1/*
2 * Copyright (c) 1999, 2008, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.  Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26package javax.management;
27
28
29/**
30 * This class is used by the query-building mechanism to represent binary
31 * operations.
32 * @serial include
33 *
34 * @since 1.5
35 */
36class BinaryOpValueExp extends QueryEval implements ValueExp {
37
38    /* Serial version */
39    private static final long serialVersionUID = 1216286847881456786L;
40
41    /**
42     * @serial The operator
43     */
44    private int op;
45
46    /**
47     * @serial The first value
48     */
49    private ValueExp exp1;
50
51    /**
52     * @serial The second value
53     */
54    private ValueExp exp2;
55
56
57    /**
58     * Basic Constructor.
59     */
60    public BinaryOpValueExp() {
61    }
62
63    /**
64     * Creates a new BinaryOpValueExp using operator o applied on v1 and
65     * v2 values.
66     */
67    public BinaryOpValueExp(int o, ValueExp v1, ValueExp v2) {
68        op   = o;
69        exp1 = v1;
70        exp2 = v2;
71    }
72
73
74    /**
75     * Returns the operator of the value expression.
76     */
77    public int getOperator()  {
78        return op;
79    }
80
81    /**
82     * Returns the left value of the value expression.
83     */
84    public ValueExp getLeftValue()  {
85        return exp1;
86    }
87
88    /**
89     * Returns the right value of the value expression.
90     */
91    public ValueExp getRightValue()  {
92        return exp2;
93    }
94
95    /**
96     * Applies the BinaryOpValueExp on a MBean.
97     *
98     * @param name The name of the MBean on which the BinaryOpValueExp will be applied.
99     *
100     * @return  The ValueExp.
101     *
102     * @exception BadStringOperationException
103     * @exception BadBinaryOpValueExpException
104     * @exception BadAttributeValueExpException
105     * @exception InvalidApplicationException
106     */
107    public ValueExp apply(ObjectName name) throws BadStringOperationException, BadBinaryOpValueExpException,
108        BadAttributeValueExpException, InvalidApplicationException  {
109        ValueExp val1 = exp1.apply(name);
110        ValueExp val2 = exp2.apply(name);
111        String sval1;
112        String sval2;
113        double dval1;
114        double dval2;
115        long   lval1;
116        long   lval2;
117        boolean numeric = val1 instanceof NumericValueExp;
118
119        if (numeric) {
120            if (((NumericValueExp)val1).isLong()) {
121                lval1 = ((NumericValueExp)val1).longValue();
122                lval2 = ((NumericValueExp)val2).longValue();
123
124                switch (op) {
125                case Query.PLUS:
126                    return Query.value(lval1 + lval2);
127                case Query.TIMES:
128                    return Query.value(lval1 * lval2);
129                case Query.MINUS:
130                    return Query.value(lval1 - lval2);
131                case Query.DIV:
132                    return Query.value(lval1 / lval2);
133                }
134
135            } else {
136                dval1 = ((NumericValueExp)val1).doubleValue();
137                dval2 = ((NumericValueExp)val2).doubleValue();
138
139                switch (op) {
140                case Query.PLUS:
141                    return Query.value(dval1 + dval2);
142                case Query.TIMES:
143                    return Query.value(dval1 * dval2);
144                case Query.MINUS:
145                    return Query.value(dval1 - dval2);
146                case Query.DIV:
147                    return Query.value(dval1 / dval2);
148                }
149            }
150        } else {
151            sval1 = ((StringValueExp)val1).getValue();
152            sval2 = ((StringValueExp)val2).getValue();
153
154            switch (op) {
155            case Query.PLUS:
156                return new StringValueExp(sval1 + sval2);
157            default:
158                throw new BadStringOperationException(opString());
159            }
160        }
161
162        throw new BadBinaryOpValueExpException(this);
163    }
164
165    /**
166     * Returns the string representing the object
167     */
168    public String toString()  {
169        try {
170            return parens(exp1, true) + " " + opString() + " " + parens(exp2, false);
171        } catch (BadBinaryOpValueExpException ex) {
172            return "invalid expression";
173        }
174    }
175
176    /*
177     * Add parentheses to the given subexpression if necessary to
178     * preserve meaning.  Suppose this BinaryOpValueExp is
179     * Query.times(Query.plus(Query.attr("A"), Query.attr("B")), Query.attr("C")).
180     * Then the original toString() logic would return A + B * C.
181     * We check precedences in order to return (A + B) * C, which is the
182     * meaning of the ValueExp.
183     *
184     * We need to add parentheses if the unparenthesized expression would
185     * be parsed as a different ValueExp from the original.
186     * We cannot omit parentheses even when mathematically
187     * the result would be equivalent, because we do not know whether the
188     * numeric values will be integer or floating-point.  Addition and
189     * multiplication are associative for integers but not always for
190     * floating-point.
191     *
192     * So the rule is that we omit parentheses if the ValueExp
193     * is (A op1 B) op2 C and the precedence of op1 is greater than or
194     * equal to that of op2; or if the ValueExp is A op1 (B op2 C) and
195     * the precedence of op2 is greater than that of op1.  (There are two
196     * precedences: that of * and / is greater than that of + and -.)
197     * The case of (A op1 B) op2 (C op3 D) applies each rule in turn.
198     *
199     * The following examples show the rules in action.  On the left,
200     * the original ValueExp.  On the right, the string representation.
201     *
202     * (A + B) + C     A + B + C
203     * (A * B) + C     A * B + C
204     * (A + B) * C     (A + B) * C
205     * (A * B) * C     A * B * C
206     * A + (B + C)     A + (B + C)
207     * A + (B * C)     A + B * C
208     * A * (B + C)     A * (B + C)
209     * A * (B * C)     A * (B * C)
210     */
211    private String parens(ValueExp subexp, boolean left)
212    throws BadBinaryOpValueExpException {
213        boolean omit;
214        if (subexp instanceof BinaryOpValueExp) {
215            int subop = ((BinaryOpValueExp) subexp).op;
216            if (left)
217                omit = (precedence(subop) >= precedence(op));
218            else
219                omit = (precedence(subop) > precedence(op));
220        } else
221            omit = true;
222
223        if (omit)
224            return subexp.toString();
225        else
226            return "(" + subexp + ")";
227    }
228
229    private int precedence(int xop) throws BadBinaryOpValueExpException {
230        switch (xop) {
231            case Query.PLUS: case Query.MINUS: return 0;
232            case Query.TIMES: case Query.DIV: return 1;
233            default:
234                throw new BadBinaryOpValueExpException(this);
235        }
236    }
237
238    private String opString() throws BadBinaryOpValueExpException {
239        switch (op) {
240        case Query.PLUS:
241            return "+";
242        case Query.TIMES:
243            return "*";
244        case Query.MINUS:
245            return "-";
246        case Query.DIV:
247            return "/";
248        }
249
250        throw new BadBinaryOpValueExpException(this);
251    }
252
253    @Deprecated
254    public void setMBeanServer(MBeanServer s) {
255        super.setMBeanServer(s);
256     }
257 }
258