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Java > Open Source Codes > net > sf > saxon > value > Cardinality


1 package net.sf.saxon.value;
2
3 import net.sf.saxon.expr.StaticProperty;
4
5 /**
6 * This class contains static methods to manipulate the cardinality
7 * property of a type.
8 * Cardinality of expressions is denoted by one of the values ONE_OR_MORE, ZERO_OR_MORE,
9 * ZERO_OR_ONE, EXACTLY_ONE, or EMPTY. These are combinations of the three bit-significant
10 * values ALLOWS_ZERO, ALLOWS_ONE, and ALLOWS_MANY.
11 */
12
13 public final class Cardinality {
14
15     /**
16     * Private constructor: no instances allowed
17     */
18
19     private Cardinality() {}
20
21     /**
22      * Determine whether multiple occurrences are allowed
23      */
24
25     public static final boolean allowsMany(int cardinality) {
26         return (cardinality & StaticProperty.ALLOWS_MANY) != 0;
27     }
28
29     /**
30      * Determine whether empty sequence is allowed
31      */
32
33     public static final boolean allowsZero(int cardinality) {
34         return (cardinality & StaticProperty.ALLOWS_ZERO) != 0;
35     }
36
37     /**
38     * Form the union of two cardinalities. The cardinality of the expression "if (c) then e1 else e2"
39     * is the union of the cardinalities of e1 and e2.
40     * @param c1 a cardinality
41     * @param c2 another cardinality
42     * @return the cardinality that allows both c1 and c2
43     */
44
45     public static final int union(int c1, int c2) {
46         int r = c1 | c2;
47         // eliminate disallowed options
48 if (r == (StaticProperty.ALLOWS_MANY |
49                     StaticProperty.ALLOWS_ZERO ))
50             r = StaticProperty.ALLOWS_ZERO_OR_MORE;
51         return r;
52     }
53
54     /**
55      * Form the sum of two cardinalities
56      */
57
58     public static final int sum(int c1, int c2) {
59         if (allowsMany(c1) || allowsMany(c2)) {
60             return c1 | c2;
61         }
62         if (!allowsZero(c1) && !allowsZero(c2)) {
63             return StaticProperty.ALLOWS_ONE_OR_MORE;
64         } else {
65             return StaticProperty.ALLOWS_ZERO_OR_MORE;
66         }
67     }
68
69     /**
70     * Test if one cardinality subsumes another. Cardinality c1 subsumes c2 if every option permitted
71     * by c2 is also permitted by c1.
72     * @param c1 a cardinality
73     * @param c2 another cardinality
74     * @return true if if every option permitted
75     * by c2 is also permitted by c1.
76     */
77
78     public static final boolean subsumes(int c1, int c2) {
79         return (c1|c2)==c1;
80     }
81
82     /**
83      * Add two cardinalities
84      */
85
86     public static final int add(int c1, int c2) {
87         if (c1==StaticProperty.EMPTY) {
88             return c2;
89         }
90         if (c2==StaticProperty.EMPTY) {
91             return c1;
92         }
93         boolean allowsZero = Cardinality.allowsZero(c1) && Cardinality.allowsZero(c2);
94         return StaticProperty.ALLOWS_ONE_OR_MORE | (allowsZero ? StaticProperty.ALLOWS_ZERO : 0);
95     }
96
97     /**
98      * Multiply two cardinalities
99      */
100
101     public static final int multiply(int c1, int c2) {
102         if (c1==StaticProperty.EMPTY || c2==StaticProperty.EMPTY) {
103             return StaticProperty.EMPTY;
104         }
105         if (c2==StaticProperty.EXACTLY_ONE) {
106             return c1;
107         }
108         if (c1==StaticProperty.EXACTLY_ONE) {
109             return c2;
110         }
111         if (c1==StaticProperty.ALLOWS_ZERO_OR_ONE && c2==StaticProperty.ALLOWS_ZERO_OR_ONE) {
112             return StaticProperty.ALLOWS_ZERO_OR_ONE;
113         }
114         if (c1==StaticProperty.ALLOWS_ONE_OR_MORE && c2==StaticProperty.ALLOWS_ONE_OR_MORE) {
115             return StaticProperty.ALLOWS_ONE_OR_MORE;
116         }
117         return StaticProperty.ALLOWS_ZERO_OR_MORE;
118     }
119
120     /**
121     * Display the cardinality
122     */
123
124     public static String JavaDoc toString(int cardinality) {
125         switch (cardinality) {
126             case StaticProperty.ALLOWS_ZERO_OR_ONE:
127                 return "zero or one";
128             case StaticProperty.EXACTLY_ONE:
129                 return "exactly one";
130             case StaticProperty.ALLOWS_ZERO_OR_MORE:
131                 return "zero or more";
132             case StaticProperty.ALLOWS_ONE_OR_MORE:
133                 return "one or more";
134             case StaticProperty.EMPTY:
135                 return "exactly zero";
136             case StaticProperty.ALLOWS_MANY:
137                 return "more than one";
138             default:
139                 return "code " + cardinality;
140         }
141     }
142
143     /**
144      * Get the occurence indicator representing the cardinality
145      */
146
147     public static String JavaDoc getOccurrenceIndicator(int cardinality) {
148         switch (cardinality) {
149             case StaticProperty.ALLOWS_ZERO_OR_ONE:
150                 return "?";
151             case StaticProperty.EXACTLY_ONE:
152                 return "";
153             case StaticProperty.ALLOWS_ZERO_OR_MORE:
154                 return "*";
155             case StaticProperty.ALLOWS_ONE_OR_MORE:
156                 return "+";
157             default: throw new AssertionError JavaDoc("unknown cardinality value");
158         }
159     }
160 }
161
162 //
163 // The contents of this file are subject to the Mozilla Public License Version 1.0 (the "License");
164 // you may not use this file except in compliance with the License. You may obtain a copy of the
165 // License at http://www.mozilla.org/MPL/
166 //
167 // Software distributed under the License is distributed on an "AS IS" basis,
168 // WITHOUT WARRANTY OF ANY KIND, either express or implied.
169 // See the License for the specific language governing rights and limitations under the License.
170 //
171 // The Original Code is: all this file.
172 //
173 // The Initial Developer of the Original Code is Michael H. Kay
174 //
175 // Portions created by (your name) are Copyright (C) (your legal entity). All Rights Reserved.
176 //
177 // Contributor(s): none.
178 //
179
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