scan.java

JAVA在编译原理上的应用。

package lolo;

import java.io.IOException;
import java.io.Serializable;

/** The abstract base class for recognizer classes.
 *
 * @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 abstract class Scan implements Serializable {   
    /** Resets this instance. */
    public abstract void reset();
    
    /** The action object; can be <tt>null</tt> for no action.
     *
     * @serial if action is serializable and not <tt>null</tt>.
     * @see lolo.Scan.Action
     */
    protected transient Action action;
    /** Returns the action object.
     *
     * @return the action object.
     * @see lolo.Scan.Action
     */
    public Action getAction() {
        return action;
    }
    /** Sets the action object.
     *
     * @param action the new action object.
     * @see lolo.Scan.Action
     * @return <tt>this</tt> for cascading method calls.
     */
    public Scan setAction(Action action) {
        this.action = action;
        return this;
    }
    /** If <tt>action</tt> is not <tt>null</tt>, then the action method is called for this object.
     *
     * @param buffer the character buffer holding the characters of the symbol.
     * @param off offset into the buffer.
     * @param len number of characters for the symbol.
     * @see lolo.Scan#action
     */
    public void action(char [] buffer, int off, int len) {
        if (action != null)
            action.action(this, buffer, off, len);
    }
    /** Action code for a recognized symbols is represented by <tt>Action</tt> objects.
     *
     * @author <a href="http://www.inf.uos.de/bernd" target="_blank">Bernd K&uuml;hl</a>
               (<a href="mailto:[e-mail]">[e-mail]</a>)
     * @see lolo.Scan#getAction
     * @see lolo.Scan#setAction(lolo.Scan.Action)
     * @see lolo.Scan#action
     */
    public interface Action {
        /** Called to perform action code for a scanned symbol.
         *
         * @param sender the symbol scanner object as sender of this method.
         * @param buffer the character buffer holding the characters of the symbol.
         * @param off offset into the buffer.
         * @param len number of characters for the symbol.
         */
        public void action(Scan sender, char [] buffer, int off, int len);
    }
        
    /** Marks if the symbol will be ignored. */
    protected boolean ignore;
    /** Sets the ignore state.
     *
     * @param ignore the new ignore state.
     * @return <tt>this</tt> for cascading method calls.
     */
    public Scan setIgnore(boolean ignore) {
        this.ignore = ignore;
        return this;
    }
    /** Returns the ignore state.
     *
     * @return the ignore state.
     */
    public boolean getIgnore() {
        return ignore;
    }

    /** Subclasses have to implement this method to indicate whether some
     * other object is &quot;equal to&quot; this one.
     *
     * @return <tt>true</tt> if this object is the same as the argument; <tt>false</tt> otherwise.
     */
    public abstract boolean equals(Object o);
    /** Subclasses have to implement this method to return a hash code value
     * for the receiver.
     *
     * @return a hash code value for this object.
     */
    public abstract int hashCode();
        
    /** Called by a <tt>Scanner</tt> for every new character.
     *
     * @return a <tt>State</tt> object to signal whether more characters are wanted and whether a symbol is found.
     * @see lolo.Scan.State
     * @see lolo.Scanner
     */
    public abstract State nextChar(char ch);
    /** A simple class to mark the result for <tt>nextChar()</tt>.
     *
     * @author <a href="http://www.inf.uos.de/bernd" target="_blank">Bernd K&uuml;hl</a>
               (<a href="mailto:[e-mail]">[e-mail]</a>)
     * @see lolo.Scan#nextChar(char)
     */
    public static class State implements Serializable {
        /** Creates a State object. */
        public State() {}
        /** Sets the object to signal whether more characters are wanted and whether a symbol was found.
         *
         * @param more The <tt>Scan</tt> instance wants more characters?
         * @param found The <tt>Scan</tt> instance just found a symbol?
         * @return <tt>this</tt>.
         */
        public State set(boolean more, boolean found) {
            this.more = more;
            this.found = found;
            return this;
        }
        /** The <tt>Scan</tt> instance wants more characters? */
        public boolean more;
        /** The <tt>Scan</tt> instance just found a symbol? */
        public boolean found;
        /** Returns a string representation of the object.
         *
         * @return a string representation of the object.
         */
        public String toString() {
            return "State[more: "+more+",found: "+found+"]";
        }
    }

    /** Deserializes a <tt>Scan</tt> object and (optional) the serialized action object. */
    private void readObject(java.io.ObjectInputStream stream) throws IOException, ClassNotFoundException {
        stream.defaultReadObject();
        if (stream.readBoolean())
            action = (Action) stream.readObject();
    }
    
    /** Serializes the <tt>Scan</tt> object and it's action object (if that is serializable). */
    private void writeObject(java.io.ObjectOutputStream stream) throws IOException {
        stream.defaultWriteObject();
        boolean b = action != null && action instanceof Serializable;
        stream.writeBoolean(b);
        if (b)
            stream.writeObject(action);
    }
}