Source code: com/sun/xacml/cond/NOfFunction.java
1
2 /*
3 * @(#)NOfFunction.java
4 *
5 * Copyright 2003-2004 Sun Microsystems, Inc. All Rights Reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions are met:
9 *
10 * 1. Redistribution of source code must retain the above copyright notice,
11 * this list of conditions and the following disclaimer.
12 *
13 * 2. Redistribution in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in the
15 * documentation and/or other materials provided with the distribution.
16 *
17 * Neither the name of Sun Microsystems, Inc. or the names of contributors may
18 * be used to endorse or promote products derived from this software without
19 * specific prior written permission.
20 *
21 * This software is provided "AS IS," without a warranty of any kind. ALL
22 * EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND WARRANTIES, INCLUDING
23 * ANY IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE
24 * OR NON-INFRINGEMENT, ARE HEREBY EXCLUDED. SUN MICROSYSTEMS, INC. ("SUN")
25 * AND ITS LICENSORS SHALL NOT BE LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE
26 * AS A RESULT OF USING, MODIFYING OR DISTRIBUTING THIS SOFTWARE OR ITS
27 * DERIVATIVES. IN NO EVENT WILL SUN OR ITS LICENSORS BE LIABLE FOR ANY LOST
28 * REVENUE, PROFIT OR DATA, OR FOR DIRECT, INDIRECT, SPECIAL, CONSEQUENTIAL,
29 * INCIDENTAL OR PUNITIVE DAMAGES, HOWEVER CAUSED AND REGARDLESS OF THE THEORY
30 * OF LIABILITY, ARISING OUT OF THE USE OF OR INABILITY TO USE THIS SOFTWARE,
31 * EVEN IF SUN HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
32 *
33 * You acknowledge that this software is not designed or intended for use in
34 * the design, construction, operation or maintenance of any nuclear facility.
35 */
36
37 package com.sun.xacml.cond;
38
39 import com.sun.xacml.EvaluationCtx;
40
41 import com.sun.xacml.attr.AttributeValue;
42 import com.sun.xacml.attr.BooleanAttribute;
43 import com.sun.xacml.attr.IntegerAttribute;
44
45 import java.util.HashSet;
46 import java.util.Iterator;
47 import java.util.List;
48 import java.util.Set;
49
50
51 /**
52 * A class that implements the n-of function. It requires
53 * at least one argument. The first argument must be an integer
54 * and the rest of the arguments must be booleans. If the number of
55 * boolean arguments that evaluate to true is at least the value of the
56 * first argument, the function returns true. Otherwise, it returns false
57 * (or indeterminate, as described in the next paragraph.
58 * <p>
59 * This function evaluates the arguments one at a time, starting with
60 * the first one. As soon as the result of the function can be determined,
61 * evaluation stops and that result is returned. During this process, if
62 * any argument evaluates to indeterminate, an indeterminate result is
63 * returned.
64 *
65 * @since 1.0
66 * @author Steve Hanne
67 * @author Seth Proctor
68 */
69 public class NOfFunction extends FunctionBase
70 {
71
72 /**
73 * Standard identifier for the n-of function.
74 */
75 public static final String NAME_N_OF = FUNCTION_NS + "n-of";
76
77 /**
78 * Creates a new <code>NOfFunction</code> object.
79 *
80 * @param functionName the standard XACML name of the function to be
81 * handled by this object, including the full namespace
82 *
83 * @throws IllegalArgumentException if the function is unknown
84 */
85 public NOfFunction(String functionName) {
86 super(NAME_N_OF, 0, BooleanAttribute.identifier, false);
87
88 if (! functionName.equals(NAME_N_OF))
89 throw new IllegalArgumentException("unknown nOf function: "
90 + functionName);
91 }
92
93 /**
94 * Returns a <code>Set</code> containing all the function identifiers
95 * supported by this class.
