule.getAction() == STRIP_SPACE) {
		strip = true;
	    }
	}
	// Return with default action: PRESERVE_SPACE
	if (!strip) {
	    rules.removeAllElements();
	    return PRESERVE_SPACE;
	}

	// Remove all rules that are contradicted by rules with higher priority
	for (int idx = 0; idx < rules.size(); ) {
	    currentRule = (WhitespaceRule)rules.elementAt(idx);
	
	    // Remove this single rule if it has no purpose
	    if (findContradictingRule(rules,currentRule) != null) {
		rules.remove(idx);
	    }
	    else {
		// Remove all following rules if this one overrides all
		if (currentRule.getStrength() == RULE_ALL) {
		    defaultAction = currentRule.getAction();
		    for (int i = idx; i < rules.size(); i++) {
			rules.removeElementAt(i);
		    }
		}