quotedchar.java

JAVA在编译原理上的应用。

package lolo.scans;

/** A class to scan for one quoted character.
 *
 * @author <a href="http://www.inf.uos.de/bernd" target="_blank">Bernd K&uuml;hl</a>
           (<a href="mailto:[e-mail]">[e-mail]</a>)
 */
public class QuotedChar extends Scan {
    /** Holds the unescaped recognized quoted character. */
    protected final char[] found = new char[1];
    /** Marks the current state. */
    protected transient boolean start, middle, end;
    /** Is the character escaped? */
    protected transient boolean escape;
     
    public void reset() {
        start = true;
        middle = end = escape = false;
    }
    
    /** The quote character. */
    protected final char quote;
    
    /** Returns the quote character.
     *
     * @return the quote character.
     */
    protected char getQuote() {
        return quote;
    }
    /** Just calls <tt>this('\'')</tt>. */
    public QuotedChar() {
        this('\'');
    }
    /** Constructs a recognizer to scan for a quoted character. <tt>quote</tt> is
     * the quote character.
     *
     * @param quote the quoted character.
     */
    public QuotedChar(char quote) {
        if (quote == '\\')
            throw new IllegalArgumentException("illegal quote character \\");
        this.quote = quote;
    }
    
    public State nextChar(char ch) {
        // start state
        if (start) {
            start = false;
            middle = true;
            return stateObject.set(
                ch == quote,    // more
                false           // found
            );
        }
        
        // middle state
        if (middle) {
            if (!escape)    // nicht im escape modus
                if (ch == '\\')
                    escape = true;
                else {
                    end = true; middle = false;
                    found[0] = ch;
                }
            else {          // escape modus
                if (ch == quote)
                    found[0] = quote;
                else switch (ch) {
                    case 't':	found[0] = '\t'; break;
                    case 'n':	found[0] = '\n'; break;
                    case '\\':	found[0] = '\\'; break;
                    case 'r':	found[0] = '\r'; break;
                    case 'b':	found[0] = '\b'; break;
                    default:	return stateObject.set(
                                    false,   // more
                                    false   // found
                                );
                }
                end = true; middle = false;
            }
            return stateObject.set(
                true,   // more
                false   // found
            );
        }
        
        // end state
	    return stateObject.set (
            false,	    // more
            ch == quote	// found
	    );
    }
    
    /** Returns a hash code value for this object.
     *
     * @return a hash code value for this object.
     */
    public int hashCode() {
        return new Character(quote).hashCode();
    }

    /** Indicates whether some other object is &quot;equal to&quot; this one.
     * 
     * @return <tt>true</tt> the argument is a <tt>QuotedChar</tt> and uses the same quote character,
     * <tt>false</tt> otherwise.
     */
    public boolean equals(Object o) {
        if (o == null || !(o instanceof QuotedChar))
            return false;
        return this == o || quote == ((QuotedChar) o).quote;
    }
    
    public void action(char [] buffer, int off, int len) {
        if (action != null)
            action.action(this, found, 0, 1);
    }
    /** Returns a string representation of the object.
     *
     * @return a string representation of the object.
     */
    public String toString() {
        return getClass().getName()+"["+quote+"]";
    }
}