quotedtext.java

JAVA在编译原理上的应用。

package lolo.scans;

/** A class to scan for quoted text. The quoted text can span more then one line.
 *
 * @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 QuotedText extends Scan {
    /** Marks if the recognition is after the quote character. */
    protected transient boolean inside;
    
    public void reset() {
        if (reset) return;
        inside = false;
        last = ' '; // not \
        reset = true;
    }
    
    /** 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 QuotedText() {
        this('"');
    }
    /** Constructs a recognizer who uses <tt>quote</tt> as the quote character.
     *
     * @param quote the quote character.
     */
    public QuotedText(char quote) {
        if (quote == '\\')
            throw new IllegalArgumentException("illegal quote character \\");
        this.quote = quote;
    }
    
    /** Holds the last scanned character. Used to handle escaped characters. */
    protected transient char last;
    
    public State nextChar(char ch) {
        reset = false;
        
        if (!inside) {
            inside = true;
            return stateObject.set(
                ch == quote,    // more
                false           // found
            );
        }
        if (ch == quote && last != '\\')
            return stateObject.set(
                false,  // more
                true    // found
            );
        
        last = last == '\\' ? ' ' // not \
                              : ch ;
        
	    return stateObject.set (
            true,	// more
            false	// 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>QuotedText</tt> and uses the same quotre character,
     * <tt>false</tt> otherwise.
     */
    public boolean equals(Object o) {
        if (o == null || !(o instanceof QuotedText))
            return false;
        return this == o || quote == ((QuotedText) o).quote;
    }
    
    /** Used the collect the unescaped scanned characters. */
    protected transient char [] help;
    
    public void action(char [] buffer, int off, int len) {
        if (action != null) {
            if (help == null)
            	help = new char[len];
            if (help.length < len)
            	help = new char[len];
            int length = 0;
            boolean escape = false;
            
            for (int i = 1; i < len-1 ; i++) {
                char ch = buffer[off+i];
                if (escape) {
                    switch (ch) {
                        case 'r':	help[length++] = '\r'; break;
                        case 'n':	help[length++] = '\n'; break;
                        case 'b':	help[length++] = '\b'; break;
                        case 't':	help[length++] = '\t'; break;
                        case '\\':	help[length++] = '\\'; break;
                        case '"':	help[length++] = '"'; break;
                        default:	help[length++] = '\\'; help[length++] = ch; break;
                    }
                    escape = false;
                } else if (ch == '\\')
                    escape = true;
                else
                    help[length++] = ch;
            }
            if (escape)
                throw new RuntimeException("escape is true");
        
            action.action(this, help, 0, length);
        }
    }
    /** Returns a string representation of the object.
     *
     * @return a string representation of the object.
     */
    public String toString() {
        return getClass().getName()+"["+quote+"]";
    }
}