96 *
97 * @return a <code>Set</code> of <code>String</code>s
98 */
99 public static Set getSupportedIdentifiers() {
100 Set set = new HashSet();
101
102 set.add(NAME_N_OF);
103
104 return set;
105 }
106
107 /**
108 * Evaluate the function, using the specified parameters.
109 *
110 * @param inputs a <code>List</code> of <code>Evaluatable</code>
111 * objects representing the arguments passed to the function
112 * @param context an <code>EvaluationCtx</code> so that the
113 * <code>Evaluatable</code> objects can be evaluated
114 * @return an <code>EvaluationResult</code> representing the
115 * function's result
116 */
117 public EvaluationResult evaluate(List inputs, EvaluationCtx context) {
118
119 // Evaluate the arguments one by one. As soon as we can return
120 // a result, do so. Return Indeterminate if any argument
121 // evaluated is indeterminate.
122 Iterator it = inputs.iterator();
123 Evaluatable eval = (Evaluatable)(it.next());
124
125 // Evaluate the first argument
126 EvaluationResult result = eval.evaluate(context);
127 if (result.indeterminate())
128 return result;
129
130 // if there were no problems, we know 'n'
131 long n = ((IntegerAttribute)(result.getAttributeValue())).getValue();
132
133 // If the number of trues needed is less than zero, report an error.
134 if (n < 0)
135 return makeProcessingError("First argument to " + getFunctionName()
136 + " cannot be negative.");
137
138 // If the number of trues needed is zero, return true.
139 if (n == 0)
140 return EvaluationResult.getTrueInstance();
141
142 // make sure it's possible to find n true values
143 long remainingArgs = inputs.size() - 1;
144 if (n > remainingArgs)
145 return makeProcessingError("not enough arguments to n-of to " +
146 "find " + n + " true values");
147
148 // loop through the inputs, trying to find at least n trues
149 while (remainingArgs >= n) {
150 eval = (Evaluatable)(it.next());
151
152 // evaluate the next argument
153 result = eval.evaluate(context);
154 if (result.indeterminate())
155 return result;
156
157 // get the next value, and see if it's true
158 if (((BooleanAttribute)(result.getAttributeValue())).getValue()) {
159 // we're one closer to our goal...see if we met it
160 if (--n == 0)
161 return EvaluationResult.getTrueInstance();
162 }
163
164 // we're still looking, but we've got one fewer arguments
165 remainingArgs--;
166 }
167
168 // if we got here then we didn't meet our quota
169 return EvaluationResult.getFalseInstance();
170 }
171
172 /**
173 *
174 */
175 public void checkInputs(List inputs) throws IllegalArgumentException {
176 // check that none of the inputs is a bag
177 Object [] list = inputs.toArray();
178 for (int i = 0; i < list.length; i++)
179 if (((Evaluatable)(list[i])).evaluatesToBag())
180 throw new IllegalArgumentException("n-of can't use bags");
181
182 // if we got here then there were no bags, so ask the other check
183 // method to finish the checking
184 checkInputsNoBag(inputs);
185 }
186
187 /**
188 *
189 */
190 public void checkInputsNoBag(List inputs) throws IllegalArgumentException {
191 Object [] list = inputs.toArray();
192
193 // check that there is at least one arg
194 if (list.length == 0)
195 throw new IllegalArgumentException("n-of requires an argument");
196
197 // check that the first element is an Integer
198 Evaluatable eval = (Evaluatable)(list[0]);
199 if (! eval.getType().toString().equals(IntegerAttribute.identifier))
200 throw new IllegalArgumentException("first argument to n-of must" +
201 " be an integer");
202
203 // now check that the rest of the args are booleans
204 for (int i = 1; i < list.length; i++) {
205 if (! ((Evaluatable)(list[i])).getType().toString().
206 equals(BooleanAttribute.identifier))
207 throw new IllegalArgumentException("invalid parameter in n-of"
208 + ": expected boolean");
209 }
210 }
211
212 }