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Java > Open Source Codes > com > caucho > es > wrapper > MethodDispatcher


1 /*
2  * Copyright (c) 1998-2006 Caucho Technology -- all rights reserved
3  *
4  * This file is part of Resin(R) Open Source
5  *
6  * Each copy or derived work must preserve the copyright notice and this
7  * notice unmodified.
8  *
9  * Resin Open Source is free software; you can redistribute it and/or modify
10  * it under the terms of the GNU General Public License as published by
11  * the Free Software Foundation; either version 2 of the License, or
12  * (at your option) any later version.
13  *
14  * Resin Open Source is distributed in the hope that it will be useful,
15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE, or any warranty
17  * of NON-INFRINGEMENT. See the GNU General Public License for more
18  * details.
19  *
20  * You should have received a copy of the GNU General Public License
21  * along with Resin Open Source; if not, write to the
22  * Free SoftwareFoundation, Inc.
23  * 59 Temple Place, Suite 330
24  * Boston, MA 02111-1307 USA
25  *
26  * @author Scott Ferguson
27  */
28
29 package com.caucho.es.wrapper;
30
31 import com.caucho.es.Call;
32 import com.caucho.es.ESBase;
33 import com.caucho.es.ESNull;
34
35 /**
36  * Dynamic selection of overloaded methods. This is really a last
37  * resort.
38  */
39 public class MethodDispatcher {
40   private Class JavaDoc [][]parameterTypes;
41
42   public MethodDispatcher(Class JavaDoc [][]parameterTypes)
43   {
44     this.parameterTypes = parameterTypes;
45   }
46
47   /**
48    * Selects the best method among the list.
49    */
50   public int select(Call call, int length)
51     throws Exception JavaDoc
52   {
53     int bestCost = Integer.MAX_VALUE;
54     int bestMethod = -1;
55
56     for (int i = 0; i < parameterTypes.length; i++) {
57       Class JavaDoc []parameters = parameterTypes[i];
58
59       int cost = 0;
60       for (int j = 0; j < parameters.length; j++) {
61         ESBase obj = call.getArg(j, length);
62         Class JavaDoc cl = obj.getJavaType();
63         Class JavaDoc param = parameters[j];
64
65         if (cl.equals(param))
66           continue;
67
68         // cl is the actual class, so don't need to worry about casting
69 else if (param.isAssignableFrom(cl))
70           cost += 10;
71
72     else if (obj instanceof ESNull)
73       cost += 50;
74
75     else if (cl.equals(void.class))
76       cost += 50;
77
78         else if (cl.isPrimitive() && param.isPrimitive())
79           cost += 100;
80
81         else {
82           cost = Integer.MAX_VALUE;
83           break;
84         }
85       }
86
87       if (cost < bestCost) {
88         bestMethod = i;
89         bestCost = cost;
90       }
91     }
92
93     return bestMethod;
94   }
95 }
96
97
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