HashCmds.java

/* Copyright 2006 David N. Welton

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.
*/

package org.hecl;

import java.util.Enumeration;
import java.util.Hashtable;
import java.util.Vector;

/**
 * The <code>HashCmds</code> class takes care of loading and
 * implementing the Hecl commands that deal with hash tables, which
 * are in turn implemented in the HashThing class.
 *
 * @author <a href="mailto:davidw@dedasys.com">David N. Welton</a>
 * @version 1.0
 */
class HashCmds extends Operator {
    public static final int HASH = 0;
    public static final int HGET = 1;
    public static final int HSET = 2;
    public static final int HKEYS = 3;
    public static final int HCLEAR = 4;
    public static final int HREMOVE = 5;
    public static final int HCONTAINS = 6;


    public Thing operate(int cmd, Interp interp, Thing[] argv) throws HeclException {
	Hashtable hash = cmd != 0 ? HashThing.get(argv[1]) : null;
	Thing result = null;

	switch (cmd) {
	    case HASH:
		result = HashThing.create(HashThing.get(argv[1]));
		break;

	    case HGET:
		result = (Thing)hash.get(argv[2].toString());
		break;

	    case HSET:
		result = argv[3];
		hash.put(argv[2].toString(), result);
		break;

	    case HKEYS:
		Vector v = new Vector(hash.size());
		Enumeration e = hash.keys();
		while(e.hasMoreElements()) {
		    v.addElement(new Thing((String)e.nextElement()));
		}
		return ListThing.create(v);

	    case HCLEAR:
		hash.clear();
		result = argv[1];
		break;

	    case HREMOVE:
		Object o = hash.remove(argv[2].toString());
		result = o != null ? (Thing)o : new Thing("");
		break;

	    case HCONTAINS:
	        result = new Thing(hash.containsKey(argv[2].toString()) ?
				   IntThing.ONE : IntThing.ZERO);
		break;
		
	    default:
		throw new HeclException("Unknown hash command '"
					+ argv[0].toString() + "' with code '"
					+ cmd + "'.");
	}
	return result;
    }


    public static void load(Interp ip) throws HeclException {
	Operator.load(ip,cmdtable);
    }


    public static void unload(Interp ip) throws HeclException {
	Operator.unload(ip,cmdtable);
    }


    protected HashCmds(int cmdcode,int minargs,int maxargs) {
	super(cmdcode,minargs,maxargs);
    }

    private static Hashtable cmdtable = new Hashtable();

    static {
        cmdtable.put("hash", new HashCmds(HASH,1,1));
        cmdtable.put("hget", new HashCmds(HGET,2,2));
        cmdtable.put("hset", new HashCmds(HSET,3,3));
        cmdtable.put("hkeys", new HashCmds(HKEYS,1,1));
        cmdtable.put("hclear", new HashCmds(HCLEAR,1,1));
        cmdtable.put("hremove", new HashCmds(HREMOVE,2,2));
        cmdtable.put("hcontains", new HashCmds(HCONTAINS,2,2));
    }
}